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A global research group has designed a novel cooling system for photovoltaic modules based on multiple cooling sources. The proposed system was able to reduce the temperature of a photovoltaic system up to 16.7ºC and increase energy production by more than 9%.
An international research team has designed a novel cooling system for photovoltaic modules that includes a phase change material (PCM), heat dissipating fins and water. The experimental system uses passive cooling, since it takes advantage of the latent heat of fusion of the PCM and the latent heat of evaporation of water.
PCMs can absorb, store and release large amounts of latent heat in defined temperature ranges. They have often been used in research for cooling photovoltaic modules and heat storage.
“The drawback of the PV-PCM system is mitigated by the use of heat dissipation fins, which efficiently extract heat from the PCM. Meanwhile, water continues to be used to accelerate the heat transfer process through energy storage and evaporation,” the researchers explain.
In the article “ An experimental investigation on coalescing the potentiality of PCM, fins and water to achieve sturdy cooling effect on PV panels ” cooling in photovoltaic panels), published in Applied Energy , the system prototype consists of a 5 W polycrystalline photovoltaic panel embedded with PCM HS 29 about 0.02 m thick.
PCM HS 29, which has a melting temperature of 29ºC, was chosen based on the location and thermal characteristics of the system. A 21 cm × 21 cm flat plate of heat-dissipating fins is adhered to the bottom surface of the PCM. The system is placed inside a plastic container, with 3.3 liters of water covering the fins.
The system was compared to a reference 5W polycrystalline PV panel without cooling. The experiment was conducted in the southern Indian city of Madurai in early October 2020. The electrical, thermal and efficiency characteristics were measured daily from 9 a.m. to 5:30 p.m. 30 minute intervals. Using a series of equations, some of the results were scaled up to a 1 MW large-scale PV system.
According to the research team, the daily power in W of the proposed configuration was 8.12% and 9.39% higher than that of the reference panel. Furthermore, the maximum power obtained with the cooled panel was 20.25% higher than that of the reference panel.
“The output power of the reference PV panel ranges between 2,579 W and 3,062 W on October 3, while it ranges between 2,785 W and 3,538 W on October 4,” the researchers noted. “On the other hand, the power output of the proposed configuration ranges between 2,538 W and 3,336 W on October 3, and between 2,880 W and 3,864 W on October 4.”
On average, the novel system helped reduce panel temperature by 10.14ºC. The greatest temperature difference, 16.7 ºC, was obtained at 10:30 a.m. on October 4. When it was expanded to a 1 MW plant, scientists found that lowering the temperature extended its useful life from 25 to 31 years.
“The proposed photovoltaic cooling scheme shows an additional CO2 reduction of 9.4% compared to normal solar photovoltaics,” the researchers add. “With the proposed cooling technique, a CO2 reduction of 2,130.578 tons can be achieved using a 1 MW solar photovoltaic.” They also added that the cooling strategy saves 9.4% energy per day, which, scaled to a large plant, represents 366.5 MW per year.
Regarding efficiency in relative terms, the researchers observed that the proposed system improved it by 20.3% on the first day and 13% on the second. However, the average efficiency improvement ranged from 0.78% to 1.08%.
“The designed cooling system can be used for residential photovoltaic solar panels,” the academics conclude. “This pilot study can also be equipped with a water heat collection system to form a PV-T system. “Furthermore, this research paves the way to explore the feasibility of employing this cooling approach in floating panels, as they float in motionless bodies of water.”
The research group is made up of scientists from the Australian University of Queensland, the American University of California in Los Angeles (UCLA) and the Thiagarajar School of Engineering in Madurai (India). |
