Jean-Louis Queri
Part-time lecturer in PHY 585
Département Enseignement - Recherche de Physique
Palaiseau, le 20th of March 2017
First of all, we would like to thank Dr Serena Bastiani-Ceccotti, who has kindly supervised and hosted
the projects in the PHY585 course, of which she is the teaching Coordinator.
Secondly we thank the Dr Asfafaw Haileselassie, the Dr Kindeya President of Mekkele University and
Dr Sebastien Fernandez, Dr Bernard Drevillon for the Partnership between Mekkele University and Ecole
Polytechnique.
Last but not least, we would like to thank Mr. Bernard Malherbe of the EDF Humanitarian Foundation
and Mr. Bernard Salha, Director of EDF R & D, Mr. Jean François Dedhain and Mr. Jean Angles of the LNHE
Department and Central Functions for the missions carried out and Mr. Jean-Paul Charrin Energie Without
borders for transport logistics in Ethiopia.
This year, as part of the PHY585 course, students carried out 5 projects related to renewable energies
and associated instrumentation & control. As we have seen before, these projects are part of a broader
partnership between the Ecole Polytechnique and the University of Mekkele, which aims to help the Ethiopian
population to use new breakthrough technologies such as shortcuts to progress.
The two first studies concern the supplementary electric supply of a condominium for cooking Injeras
from a solar roof (Jeanne Mermet / Philippe Blanc), with an original distribution strategy that allows
serving all apartments with only a single 4 KW power plant ( Antonin Adolphe / Anne Claire BillaultRoux).
We continued with the improvement of the cold chain of the fishermen of the Tigray lakes with a Vortex
Ranque Hilsch tube (Benoit Dabas / Mehdi Kechiar) and a simplified instrumentation & control based on
Arduino modules (Tamara Sabitova / Zhongya Liu). Prior to establishing the cold chain in the Lake
District, we are asked by the French Embassy and a local association to conduct an impact study on the fish
population. For this, EDF R & D department of LNHE offered a laboratory boat (Tiboulen / Mitiku Haile cf picture
below) to the university of Mekkele which takes care of its transport to Ethiopia as soon as possible.
At last we present a study of a "low cost" robot to incite the students to make electronic assemblies
(Henri Her / Chryseïs Salomez).
ÉCOLE POLYTECHNIQUE . F - 91128 PALAISEAU CEDEX
The Laboratory Boat TIBOULEN / MITIKU HAILE
The 5 pairs of students at Polytechnic
ÉCOLE POLYTECHNIQUE . F - 91128 PALAISEAU CEDEX
Mr. M. Asfafaw Haileselassie (Director of the new Institute of Energy of the University of
Mekkele) and Sébastien Fernández (Directorate of International Relations of X) at
Partnership signature on 14 March 2017.
ÉCOLE POLYTECHNIQUE . F - 91128 PALAISEAU CEDEX
Département Enseignement – Recherche de Physique
Palaiseau, March 20th, 2017
The reports collected in this booklet describe the experimental activities performed by eight Ecole
Polytechnique’s students in the framework of their 3rd year engineering program (a 4‑year program to obtain
Ecole Polytechnique’s Diploma). These students have followed an advanced program in Environmental
science and their experimental works were performed during their “PHY585 – Experimental works in
environmental physics” course. This is a 32‑hour course which aim to give students an original approach to the
experimental physics, letting them solve a problem related to environmental issues. The spirit of the course is
to pose a problem to the students, and let them as free as possible to solve it, encouraging them to be creative,
original and, of course, efficient. In this context, I collaborate with M Jean-Louis Quéri since 2011. His
involvement in PHY585 has become more and more important, leading this year to an extensive work whose
results are reported here. I’m honored to contribute to the partnership between the Ecole Polytechnique and the
Mekkele University, and look forward to other always interesting exchanges
Serena Bastiani-Ceccotti
Lecturer at Ecole Polytechnique
Teaching coordinator of PHY585
SERENA BA STIA NI-C EC C O TTI
ÉC O LE PO LYTEC HNIQ UE - F 91128 PA LA ISEA U C EDEX - T. +33 (0)1 69 33 54 04 - F. +33 (0)1 69 33 54 82
PHOTOVOLTAIC PRODUCTION
COUPLED TO A STORAGE SYSTEM
Application on Jemo condominiums, Ethiopia
Philippe Barbe
Jeanne Mermet-Guyennet
ACKNOWLEDGEMENTS
We would like to acknowledge Mr Quéri, our supervisor, for this project. He accompanied us
all along and gave us informations about Ethiopian, batteries, supercapacitor and solar panels.
We hope his dancing robot will have him the success he deserves.
We also give our aknowledgements to Mrs. Serena Bastiani for proposing this interesting
project and following its progress.
Finally, we thank Mr. Le Tallec, our program director, for his advices and guidance over
the year.
2
Abstract
This report contains first a fast description of the condominiums and solar resources
in Ethiopia. Then, it explains and analyse the whole installation containing specific solar
panels and a storage device, by giving qualitative and quantitative analysis of the elements
composing it. Matlab simulation are shown and explain in order to see the functioning of
the complex components.
CONTENTS
1 Context
1.1 Urbanisation plan of Addis-Abeba . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Presentation of the condominiums . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Presentation of the solar resources of Ethiopia . . . . . . . . . . . . . . . . . . .
2 The photovoltaic installation
2.1 Individual solar cell . . . . . . . . . . . . . . . . .
2.2 Module characteristics and simulation . . . . . . .
2.2.1 IV curve . . . . . . . . . . . . . . . . . . .
2.2.2 Maximum Power Point Tracking . . . . . .
2.3 Sizing and modeling of the whole PV installation
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3 Storage system
3.1 Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Supercapacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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4 Complete system
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4.1 DC/DC converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2 Complete installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3
LIST OF FIGURES
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Condominiums construction site . . . . . . . . . . . . . . . . . . .
Daily consumption in a 3 bed flat in a condominium . . . . . . . .
Soda’s data of solar irradiance in Adis Adeba . . . . . . . . . . . .
Equivalent diagram of a solar cell . . . . . . . . . . . . . . . . . .
IV curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Illustration of maximum power point varying with output resistive
Flow-chart algorithm of the Perturb%Observe method . . . . . .
Power curve of the PV array . . . . . . . . . . . . . . . . . . . . .
Discharge characteristics of the battery . . . . . . . . . . . . . .
charge characteristics of the supercapacitor . . . . . . . . . . . . .
Comparison between supercapacitor and batteries . . . . . . . . .
Equivalent diagram of a DC/DC buck converter (ref) . . . . . . .
Overall diagram of the complete PV/converter/storage system . .
Simulink diagram of the complete system . . . . . . . . . . . . . .
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18
INTRODUCTION
Ethiopia is witnessing a massive rural exodus. Cities are not equipped to respond the increasing of housing demands. The government has then decided to finance the construction
of buildings containing low-cost apartments in the suburbs. This incentive had the effect to
create energy demands, however the national grid is insufficient to respond to this concentrated
electricity demand increase. These projects are helped by the EDF fundation.
In this area, where the grid can suffer some cuts, the installation of solar panel seems to be
the solution. However, Ethiopian’s law forbid the users of solar panel to send their electricity in
the national grid. This law and the issue of solar energy intermittency creates a need of storage.
This need can be fulfilled by two devices: battery or supercapacitor. The second one is never
used because of its price is about 10 times the one of a battery. Nevertheless, its price keeps
on going down so it may be interesting to look for this solution. We propose a quantitative
analysis and comparison of this two storage devices.
The goal of this project is first of all to size the solar panels installation and then to find
the adapted way of storing some of the energy. The objective is to have enough energy to make
an injera oven work during the day, then each apartments of the condominium will have access
to this energy at specific days so they can share the installation.
Matlab Simulink shows us how the system responds to the demand and the solar irradiance. The aim is to simulate the optimal performance of this small grid. An other group is
working on how the electricity is distributed to a flat or another. We have simulated various
components of the whole photovoltaic installation in order to visualize how the loading system
can be harmonized with the solar panels.
5
1. Context
Figure 1: Condominiums construction site
1
CONTEXT
1.1 Urbanisation plan of Addis-Abeba
Since the 80’s, Ethiopa has been facing a huge rural exodus, especially in the capital AddisAbeba. As a consequence, the government has created the Integrated Housing Development
Program [8] whose purpose is to create employment and 200 000 accommodations for Ethiopian
families. Those social housing are called condominiums.
The attribution of those flats follows this scheme: the Ethiopian family is participating to a
“lottery” in order to pick an apartment. Then they have to pay a 20% advance payment, and
pay back the other 80% over 15 years.
The fact is that in Ethiopia it is quite difficult to obtain a private housing because the offer
is not big enough. As a result this policy is beneficial for the middle and the upper class. Many
of the owners become landlords and decide to privately rent their flats.
This implantation of numerous housing creates an overconsumption, especially between 10h
and 16h. These are the hours of injera’s cooking. Injera is an East African flatbread which is
the base of the Ethiopian food. To respond to this consumption, EDF foundation has decided
to install solar panel on the condominium’s rooftop.
1.2 Presentation of the condominiums
A basic condominium is composed of 5 floor with 5 apartments by floors. These flats can
have 1,2 or 3 bedrooms. Tens of buildings are constructed around green areas, creating small
cities with school and market.
6
1. Context
The electric consumption in this buildings is quite low during a day except during the afternoon when habitants are using 4kW oven to cook injeras. The consumption can be described
by the figure 2.
The goal of this project is to quantify the solar installation in order to respond to the peak
demand during the afternoon. We will explain what are the most adapted solar panels and
means of storage. We aim to find an equilibrium between efficiency and price.
Figure 2: Daily consumption in a 3 bed flat in a condominium
1.3 Presentation of the solar resources of Ethiopia
We have used the data from the Solar Radiation Data website to get a mean solar irradiance
during a basic day (in February). We didn’t have so much doubt about the solar resources in
Ethiopia but this graph shows us that solar panels are much profitable in this area.
Figure 3: Soda’s data of solar irradiance in Adis Adeba
7
2. The photovoltaic installation
2
THE PHOTOVOLTAIC INSTALLATION
In order to respond to the consumption peak occuring between 10am and 16pm in the condominiums, we chose to provide cheap but reliable PV modules: the PVL-144 model fabricated
by UNI-SOLAR. The choice of those modules was motivated by :
• Their flexibility and lightweight, which made them easily transportable, especially for the
building’s roof.
• Their simple installation and fast connection cables.
• Their sustainability and adaptability to high temperature environments.
• Their cost, about 250 euros, sometimes EDF Fundation get them for free.
The Matlab Simulink environment provides really good simulation tools for renewable energy systems, as well as performing power conversion components. This section will thus
describe the modeling of a PV array, and its sizing with respect to the condominiums consumption.
2.1 Individual solar cell
A solar cell is a device that converts solar irradiance (W.m−2 ) into available electrical power.
It can be modeled by the following equivalent circuit:
Figure 4: Equivalent diagram of a solar cell
Where Iph represent the input photocurrent generated by the sun, the diode D models the
behavior of the solar cell. Rsh and Rs are the shunt and series resistances of the cell, respectively. I and V are the output current and voltage of the cell. For an individual solar cell,
the shunt resistance represent the defects located in the junction and at its interfaces, and the
series resistance is due to the electrical contacts at the front and at the back of the junction. For
8
2. The photovoltaic installation
The following equation [2] gives the I-V characteristics of the solar cell:
q(V + Rs I)
V + Rs I
] − 1) −
(1)
nkTk
Rsh
n is the ideality factor which value is between 1 and 2 and expresses the quality of the cell and
I0 the saturation current of the diode.
In order to fully characterize a solar cell, we determine Voc and Isc , the open-circuit voltage
and short-circuit current. Those parameters, with the shunt and series resistances, will provide
us with all the elements to determine the maximum power point of the cell. To study the
behaviour of a single solar cell, it is possible to implement the I = f(V) equation as a block
diagram, or the equivalent circuit directly in Matlab Simulink. We will study directly in the
next paragraph the PV module, which is actually formed by 22 cells connected in series.
I = Iph − I0 (exp[
2.2 Module characteristics and simulation
As mentioned previously, the simulation of the module could be done by creating a cell
model and connecting 22 of those in series. The user would then have to determine on his
own the intern parameters of the module such as the series or shunt resistances. However,
the Simulink library, SimPowerSystems [1] already implemented a PV array block, allowing
us to study the behaviour of our panel by entering its characteristics quantities read from the
constructor sheet 1 .
2.2.1 • IV curve
(a) IV curve from constructor data-sheet
(b) IV curve from Simulink model
Figure 5: IV curves
1
There are a lot of modules already implemented in Simulink, but the model we chose for this project was
not.
9
2. The photovoltaic installation
The PVL-144 module has an open-circuit voltage (Voc) of 33V and a short-circuit current
(Isc) of 4.36A. As you can see the IV curves from the Matlab model and the constructor datasheet slightly differ. The maximum power indicated by the constructor, under Standard Test
Conditions (STC)2 is 144W and the Matlab model gives us 143.8W, this is not a significant
difference but during the simulations we were not able to overcome 140W for one panel, due to
the losses in the circuit. We can also notice that the shunt resistance (the inverse of the slope
at a zero voltage) is not the same depending on the data source.
2.2.2 • Maximum Power Point Tracking
PV modules have a very specific current/voltage behaviour, as you can see in eq (1) and the
previous figures. A given PV module’s IV characteristics will vary with the sun irradiance and
the temperature. Therefore, for each (Irradiance, Temperature) couple, the maximum power
point will vary and correspond to a given (I, V) couple. Since the PV array’s voltage will be
dictated by the load, it won’t be necessarily operating at the maximum power point at every
moment. In order to fully optimize the module and to extract the maximum available power,
we need to set the output voltage at the maximum power point. This can be achieved by a
Maximum Power Point Tracking algorithm controlling a DC/DC converter at the output of the
PV array.
Figure 6: Illustration of maximum power point varying with output resistive load
There are several algorithms for MPPT, such as Fixed Duty Cycle, Constant Voltage, Perturb and Observe (P&O) and Modified P&O, Incremental Conductance (IC) and Modified IC,
Ripple Correlation and System Oscillation methods [3]. The most commonly used algorithm is
the Perturb & Observe method, which takes as inputs the PV voltage and current, calculates
a duty cycle, ratio between Vmpp (maximum power point voltage) and the actual Vpv (PV
voltage) by calculating step-by-step the output power of the array with its previous value and
modifying the duty cycle in consequence. When the power calculated is the same as the previous (meaning that the the power’s derivative equals zero), the optimal duty cycle has been
found and the algorithm stops (flowchart in Figure 7).
2
STC for PV panel characterization : 1000 W/m2 (one sun illumination) and 25◦ C
10
2. The photovoltaic installation
Figure 7: Flow-chart algorithm of the Perturb%Observe method
2.3 Sizing and modeling of the whole PV installation
We have seen in the irradiance data sheet that the mean irradiance between 10am and
15pm is about 800 W.m−2 . For this value and at optimum power 110Wc (value taken from the
constructor sheet), the solar panel provides a tension of about 30V and an intensity of 3.6A.
As a consequence we have to install 7 panels in series to get a tension of 220V and we have to
connect in parallel 5 set of this 7 series panel, that is to say we have 35 panels to get 4kW of
power for the oven. The total price of the solar panels would be 8750 euros.
