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South Korean scientists have developed a WD-ER cooling system that can reduce the operating temperature of a photovoltaic panel by up to 14.9ºC, with an average heat transfer coefficient of 64.1 W/m2.
A research team from Korea University has created a passive cooling system for solar panels that uses a water desorption process and an endothermic reaction dissolution process.
The method is similar to that of phase change materials (PCMs), which absorb, store, and release a large amount of latent heat in a specific temperature range, and are often used for research-level cooling of PV modules. . The system is cheap, consumes no power, and has self-healing properties, making it highly versatile.
“The proposed method does not consume energy and is made up of cheap materials, making it highly applicable,” the scientists say. "In addition, it can be used repeatedly, due to its self-healing characteristics."
The researchers describe the technique as an atmospheric water desorption refrigeration system that uses Zeolite 13X, a commercially available aluminum silicate material, to desorb water molecules producing a latent cooling effect. When heat is applied, water desorbs from the 13X Zeolite and dissolves ammonium nitrate (NxH4NO3) to induce cooling by endothermic reaction, giving rise to a reversible process that recovers overnight.
Water Desorption Driven Endothermic Reaction (WD-ER) Refrigeration System can absorb heat from solar radiation and desorb solvent, which generates secondary cold energy by dissolving solute. The cooling effect is achieved because the water adsorption capacity of 13X zeolite is inversely proportional to temperature, and water can dissolve more ammonium nitrate at higher temperatures.
The Korean team attached the WD-ER system to the back of a urethane-sealed solar cell to protect it from moisture. They coated the cell with 13X Zeolite particles and a negligible amount of polyvinyl, then saturated these particles with water and added a layer of NH4NO3 crystals to form a thin film.
The WD-ER system had an average effective heat transfer coefficient of 64.1 W/m2, and thermal images taken at 2 pm showed that the surface temperature of the PV cell with the WD-ER cooling unit it was 39-43 ºC, significantly lower than that of natural air cooling (51-56 ºC). The average temperature of the PV cell with WD-ER was reduced by 14.9 ºC.
The researchers suggest that this novel refrigeration system may outperform other refrigeration methods described in the literature, although they do not provide a detailed analysis of production costs or possible commercial applications.
They presented their findings in “ Self-recovering passive cooling utilizing endothermic reaction of NH4NO3/H2O driven by water sorption for photovoltaic cell, ” published recently. in Nature Communications. |
