2nd German-West African Conference on Sustainable, Renewable Energy Systems SusRES – Kara 2021

Photovoltaic

https://doi.org/10.52825/thwildauensp.v1i.4

Published: 15 June 2021

Design and implementation of a photovoltaic
characterization platform at FaST

Moudjibatou AFODA 1, N’detigma KATA 1,2, Dambé. DOUTI1, Hodo-Abalo SAMAH1, Amadou
Séidou MAIGA2

1 Faculté des Sciences et Techniques (FaST), Université de Kara, Togo
2 Laboratoire d’Électronique Informatique Télécommunication et Énergies Renouvelables, Université

Gaston Berger, 32000 Saint-Louis, Sénégal

Abstract. The site that houses the FaST faces high dusty winds and considerable
temperature variation. Weather conditions such as solar radiation, temperature, and wind
speed greatly affect the performance of PV modules. But the data from PV equipment
manufacturers do not allow for proper sizing. Therefore, a rigorous study is needed to find
the most suitable PV module technology for the study area. For this purpose, platforms for
the acquisition of meteorological parameters and module characterization are indispensable.
This platform project at FaST will serve training and pedagogy because its configuration will
allow master and bachelor students to carry out practical work, to carry out studies on new
cell technologies under the influence of external factors specific to the sub-Saharan zone and
will bring an added value by providing additional information on real conditions and especially
the influence of local external factors. Our study consisted first of all in the realization of the
platform on the roof of the FaST, then in the design and the programming of a module of
acquisition of the measured parameters on the basis of the Arduino microcontroller card and
finally in the test of characterization of the modules used for the platform thanks to an
electronic load on the basis of MOSFET of power controlled by a microcontroller that we
realized.
Keywords: platform, acquisition, electronic load.

Introduction

The performance of PV modules is highly dependent on weather conditions such as solar
radiation, temperature and wind speed. To provide energy continuously over a long period of
time, a PV system must be correctly dimensioned. This requires a fairly rigorous study in
order to make the right choice. To do this, platforms for acquiring meteorological parameters
and characterizing the panels are indispensable. This platform project at the FaST will
achieve the following objectives: the platform at the service of training and pedagogy: with
the instantaneous taking of measurements, the platform will allow learners and visitors to
observe the behavior of the modules according to the conditions in which the modules are
located. Its configuration will allow practical work to be carried out without influencing the
long-term measurements. Thus, master and bachelor students will be able to carry out their
practical work. The platform at the service of research: In the research of photovoltaic
technologies best adapted to the sub-Saharan zone, the platform will allow to realize studies
on new cell technologies with the influence of external factors specific to the sub-Saharan
zone. The PV modules sold to the local market can be characterized through this platform to
reassure investors and customers. The platform at the service of projects: most projects in
the northern part of Togo are based on software data that may not correspond to the reality
on the ground. This platform will bring an added value by providing additional information on
real conditions and especially the influence of local external factors. Our work consisted in

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Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

the realization of the platform on the roof of the Faculty of Sciences and Technologies
(FaST), then in the design of a variable electronic load based on MOSFET and finally in the
design, the realization and the programming of the acquisition module based on the Arduino
microcontroller.

Methodology

We have defined the parameters that must be acquired by making a bibliographic study.
During a visit to meteorological centers, we noticed that the available data are the ambient
temperature, relative humidity, wind speed and direction. These centers do not acquire solar
irradiation. From these researches, we have established a list of materials [1] of the platform
and the right way to make their different assemblies. We have thus realized a diagram
presenting in a general way the platform.

Figure 1: Schematic of the whole system
I-Power block II-Acquisition block
1-Solar modules 10-Pyranometer
2-Inverter switch 11-Temperature sensor
3-Regulator 12-Wind vane-anemometer
4- Battery 13- DHT22 sensor
5- Inverter 14-15- Voltage sensors
6-7-8-9-Fuses 16-17- ACS712 current sensors
18-Digital potentiometer
19-Arduino board
20-ESP32 MCU node
21-Computer
As illustrated by the block diagram in Figure 1, the I-V measurement platform for photovoltaic
modules consists of two main parts: the production block and the acquisition block. These
two blocks are controlled by a programmable changeover switch that serves as a flip-flop.