These panels have a surface of 2.1m2 so we need at least 70m2 on the roof, we have learned
that the roof usable surface was 90m2 , but we didn’t get to see the plans to make a real scheme
of the installations. How the panels must be orientated ? We calculate the best orientation
given the month of the year when the solar irradiance is the lowest, we found out that the panel
must be orientated with an angle of 2◦ toward the south. In application, it is way much simpler
only to install it horizontally and the difference of performance is less than 1%.
It is possible in the Simulink library to choose the number of series modules and parallel
strings in order to simulate our array (Figure 7). Since we have 5 parallel strings of 7 seriesconnected modules, the open-circuit voltage and the short-circuit current of the array will be:
Vocarray = 7Voc = 231V
(2)
Iscarray = 5Isc = 21, 8A
(3)
The maximum power point for a 800 W/m2 irradiance is slightly above 4kW, our approx-
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2. The photovoltaic installation
Figure 8: Power curve of the PV array
imate sizing was accurate, however the storage system and the building grid will have to be
adapted to the power surplus that will occur in particularly bright days.
12
3. Storage system
3
STORAGE SYSTEM
There are two main reasons for the installation of a storage system:
• The first one is that the inhabitants need to be able to make the injera oven work for one
hour even if there is not enough solar irradiance.
• The second one is that we don’t want to waste the excess of solar energy during very
bright day.
The power grid distribution in the building will be implemented by another group in order
to manage the case where the batteries are fully charged and that there is a power surplus
generated by the PV array.
3.1 Batteries
Nowadays, the best results of storage systems for PV generation are achieved with Li-ion
battery [4]. A classic Li-ion battery has a nominal voltage of 12V and a rated capacity of 110Ah
which gives 1.2kWh of storage and costs 200 euros. But, in order to preserve the life cycle of
this battery, it must be charged and discharged at 25% of its maximum capacity. As a result
the installation need 16 batteries for a cost of 3600 euros. Figure 8 represents the simulation
of our battery discharge with different values of output current. The aim is to prove that this
characteristics are adapted to the installations if the batteries are put in series.
Figure 9: Discharge characteristics of the battery
An other solution for the storage installation is an innovating battery created by Tesla. It is
called powerwall and offers 10kwh of storage for 6 000 euros which make it cheaper than classic
13
3. Storage system
battery. It can be installed offgrid and combined with other powerwall to increase the storage
capacity. It is Li-ion based and completely automatised which make it very simple to use and
very adapted to the ethiopian buildings.
3.2 Supercapacitors
Supercapacitors have not been used as much as classic batteries for 2 main reasons, their
price and their poor energy density. Nonetheless, they have some assets to their use [7]. First,
they have a quasi-unlimited longevity because they can handle millions of cycle. Moreover,
they can be charged quasi-instantly and they can provide a huge power when discharged, which
is quite relevant for the current situation because an injera oven need 4kW to work. Second,
contrary to most batteries they present no risk of use. However others factors can limit their
use, especially its self-discharge that is higher than the one in battery.
Figure 10: charge characteristics of the supercapacitor
Figure 9 represents the charge curve of a supercapacitor with characteristics of 3000F and
2,7V.This type of devices cost 20 euros, Maxwell is a chinese company which produces the most
supercapacitors. It store about 3Wh, calculated with the following equation.
Estored = 0.5 V 2 C
(4)
As a consequence the installation require 1300 pieces. It can seem very impressive but these
supercapacitors are quite small and can be easily connected. As a consequence the price for
the installation would be 26 000 euros.
14
3. Storage system
Figure 11: Comparison between supercapacitor and batteries
3.3 Comparison
The figure 10 resume the different properties explained in the last section. It is excrcted
from the website of Maxwell company. The charge time was already given by the previous
figure. It provides us infomration about the working temperature, supercapacitors can operate
in wider conditions than batteries. These informations date from 2013 so the prices have already
evolved. Service life for supercapacitor are here described for vehicule use, the valuable point
is the cycle life.
The battery installation is 7 times cheaper than the supercapacitor. Nevertheless, one must
take into account that battery has to be changed at least every 5 years when supercapacitor
can be kept during a lifetime or even more. In fact, supercapacitor are a bigger investment but
are more cost effective in the long term.
To conclude, using batteries is still the cheapest way to store energy on the short term but
supercapacitor are lesser and lesser expensive and lithium is getting more expensive. In a few
years, supercapacitors could became the new main device to store energy.
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4. Complete system
4
COMPLETE SYSTEM
4.1 DC/DC converter
As mentioned previously, we need a DC/DC converter in order to regulate the voltage at
the output of the PV array. There are three types of DC/DC converters: the buck, boost and
buck/boost converters [5]. The buck converter (step-down converter) lowers the voltage that it
receives as an input, whereas the boost steps it up. In our system we will use a buck converter.
The equivalent circuit of a buck converter is shown in Figure 11.
Figure 12: Equivalent diagram of a DC/DC buck converter (ref)
DC/DC converters devices operates thanks to two semiconductors switching devices: a
diode (D on Figure 11) and a controlled switch: a MOSFET (SW). An IGBT diode can also
be used as controlled switch, but MOSFETs are more fitted to high voltage power application.
This type of switching device has three ports: a gate (g), a source and a drain. The MOSFET’s
ON and OFF states are controlled by a pulse signal connected to its gate input.
Assuming an ideal switch (zero on- resistance, infinite off-resistance and zero switching time)
and an ideal diode, and ideal capacitors and inductors, the differential equations characterizing
a buck converter are:
C
dv
vc
= iL − − io
dc
R
(5)
di
= uvpv − vc
(6)
dt
Where u is the state of the switching device (= 0 or 1). The working principles of a buck
converter can be explained as follows. In the buck mode, when the switch is on position 1,
L
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4. Complete system
the DC source supplies power to the circuit which results with an output voltage across the
load resistor. When the switch changes its position to 0, the energy stored in the inductor and
capacitor will discharge through the resistor. Appropriately controlling the switching position
can maintain the output voltage at a desired level lower than the source. The duty cycle of a
buck converter (α) is the ratio between the output and the input voltages. It also represents the
percentage of the switching period where the switch is ON, thus providing us a direct control
of the ratio between voltages.
The values of the inductance and capacitance are given by the following equations [6]:
Lmin =
(Vpv − Vload ) α
LIR Iload,M AX fSW
(7)
LIR Iload,M AX
8 fSW CV R Vload
(8)
Cmin =
Where LIR and CVR are the inductor current ripple ratio and the capacitor voltage ratio,
respectively, fSW is the switching frequency of the MOSFET, α is the duty cycle, Vload and Iload
are the voltage and current of the load, in our case of the storage system. LIR and CVR can be
set as 0.05, meaning that the ripple current of the inductor will represent 5% of the maximum
output current and the ripple voltage of the capacitor will represent 5% of the output voltage.
4.2 Complete installation
Finally, the schematic diagram of the complete installation, connecting the PV array, the
buck converter with MPPT control and the load (battery) is represented in Figure 12.
The corresponding Simulink diagram is represented in Figure 13. The MPPT algorithm
using the Perturb%Observe method measure for each input irradiance and temperature couple
the voltage and current of the PV array and calculates the optimal duty cycle α. This duty
cycle is then placed at the intput of a PWM (Pulse Width Modulation) generator that generates
a pulse signal with a 30KHz frequency. The buck converter, depending on the voltage of the
battery, that is, its SOC (State Of Charge), will then set the output voltage of the PV array
at the maximum power point. It is missing in this system a three-phases inverter (DC/AC
converter) that would convert the current and generate the appropriate AC mode that will be
distributed in the condominium grid and two appropriate control loops in order to adapt the
voltage and current of the battery to the grid demand. However, we were missing appropriate
informations about this grid and its control system distributing the power in the different
apartments and the battery system can be charged in DC mode.
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4. Complete system
Figure 13: Overall diagram of the complete PV/converter/storage system
Figure 14: Simulink diagram of the complete system
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4. Complete system
CONCLUSION
Solar resources in Ethiopia are abundant. Solar installation is very profitable in this area
and there is a real need of power supply because of the non-controlled increase of the suburbian
population. We could have chosen to size the biggest installation we could install in order to
generate the maximum power and to respond to the overall electricity demand of the condominiums. But the point was not to providethe maximum power but to find a solution adapted
to the overconsumption occuring between 10am and 15pm. That is to say the most economic,
long term and simple solution. This also can be applied to the storage system. Batteries are
economic and simple to use, especially because it is widespread. Nevertheless, supercapacitor
are better in the long term and as a result more economic, but since their technology is not yet
well spread in the industrial sector and for this type of application, they were more difficult to
consider as a concrete solution and we chose the more reliable solution: batteries.
The secondary objective of this project, after having proposed a good and efficient system,
was to implement it in Matlab Simulink, in order to analyse the different steps of power conversion needed to use such systems. However, we encountered several practical issues during
the simulation and the documentation about the simulation and control of those systems did
not allow us to solve them within the time limit of this project.
To conclude, given the components we used the cheapest investment for such an installation
would be around 12 000 euros just for the solar and storage devices without the distribution
system. Obviously, this kind of installation can’t be paid by the occupants of these buildings
but the government and some foundation may provide financial help.
The next step in this project is to write down the specifications of the installation like the
support of the panel, which can be concrete block, the connection of the batteries and the
connection to the whole grid. We must also add the maintenance protocol of the solar panels:
how to clean and change them. Then we would have to make concrete researches about the
cost of installation depending on the labor cost in Ethiopia and the transport of the devices to
get the real cost of the project.
19
REFERENCES
[1] Simpowersystems library, mathworks. https://www.mathworks.com/products/simpower.html.
Accessed: 2010-09-30.
[2] Habbati Bellia, Ramdani Youcef, and Moulay Fatima. A detailed modeling of photovoltaic
module using {MATLAB}. {NRIAG} Journal of Astronomy and Geophysics, 3(1):53 – 61,
2014.
[3] M. A. G. de Brito, L. P. Sampaio, G. Luigi, G. A. e Melo, and C. A. Canesin. Comparative
analysis of mppt techniques for pv applications. pages 99–104, June 2011.
[4] Fei Ding, Peng Li, Bibin Huang, Fei Gao, Chengdi Ding, and Chengshan Wang. Modeling
and simulation of grid-connected hybrid photovoltaic/battery distributed generation system.
pages 1–10, Sept 2010.
[5] Samet H. Kolsi, S. and M. Amar. Design analysis of dc-dc converters connected to a
photovoltaic generator and controlled by mppt for optimal energy transfer throughout a
clear day. Journal of Power and Energy Engineering, pages 27–34, 2014.
[6] ON Semiconductors. LC Selection Guide for the DC-DC Synchronous Buck Converter,
2014.
[7] Mohamed Ansoumane Camara Pierre-Olivier Logerais, Olivier Riou and Jean-Félix Durastanti. Study of photovoltaic energy storage by supercapacitors through both experimental
and modelling approaches. Journal of Solar Energy, 2013.
[8] UN-Habitat. CONDOMINIUM HOUSING IN ETHIOPIA: The Integrated Housing Development Programme, 2011.
20
Solar roofs for low-cost housing in Ethiopia
and management of electricity supply
Contents:
Introduction
I.
Overview of the context
A. Social and societal context
B. Technical context
C. Low-cost housing in Addis Abeba
II. System for sharing electricity supply
A. Specifications
B. Choice of a fair supply method
III. Technical aspects and accomplishments
A. Arduino
B. Small-scale model
IV. Practical implementation method for the project
A. From the layout to real-size
B. Economic and legal aspects
Conclusion
Bibliography
Appendix
Introduction
In Ethiopia’s capital, Addis Ababa, the Ethiopian government has launched since
twenty years an ambitious housing program for people who lived in the slums. Ethiopia is
indeed going through an impressive growth, with one of the highest growth rates in Africa: as
a consequence, urban population is skyrocketing. Addis Ababa, in particular, now has more
than 3.5 million inhabitants. The situation in terms of housing is disastrous, and the
government responds by building as fast as possible low-cost housing to try and solve the
“wild crisis” which the capital city is experiencing, as expressed the official in charge of the
public project.
Yet, this social housing brings some new questions, on both social and technological stakes.
The poor electricity network prevents inhabitants from having a satisfactory access to energy
in their daily needs, especially for feeding and cooking injeras, which are at the basis of
Ethiopian food.
One response to this new stake might come from new opportunities linked with photovoltaics,
which might provide an extra contribution to the electricity supply.
This was the startpoint to our work and reflection: how might new energy technologies help
solve this social crisis? How can sustainable development be associated with the
improvement of living conditions? And in practice, how could the photovoltaics power
supply be fairly distributed among the inhabitants of a low-cost housing building.
During the three months of our project, we have studied the social and technological
problems which could occur on the field. We hope that this report can help pursue a concrete
implementation of the solutions which we suggest. In this perspective, we have built a small
lay-out that illustrates our work, and shows that the project could well fit to the situation in
Addis Ababa.
We also want our project to come within the scope of the intense development of Ethiopia,
while promoting the use of renewable energy. The project might also give the incentive for
local entrepreneurship, since it could allow groups of houses to achieve autonomy in terms of
energy supply. Finally, our project was designed in order to avoid disputes among the
buildings’ inhabitants, and between the inhabitants and the owners of the PV solar panels.
I. Context of the project
A. Social and societal context
To begin with, the social and societal context in which the project takes place needs to be
recalled, that is, the development of Ethiopia. The project relates to it in three major ways:
urbanisation and real-estate development; food security in cities and suburbs; the
development of the still precarious electricity network and the implementation of renewable
energies in the country.
The first point results from the government’s response to demographic growth and to the
accelerated urbanisation in Ethiopia. Priority is set on housing development, in order to build
new residential areas and put an end to the squalid slums near Addis Ababa. Before the
1990s, there were few government-owned social housing buildings, as recalls Demissachew
Shiferaw article1. There was a real lack for decent housing: in 1994, 57% of Addis Ababa’s
population had no access to real housing. As a response, there were mainly small-scale
private initiatives. Inhabitants took spontaneous actions to develop their quarters.
More recently, government housing plans were launched. The two main causes are, of course,
demographic growth, but also deforestation which provokes a strong erosion in some areas hence a rural exodus - and also reduces the possibility of using wood for house-building,
since the wood goes to other uses2. An economic aspect is added to the demographic one: the
real-estate development adds to the dynamism of the Ethiopian economy. Between 2006 and
2010, 171 000 low-cost housing buildings were built 1. The first goal is to eradicate slums; it
will also allow the government to recover plots of land, for example in order to build business
districts.
But the social consequence of these societal changes is not yet clear. Many inhabitants are
reluctant to leaving the slums in which they are established. It is indeed not clear wether their
living conditions would really be improved is they moved to the newly-built condominiums.
One of the major reasons for discontent is linked to the poor quality of the electrical network:
in average, cuts in electricity supply happen during 6 hours each day in Addis Ababa. As a
result, inhabitants cannot count on a reliable electricity supply for their various needs.
Ethiopia is still today the country where the energy consumption per inhabitant is the lowest.
The electrical network, owned by Ethiopian Electric Power (EEP), suffers from a lack of
maintenance. EEP has indeed to work both on the quality of the service which they provide,
1 Self-initiated transformations of public-provided dwellings in Addis Ababa, Ethiopia ; D. Shiferaw ; Cities
(1998)
2 Introduction of Sustainable Low-cost Housing in Ethiopia – an Innovation Diffusion Perspective; B. Hjort, K.
Widen; Procedia Economics and Finance Volume 21, p. 454-460 8th Nordic Conference on Construction
Economics and Organization (2015)
and on the extension of the electricity network to new areas. At this point, the lack of
reliability is a real issue for the low-cost housing buildings, mostly in terms of food security.
