The performances of an exposed to a light source photovoltaic solar panel decrease when its temperature increases. In this work, we present a cooling device ...
Design, Implementation and Characterization of a cooling photovoltaic solar panel device C. Hajjaj1, A. El Rhassouli2, H. Amiry1 , A. El Hasnaoui1, S. Bounouar1, R. Bendaoud1, A. Obbadi1,S. Sahnoun1, M. Benhmida1 1Laboratory
of Electronic, Instrumentation and Energetic, Physics Department, Chouaïb Doukkali University, El Jadida, Morocco 2Lycée Technique Louis Aragon, Académie de Franche Comté, Héricourt, France
Abstract The performances of an exposed to a light source photovoltaic solar panel decrease when its temperature increases. In this work, we present a cooling device constituted by a copper serpentine, a pump with an adjustable flow rate and a metallic plate exposed to solar irradiations. This system is intended to study experimentally the coolant flow effect on decreasing of metallic plate temperature. The absorbed energy evacuation is made through a heat exchanger endowed with another outside circuit. The cooling of the plate is estimated by comparing the thermal images taken by an infrared camera before and after the cooling fluid flow. We also present an experimental device which permits to acquire simultaneously measured solar panel tension, current intensity and ambient temperature. The device being placed on isolated site, the transmission of the data is made by WiFi. A specific computer program was developed to record the results on the database of a remote server. Keywords: Hybrid photovoltaic/thermal collector (PV/T), Temperature dependence, Heat transfer.
Introduction Solar energy undoubtedly represents the most promising source of renewables energies. Photovoltaic energy is more accessible to exploitation on a larger scale when compared to the thermodynamic solar energy. Its development is governed by two great obstacles: • the cost of storage • the decrease of solar panel efficiency with temperature increasing[1-4]. In this work, we carried out an experimental study of the coolant effect on the temperature decrease of a steel metallic plate. The cooling of the plate is assessed by comparing the thermal images taken by an infrared camera before and after the coolant circulation. Furthermore, we present an experimental device for measuring voltage and current intensity delivered by a solar panel, thus as ambient temperature, and that permits their remote transmission on the database of a server.
Experimental device and measurements’ results Principle The electrical efficiency of a photovoltaic cell is given by the following expression [4]: 𝐺 ηel= ηn [1-β (Tcell -Tref)+γlog ] 1000 Where ηn : nominal electrical efficiency at the reference temperature Tref = 25 °C. Tcell : solar cell temperature. G : solar irradiation intensity (W/m2). β : efficiency correction coefficient for temperature. γ : efficiency correction coefficient for solar radiation.
[Fig.8] presents the operating principle of the device for measurements and transmission to a remote server database. An arduino card YUN[5] is configured for transmission of voltage, current intensity delivered by a solar panel thus as ambient temperature value to a remote MySQL server. Access to results is then possible from anywhere via internet.
Experimental device The implemented cooling system [Fig.1] is primarily composed of a metallic plate (1), a flask of 50 l (2) and a circuit for coolant flow. The system is equipped with a copper serpentine (3) a pump with an adjustable flow rate (4), an expansion tank absorbing excess pressure in the circuit (5), pressure and temperature sensors. The coolant flow rate is controlled by a variable speed pump (WILO). Metal wool is used to promote better heat exchange between the serpentine and the metallic plate [Fig.2]. The system is covered with an aluminum film to limit heat exchange with the external atmosphere and to promote the water heating [Fig.5].
Figure 3: The flask and the heat exchange circuit with external environment
Figure 1: Block diagram of the cooling system
Figure 4: The metallic plate is coated with a layer of matt black paint improving greatly its absorbed irradiations rate. The plate is oriented southward with an inclination matching with the local latitude of ELJADIDA (of about 330)
Figure 2: Metal wool is confined between the Copper serpentine and the metallic plate
Cooling system operation Cooling metallic plate by the coolant flow is evaluated by comparison of coolant temperatures at the inlet and outlet of the serpentine. The absorbed energy is evacuated through a heat exchanger endowed with another outside circuit. The flask of 50 L [fig.3] used is thermally insulated with polyurethane foam, whose density and thickness limit the thermal losses. The surface finish is made of polyester reinforced with glass fibers, ensuring high durability. The flask is equipped with a security group to avoid overpressure. Time
T2 Output temperature 24.1
Flow rate m3/h
11 h 09 min
T1 input temperature 23.3
0
irradiation intensity (w/m2) 863
11 h 24 min
24.6
25
0
865
11 h 48 min
25
26
1,10
770
12 h 04 min
25
27
1,10
775
14 h 52 min
26
27
1,10
798
Table1: experimental measurements of temperatures, flow rate and irradiation intensity
Figure 5: The rear face of the metallic plate support is coated with an aluminium film. The thermocouples are placed at the input (T1) and the output (T2) of the serpentine
Figure 8: diagram of the chain of acquisition and transmission of data
Conclusion • Achieved cooling system limit the degradation of solar panel efficiency when ambient temperature increases. • Efficiency of the implemented system and reliability of achieved experimental measures have been tested. • The characteristics of system components (metal plate, metal wool, serpentine ..) as well as the efficiency of their heat exchange can be improved. • Accurate assessment of involved heat exchange performance requires the installation of temperature sensors at serpentine inlet and outlet. • The remote data transmission requires using devices transmitting over distances beyond the reach of the 100 m authorized by the Arduino Yun card.
References Figure 6: the steel plate thermal image before circulation of the coolant (water) was taken by a infrared camera FLIR I3
Figure 7: the steel plate thermal image after circulation of the coolant (water) was taken by a infrared camera FLIR I3
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