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

Production block

Figure 2: Production block

The production block allowing to feed the laboratory of physics of the Faculty of Sciences
and Technologies (FaST), is constituted of:

A small photovoltaic field consisting of four solar modules placed on a metal structure
that we have made (Figure 3) and installed (Figure 4 and 5) on the roof of the Faculty of
Sciences and Technologies.

Figure 3: Assembly of metal structures

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

Figure 4: Installation of metal structures

Figure 5: Photovoltaic field installed on the roof of the FaST

- A regulator to control the charge of the batteries and limit their discharge
- Batteries to store energy for times of no sunlight
- An inverter to convert the direct current from the solar modules into alternating current that
can be used to power the physics laboratory

Acquisition block
This block consists of different devices for the measurement of solar irradiation
(pyranometer), of the temperature of the modules in operation (temperature probes), of the
direction and speed of the wind (wind vane-anemometer), of the ambient temperature and
relative humidity (DHT22), of the measurement of the current (ACS712) and of the voltage.
For the representation of the I-V characteristic from the current and voltage measurements, it
is necessary to vary the impedance in order to have different voltage and current values,
hence the usefulness of the digital potentiometer.

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

Digital potentiometer

The characteristics of potentiometers available on the market do not correspond to those of
the modules we have for this study, it was therefore important to opt for a variable electronic
load.

Electronic load

Photovoltaic modules are usually tested using direct current electronic loads. These loads
are often very expensive. However, with the help of very simple and much cheaper circuits, it
is possible to build an electronic load. It varies the resistance over the entire measurement
range in a very short time.

Figure 4: Circuit of the electronic load

For this electronic load, we have connected in parallel resistors that are controlled by a
microcontroller that generates control signals. We have used the PIC microcontroller for its
efficiency and its availability on the market, to generate the signals that applied to the
transistors allow to define the value of the resistance [2]. The MOSFET transistors are
chosen for their simplicity, their speed and their lower cost and used in this case as
electronic switches.

Data acquisition

Measurements made by the pyranometer, the vane anemometer, the temperature and
humidity sensor, the thermocouples, the temperature sensor, the voltage and current
sensors are retrieved by the Arduino board and then transferred to the MCU node.
Potentiometers to adjust the periodicity of sending data to the Node MCU, the MAX485
module, a data receiver to transmit the data from the pyranometer to the Arduino, the RTC
module, a real time clock to give the time at any time and an LCD screen to display the date,
time and ambient temperature are added to allow a better understanding of the data to be
acquired.

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

Figure 5: Assembly of the different Arduino sensors

1-Arduino 11- Anemometer- Wind vane
2,3-Current sensors ACS712 12- LCD screen
4,5-Voltage sensors 13- RTC module
6-Max485 module 14- DHT22 humidity and temperature sensor
7-Pyranometer Temperature sensors 15- Temperature sensor KY-028
8-9- Potentiometers 16-ESP32 MCU node
10-Thermocouples MAX31855 17-SD card
In order to acquire the data from the different sensors, we created two programs [3]. A first
program that we uploaded on Arduino [4], [5] to recover the measurements made by the
different sensors and then transmit them to the Node MCU. The second program is uploaded
on the Node MCU allowing it to recover the data, to transfer them on a web server and on a
SD card while allowing to download them.

Flowcharts

The following figure shows the execution steps of the algorithm that we used to develop the
programs in C language that we uploaded on the Arduino board and on the Node MCU.

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

Figure 5a: Flowchart of the program driving the Arduino board

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

Figure 5 b: Flowcharts of the programs driving the ESP32 Node MCU

Results and discussions

This project of characterization platform being in progress, in this part, we present only the
variation of some climatic parameters according to time. A test was carried out on
26/03/2021 from 8h30 am to 7h30 pm on the characterization platform allowing us to present
these results.