Indeed, in practice, the only cooking mode which is allowed in urban areas is electric
cooking. Having a fire in a flat in a low-cost housing building is out of the question. This is
the reason why some tensions are felt in quarters where lack of electricity is an obstacle to
correct nutrition. Paradoxically, in the eyes of the inhabitants, life in the slum was a warrant
for a relative food security, with the possibility of having a fire to cook their food, and with an
access to food supply which was rather better than in the new quarters, which are very
densely populated. As a whole, those new housing plans are rather not welcome in the
population, and they are far from being adopted. This shows that food habits and lifestyle
have to be considered as important factors in the development of any such project. Boesch’s
theory also insist on the fundamental role of housing in the well-being of a population.
Our study also includes, from the societal point of view, the Ethiopian project to vary the
country’s energy resources, and implement among others solar photovoltaic panels. Indeed,
the Ethiopian government has started a new program for renewable energy, with an aim of
12GW by 2020. Today, 89% of the energy in Ethiopia comes from biomass, which is mainly
coal and wood, and which proves not to be sustainable on the long term, since the
deforestation rate is excessive. Among the new energy resources whose development is being
fostered in Ethiopia, there is before all hydro-electric power. Still, the second Growth and
Transformation Plan (GTPII) also includes a project of 300MW of PV power, with solar
centrals byt also residential solar panels. In 2013, 13200 residential PV systems had thus
already been put in place in rural areas.
All those elements of context push for the research of new solutions for energy resources, in
particular for electrical needs, at the level of the capital and especially for the newly-built
low-cost housing areas. It is crucial to get the support and goodwill of the local population, so
that they might welcome the project and agree with it. The project of solar roofs is thus a
potential solution, that would allow to extend the development of renewable energies to urban
areas, while solving the problem of the precarious electrical network. At the same time, the
inhabitants would be less reluctant to leave the slums if they have the certainty to have a more
reliable electrical supply.
B. Technical context – solar PV panels
Within the frame of this project, it is also useful to have in mind the basic data concerning
solar radiation and the power available for solar PV panels in the region of Addis Ababa. The
conception of solar roofs goes beyond our own project, since we have mostly focused on how
to use this power for cooking purposes, for the supply of injera ovens.
Beyond this project, if the solar panels have a sufficient yield, they could become the major
source of electricity for the buildings, and suffice for all the basic needs of the inhabitants.
But this is not what we have focused on.
The data of solar power is shown on the following graph, which was provided to us by
another group working on the solar roof project itself; it was made with data from Climate
SAD-PVGIS, which gives the PV power available at almost any place on Earth. This graph
shows solar radiation over a daytime, for different kinds of conditions.
Power of solar radiation in different weather conditions over one day (January)
Without getting into too much detail, some information can be deduced from this.
On the one hand, this curve allows to define, for each month, the best time to use solar panels.
In average, over the year, It can be considered that the time slot when the power available is
the highest, and when the solar roof should be used, is between 10:00 and 16:00. It should be
noted that this is an average estimation, and that this aspect of the work could be refined in
order to adjust more precisely this time slot, for example depending on the period of year.
On the other hand, the data about solar power allow to determine the size of solar panels; the
meteorological conditions in Addis Ababa are such that it is a good approximation to suppose
that the situation is generally a “global real sky” type one, which takes into account average
cloudiness.
The next question that needs to be addressed regards energy storage: in order to benefit from
the solar panels outside of the timeslot where the solar power is the greatest, and in order to
smoothen the power supply, a system for storage should be put in place. Research in this field
points to two options: either a battery system, or hypercondensers. The latter is a new
technology whose advantage is to last much longer than batteries. The size of this storage will
depend on the contract that is subscribed by the inhabitants of the building. In the frame of
this project, it will be supposed that the solar panels work without any storage system linked
to them.
C. Social context: low-cost housing in Addis Ababa
The standard buildings on which we have based our study contain 25 flats, split up into 5
floors of 5 flats each. It is indeed the medium size of the newly-built low-cost buildings,
which would host the project.
Those buildings are linked to the electrical network of the capital, which suffers from
frequent cuts, especially during droughts when the dams cease to work because there is not
enough water. The network is also pirated, which provokes even more cuts.
Every flat corresponds to a family of 3 to 10 people. The needs in terms of food for a family
therefore represent a few injeras per day. Since those injeras can be kept for a few days once
they have been cooked, we have come to the conclusion that each family should be able to
cook injeras at least once a week.
The inhabitants should thus have access to electricity at least at this frequency, especially
those who have not yet been connected to the national electricity network owned by EEPCO
(ref: Power Sector, Market Report, Ethiopia).
An injera pan uses a power of approximately 2kW, but the electric oven which is more
frequently used, uses 4kW. This is the power which we have assumed to be available during
the whole time slot of 10:00-16:00 from the solar PV panels. For an average family of 5, it
should take about 1 hour to cook all the injeras. This is what has been supposed from now on
in this study.
II.
System for sharing the electricity supply from solar panels
A. Specifications
After having studied the context, it was determined that the specifications of the project are
the following:
1) Each family should receive electricity with a power of 4kW during an hour, at least
once a week.
2) The sharing out should be fairly established between the different households, whether
the weather is favorable or not, and the timeslot allotted to each flat should vary, so
that one household should not feel disadvantaged when compared to another one.
3) The sharing out should be visible in advance, so that the inhabitants might organize
their timetable according to it, and use the electricity when it is their turn.
4) The history of the sharing out should be kept, in order to avoid unjustified complaints
from
inhabitants.
B. Choice of a fair supply method
Here is then the description of project which was drafted to respond to those requirements.
1.
“Each family should receive electricity with a power of 4kW during an hour, at least once a
week.”
What we recommend is to put in place on the buildings’ roofs solar panels of medium range,
which can provide at least 4kW during 6 hours per day, between 10:00 and 16:00. What was
opted for in this first version is panels without storage system, in order to reduce the costs (cf.
Technical context on solar panels).
Six families per day would therefore benefit from their one-hour time slot. In 4 days, every
family but one will have had their access to this electricity supply. The time slot for a family
comes every 4 days, with a time difference of one hour.
Other options could have been possible for this sharing out system, like using tokens. But this
option, which might look attractive at first, would lead to some time slots non-utilization, and
would create some competition over the most favorable times of the day.
Moreover, the advantage of this rotation system is how simple it is: the inhabitants do not
need to worry about getting their electricity supply. It is important that the power supply
should not be a further burden for the families, and that it should be adopted easily. This takes
out the too complex systems for sharing out electricity.
Example: If family A gets its time slot on Monday à 1 pm, it will get the next one on Friday at
2 pm. The only exception is if the family has the 3-4 pm slot: the next will be five days later,
at 10-11 am.
Simplicity goes with reliability: the system needs to work without a very intensive technical
support, and the aim is that the installation is almost autonomous. In practice, this means that
the technology employed should be minimal and robust. Supervising the power supply and the
sharing out of electricity will be done with a program implemented on an Arduino, that is put
between the solar panels and the flats. More detail will be given further on in this report.
2.
“The sharing out should be fairly established between the different households”
In order to solve the problem of uncertainty linked to bad weather conditions, which result in
a decreased solar power, our hypothesis is a mathematical one. The law of large numbers
shows that in the long term (over a year for instance) all the inhabitants will each have had
approximately the same number of disadvantageous slots with meteorological uncertainties.
Over time, inequalities will compensate.
Moreover, with a postulate of “concertation”, the system can be made even fairer, and
resilient to bad meteorological conditions. Our hypothesis is that the inhabitants might be
willing to exchange their timeslots by giving their neighbor access to their kitchen. Thanks to
the LED lights on the forefronts of the apartments, everybody knows who benefits from the
electric power at any time, thus they can negotiate internally an exchange of timeslots.
The good functioning of the whole system obviously relies on a sharing approach and thus
requires mutual trust among users. To help on that point, we designed an engagement contract
that has to be signed by everybody and that defines the terms and conditions of the sharing
and the use of individual timeslots (cf Annexe)
3. “The distribution must be defined and visible ahead of time”
In order to enable people to anticipate on their timeslots, we have to set up a global schedule
easy to understand for everybody. Monthly schedules will thus be displayed in the hall of
every building, indicating the day and the time of timeslots for each apartment. The person
responsible for the building will receive such schedules for the whole year, and will have to
display them one by one, every month.
In practice, each apartment will be equipped with two LED lights (green and orange), placed
over the front door. They will allow everybody to know where is the distribution happening,
and thus when it will come to their own apartment. The orange LED will be automatically
turned on one hour before the timeslot, while the green LED will be turned on when the
electricity is actually available. The simplest way to realize this electrical circuit is to have the
orange LED of the apartment N connected in series with the green LED of the apartment
N+1, as shown in the following diagram.
Diagram of the power distribution system and the LED cycle of functioning
Last, in order to be able to trace the history of the distribution of the power, we propose to
add an SD card to the Arduino system, where the data will be temporarily saved during a
year. If necessary, e.g. in case of claim from one user. So, at the moment of the change of
time slot, the system memorizes that the change has actually been made. The memory of the
SD card will thus allow to help on any litigation management, by providing safe data about
the distribution and the availability of the power.
C. Other objectives
Regarding the preliminary project we are leading in the lab of Ecole polytechnique, we added
some supplementary objective:
5) Write down a template of engagement contract for the users of the solar electricity.
6) Create a scale model of the electrical system we designed
7) Lead a study on the economical, social and environmental impacts resulting in the
implementation of our system in Addis Abeba.
III.
Technical aspects and realization of the scale model
A. The Arduino, the key component of the system
The essential of the technology we use in our scale model lies in the Arduino card.
● Presentation of the technology used
Let’s come back quickly to the main characteristics of Arduinos, widely used now. “Arduino”
refers to a system frequently used in robotics and applied programming. In includes an
hardware: an integrated electrical circuit, associated with inputs and outputs on wich the user
can plug different components, captors, electronical devices, and so on…
Arduino also includes a software that enables the user to communicate with the hardware
through a computer interface. A programming environment is associated to it, which language
is very close from the C or C++ languages.
Besides its performances, what makes the Arduino technology so adapted to our project is its
very low price: prices varies from a model to another but are around 30€.
We have also detailed our needs for an external memory to store the data related to the
distribution history of the power through the apartments. The Arduino enables this data
storage, as it is possible to link an SD card to the Arduino,and write on it. It is necessary,
though, to add a plug-in hardware called “SD Shield” that we ordered through the TREX.
This extra hardware just plugs in directly on the base card, so that we eventually get a “twofloor” Arduino, in which we can insert the SD card.
The Arduino in practice in the building
The Arduino works thanks to a 9V generator, that we can suppose regularly reloaded, either
by the solar roof, or by the local grid when it is available. The Arduino card will be placed in
a locked technical wardrobe, according to the availabilities in the building. The objective is,
of course, to have it unaccessible from the occupants without permission, so that the
distribution is never disturbed, by accident or on purpose.
In practice, different sizes of Arduino cards exist; we used the most common one, the
Arduino “UNO”, a middle-sized one. It was the most relevant to create our scale model - a
bigger card was not needed because we did not need more inputs and outputs, and smaller are
used when the goal is to minimize the size of the system, which was not our purpose.
In the final project, it will be necessary to use a MEGA card, which is bigger and has a larger
amount of outputs/inputs (54 instead of the 13 on the UNO card).
● Program
Principle:
The principle of the program lies on a double loop.
- First loop: it runs until the system works. The first loop is a priori endless, meaning
that the end is ordered by the user.
- Nested loop: it is a N-step loop, where N is the number of apartments.
At each step i, we order the closing of the supply circuit for the apartment number i,
which allows this apartment to receive the power. In parallel, we order the writing of
the data we want to save on the SD card. We wait until the time is elapsed (1 hour).
Functional analysis:
About the green box on the left: it il possible to include an hardware that gives the exact time,
and to link it to the Arduino card. It enables to have more precise data for the history of the
distribution. As we did not have this hardware, we just mention it here, without further
details. But given its low price, it would be relevant to add it in the final system.
Program and comments: (program list: see annex)
#include <SPI.h> // We load the necessary libraries to write on the SD card.
#include <SD.h>
// Definition of variables //
int App[8]={1,2,3,4,5,6,7,8}; // Number of apartments: here, 8 (for our model)
File historique; // File containing the data history on the SD card
int timeslot=30000; // Duration of the timeslot, in milliseconds: here, 30 seconds (model)
// Initialization //
void
setup(){
// Definition of the Arduino’s outputs: they are the circuits towards the apartments.
for (int i=0; i<8; i++){
pinMode(App[i],OUTPUT);
}
// When the Arduino works with the USB input, we open the terminal, which requires some
supplementary steps and a waiting time for the opening:
Serial.begin(9600);
while (!Serial){
;
}
// We initialize the SD card and we send an error message if it does not work, and a confirmation
message if it works.
Serial.print("Initializing SD card...");
if (!SD.begin(4)) {
Serial.println("initialization failed!");
return;
}
Serial.println("initialization done.");
// We open the file that contains the data history, in writing mode
historique=SD.open("hist.txt", FILE_WRITE);
// If correctly opened, we write down the title
if(historique){
Serial.print("Data writing in progress");
historique.println("Data history of the
electric power");
distribution
// Then we close the file.
historique.close();
Serial.println("titre écrit");
}
// In case the opening failed
else{
Serial.println("error on the writing in the file");
}
}
// Loops for the timeslots distribution //
void loop() {
of
the
// Loop on the apartments
for(int i=0; i<8; i++){
digitalWrite(D[i],HIGH); // we provide power to apartment i (and it also turns the
orange LED of the apartment i+1 on)
historique=SD.open("hist.txt", FILE_WRITE); // We open the file and we
write that it actually receives the power
historique.print("l'appartement ");
historique.print(i);
historique.println("est alimenté pour le four");
delay(creneau); // We wait one hour (one minute in our model)
digitalWrite(D[i],LOW); // We stop the supply of the apartment i.
// We write down that the supply is finished for the apartment i.
historique.print("l'appartement ");
historique.print(i);
historique.println(" cesse d'être alimenté");
}
}
B. Our layout
In the framework of our work for Ecole polytechnique, we created a small layout, a scale
model that represents a whole building and the electrical circuits for the distribution system
we propose to implement.
The goal was not to test the part of the solar roof - so there are no photovoltaic panels on our
model. Anyways this would have been of very small interest given the difference of sunlight
received in Saclay and in Addis Abeba.
So we made a scale model, that contains 8 apartments spread on two floors, and which aims
at simplifying a standard building in Adis Abeba’s suburb. In each apartment, we put two
LED (one green and one red) and one resistance that represents the injera oven. As mentioned
above, the green LED of the the apartment N is connected in series with the resistance of the
same apartment and the red LED of the next apartment.
There is a double interest in building such a scale model. On the one hand, it enabled us to
defined more precisely the practical requirements of our system, and to try the Arduino
program in series with the LEDs. On the other hand, this scale model will help us to explain
our project to local entrepreneurs. So the other goal is to make our model user-friendly, and
attention-catching.
IV.
Practical implementation in low-cost housing buildings
A. From the scale model to the reality
Several questions have to be raised when we think about implementing our small model into
real housing buildings in Ethiopia
● Implementation of a trial period
The first step of the implementation must be the testing of a prototype of our system in some
buildings. During this step, several aspects will be studied, apart from the good general
functioning of the system. This step will start with the choice of a 20-building sample, in
different locations in the city. Information sessions and a strong communication towards
inhabitants will be necessary before the implementation, in order to trigger their adherence for
the system. Only after this the solar panels and the electrical system (including the Arduino
and the LEDs) can be set up.
