A research team in India developed a passive cooling method for solar panels using a thin, stagnant layer of seawater placed over the module surface. Tests showed that while a thick layer of water greatly reduced energy production, a thin layer of 5 mm reduced module temperatures and increased daily energy generation by as much as 8.86%.
A research team led by the Indian Institute of Petroleum and Energy (IIPE) has developed a new passive evaporative cooling system with solar panels that uses a layer of still seawater over a horizontally oriented module.
“Full or partial immersion of PV modules in water for cooling can cause quality deterioration and corrosion of module frames, necessitating the need for additional protection for the module junction box,” said corresponding author H. Sharon. pv magazine. “That is why we propose a concept where seawater remains stationary above the module, while avoiding submersion of frames and the junction box. In addition, water circulation is also avoided. The concept is safe, economical and has less impact on the environment.”
This cooling technique was tested experimentally against an uncooled reference module and with varying seawater layer thickness.
For their research, the group used a 10 W polycrystalline module with a surface area of 0.105 m2. Four clear window glass strips, each 0.003 m thick and 0.03 m high, were placed along the inner perimeter of the module using silicone adhesive, creating space for seawater. The salinity of the seawater was 30.00 PPT with a pH value of 8.04. The thickness of the seawater layer was 30 mm, 5 mm or 4 mm.
“The experiments were conducted on the terrace of the IIPE, Visakhapatnam, India, for four consecutive days in October 2023,” the team said. “In this work, no pumps were used and the seawater was manually poured over the Cool PV module just before the start of each day’s experiments. At the end of each day’s experiment, the unevaporated water over the module was discarded and the experiment was resumed the next day with a fresh batch of seawater. Each experiment lasted from 10am to 3pm each day and all essential readings were recorded manually every 30 minutes and were used for analysis.”
Image: Indian Institute of Petroleum and Energy (IIPE), Unconventional Resources, CC BY 4.0
On day 1, when testing the module with 30 mm of seawater, the average solar radiation intensity was 602.0 W/m2 and the ambient temperature was 30.8 C. On day 2, the layer had a thickness of 4 mm, while the average solar radiation intensity was 555.0 W/m2 and the ambient temperature was 30.5 C. On days 3 and 4, the thickness was 5 mm, the radiation was 781.0 C. W/m2 and 631.0 W/m2, and the temperatures were 31.8 C and 31.5 C, respectively.
The Cool PV module with an initial seawater layer of 30.0 mm was found to generate 42.2% less daily energy than the reference module, because the thick water layer significantly reduced light transmission. In contrast, the module with a 5.0 mm seawater layer produced approximately 2.57–8.86% more daily energy than the reference module.
Image: Indian Institute of Petroleum and Energy (IIPE), Unconventional Resources, CC BY 4.0
The scientists also found that Cool PV had daily average operating temperatures approximately 7.6 C, 8.0 C and 8.0-10.0 C lower than those of the reference module, for thicknesses of 40 mm, 4 mm and 5 mm respectively. In addition, salt deposition was observed on the Cool PV module, with a 4.0 mm thick seawater layer due to dehydration caused by rapid evaporation, aided by relatively low relative humidity and strong wind speed. As a result, daily energy production decreased by 12.14% compared to the reference module.
“We plan to conduct more experimental studies in the near future under different climatic conditions with changing seawater depths and salt concentrations to better understand the thermal management capability of the cool PV module and its year-round performance,” concludes Sharon.
The passive cooling technology was described in “Cooling of photovoltaic modules with a layer of stagnant seawater – Experimental researchy,” published in Unconventional resources. Researchers from the Indian Institute of Petroleum and Energy (IIPE), India’s Andhra University and Spain’s University of Jaén participated in the study.
This content is copyrighted and may not be reused. If you would like to collaborate with us and reuse some of our content, please contact: editors@pv-magazine.com.
Popular content