:36
:28

0:2
5:2

1:1
5:3

1:5
9:5

2:4
3:1

3:8
:41

3:3
4:1

3:5
9:4

4:2
5:9

4:5
0:2

5:1
5:4

5:4
6:4

6:1
2:4

6:3
7:2

7:2
:31

7:2
7:3

7:5
2:4

8:1
8:4

8:4
4:2

9:2
8:1

1
10

60 Relative humidity
temperature

Hour-Minute-Second

Re
la

tiv
e

hu
m

id
ity

(e
n

%
)

A
m

bi
en

t t
em

pe
ra

tu
re

(°
C)

Figure 6 a: Variation of relative humidity and ambient temperature

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

:36
:28

0:2
5:2

1:1
5:3

1:5
9:5

2:4
3:1

3:8
:41

3:3
4:1

3:5
9:4

4:2
5:9

4:5
0:2

5:1
5:4

5:4
6:4

6:1
2:4

6:3
7:2

7:2
:31

7:2
7:3

7:5
2:4

8:1
8:4

8:4
4:2

9:2
8:1

1
-10

70
Solar panel temperature
Ambient temperature

Hour-Minute-Second

So
la

r p
an

el
te

m
pe

ra
tu

re
(°

A
m

bi
en

t t
em

pe
ra

tu
re

(°
C)

Figure 6b: Variation of the temperature of the solar modules and the ambient temperature

:36
:28

0:2
5:2

1:1
5:3

1:5
9:5

2:4
3:1

3:8
:41

3:3
4:1

3:5
9:4

4:2
5:9

4:5
0:2

5:1
5:4

5:4
6:4

6:1
2:4

6:3
7:2

7:2
:31

7:2
7:3

7:5
2:4

8:1
8:4

8:4
4:2

9:2
8:1

20
Wind speed
Atmospheric pressure

Hour-Minute-Second

W
in

d
sp

ee
d(

Km
/h

)

0,0

0,5

1,0

1,5

2,0

A
tm

os
ph

er
ic

p
re

ss
ur

e
( b

ar
)

Figure 6c: Variation of wind speed and atmospheric pressure

Figure 6a shows a decrease in humidity, reaching an almost constant value around 2pm and
starting to increase around 5pm. The ambient temperature increases until it reaches its
maximum value around 2:00 pm, a critical time used in the environment for air conditioning
projects.
Curve 6b shows that the temperature of the modules is generally higher than the ambient
temperature during the day because these panels absorb light and heat up.
The atmospheric pressure at the platform site is about 1 bar (Figure 6c), which is roughly
equal to normal atmospheric pressure (101.3mbar). The wind speed varies a lot with several

Afoda et al. | TH Wildau Eng. Nat. Sci. Proc.1 (2021) “SusRES 2021”

spikes during this day carrying a lot of dust on the solar modules. The impact of dust will be
studied when all the characterization sensors are installed.

Conclusion

This article presents the work done for the realization of the solar module characterization
platform implemented at FaST. Currently, it is possible to acquire meteorological data.
However, the work continues in order to acquire the current-voltage characteristics of the
solar modules as well as the solar irradiation in order to evaluate the consequences of the
effect of the climatic conditions (temperature and dust) on the production of solar modules.

Acknowledgements

We offer all our recognitions to German Academy Exchange Service DAAD for financially
supporting this project through WILDAU University

References

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[2] Akoro E, Tevi G, Faye M, Sene M, Maiga A. Modelling and simulation of an automatic
solar module characteristics data acquisition system. OAJ Materials and Devices. 2019.
https://doi.org/10.23647/CA.MD20191602

[3] Asch G, Néel L. Acquisition de données : du capteur à l'ordinateur. 1 Vol.. 3e édition.
Paris: Dunod; 2011.

[4] Nfaoui M, El-Hami K. Conception et réalisation d'un système de métrologie et supervision
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[5] Tavernier C. Arduino : Applications avancées. Dunod; 2012.

https://doi.org/10.23647/CA.MD20191602
https://www.openscience.fr/IMG/pdf/iste_incertfia17v2n5.pdf.%202017

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