The next step will then be making the sharing calendar, for the first weeks of the trial.
The system will then be able to be run, and the using informations collected.
● Field study
The field study will allow us to provide answers to decisions that cannot be made remotely.
The most important data is certainly the users’ feedbacks on the system. We have to
determine whether the system suits their habits, if it is user-friendly and intuitive, if they use
it, or not. Indeed, in a sense the system requires an adaptation: so the question is to know
whether this adaptation is easy or not.
Through polls and investigations among the inhabitants, ideas of improvements will naturally
emerge. For example, maybe we will figure out that some timeslots are not relevant and not
usable for any family, because of their living habits.
One of theses aspects regards the “concertation”hypothesis that we made in part II. In case a
family cannot use its timeslot, are the users actually likely to exchange their timeslots among
themselves, and use their neighbour’s oven?
It hinges on the global community lifestyle in the building, which is a key parameter,
impossible to figure out from outside.
It this kind of exchange is not working in practice, another system should be implemented to
allow people to formally exchange their timeslots. This implies occasional modifications of
the Arduino software by an operator. But it also implies to set up enough control processes to
make sure that nobody is stealing the other users’ timeslots without their agreement.
Then, in terms of technical data, it will be essential to measure the actual power delivered
by the photovoltaic panels, and its variations during the day, in order to optimize the sizing of
future projects. Maybe we will figure out that it is necessary to adapt the timeslots to optimize
the power received by every family.
In the same category of ideas, another necessary question is about the actual meteorological
conditions. How many hours are lost every season because of bad weather? This parameter
will enable to study in further details the issue of the energy storage, that we decided not to
address in the first step of this project.
It will also be indispensable to define the frequency of maintenance necessary for the system.
Is a technician necessary to come every week and check the system, and help users to change
their timeslots? Or is a remote control enough, with only a monthly maintenance? The
answers will both depend on the users’s engagement in the project, and on exterior factors
that could damage the solar panels. Maintenance is a key issue if we want our system to
meet the sustainable criteria, and if we want to spread it over the city, the country, or the
continent. Thus, a partnership with a local maintenance structure may be necessary, if it is not
realized by the retailer itself.
B. Economic and judiciary terms
In our study, we mainly focused on technical aspects of the implementation of the distribution
system in the buildings of Addis Abeba. In practice, the question is: who will be the owner of
the project? It could be the main activity of an independent local company (like a start up).
But it could also be part of the realisations of a bigger electrical company.
What lies behind this question is related to the costs of the project. It is obvious that a wide
implementation will requires external foundings, that could be provided either by a state
policy to promote renewable energies, or by a private company willing to develop its
photovoltaic sector.
A financial participation of the inhabitants will be certainly required, but this decision will be
taken by the future project owner. As we discussed above, we could imagine different types
of contracts that include more or less safety in the supply. For example, to have access to a
system which is not dependant on the weather, additional investments should be made on
energy storage. And these investments would probably have an impact on the price paid by
the users. On the contrary, if it is agreed that there remains a part of chance - with a
probability that should be quantified - this would bring down the cost of the storage system.
Conclusion: social, environmental and economical overview
Social overview:
The installation of photovoltaic panels on the roof of low-cost housings in Addis Abeba
would grant the inhabitants with better living conditions, by being less dependant from the
defective electrical grid of the city. Besides, this additional supply of electricity would allow
them to support their basic needs for cooking injeras. The main direct return of the panels
would consequently be for the inhabitants of the suburbs of Addis Abeba, who used to live in
slums. Moreover, the fair and transparent sharing of electricity we designed is likely to
enhance social bonds among communities and families, by encouraging people to meet in
order to share better this new source of energy..
Environmental overview:
Most families are today resorting to personal gas generator to support with their needs of
electricity. These personal generators are a short-term solution: they are cheap to buy, but on
the long term, they are more expensive that photovoltaic panels. Their environmental impact
is also much bigger, as it operates a direct combustion of fossil fuels. Using wood as before is
no longer possible neither, as 99% of Ethiopia’s primary forest are now destroyed. There has
to be a more sustainable solution for energy access in Africa. The use of photovoltaic
electricity is a viable and necessary alternative to these fossil fuels, even if it will require
significant investments both from public and private actors. Our project aims at encouraging
this energetic transition in Ethiopia, by providing solutions to the implementation of new
types of energy. At the scale of the whole country, it could be a major lever to conduct the
energy transition.
Economic overview:
We did not discuss in details, in this report, the buying conditions of the photovoltaic panels.
Will they be paid by local entrepreneurs, local collectivities, or big companies? In any case, in
the long term, it should lead to an increase of the buying power of the inhabitants of the poor
suburbs, thanks to the money they will save on getting electricity. And local entrepreneur will
be likely to boost the global economic activity of the sector in Ethiopia.
To conclude, we do not see any drawback regarding the implementation of our project of
electrification of Addis Abeba’s roofs. We have shown, thanks to our scale model, how to
realize it in practice, and we designed a simple, cheap and user-friendly system. We hope that
our project will participate to the sustainable development of Ethiopia.
Bibliography
“Expanding sustenance in Ethiopia based on renewable energy resources – A comprehensive
review” ; Mesfin Berhanu, S. Anuradha Jabasingh, Zebene Kifile (Oct. 2016)
“Self-initiated transformations of public-provided dwellings in Addis Ababa, Ethiopia” ;
Demissachew Shiferaw ; Cities (1998)
“Introduction of Sustainable Low-cost Housing in Ethiopia – an Innovation Diffusion
Perspective”; Bengt Hjort, Kristian Widen; Procedia Economics and Finance Volume 21,
Pages 454-460 8th Nordic Conference on Construction Economics and Organization (2015)
“Two novel solar appliances for developing countries: 1. Convective Solar Cooker (CSC) 2.
Solar Medical Sterilizer”; Advances In Solar Energy Technology; Michael Grupp, Hannelore
Bergler, Damien Smagghe, Frédéric Vidoni (1988)
“Technological innovation system building for diffusion of renewable energy technology: A
case of solar PV systems in Ethiopia”; Kassahun Y. Kebede,Toshio Mitsufuji, Technological
Forecasting and Social Change (January 2017)
“Solar cooking system with or without heat storage for families and institutions”; Klemens
Schwarzer, Maria Eugênia Vieira da Silva; Solar Energy (July 2003)
“Urban growth and the housing problem in Ethiopia”, Girma Kebbede, Mary Jacob, Cities
(1985)
http://www.rfi.fr/emission/20161022-ethiopie-construit-tour-bras-batiments-societedeveloppement-environnement
Appendix: Contract for solar power supply in the building, to be signed by all
contracting parties
The contracting parties are:
- The owners of the solar panels (referred to as “the provider”)
- The inhabitants of the low-cost housing building (referred to as “the users”)
Article 1: Commitment of the provider
1.1 The provider commits to providing electricity to 6 households, during one hour each,
between 10 am and 4 pm. The power delivered will depend on the meteorological conditions.
1.2. The provider commits to keeping track of the power delivery in the households, in order
to avoid any dispute.
Article 2: Commitment of the users
2.1 The users will acquaint the calendar that is set up for the supply distribution each month.
2.2. The users understand that the power supply will be lower in case of bad weather, and
they commit to taking this into account in their electricity consumption.
Article 3: Settlement of disputes
3.1 The provider has access to the history of power supply. Therefore, the users cannot
attempt to make unjustified complaints against him, nor try to discredit the data which he
possesses.
3.2. However, if the electricity supply is defective, the provider commits to paying a
compensation to the users, equal to the price of electricity on this day, equivalent to 4 kWh
(when the solar panels are functional).
User
Name, First Name:
Telephone:
Signature:
Provider
Company:
Telephone:
Signature:
EA Report
The Ranque Hilsch tube and its use as a
refrigerating system
Ecole polytechnique
PHY 585 : Experimental work in environmental physics
Benoit DABAS & Mehdi KECHIAR
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Table of Contents
Table of Contents
1
Introduction
2
I. Social and societal impact of our project
Ethiopia : economics and society
2. Mekele fishermen, issues and solutions
3. Social and societal impact
3
3
4
5
II. Functioning of the Ranque-Hilsch tube
6
III. Rapid prototyping and testing
1. Factory model
2. Model 1
3. Model 2
4. Model 3
5. Model 4
9
10
11
11
12
12
IV. Economic characterization of our system
1. Unit cost of Ranque-Hilsch
a. Factory Model
b. Printed Model 4
2. Theoretical study
a. Cold air flow
b. System to be cooled
c. Thermal transfer modeling
d. Filling experience
e. Practical application
15
15
15
15
15
15
16
16
17
17
Conclusion
19
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Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Introduction
Our project involves the realization of an inexpensive refrigeration system that can
be implemented in environments where power distribution networks are poorly developed.
In our case, Ethiopia.
More precisely, we try to integrate a Ranque-Hilsch system in this refrigeration process as
it does not require any electrical input and can thus function independently of the energy
supply. Indeed, its basic operation relies on the kinetic separation of a flow of air entering
at high pressure into a hot air outlet and a cold air outlet. For example, a compressed-air
cylinder would be sufficient to operate the system without having to suffer the frequent
electrical cuts in Ethiopia, which have negative consequences for the conservation of fresh
products, especially fish.
The objectives set out at the beginning of our project were wide and gave way to a great
deal of initiative: it was a matter of studying, in theory and using the available
measurement system, the functioning of the Ranque-Hilsch system and its relevance In
the refrigeration project. There were then several possible approaches. We could study the
tube that was available at the beginning of the project, characterize its properties and its
cooling potential according to several parameters.
Nevertheless, since the price of this tube was high, it seemed difficult to imagine that it
would be used in mass in Ethiopia. To achieve a more affordable price, we would have
had to use a less precise, less efficient material and the studies that we would have
carried out could have proved to be too optimistic later. We have therefore chosen a
second approach with new objectives: the aim of our project has therefore been to study
the feasibility of a cheap Ranque-Hilsch tube, which can be manufactured in series and to
characterize in a Secondly its properties and its economic relevance.
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Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
I. Social and societal impact of our project
1. Ethiopia : economics and society
Figure 1 - Map of Ethiopia
Ethiopia is the second most populous country in Africa with 97 million inhabitants by 2015.
Although GDP per capita has doubled in 10 years, contributing to a significant decline in
poverty, One of the lowest GDPs in the world.
Agriculture is the socio-economic pillar of the country, with 41.9% of the GDP1.
Following the success of the first "Growth and Transformation Plan", a five-year
development plan from 2010 to 2015, the government launched the second Growth and
Transformation Plan, covering the period 2015-2020. This plan focuses on the
development of transport infrastructure (road and rail), energy (in particular renewable
energy) and telecommunications.
1
“Situation économique de l’Ethiopie”, French embassy in Ethiopia
3
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Let us take a closer look at this energy development. According to an article by the French
embassy in Ethiopia, only 55%2 of the population has access to electricity. This is
compounded by the lack of reliability of the energy distribution network. To solve this
problem, the EDF foundation advocates the development of alternative solutions such as
secondary micro-networks based on renewable photovoltaic or wind power, resources with
high potential under-exploited.
Figure 2 - Renewable energy potential by source of production
2. Mekele fishermen, issues and solutions
Keeping in mind this economic and energy context, we are now interested in the problem
of fishermen in the Mekele region.
These fishermen currently have no means of storing and transporting their fishery products
without breaking the cold chain. This can lead to a loss in the sales figure, but can also
constitute a danger for consumers. This situation also limits fishing capacity since
conservation is made difficult.
A potential solution must meet several criteria for our specifications in order to be in line
with the limited means of the local populations.
➔
➔
➔
➔
➔
2
Simple and easy to set up
Portable solution
Low cost solution
Efficient, low power consumption solution
Ability to maintain for a few hours a 30L cooler at 5 ° C
Le secteur de l’énergie en Ethiopie, enjeux et perspectives. French embassy in Ethiopia
4
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
3. Social and societal impact
The use of such a system by the fishermen of Mekele would allow them to keep their fish
longer and to sell it in better condition. This would not only reduce the health risks inherent
in a cold chain break but also have a positive impact on the fishery, which could then
intensify.
This intensification of fishing in this area of lakes could in the long term have an impact on
the lake ecosystem. Such a technological break would thus also require control of the
fauna of the lakes
Figure 3 - Ethiopian fisherman
5
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
II. Functioning of the Ranque-Hilsch tube
The Ranque Hilsch generator is a thermal machine that relies on a transfer of
energy between two gas flow.
The air enters through a tube tangent to
a circular chamber. It then starts to
rotate at a speed of the order of 200 m /
s inside this chamber, the two ends of
which are partially obstructed.
On one side (h-side in the diagram), the
air can escape only at the periphery of
the cylinder, the center bounces, while
on the other side (c-side) air escapes in
the center .
It is precisely this "rebound" of a part of the air injected on the reflector located on the h
side which will allow the exchange of energy and the cooling of this part of the air.
Indeed, the fraction of the air situated towards
the center will be able to lose its energy by
giving it by friction to the fraction of the air
turning towards the edge of the cylinder. By
preserving the angular momentum, the closer
you get to the center, the faster the air turns. It
is this difference in speed between the two
streams which will cause friction.
On the other hand, the outside air also stores
energy by friction with the wall.
This energy exchange is modeled by the conservation equation of energy:
By this simple information, it can thus easily be deduced that increasing the length of the
tube increases the heat exchanges and will increase the temperature difference at the
outlet.
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Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Let us now observe the velocity profile along the axis of the cylinder supposed to be inside
the tube3 :
Figure 4 - Axial speed profile in the cylinder
This gives us a first order of magnitude for the diameter of the tube opening on the cold
side at about ⅓ the radius of the cylinder. However, by looking at the indoor air circulation,
we realize that we have every interest, to get the smallest temperature, we have a vested
interest in reducing the size of the opening, In order to promote recirculation of the air in
the main cylinder.
● Importance of insulation
Let us note the importance of the insulation of the
Hansch Ranque in its performance.
Indeed, it is noted that isolating the tube makes it
possible to obtain higher temperature differences of
5 ° C. for cold air and 30 ° C. for hot air4.
“Numerical investigations of the compressible flow and the energy separation in the RanqueÐHilsch vortex
tube”. W. Frohlingsdorf, H. Unger
4
“An investigation of energy separation in a vortex tube” - K. STEPHAN, S. LIN, M. DURST, F. HUANG and
D. SEER
3
7
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Figure 5 - On the left: Thermal image of the Hilsch Ranque present in the laboratory | On
the right: Thermal image of our prototype
The Ranque Hilsch tube present in the laboratory, better insulated because of a less
conductive material, has no visible loss at the level of its body but only at the outlet of
warm air, which is normal. Unlike him, our prototype, made of plastic material insufficient,
faces major losses of energy in his body.
8
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
III. Rapid prototyping and testing
The main limit of the Ranque-Hilsch tube which we had at our disposal to conduct
our experiments, in the context of the Ethiopian market of ours, was obviously its high
price. Indeed, a standard Ranque-Hilsch is around 200 €. It is therefore difficult to
envisage it being of great economic relevance when the objective is to sell this device to
Ethiopian fishermen.
Moreover, it does not take a long time browsing the internet to realise that this device is
made from inexpensive materials and is even makeable in 3D printing. We found, on
various websites quoted in source, printing plans of several models of Ranque-Hilsch that
we decided to print at the PEI5 of the school. These models are outlined in the next lines.
