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Malaysian scientists have tested bio-inspired coconut fiber to cool solar modules. The cooling system consists of a moist coconut pith encapsulated with a polyurethane sheet. It is placed on the back of the surface of a PV module and acts as a heat sink.
Researchers at Malaysia Pahang University have developed a novel passive cooling technique for solar modules that uses moist coconut fiber as a cooling agent.
“Our solution uses a bioinspired coconut fiber for thermal regulation,” researcher Sudhakar Kumarasamy explained to pv magazine . “It can be used for building-integrated photovoltaics (BIPV) systems on rooftops, ground-mounted plants, and agrivoltaics.”
The researchers described their findings in " Thermal and Electrical Performance of Uncooled, Nature-Cooled, and Photovoltaic Thermal Module ," recently published in the International Journal. of Photoenergy. The cooling system consists of a moist coconut pith encapsulated in a polyurethane sheet. It is placed on the back of the surface of a photovoltaic module to act as a heat sink.
“With the help of the coconut fiber, the water molecules directly come into contact with the rear surface of the PV module thanks to the high water retention capacity of the coconut fiber, which reduces the temperature of the rear surface of the PV module. module”, explain the scientists. “Next, the sensible heat will be absorbed by the water molecules present in the coconut fiber. Finally, when the water molecules have absorbed enough heat energy, they will act as a heat removal agent, evaporating through the perforations present in the encapsulation of the polyethylene sheet.”
The researchers compared the temperature behavior and performance of a PV module equipped with the system with that of a water-cooled photovoltaic-thermal (PVT) module. They found that the PV module with passive cooling had a maximum operating temperature of 44.6 ºC, while the PVT panel and a reference PV panel without cooling registered higher temperatures of 47.8 ºC and 57.2 ºC, respectively.
“By integrating wet coconut, the surface temperature of the PV module decreased by 22.03% and 23.46%, while the PVT system reduced the surface temperature of the PV module by 16.43%,” explained the scientists. “The maximum power point (MPP) for the coconut fiber passively cooled PV module, PVT system, and reference module is 24.21 W, 20.21 W, and 14.65 W, respectively.”
They claimed that the passively cooled PV module power output increased by 65.26%.
"The PVT system, however, only managed to increase power by 37.95%." “Convection moving water molecules away from the back of the PV module increases heat loss from the back surface and consequently from the front cover of the passively cooled PV module compared to the PVT system.”
The same research group also published in October 2021 an extensive review of all passive and cooling techniques applied to photovoltaics. The study examined active techniques such as air cooling, liquid cooling, forced water circulation, liquid immersion cooling, and water spray. Passive methods such as PCM cooling, heat pipes, heat sinks or fins and heat exchangers, microchannel heat exchangers, radiative sky cooling, nanofluid-based cooling, thermoelectric cooling, evaporative cooling and cooling by spectral filter. |
