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Egyptian researchers have used paraffin as a phase change material (PCM) to reduce the operating temperature of photovoltaic modules. They have found that the material improves energy efficiency by more than 15%, compared to a reference module without cooling.
Researchers at Egypts Sohag University have developed a passive cooling system for solar panels that uses a PCM known as RT-42 paraffin wax.
PCMs can absorb, store and release large amounts of latent heat in a defined temperature range and have often been used, at the research level, for cooling photovoltaic modules. Paraffin is obtained from petroleum by dewaxing light lubricating oils and is used in candles, waxed paper, polishes, cosmetics, and electrical insulators.
The scientists placed the cooling system in a 40 W polycrystalline panel with a size of 55 cm × 65 cm and compared its performance with that of an identical reference panel without cooling. They tested the panels with tilt angles of 15, 20, 25 and 30 degrees and with different PCM thicknesses.
The two modules have an efficiency of 16.5%, an open circuit voltage of 12 V, a short circuit current of 4.3 A, and a fill factor of 0.78.
“To house the photovoltaic panels, a rectangular PCM container with interior dimensions of 55 cm × 65 cm x 4 cm made of 2 mm-thick galvanized sheet metal is used,” the group explains. “The container mounts to the back of the PV panel and is coated with a silicone cling to prevent potential leakage when the PCM is fully molten.”
The academics measured the temperature distribution on the front surface of the PV panels in different sections using an infrared camera. During the experiment, they observed that, for all PCM thicknesses, increasing the angle of panel inclination reduces the surface temperature. “
“When the PV-PCM panel is installed at an angle of 15 degrees, the highest temperature distribution on the panel surface is recorded, while the lowest temperature is recorded for the solar panel surface with a tilt angle of 30 degrees”, they stressed. "This is likely because the energy flow within the PCM due to convection is very low when the tilt angle is small."
The cooled panel, when installed at a 30 degree tilt angle, achieved 15.8% higher energy efficiency than the non-cooled reference module.
“Changing the tilt angle from 15 degrees to 30 degrees improves the electrical efficiency of the 3 cm thick PV PCM by 7.4%,” the scientists stated. “Lastly, the use of PCM with a thickness of 3 cm increases the electrical efficiency of the PV-PCM panel by 14.4% compared to the reference PV panel.”
The scientists did not provide information on the cost of the proposed technology or its applicability to commercial production. They described the passive cooling technique in “Performance enhancement of PV panels using phase change material (PCM): An experimental implementation”, recently published in Case Studies in Thermal Engineering . |