In the following images, the operating principle is always that of the classic Ranque-Hilsch,
the annotated schemes will be as follows :
A : Pressurized inlet flow
B : Cold outlet
C : Hot outlet
The laboratory compressed air network was used to perform the tests. Its theoretical
pressure is 8 bar. A volumetric meter is disposed on the path of the air, creating a
non-measurable discharge.
The temperature can be measured using a digital thermometer connected to an arduino
chip and an analogue thermometer. Nevertheless, these measures remain very uncertain.
Indeed, the outlets of the various tubes, in particular the hot outlets, are difficult to isolate
and this results in undervaluation of hot temperatures and over-evaluation of cold
temperatures. In order to compensate in part for this problem, a measuring box has been
designed and printed in 3D so that it is connected at the cold outlet into which the sensors
are placed for better insulation.
Figure 6 - Boitier de mesures
The inlet temperature, that is to say out of the school network, is 17.7 ° C
5
Pôle entrepreneuriat et innovation (Entrepreneurship and innovation pole)
9
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
1. Factory model
Figure 7 - Factory Ranque-Hilsch
The temperatures measured on this Ranque-Hilsch are:
T hot = 53.0 °C
T cold = − 17.4°C
ΔT = 70.4°C
Figure 8 - Acquisition of temperature Tcold
10
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
2. Model 1
Figure 9 - Model 1
Model 16 could not be tested because one of the drawings, that of the hot air outlet
(C), required too much detail to be correctly machined by the school's 3D printers.
Nevertheless, the model is presented in this report because it could still be useful for the
rest of the project.
3. Model 2
Figure 10 - Modèle 2
Model 27 is made up of 2 half-tubes that have to be sticked together and reinforced
with tape to avoid leaks
The measures of model 2 are as follows:
T hot = 30.2 °C
T cold = 14.9°C
ΔT = 15.3°C
At a cold temperature exceeding 5 ° C, the use of the Hilsch Ranque as a refrigerating
solution is difficult to envisage. Model 2 is therefore not suitable.
6
7
http://www.thingiverse.com/thing:986928
http://www.thingiverse.com/thing:437642
11
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
4. Model 3
Figure 11 - Model 3
Model 38 has several features compared to the two previous models. First, it has
two air intakes pressurized tangentially and symmetrical with respect to the center. The
benefits of this option are far from clear. We can think of less turbulence at the entrance of
the flow, or else a better resistance due to a drop in the flow at each input compared to an
input alone. Nevertheless, its counterpart is felt: it has been necessary to manufacture a
system separating the pressurized air flow in two and the overall system is less convenient
to handle. Another feature is that the reflector at the end of the hot outlet (center and right
images) is movable and thus allows the hot output rate and the reflection plane position
within the tube to be adjusted.
At the best settings found (maximum reflector deflection), the measurements are as
follows:
T hot = 32.1°C
T cold = 11.4°C
ΔT = 20.7°C
Same conclusion as for model 2, the use of this model is not possible, the cold
temperature is too high.
5. Model 4
Model 4 does not come from the internet. It is the direct result of the experiments
carried out with the first three tubes and the bibliographical research which preceded them.
It is inspired by the aesthetics of the model 3 and its mobile reflector. However, it is longer
(comparable in size to the metal Ranque-Hilsch), has a single pressurized air inlet and the
height of the reflector can be precisely adjusted by means of a screw-nut system. In
addition, an extension was added to the cold outlet to allow a 6 mm tube to be inserted
and to orient the flow.
8
http://www.thingiverse.com/thing:250168
12
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Figure 12 - Model 4
Les mesures donnent :
T
= 42°C
T cold = − 1.8°C
ΔT = 43.8°C
hot
Figure 13 - Photos of the experiment with model 4
13
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
This model then passes the 5 ° C bar under which fresh food can be stored. However,
further study is needed to determine the economic relevance of this scheme.
The cold temperature has been very delicate to obtain, turning the screw of the reflector by
a few tenths of a degree from 3 ° C to -1.8 ° C. For industrial use, it is therefore necessary
to consider a means of freezing the position of the reflector once calibrated.
These prints were made using PLA material melted at 225°C. Its softening point is
approximately 110°C. However, the hot outlet of a current vortex tube is close to 70°C.
Thus, the use of 3D printing allows normal use of Ranque-Hilsch without risk of damaging
it, but it nevertheless limits us in the prospects of use of the hot source which should not
be too much. It is conceivable to use other 3D printing materials which have a higher
softening temperature. Moreover, since the measurements on the hot sources of the
printed models have not exceeded 50 °C, the question does not arise as is.
14
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
IV. Economic characterization of our system
1. Unit cost of Ranque-Hilsch
a. Factory Model
As mentioned above, the unit cost of a Ranque-Hilsch, although very variable, is close to
200 €.
b. Printed Model 4
The main cost components of our model are:
-
28g of ABS aramid fiber (for a better mechanical resistance, the PLA being
biodegradable) (78,60 € / kg): 2.2 €
Screws, nuts, glue: <2 €
Energy cost of 3D printing: 78W for 2h28 printing or 192.7Wh ie less than 0.007 € in
Ethiopia (about 0.044USD / kWh or 0.037 € / kWh)
Total : 4€ - 4.20€
However, it is necessary to count the price of the 3D printer to distribute on all the models
printed. The model Ultimaker9 used costs 1195€.
2. Theoretical study
a. Cold air flow
It was not possible with the available instruments to measure the volume flow at the
outlet of the cold and hot springs. Thus, literature10 data are used, namely 24% of the total
mass flow in the cold source and 76% in the hot source.
Figure 14 - Distribution of the air mass in the Ranque-Hilsch
The volumetric meter indicates a flow rate of 39L / min of air at 8 bar.
https://ultimaker.com/en/products/ultimaker-2-go/specifications
Numerical investigations of the compressible flow and the energy separation in the Ranque-Hilsch vortex
tube.” W. Frohlingsdorf, H. Unger
9
10
15
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
b. System to be cooled
The case of a perfectly insulated 30L container containing 1kg of fish is studied
here. The volume of fish is neglected so that the overall system to be cooled consists of
30L of air and 1kg of fish. The problem is investigating the energy cost of switching from
22 ° C to 5 ° C. The ambient air will be considered as a perfect gas.
The thermal capacity of the fish is approximately 0.93Wh/(kg.K)11.
ΔH = C f ish · ΔT
C f ish = 0.93W h.K −1
ΔT = 22°C − 5°C = 17°C
The energy to be supplied for the desired temperature reduction is thus obtained:
ΔH = 15.81W h = 56, 9kJ
c. Thermal transfer modeling
Consider the most efficient and simple case or the cold air arrives in the cooler in
direct contact with the fish without passing through a heat exchanger. It should be noted
that this case would be harmful for the conservation of the fish because the air would not
be confined. Nevertheless, the calculations are simplified and make it possible to obtain an
order of magnitude.
The fish is considered as a block of characteristic length L = 5 cm of thermal conductivity
which will be taken equal to that of water λ = 0, 6 W .m⁻¹.K⁻¹ with a thermal capacity
C f ish = 0, 93 W h.K⁻¹ .
The equation of diffusion of the temperature is written:
∂T
∂t
2
λ
=
ρC
poisson
~
ρC
poisson
ρC
poisson
· ∂∂x T2
By reasoning in law of scale,
T
Δt
And so we have:
Δt ~
Then :
λ
· LT2
λ
·L 2
Δ t ~ 1h
The result obtained by a scale law gives us the time necessary to bring the fish to the
temperature of the medium, either assuming sufficient fresh air flow, a temperature of -1.8
11
https://www.energieplus-lesite.be/index.php?id=11439#c3936
16
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
° C. Our case study requires a temperature of 5 ° C. The Δt will therefore necessarily be
inferior, but the law of scale nevertheless provides an order of magnitude.
Nevertheless, in order to counterbalance this overestimation of the Δt , our study has the
optimism of neglecting the filling time of the cooler in fresh air.
d. Filling experience
We conducted the experiment with the cooler available and the Ranque-Hilsch that
we printed.
Figure 15 - Cooler filling experience
The ambient air temperature was 22 ° C. Bringing the empty cooler to 5 ° C required 42
minutes.
The cooler did not have a lid and was insulated by attaching a polystyrene plate. Of
course, the resulting insulation was far from perfect. Nevertheless, experience shows that
a total Δt of one hour is far from being an overly pessimistic approximation.
17
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
e. Practical application
The load of a compressor of 24L and 8bar lasts 1min15 for 25s of discharge.
Although this is not the case, it will be considered that this is done at 8bar throughout.
However, bringing the fish to a temperature of 5 ° C. requires, in order of magnitude 1 hour
of discharge, approximately 144 loads of compressor. The order of magnitude of the
hundred charges will be preserved. Our compressor has a power of 1800W or 1.8kWh. At
the Ethiopian market price, this amounts to 0.066 €.
A solar panel produces 4kWh. This system can therefore be coupled to a solar panel.
Economically, by neglecting the thermal losses of the cooler and therefore the need to use
the Ranque-Hilsch to maintain the temperature constant, this solution is inexpensive. The
problem arises at the practical level. It is difficult to envisage operating as many cycles on
a compressor, all the more so as these 144 loads represent a duration of 3 hours which
intersects the cooling time and limits its effectiveness.
18
Ecole polytechnique - PHY 585 - The Ranque-Hilsch tube
Conclusion
With a basic investment, however, at a ridiculous cost of production, we have
succeeded in producing a portable refrigeration system that is practical and reaches less
than 5 ° C, the temperature required to properly store fish.
Let us note however the necessity of a precise adjustment of the Ranque Hilsch if one
wants to reach the point of operation hoped for. This probably requires rethinking our
design by including a means to adjust even more precisely, as well as to ensure a
positional maintenance of the adjustment. Also note the efficiency gained by isolating the
Ranque Hilsch, which we did not do. Much of the energy is still lost. We believe that a
good line of study for the sequel can be the use of the heat released by the hot source.
There remains the problem of the practicality of this solution, which for the moment does
not make it viable. With scuba diving bottles which reach a pressure of 200 bars for about
11 liters, it is possible to divide the number of discharges by ten.
From an already existing system that we have adapted to our problem, we have provided
an economically viable answer that remains very impractical. It is therefore not applicable
in the present state of affairs. Nevertheless, improved performance of Ranque-Hilsch and
improved isolation of the cooler could be more effective.
19
Automation of a bench measurement.
Management and signal operating
Study conducted by the experimental work with the vortex tube and
the microcontroller Arduino.
Tamara SABITOVA, Zhongya LIU
Ecole polytechnique - Friday 10 March 2017
Abstract
People often describe sustainable development as requiring a joint and
long-term outlook by society that integrates social, economic and environmental
objectives. Today, the private sector’s contributions come from developing and
using environmentally better, eco-efficient, ways to produce and provide products
and services and by creating wealth and employment respectful of changing
expectations of corporate responsibility and behavior. Delivering and extending
this contribution beyond eco-efficiency depends upon the continued innovation
that effective design and the development and use of better technologies will make
possible. Sustainable development is a metaphor for opportunity and progress as
well as a reminder of obligations and uncertainty. It requires a step-change
improvement in performance, innovate. Better design and new technologies
provide the means to act smarter and more sustainably but this technology also
creates uncertainties, for example about the consequences of the scale and scope
of application. Using these tools well depends upon understanding what the public
is expecting and being able to meet these needs cost-effectively and without
raising alarms and fears.
The possible scope of the vortex devices is quite broad and includes almost all
sectors of industry and the national economy. Devices based on vortex tubes leave
almost no alternatives in the presence of an already established source of
compressed gas. In our project we consider the use of vortex tube as a
refrigeration plant in the food industry and trade, specifically for the transport of fish
from water basin to its designated storage and further distribution. Taking the
fishing industry in Ethiopia as example, by analyzing the natural conditions of the
terrain and geographical location of the water ponds, we came to the conclusion
that the optimum temperature for fish transportation and preservation of it on
suitable eating conditions along the way is 0-5°C. The major issue was
optimization of the processing system with temperature data by programming the
microcontroller Arduino.
Introduction
Fish has historically played an important role in food security in many countries
and contributes to do so in globally, providing 15-20 percent of animal protein
intake. Fish farming has been practiced in different parts of the world like Europe.
At present, the country Ethiopia has an estimated annual total exploitable fish
potential of 51,481 tons, which can meet only 79 percent of the current actual
demand, 55 percent of the projected demand in 2010 and 44 percent of the
projected demand in 2015, based solely on population size.
Fresh fish must reach the holding or distribution center as quickly and
economically as possible, not losing the freshness or quality, which the buyer and
consumer rightly expect. Various species of fish may require more care in canning,
packing and cooling, but the initial period of time between the moment the fish are
taken out of the water and their placing under chilled or iced conditions is vitally
important to the end quality of the product.
The preservation of fish is an extremely important factor in more distant and
isolated areas, where days or weeks may pass before a fisherman can export his
commodity to the village or town centers. Most of major lakes in Ethiopia are
situated in central Highlands, as Fig. 1 below. His product still has to be a quality
product, and the steps he takes to ensure preservation and correct packing are of
great importance. The preserved fish must last two or three weeks before
deteriorating in quality.
Fig. 1. Topographic map of the Ethiopian Highlands and major lowlands including the Great East
African Rift Valley, and fractured mountain ranges (Modified from source: Sadalmelik, I. (2007);
1. Environmental context
Fishes constitute a major part of the aquatic ecosystems that cover about 2/3 of
the world. Fisheries provide nutritious food of major importance as well as
livelihoods, export incomes, recreation, etc., and could play an important role for
development and poverty reduction. However, donors and developing countries
have failed fully to take advantage of the potential. Fish stocks are under pressure
in most parts of the world. Responsible and pro table aquaculture has to be
promoted, and changes are urgently needed to make the fisheries sector more
sustainable, both ecologically and socio-economically. How can the unsatisfying
status of so many valuable fish stocks all over the world be improved, and the
increasing demand for fish in the long run? How can fisheries in developed and
developing countries progress in harmony, and at the same time contribute to
sustainable development? These questions are the objects of our project.
Our project consist on the following goals of sustainable development:
The sustainable use and preservation of marine and coastal ecosystems and
their biological diversity. Oceans, along with coastal and marine resources, play an
essential role in human well-being and social and economic development
worldwide. They are particularly crucial for people living in coastal communities,
who represented 37 per cent of the global population in 2010. Oceans provide
livelihoods and tourism benefits, as well as subsistence and income. They also
help regulate the global ecosystem by absorbing heat and carbon dioxide from the
atmosphere and protecting coastal areas from flooding and erosion. In fact,
coastal and marine resources contribute an estimated $28 trillion to the global
economy each year through ecosystem services. However, those resources are
extremely vulnerable to environmental degradation, overfishing, climate change
and pollution. Since the beginning of the industrial revolution, the ocean has
absorbed about one third of the carbon dioxide released by human activities,
thereby mitigating the full impact of climate change. Fisheries contribute
significantly to global food security, livelihoods and the economy. However, if not
sustainably managed, fishing can damage fish habitats. Ultimately, overfishing
impairs the functioning of ecosystems and reduces biodiversity, with negative
repercussions for sustainable social and economic development. In order to
achieve a healthy balance, fish stocks must be maintained within biologically
sustainable limits, at or above the abundance level that can produce maximum
sustainable yields. Based on an analysis of assessed stocks, the percentage of
world marine fish stocks within biologically sustainable levels declined from 90 per
cent in 1974 to 69 percent in 2013. Fortunately, the downward trend has slowed
and appears to have stabilized since 2008. Biodiversity of marine sites require
safeguarding to ensure sustainable long-term use of their precious natural
resources.
Clean energy. Energy is crucial for achieving almost all of the Sustainable
Development Goals. The share of renewable energy (derived from hydropower,
solid and liquid biofuels, wind, the sun, biogas, geothermal and marine sources,
and waste) in the world’s total final energy consumption has increased slowly, from
17.4 per cent in 2000 to 18.1 percent in 2012. More telling is the fact that modern
renewable energy consumption, which excludes solid biofuels used for traditional
purposes, grew rapidly, at a rate of 4 per cent a year between 2010 and 2012, and
accounted for 60 per cent of all new power-generating capacity in 2014. In
absolute terms, about 72 per cent of the increase in energy consumption from
modern renewable sources between 2010 and 2012 came from developing
regions, mostly from Eastern Asia. The technologies making the largest
contribution have been hydropower, wind and solar energy; together they account
for 73 per cent of the total increase in modern renewable energy between 2010
and 2012.Energy intensity, calculated by dividing total primary energy supply by
GDP, reveals how much energy is used to produce one unit of economic output.
Globally, energy intensity decreased by 1.7 per cent per year from 2010 to 2012.
This represents a considerable improvement over the period from 1990 to 2010,
when it decreased by 1.2 per cent a year. As a result, global energy intensity,
which stood at 6.7 (mill joules (mj) per 2011 United States dollar ppp) in 2000 fell to
5.7 by 2012. The proportion of the world’s energy use covered by mandatory
energy efficiency regulation, which has almost doubled over the past decade, from
14 per cent in 2005 to 27 per cent in 2014, was a factor. Still, current progress is
only about two thirds of the pace needed to double the global rate of improvement
in energy efficiency. Among end-use sectors, industry was the largest contributor
to reduced energy intensity, followed closely by transportation. About 68 per cent
of the savings in energy intensity between 2010 and 2012 came from developing
regions, with Eastern Asia as the largest contributor.
Human’s well-being and no hunger. In a world where more than 800 million
continue to suffer from chronic malnourishment and where the global population is
expected to grow by another 2 billion to reach 9.6 billion people by 2050 – with a
concentration in coastal urban areas – we must meet the huge challenge of
feeding our planet while safeguarding its natural resources for future generations.
Never before have people consumed so much fish or depended so greatly on the
sector for their well being. Fish is extremely nutritious – a vital source of protein
and essential nutrients, especially for many poorer members of our global
community. Fisheries and aquaculture is a source not just of health but also of
wealth. Employment in the sector has grown faster than the world’s population.
The sector provides jobs to tens of millions and supports the livelihoods of
hundreds of millions. Fish continues to be one of the most-traded food
commodities worldwide. It is especially important for developing countries,
sometimes worth half the total value of their traded commodities.
2. One concern for preservation in Ethiopia is local average temperature.
Ethiopia constitutes the bulk of the Horn of Africa, and as such spans subtropical
and tropical east Africa. The Ethiopian section of the Great Rift Valley runs
north-east to south-west, from Eritrea to northern Kenya’s Lake Turkana, and
much of the country’s northern, western, central and southern areas are
dominated by a series of highlands collectively known as the Ethiopian Plateau.
As a result of its position and its varied topography, Ethiopia’s climate varies –
broadly speaking - from tropical in the northeastern lowlands and southeastern
lowlands to temperate and cool in the highlands. Temperatures in the tropical
lowlands average out at around 27°C, while those in the highlands are dependent
on altitude, and range between 16 and 22°.
Fig.2.Yealy averaged rainfalls and temperature in Ethiopia
3. The best range of temperature for preservation
A. Chill storage (0-25°C)
It is well known that both enzymatic and microbiological activity is greatly
influenced by temperature. However, in the temperature range from 0 to 25°C,
microbiological activity is relatively more important, and temperature changes have
greater impact on microbiological growth than on enzymatic activity (Figure 3).
Fig.3.Relative enzyme activity and growth rate of bacteria in relation to temperature
B. Super chilling (0°C to -4°C)
Super chilling extends product shelf life, but a negative effect on
freshness/prime quality has been observed for some fish species. It has been
suggested that negative effects of super chilling on drip loss, appearance, and
texture of cod and haddock are due to formation of large ice crystals, protein
denaturation and increased enzymatic activity in the partially frozen fish (Love and
Elerian, 1964). Simpson and Haard (1987), however, found only very little
difference in biochemical and chemical deterioration of cod (Gadus morhua) stored
at 0°C and at - 3°C
Therefore it is important to decrease the temperature to 0°C as soon as possible
after catching. For fish in Ethiopia where the ambient temperature is around 16 –
25°C, the rate of spoilage can be 25 times higher than when kept at 0°C (Huss
1994).
So from all the concerns above, we set our cooling instruments into the
temperature around 0-5°C.
Context of techniques
1. Tube of ranques-hilsche
The vortex tube (also called the Ranque–Hilsch vortex tube) is a mechanical
device operating as a refrigerating machine without any moving parts, by
separating a compressed gas stream into a low total temperature region and a
high one. Such a separation of the flow into regions of low and high total
temperature is referred to as the temperature (or energy) separation effect. The
vortex tube was first discovered by Ranque, the counter-flow vortex tube, as
shown in Fig. 4a, consists of an entrance block of nozzle connections with a
central orifice, a vortex tube (or hot tube) and a cone-shaped valve. A source of
compressed gas (e.g. Air) at high pressure enters the vortex tube tangentially
through one or more inlet nozzles at a high velocity. The expanding air inside the
tube then creates a rapidly spinning vortex. The air flows through the tube rather
than pass through the central orifice located next to the nozzles because the orifice
is of much smaller diameter than the tube. The length of the tube is typically
between 30 and 50 tube diameters, and no optimum value has been determined
between these limits. As the air expands down the tube, the pressure drops
sharply to a value slightly above atmospheric pressure, and the air velocity can
approach the speed of sound. Centrifugal action will keep this constrained vortex
close to the inner surface of the tube.
A flow-control valve, usually shaped as a cone, can vary the air that escapes at
the other end of the tube. The amount of air released is between 30% and 70% of
the total airflow in the tube. The remainder of the air is returned through the centre
of the tube, along its axis as a counter-flowing stream. Once a vortex is set up in
the tube, the air near the axis cools down while the air at periphery heats up in
comparison with the inlet temperature. This phenomenon is known as temperature
separation effect (also called the Ranque–Hilsch effect). As a result, the gas
escaping through the orifice is cold and the hot gas flows out in the other direction.
A remarkable feature of this device is the absence of moving parts and simplicity of
operation.
Fig. 4. Basic operation of vortex tubes: (a) the Ranque–Hilsch standard vortex tube or
counter-flow vortex tube and (b) the uni-flow or parallel flow vortex tube.
A.Compressed air
Cp.air· Vair· t(0-Tair) = mf · cpf · (Tf - 0)
Where:
Cp.air = heat capacity of air (kcal/kg · °C)
Vair= velocity of air volume (m3 /s)
(1.a)
T= time of air cooling
Mf = mass of fish to be cooled (kg)
Cpf = specific heat capacity of fish (kcal/kg · °C)
From (1.a) it emerges that:
T =- Cp.air· Vair· Tair / (mf · Cpf·Tf)
Experimentally we measure the Vair that maintain the temperature of fish
container around 0°C. Thus we are capable of calculating how much gas we need
to pack up.
2. Arduino
What Is Arduino?
Arduino is an open source microcontroller, which can be easily programmed,
erased and reprogrammed at any instant of time. Introduced in 2005 the Arduino
platform was designed to provide an inexpensive and easy way for hobbyists,
students and professionals to create devices that interact with their environment
using sensors and actuators. Based on simple microcontroller boards, it is an open
source-computing platform that is used for constructing and programming
electronic devices. It is also capable of acting as a mini computer just like other
microcontrollers by taking inputs and controlling the outputs for a variety of
electronics devices.
It is also capable of receiving and sending information over the internet with the
help of various Arduino shields. Arduino uses a hardware known as the Arduino
development board and software for developing the code known as the Arduino
IDE (Integrated Development Environment). Built up with the 8-bit Atmel AVR
microcontroller's that are manufactured by Atmel or a 32-bit Atmel ARM, these
microcontrollers can be programmed easily using the C or C++ language in the
Arduino IDE. Microcontroller also can help you to read information from input
devices such sensors, antennas, trimmers…and can also sent information to
output devices such as LED, speakers, LCD screens e. T. C.(Fig.5.)
Fig. 5.A labeled diagram of an Arduino Board and an IDE
a. Arduino Development Board
•
Microcontroller: This is the heart of the development board, which
works as a mini computer and can receive as well as send information or
command to the peripheral devices connected to it. The microcontroller
used differs from board to board; it also has its own various specifications.
•
External Power Supply: This power supply is used to power the
Arduino development board with a regulated voltage ranging from 9 – 12
volts.
•
USB plug: This plug is a very important port in this board. It is
used to upload (burn) a program to the microcontroller using a USB cable.
It also has a regulated power of 5V which also powers the Arduino board
in cases when the External Power Supply is absent.
•
Internal Programmer: The developed software code can be
uploaded to the microcontroller via USB port, without an external
programmer.
•
Reset button: This button is present on the board and can be
used to resets the Arduino microcontroller.
•
Analog Pins: There are some analog input pins ranging from A0 –
A7 (typical). These pins are used for the analog input / output. The no. of
analog pins also varies from board to board.
•
Digital I/O Pins: There are some digital input pins also ranging
from 2 to 16 (typical). These pins are used for the digital input / output. The
no. of these digital pins also varies from board to board.
• Power and GND Pins: There are pins on the development board that
provide 3.3, 5 volts and ground through them
b. Software
The program code written for Arduino is known as a sketch. The software
used for developing such sketches for an Arduino is commonly known as the
Arduino IDE. This IDE contains the following parts in it:
• Text editor: This is where the simplified code can be written using a
simplified version of C++ programming language.
• Message area: It displays error and also gives a feedback on saving and
exporting the code.
• Text: The console displays text output by the Arduino environment
including complete error messages and other information
• Console Toolbar: This toolbar contains various buttons like Verify, Upload,
New, Open, Save and Serial Monitor. On the bottom right hand corner of the
window there displays the Development Board and the Serial Port in use.
c. Features of Arduino IDE
•
The project file or the sketches for a project are saved with the
file extension .ino
•
Features such as cut / copy / paste are supported in this IDE.
•
There also is a facility for finding a particular word and replacing it
with another by pressing the Ctrl + F buttons on the keyboard
• The most basic part or the skeleton of all Arduino code will have two
functions.
d. PROGRAMMING BASICS
BASICS Now we’ll discuss about the programming techniques of
Arduino sketch in the Arduino IDE. There are two main parts every sketch
will always have, they are:
void setup ()
void loop ()
Experiments
In our project we faced up with optimization of the processing system with
temperature data by programming this microcontroller. For energy efficiency, we
need to have a clear view when the temperature in the refrigerating chamber drops
below 0° and when it rises above 5°. This information provides us with the
temperature sensor connected to a breadboard. The sensor has a high
measurement accuracy, the error does not exceed 0.5°C and converts the
temperature data into digital code.
Signalization of three leds characterizes the changes of the temperature: green
t= 0-5°; red t>5°; orange t< 0°.
Thus we can regulate the flow of compressed air and avoid excessive amount of
energy consumption.
Functional analysis of the program
Our system is consisting of:
Vortex tube
Arduino Uno
Bread Board
Digital sensor DS 18B20
3 Light emitting diodes leds (red, green and yellow)
4 resistors (one 4.7 Ohm, three 100 Ohm)
7 wires
Fig. 6. Digital sensor DS 18B20
The first step was to connect the sensor to the microcontroller. To provide
correct connection of the sensor to the "Arduino" we acted according to the
following algorithm:
Black contact of temperature sensor must be connected to GND of "Arduino"
Fig.6.
Red contact of temperature sensor must be connected to +5V of
"Arduino"( red contact can be connected to any free digital pin)
Place a 4.7k resistor between the positive lead (Red Wire) and the output lead
(White Wire) of the sensor Fig.7.
Fig.7. Temperature sensor Pt100
Fig.8.a & b.Breadboard with leds and leds light control
Now the next few steps are required for the LEDS:
Place a wire from the ground rail to the ground rail on the opposite side of the
breadboard.
Place the 3 leds onto the breadboard. (Red, Yellow and Green)
Connect a 100-ohm resistor to each LED and have this go to the ground rail.
Now have a wire come from the following Arduino pins: pin 3 to the green LED,
pin 2 to a yellow LED and finally red to pin 1. Fig.8.a & b
Programming Arduino
First of all we had to download the library onewire, which is significantly
simplifies the work with the Arduino and all the sensors, including the DS18B20. A
computer program is a coded series of instructions that tells the computer what to
do. Once download and open up sketch – program that run on Arduino is called
sketch. This sketch tell Arduino to read data from one of the pins, such as the one
connected to a sensor; and to write information to a different pin, such as the pin
connected to an LED or display unit. We have programmed the microntroller in
order to:
The yellow LED turn on then the sensor capture the temperature less than 0
degrees
The green LED turn on then the sensor capture the temperature between 0
and 5 degrees
The red LED turn on then the sensor capture the temperature more than 5
degrees
Fig.9. Schema of leds display
Improvements
a. Refinements of the tube
Lewins and Bejan have suggested that angular velocity gradients in the radial
direction give rise to frictional coupling between different layers of the rotating flow
resulting in a migration of energy via shear work from the inner layers to the outer
lay. The energy separation was first explained by Ranque in his patent in 1932. He
hypothesized that the inner layers of the vortex expand and grow cold while they
press upon the outer layers to heat the latter. This theory, based on invicid
non-conducting fluid flow was rejected by Ranque himself in 1933 when he stated
that the compressed outer layers in the vortex tube have low velocities while the
expanded inner layers have large velocities and hence a larger kinetic energy.
This velocity distribution gives rise to considerable friction between the different
layers which results in centrifugal migration of energy from the inner layers. Hilsch
supported the theory put forward by Ranque, stating that air in the cold stream
expands from high pressure near the wall to low pressure at the core and in the
process transfers a considerable part of its kinetic energy to the outer layers by
internal friction. This tends to establish a constant angular velocity throughout the
cross-section of the tube.
In the design of a standard vortex tube, there are several tube parameters to be
considered, such as (1) tube diameter, (2) cold orifice diameter, (3) number, size
and location of the inlet nozzles, (4) tube length and (5) hot valve shape. There are
no critical dimensions of these parameters that would result in a unique value of
maximum temperature separation. Knowledge of the temperature separation
phenomenon suggests a relative design procedure for a vortex tube with the
physical realities of its operation. For fixed inlet conditions (supply pressure) a very
small diameter vortex tube would offer considerably higher back pressures and,
therefore, the tangential velocities between the periphery and the core would not
differ substantially due to the lower specific volume of air (still high density) while
the axial velocities in the core region are high. This would lead to low diffusion of
kinetic energy which also means low temperature separation. On the other hand, a
very large tube diameter would result in lower overall tangential velocities both in
the core and in the periphery region that would produce low diffusion of mean
kinetic energy and also low temperature separation.
A very small cold orifice would give higher back pressure in the vortex tube,
resulting in low temperature separation. On the other hand, a very large cold orifice
would tend to draw air directly from the inlet and yield weaker tangential velocities
near the inlet region, resulting in low temperature separation. Similarly, a very
small inlet nozzle would give rise to considerable pressure drop in the nozzle itself,
leading to low tangential velocities and hence low temperature separation. A very
large inlet nozzle would fail to establish proper vortex flow resulting again in low
diffusion of kinetic energy and therefore low temperature separation. The inlet
nozzle location should be as close as possible to the orifice to yield high tangential
velocities near the orifice. A nozzle location away from the orifice would lead to low
tangential velocities near the orifice and hence low temperature separation.
Fig.10.Chart of different tubes
As considering the costs and efficiencies of different tubes, as Fig.10, we chose
the Scheller Tube as our cooling part. (μc: cool mass fraction)
Conclusion
As discussed above, basically our easy-built gadgets could enable to preserve
the fishes under considerably favorable conditions, at low cost, which is much
more important to promote the technology in the underdeveloped countries. For a
certain amount of fishes and distance of transportation, we are able to roughly
calculate the amount of compressed gas needed. By that, we could lighten the
loads of our equipment and turn them much more portable combining a designed
backpack-like fish tank.
A further step is to realizer the automatic control of the temperature inside the
fish containers without human interferences at all. With remaining the costs of our
equipments, we aim to insulate our containers from excessive heat diffusion (un
prototype as below). They can be even utilized as simple household refrigerators
for basic family use.
References:
2004, «The State of World Fisheries and Aquaculture Opportunities and challenges,
Food and Agriculture Organization of the United Nations Rome
2003, «Overview of the fishery sector in Ethiopia» Mebrat Alem, Fisheries
Resources Development Dept., Addis Ababa , Ethiopia
2007, Review of Ranque–Hilsch effects in vortex tubes» Smith Eiamsa-arda,
Pongjet Promvongeb,
Goals of sustainable development
http://www.undp.org/content/undp/en/home/sustainable-development-goals.html
«Environmental monitoring with Arduino», project book, E. Gertz and P. Di Justo
«Sensors and Actuators with Arduino», Hans-Petter Halvorsen, M.Sc., University
College of Southeast Norway
RAPPORT EA
Programming a fun robot
Chryséis Salomez et Henri Her
Ecole Polytechnique – Year 2016-2017
Sommaire
Introduction
I. Robotics: social and societal issues
1. History
2. Social and societal aspects of robots
II. Rob’Art : social and societal aspects
1. Social aspect
2. Societal aspect
III. Work performed
1. Description of the robot and specifications
2. Procedure
Conclusion
Bibliography
Appendix : full code
Introduction :
Rob'Art is a robot developed as part of a set of projects to improve the living conditions
in Ethiopia. The purpose of these programs is to provide the population with various
technologies that are easy to use. Portable refrigerator, nano-scale power generation, ...
However, the fact that these projects are carried out in France also reflects a
technological and scientific delay of this country, which would benefit from being
autonomous. Another objective, on the margin but no less important for a long-term vision,
is to encourage the population to take charge of this delay and to fill it. This will mean an
increase in the share of the population entering the school, and more particularly in the
university. The question that then arises: how to motivate this evolution?
From this dilemma appeared Rob'Art: a subtle cocktail of cutting-edge technologies,
through its Arduino Uno boards and its Nude speaker, serving ludic education. Its objective:
through its luminous and sonorous animations, putting stars in the eyes of the children and
giving them the envy, the passion to participate in the great scientific adventure!
We will explain here the social and societal impacts targeted by Rob'Art, as well as
those of robotics in the broad sense. In a second step, we will present the approach that we
followed in order to design the animation of Rob'Art and its different functionalities. Finally,
we will present and detail the code present on the Arduino card, before concluding.
I.
Robotics: social and societal issues
I.1 History
The history of robotics starts in the XVIIIe century with automatons. An automaton is a
device able to reproduce a sequence of predetermined actions without human intervention.
It’s a programmed device that will always perform the same actions. The first automaton
emerged in 1737.
First automaton
This automaton was designed in 1737 by Jacques Vaucanson and was able to play 11 tunes
of music.
Many factories now automate part or all of their production.
Example of automaton
The second type of robot corresponds to those equipped with sensors. Their actions are
therefore different according to the environment of the robot. There are many different
types of sensors:
Temperature sensor
Infrared sensor giving the robot the ability to detect obstacles and measure the distance
between them
- Color sensor
- Ultrasonic sensor that can be used to track a moving target or detect motion
- Pressure, brightness sensor, etc.
All these sensors will then allow the robot, using a computer program processing all this
information, to understand its environment and to act according to it.
Thus, for example, a robotic vacuum cleaner will be equipped with gap sensors to
identify the stairs and cameras in order to recognize the obstacles.
Robotic vacuum cleaner
The first robot of that type was the electric dog of Hammond and Miessner in 1915.
Electric dog of Hammond and Miessner
The operating principle of this robot was very simple: it moved according to the
luminosity thanks to its optical sensor. Thus, by lighting a flashlight, the dog moved towards
it.
So, all these robots are lacking of artificial intelligence, they can not "think" on their
own. Many robots of this type are created. In the medical sector, for example, the Da Vinci
robot is able to operate and diagnose patients.
Exemple de robot humanoïde au Japon
Robot Da Vinci
In the field of space exploration, too, the Spirit and Opportunity robots travel through
Mars to transmit the information obtained through their numerous sensors to the Earth.
The last type of robot is the one with artificial intelligence and based on complex
mathematical models such as neural networks. In addition to possessing physical sensors,
these robots can make much more complex decisions and also learn by doing mistakes as
human beings can. In Japan, for example, more and more employees are being replaced by
robots, whether as a groom, or even as an insurance advisor. These robots are therefore
humanoid, able to move in a very fluid way, to be completely aware of their environment and
are able to adapt and communicate normally with human beings. They are robots who are
always learning.
There are many robots of this type in the military field, for example:
- Spy and combat drone capable of flying unmanned, jamming enemy radars and communication
devices, sending information such as terrain configuration or enemy troop position, and so
on.
- robot dog capable of transporting up to 75kg of material, able to move on all terrains, and to
keep the balance in any circumstance
- unmanned all-terrain vehicle, adaptable to a wide range of environments
This type of robot is subject to many ethical problems. Indeed, the evolution of robotics leads to
the creation of robots more and more competent, and increasingly resembling human beings.
Many films and series, such as I Robot, Real Humans, or more recently Westworld, talk about
these ethical problems that may happen in the future if robotic technology continues to evolve
and a sort of "consciousness" is created for robots.
I.2 Social and societal aspects
I.2.1. Social aspect
The evolution of robotics has many advantages from a social point of view. Many robots
have been developed to help the elderly or disabled children.
For example, the Keepon robot is a social robot capable of interacting with children,
especially those with behavioral disorders such as autism. The robot interacts with the child
through his sense of rhythm: he moves in rhythm with music, voices, and is able to manifest
emotions such as astonishment, envy or joy. The Keepon can also respond to children's
tactile gestures (caresses, pokes, taps and tickles) with emotions and sounds, thus facilitating
its interaction with the child.
Robot Keepon
There are also therapeutic robots such as the Paro robot. The latter is intended for the
elderly and especially those with Alzheimer's disease. These people are often deprived of a
social bond (in the hospital or in a nursing home), and this companion aims to give them a
few smiles. It responds to the touch, by movements and small cries. It is a perfect social
robot success; Thanks to its appearance, it inspires sympathy and makes the smile.
Robot Paro
Robotics therefore has an enormous social impact, whether by its playfulness or to help
people in difficulty.
I.2.2. Societal aspect
The emergence of robots within society, and in the broader sense of automated
systems, has not always been welcomed. If these are well seen in Asian countries, where
robots are a form of homage to nature, we can see a reverse trend in Western countries.
Hollywood cinema in the 1980s, for example, features many anticipatory films in which robots
have the role of a powerful, dominating, and harmful entity. One can quote Terminator, or
Blade Runner, both of which stage robots whose control has escaped man.
Subsequently, the balance is more mixed: some films begin to humanize the robots in
order to bring them closer to us. We note for this Wall-E, or Robots. However, there are still
some great successes like the Matrix trilogy, in which humans are literally cultivated by
"machines". Finally, some films begin to step back, and rather than assert clear positions on
the robots, ask question. Chappie portrays a population that is globally oppressed by a fully
robotic police, presenting the dangerous facet of the latter. Thereupon, one of these robots is
captured and reprogrammed - Chappie - to be able to think by itself and feel emotions. The
film then poses the question of the danger that this one can represent, by opposing its
defenders and its detractors.
What is the role of the robots in our society?
The robot can undeniably provide service to man. From its linguistic origin, the word
robot is coming from the protoslave which means work, chores, the robot is the slave of the
man and is used to perform ungrateful tasks. It was therefore traditionally used to carry out
tasks impossible for man, or very restrictive: exploration of the planet Mars, manipulation of
radioactive pencils in the hearts of nuclear power plants, exploration of the ocean floor ...
Gradually, there was a diversification of its tasks and a growth of the associated
market, illustrated in the figure below. Since the 2000s, the miniaturization of electronic
compounds and the perpetual reduction of their cost has accelerated and diversified research.
But despite this expansion of the number of robots in the world, the opinion of the
population concerning the robots remains mixed. Thus, if it is widely accepted that having
automata to help production in a factory is far from the case of a robot that can take care of
children or the elderly. The problem of artificial intelligence is also a problem. Having robots
capable of thinking and learning from their mistakes is one of the main subjects of debate
about robots. How can we consider robots in society capable of thinking and thinking more
and more precisely, to have a normal conversation with a human being without it suspecting
that it is a robot?
The place of a robot in the present society possessing an artificial intelligence is thus
very controversial. They are therefore able to be very useful in many areas, because of their
ability to make decisions and learn with their environment, but are not yet accepted.
II.
Rob’Art : social and societal aspects
Rob'Art is a robot designed to generate light and sound ambiance. The luminous
atmosphere is generated by multicolor bulbs mounted on a rotary system, while the sound
environment is directly managed by a bluetooth speaker installed at the head of the robot.
The operator can then choose the movements to be made by the robot so as to vary the light
animation and the music diffused by the enclosure. This robot, because of its objective of
entertainment, is addressed mainly to inactive populations. Its two main targets in terms of
segment of population are then the young and the elderly.
II.1 Social aspect
II.1.1 Social aspects - Youth
The main objective is to show what can be achieved through science and to convey a
positive image of robotic creations.
For this, the robot relies heavily on the imagination. A robot that dances, which creates
beautiful light and sound atmosphere, is a door open on the dream for young people not
accustomed to new technologies.
Thus, the first objective of this robot is to give a positive image of its congeners, a
condition necessary for their good acceptability by the populations. Having been confronted
with this robot in their youth, the sensitized populations will grow with the idea that the robot
obey to men, and that it can be used to make life more beautiful.
The second objective of this robot is to sensitize young people to science. If the latter
have been little confronted with the "miracles" of science, they will have no particular desire
to study it. Conversely, a young witness on a day-to-day basis about what science can do, may
want to contribute. The idea is, through this robot demonstration, to instill the desire to study
to these young people in order to promote the intellectual and scientific development of
developing countries.
Thus, a playful robot will broadcast a beneficial image of robotics in general. It will
therefore make it possible to raise awareness of their place in society, particularly in countries
where they are not very widespread. Moreover, it aims to contribute to the personal
development of these young people by giving them the desire to study, and to make their new
technologies and their immense possibilities.
II.1.2 Social aspect - Elderly
About the elderly, the objective is different. Indeed, it is no longer a matter of
contributing to their personal development, which has already been done in their lifetime.
The robot in front of this population has two aims: on the one hand, it is a tool of
entertainment for people who often are idle in retirement home. This may be due to the fact
that they are simply bored, or that they are suffering from pathologies that prevent them from
interacting normally with others, such as Alzheimer's disease.
In the first case, it is purely an entertainment tool. One aim, secondary and common
to the two cases presented, nevertheless remains to gradually change the image of robots in
the imagination of these people. Indeed, if they have known films like Terminator, produced
in 1970, they may feel a fear or apprehension towards anything related to robotics. Such a
Robot can then positively influence their perception of these systems, which more easily
opens the door to the automation of certain tasks feasible in nursing homes.
However, in the case where the viewer is simply idle, this robot also has the aim of
stimulating the latter. The way in which the robot will inspire young people to discover the
field of possibilities open to science, and more precisely to new technologies, will give older
people a new pastime.
II.2 Societal aspect
As suggested, this robot has strong societal objectives. Indeed, this one is part of the
sustainable development project in Ethiopia, which originates in France surely because of a
lack of dedicated scientific infrastructures there.
Its role, therefore, would be to encourage this development which would allow
Ethiopia to take a real independence from a technical and scientific point of view. For this, as
we said, the robot is aimed at young people to promote and give the desire to engage in
scientific studies. In mid term, therefore, it is hoped that the school and university landscape
will change, which in the longer term will have a greater impact on the autonomy of the
country in the areas mentioned above.
Moreover, the means put in place to operate this transformation - a robot - is not
insignificant. Today, we see an increasingly rapid development of the possibilities and
applications of robotics. As an example, we will quote for example the exoskeleton developed
in South Korea, which remains a very particular robot within a huge family, visible at the
international japanese exhibition of robotics :
This development will have repercussions in fields as diverse as varied, such as for example
transport with cars without drivers. The automation of tasks by robotics also reveals the
possibility for humanity to transform its relationship to work. It may no longer be needed and therefore potentially anxiety-to become a choice and a source of fulfillment. For example,
below, robots workers in action.
Presenting such a mechanism therefore makes it possible for the Ethiopian people to become aware
of these transformations in the future, but also to be actor. In this, our Rob'Art, which evidently
constitutes a far less evolving model than those presented above, can hope to initiate this mutation
in Ethiopia.
III.
Work Performed
III.1 Description of the robot and specifications
Rob Art is made up of two arms powered by battery from 12 to 42 V followed by a DC
/ DC regulator controller which returns the voltage to 6 V for the servo motor controller
which animates the 2 servo motors one to 17 Kg of torque, The other 9.9 Kg. On each of the
arms there are 2 servomotors corresponding to the articulation of the elbow and the
shoulder.
Mecanic part of Rob’Art
The purpose of the robot is to generate atmospheres. Using his arms and his leds, he
will have to generate a luminous atmosphere while dancing. He will have to obey orders
given via bluetooth. He will also have to be able to introduce himself and to receive
information by bluetooth.
III.2 Procedure
Our approach to meeting the specifications described above can be summed up in five
successive stages:
1. Discover Arduino and Servo Motors
2. Calibration of positions and problems encountered
3. Definition of reference positions, extension to dances
4. Communication via a bluetooth module with the Arduino board
5. Make the robot talk
III.2.1 Discover Arduino and Servo Motors
Description of the board
The first step of this project was the implementation of the Arduino tool. Having at first
no knowledge in this field, we decided to take a course on the openclassroom website, which
allowed us to familiarize ourselves with the philosophy of the tool and the basic commands.
The Arduino board (shown below) has a USB serial port (1) that can be used to
connect the computer to the computer, providing serial data transmission and a 5V power
supply to the card. From this one, equipped with an Arduino development environment - we
chose Genuino - it is possible to write lines of codes. These are then uploaded onto the card
by means of the cable and stored in the memory of the microprocessor (2). It is then
possible to unplug the USB cable and allow the card to operate autonomously by means of a
power supply connected to the current input signaled by (3).
The card is equipped with several pins of different types. For this project we
considered only the digital pines from 0 to 13, as well as the pines GND - grounds.
Description of Servomoteurs
A servomotor is a rotary system with three current inputs. The first two (red and black)
are the power inputs, allocating to the actuator the energy required to carry out the controlled
movements. The third input corresponds to the command input. Physically, the position
adopted by the servomotor among the continuous set of possible positions is controlled by a
slot pulse train. The low period is fixed at 20 ms, and the value of the high period, between 1
ms and 2 ms, controls the angle adopted by the servomotor.
Thus, in our assembly, the servomotors are powered by a battery independent of
Arduino, at a voltage of 5V. The Arduino and battery masses are connected, and the actuator
inputs are connected to some digital pins on the board as shown in the following diagram for
a Servomotor.
Finally, it was necessary to take control of the various controls for controlling the actuator.
There is a specific library, called at the beginning of the code by the command:
#include <Servo.h>
Following this, the first step to use a servomotor is to declare the object in the code, through
the command:
Servo #nameOfTheServomotor ;
Once the object is created in the code, it is necessary to say to which pin the latter is linked:
Int pinServomoteur = #numberOfThePin ;
nomDuServomoteur.attach(pinServomoteur) ;
Thus, the code understands that any position command sent to the name of the Servomotor
must pass through pin number pinServomotor.
Finally, in order to adjust the position of the Servomotor to an integer value x between 0 and
179, it was only necessary to use the command:
nameOfTheServomotor.write(x) ;
III.2.2 Calibration of positions and problems encountered
Once the operation of the Arduino and the Servomotor was assimilated, it was
necessary to calibrate the angular values corresponding to the different positions. For this
we have tested different values until we find the right values.
We then came up with the following results:
However, we later noticed that the values of these shoulder angles change from
session to session. This led us to notice the existence of a clearance between the ring
connected to the servomotor and the pvc tube which constitutes the shoulder. In addition,
the rupture of part of the servomotor constituting the right elbow led us to modify the
installation.
Ultimately, we will need to re-calibrate once the robot is repaired. However, we can
be faster than the first time because we realized that we could have put the actuators in the
desired positions and use the control
nameOfTheServomotor.read()
Which has the effect of returning the value of the angle in which the servomotor is located.
III.2.3 Definition of reference positions, extension to dances
Definition of reference positions
Once the angles associated with the different positions were obtained, we could determine
some reference positions. Presented below, the position known as "Boxing Guard" and the
associated piece of code:
Extension to dances
To extend to the dances, we just had to write a periodic choreography, and to write the
sequence once. The control code is then constructed in the following manner, simplified in
pseudo code:
Void setup(){
Declaration / Initialization of Variables
}
Void dance1 (){
Instruction sequence for a loop of the periodic dance 1
}
.
.
. #Similarly for each of the dances and positions
.
.
Void loop (){
If : There is an incoming data stream,
Reading data #Which consist in a character string
Saving data in a « position » variable
Closing the conditional loop
#Thus, if no new command is sent to the card, the position variable keeps the same value
If : position = dance1
Execute dance1
Closing the conditional loop
.
.
. #Similarly for each of the dances and positions.
.
Thus, the robot is initially in a commanded position during the setup, and the
position variable is initially empty. When sending a first command, position takes a given
value, and keeps it in the absence of new data input.
At each loop, the conditional loop associated with the position value is executed: the
robot stays in place if position has a position value, for example Boxing Guard. Or, if position
has a value of dance, the robot executes to each loop the controlled movements: it dances.
Finally, if a new command is sent to the card, then the position variable is reassigned
at the beginning of the loop: the robot changes mode of operation.
All available commands :
Positions :
·
·
·
·
·
·
Bras ballants : the robot has arms alongside his body.
Jésus : the robot reaches out to the sides.
Garde de boxe : The robot gets into the position of boxing guard.
Haut les mains : the robot raises his hands as in a police arrest.
Dab gauche : The robot performs a left dab, within the limits of its degrees of freedom.
Dab droit : The robot performs a right dab, within the limits of its degrees of freedom.
Dances :
·
·
·
·
Electro : the robot performs a choreography inspired by electronic music dances.
Câlin : the robot starts from a position Jesus, then pulls his arms in front of him before
bending his elbows to take the other in his arms.
Parle : the robot performs a choreography imitating the Italian gesture of prayer.
Danse2 et Danse3 : the robot performs choreographies specially crafted from an
entertainment perspective to meet Rob'Art's ludic goal.
III.2.4 Communication via a bluetooth module with the Arduino board
To communicate via bluetooth with the arduino card, we simply added a bluetooth
module on the arduino board.
The green card above the arduino card is the bluetooth module
This bluetooth module adds a bluetooth communication function to your Arduino
card. It can thus communicate wirelessly at medium distance with any other bluetooth
device (computer, mobile phone, second bluetooth module on another Arduino card ...). We
will then be able, once the module has been set up, using our mobile phone and a mobile
application specifically created to communicate with the card, transmitting information and
orders to our robot.
From an electronic point of view, this module also works very simply: once placed on
the arduino board, the pins are connected in the same way as if one had an arduino card
alone.
Arduino board with bluetooth module connected to servomotors
We used for this project the Arduino Bluetooth Controller application which will allow us to
send information to our card which will then be able to interpret them thanks to our
computer code.
Control settings
Control part
The principle of this application is very simple. We connect via bluetooth to our
bluetooth module, then we set up the controls: so, when we press the left arrow in the
control part, the letter sequence 'Top Hands' will be sent to the bluetooth module, which
Through the computer program.
From a computer perspective, many of the functions presented earlier were created.
The only addition will be in the main loop () function.
The first objective of this function will be to read the characters sent by bluetooth. To
do this, we initialize and create before the function a string of 50 characters long, which we
will fill as we receive the information. A string is a string of characters filling out like a table.
if(Serial.available())
{ int i = 0;
while (Serial.available()!=0 && i<=49)
{
posture[i] = Serial.read();
delay(10);
i++;
}
posture[i] = '\0';
}
The Serial.available () function returns true if characters are received and false if the module
does not receive any information. Thus, if it receives information, it will read each character
received using the Serial.read () function and put them in the string posture. At the end of
this loop, we obtain a string containing all the characters received.
if(strcmp(posture,"Bras ballants") == 0)
{
brasBallants();
}
Then we have in the code a set of loops of this form. The strcmp function is a C ++
function to compare two strings. Thus, strcmp (posture, "Swinging arms") returns 0 if the
character string posture matches 'Swing arms'. For example, if 'Swing arms' have been sent to
the bluetooth module, then the armWall () function written earlier will start.
III.2.5 Make the robot talk
To do this, a bluetooth speaker was used. Then we use the application TTS (Text
To Speech). This application transforms any sentence written into speech.
Application TTS Android
One chooses the speed, the step, the volume and the language and then one writes
the text that the robot will pronounce.
Bluetooth speaker used
Conclusion
Rob Art was at first a simple statue made of recycled materials and is now capable of
bringing joy and excitement with very little equipment (some servomotors, an Arduino board,
a bluetooth module, a battery and wires). He brings good mood around him. He is thus able
to speak, to joke, to make laugh. It can also make a hug if the person in front of him is sad.
Finally, he can move and dance.
This project allowed us to learn how to use and program in Arduino. In just a few weeks,
we started with a zero knowledge in Arduino programming and we managed to master the
operation of the servo motors. We realized that with very simple and not very expensive
equipment, we can already realize things that would have seemed unthinkable only 100 years
earlier! It was therefore very interesting to carry out this project, despite the regular
headaches due to poor wired contact.
Bibliographie
https://fr.wikipedia.org/wiki/Da_Vinci_(chirurgie)
http://cjezegou.fr/wp-content/uploads/2013/11/histoire-automates-1.pdf
http://www.usinenouvelle.com/article/la-naissance-des-robots.N193599
http://ia-tpe2010.e-monsite.com/pages/l-ia-et-l-ethique/exemples-de-robotsmilitaires.html
http://www.gotronic.fr/ins-histoire-de-la-robotique-49.htm
http://intelligence-artificielle.livehost.fr/?page_id=254
http://letmeknow.fr/blog/2013/07/01/tuto-ajouter-le-bluetooth-au-arduino/
Annexe : code complet
#include <Servo.h>
char posture[50];
# Declares and assigns the numbers of pins used
int pinServo1 = 6;
int pinServo2 = 8;
int pinServo3 = 10;
int pinServo4 = 12;
# Declares the servomotors used
Servo coudeGauche;
Servo epauleGauche;
Servo coudeDroit;
Servo epauleDroite;
# Declares and affects the angular values corresponding to the movements of the
servomotors
int positionHauteCoudeGauche = 50;
int positionBasseCoudeGauche = 179;
int positionInterCoudeGauche = 115;
int positionHauteCoudeDroit = 40;
int positionBasseCoudeDroit = 169;
int positionInterCoudeDroit = 105;
int positionBasseEpauleDroite = 50;
int positionHauteEpauleDroite = 140;
int positionInterEpauleDroite = 95;
int positionBasseEpauleGauche = 170;
int positionHauteEpauleGauche = 80;
int positionInterEpauleGauche = 125;
# Initiates the data stream to 9600 bauds.
# Associates pins to the servomotors.
# Puts the robot in the initial position.
void setup()
{
Serial.begin(9600);
epauleDroite.attach(pinServo1);
coudeDroit.attach(pinServo2);
epauleGauche.attach(pinServo3);
coudeGauche.attach(pinServo4);
coudeGauche.write(179);
coudeDroit.write(169);
epauleDroite.write(50);
epauleGauche.write(170);
}
# All subsequent voids, except the loop, define the dances and position described in
the report.
void brasBallants()
{
coudeGauche.write(179);
coudeDroit.write(169);
epauleDroite.write(50);
epauleGauche.write(170);
}
void jesus()
{
coudeGauche.write(110);
coudeDroit.write(100);
epauleDroite.write(50);
epauleGauche.write(170);
}
void gardeDeBoxe()
{
coudeGauche.write(50);
coudeDroit.write(40);
epauleDroite.write(140);
epauleGauche.write(80);
}
void hautLesMains()
{
coudeGauche.write(50);
coudeDroit.write(40);
epauleDroite.write(50);
epauleGauche.write(170);
}
void dabGauche()
{
coudeGauche.write(70);
coudeDroit.write(40);
epauleDroite.write(140);
epauleGauche.write(125);
}
void electro() {
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
delay(1000);
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
delay(1000);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
delay(1000);
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
delay(1000);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
epauleGauche.write(160);
epauleDroite.write(50);
delay(1000);
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(80);
epauleDroite.write(140);
delay(1000);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
epauleGauche.write(160);
epauleDroite.write(50);
delay(1000);
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(80);
epauleDroite.write(140);
delay(1000);
epauleGauche.write(160);
epauleDroite.write(50);
delay(1000);
epauleGauche.write(80);
epauleDroite.write(140);
delay(1000);
epauleGauche.write(160);
epauleDroite.write(50);
delay(1000);
epauleGauche.write(80);
epauleDroite.write(140);
delay(1000);
}
void calin() {
coudeGauche.write(100);
coudeDroit.write(100);
epauleGauche.write(positionBasseEpauleGauche);
epauleDroite.write(positionBasseEpauleDroite);
delay(4000);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(3000);
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
epauleGauche.write(positionBasseEpauleGauche);
epauleDroite.write(positionBasseEpauleDroite);
delay(100000);
}
void parle() {
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
epauleGauche.write(positionBasseEpauleGauche);
epauleDroite.write(positionBasseEpauleDroite);
delay(2000);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(2000);
coudeGauche.write(positionInterCoudeGauche-20);
epauleGauche.write(positionInterEpauleGauche);
epauleDroite.write(positionInterEpauleDroite);
delay(2000);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit-20);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(2000);
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(2000);
}
void danse2() {
coudeGauche.write(positionBasseCoudeGauche);
coudeDroit.write(positionBasseCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(2000);
coudeGauche.write(positionInterCoudeGauche+20);
coudeDroit.write(positionInterCoudeDroit-20);
delay(400);
coudeGauche.write(positionInterCoudeGauche-20);
coudeDroit.write(positionInterCoudeDroit+20);
delay(400);
coudeGauche.write(positionInterCoudeGauche+20);
coudeDroit.write(positionInterCoudeDroit-20);
delay(400);
coudeGauche.write(positionInterCoudeGauche-20);
coudeDroit.write(positionInterCoudeDroit+20);
delay(400);
coudeGauche.write(positionInterCoudeGauche+20);
coudeDroit.write(positionInterCoudeDroit-20);
epauleGauche.write(positionInterEpauleGauche);
epauleDroite.write(positionInterEpauleDroite);
delay(400);
coudeGauche.write(positionInterCoudeGauche-20);
coudeDroit.write(positionInterCoudeDroit+20);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(400);
coudeGauche.write(positionInterCoudeGauche+20);
coudeDroit.write(positionInterCoudeDroit-20);
epauleGauche.write(positionInterEpauleGauche);
epauleDroite.write(positionInterEpauleDroite);
delay(400);
coudeGauche.write(positionInterCoudeGauche-20);
coudeDroit.write(positionInterCoudeDroit+20);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(400);
}
void danse3(){
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+10);
epauleDroite.write(positionHauteEpauleDroite-10);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+20);
epauleDroite.write(positionHauteEpauleDroite-20);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+30);
epauleDroite.write(positionHauteEpauleDroite-30);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+40);
epauleDroite.write(positionHauteEpauleDroite-40);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+50);
epauleDroite.write(positionHauteEpauleDroite-50);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+60);
epauleDroite.write(positionHauteEpauleDroite-60);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+70);
epauleDroite.write(positionHauteEpauleDroite-70);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+80);
epauleDroite.write(positionHauteEpauleDroite-80);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+90);
epauleDroite.write(positionHauteEpauleDroite-90);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+80);
epauleDroite.write(positionHauteEpauleDroite-80);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+70);
epauleDroite.write(positionHauteEpauleDroite-70);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+60);
epauleDroite.write(positionHauteEpauleDroite-60);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+50);
epauleDroite.write(positionHauteEpauleDroite-50);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+40);
epauleDroite.write(positionHauteEpauleDroite-40);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+30);
epauleDroite.write(positionHauteEpauleDroite-30);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+20);
epauleDroite.write(positionHauteEpauleDroite-20);
delay(500);
coudeGauche.write(positionInterCoudeGauche);
coudeDroit.write(positionInterCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche+10);
epauleDroite.write(positionHauteEpauleDroite-10);
delay(500);
coudeGauche.write(positionHauteCoudeGauche);
coudeDroit.write(positionHauteCoudeDroit);
epauleGauche.write(positionHauteEpauleGauche);
epauleDroite.write(positionHauteEpauleDroite);
delay(500);
}
void loop(){
# As described in the report, the if loop below retrieves incoming data and stores it in
the position variable.
if(Serial.available())
{
int i = 0;
while (Serial.available()!=0 && i<=49)
{
posture[i] = Serial.read();
delay(10);
i++;
}
posture[i] = '\0';
}
# The following if loops test the value of the position variable; according to the latter, the
robot performs one of the dances or positions.
if(strcmp(posture,"Bras ballants") == 0)
{
brasBallants();
}
if(strcmp(posture,"Jesus") == 0)
{
jesus();
}
if(strcmp(posture,"Garde de boxe") == 0)
{
gardeDeBoxe();
}
if(strcmp(posture,"Haut les mains") == 0)
{
hautLesMains();
}
if(strcmp(posture,"Electro") == 0)
{
electro();
}
if(strcmp(posture,"Danse 2") == 0)
{
danse2();
}
if(strcmp(posture,"Danse 3") == 0)
{
danse3();
}
if(strcmp(posture,"Calin") == 0)
{
calin();
}
if(strcmp(posture,"Parle") == 0)
{
parle();
}
if(strcmp(posture,"Dab gauche") == 0)
{
dabGauche();
}
}
Jeanlouis Queri