| Work Detail |
Developed by an American-Saudi research group, the novel technique uses two mirrors tilted 45 degrees on either side of a photovoltaic module. On the rear side, a selective spectral reflector allows thermal radiation to be directed towards the sky, while preventing the rear part of the module from heating up due to scattered sunlight.
An international research team has developed a novel radiative cooling method for vertical solar panels that uses V-shaped mirrors adapted for thermal management on both sides of the photovoltaic panels.
Radiative cooling occurs when the surface of an object absorbs less radiation from the atmosphere and emits more. As a result, the surface loses heat and a cooling effect is achieved without the need for energy.
“Radiative cooling facilitates the dissipation of heat from a terrestrial body to outer space and the ambient environment through thermal radiation,” the academics explain. “This cooling strategy is especially suitable for hot PV panels, as they can take full advantage of the atmospheric transparency window in the range of 8-13 mm, and even beyond, due to their operating temperatures being significantly higher than “ambient temperature.”
The novel cooling method is called v-PV and uses two mirrors inclined at 45 degrees on both sides of a photovoltaic module. An aluminum mirror has been used on the front that allows incident sunlight to be reflected onto the module, while thermal radiation from the front can be directed to the sky. On the back of the panel, a selective spectral reflector was installed, which allows thermal radiation to be directed towards the sky, while preventing the back of the module from heating up due to scattered sunlight.
To test the proposed method, the scientists carried out three experiments: one under laboratory conditions, another in Buffalo (New York) and a third in Thuwal (Saudi Arabia).
In the laboratory experiment, they used the v-PV with an 18 V polycrystalline module under solar illumination and on a 1,000 O resistor to simulate a realistic operating scenario. “Double-sided radiative cooling can significantly reduce the operating temperature of a photovoltaic module by up to 10.6ºC, leading to an increase in output voltage of 0.80V,” they found.
They then conducted a field test in New York with the same system configuration. They compared the performance of a cooled module with that of a panel without the selective spectral mirror on the rear (sv-PV) and that of a horizontal reference panel without mirrors (h-PV).
“At 12:40, when the solar irradiance reached its peak, the v-PV recorded a temperature of 59.6 ºC, which was still 9 ºC lower than that of the h-PV system (68.6 ºC) and 4 .7 ºC lower than that of the sv-PV module (64.3 ºC)”, they explained. “These different operating temperatures affected production. The v-PV achieved a Voc of 18.49 V, outperforming the h-PV by 0.59 V (17.9 V) and the sv-PV system by 0.20 V (18.29 V).”
The group highlighted that, due to its vertical orientation and its V-shaped emitting mirror, the v-PV system receives greater solar irradiance than the h-PV at latitudes greater than 46 degrees. “The v-PV design can achieve significantly higher production in high-latitude regions such as Europe and Canada,” they noted.
At the Saudi proving ground, researchers tested a modified version of the system. They adjusted the installation angles of the solar panels to 22 degrees and the selective reflectors on the rear to 0 degrees. The front mirror remained unchanged at 45 degrees.
The test showed that the surface temperature of the v-PV was 54.5ºC, compared to 54.7ºC for the h-PV and 55.7ºC for the sv-PV. This also translated into an improvement in power, as the different configurations reached maximum powers of 5.77 W, 4.94 W and 5.67 W, respectively. The conversion efficiency was 10.53% for v-PV, 10.31% for h-PV, and 10.41% for s-PV.
“When the solar irradiance collection efficiency of the solar panel was increased by 15% compared to a horizontally aligned photovoltaic module, the proposed v-PV system maintained a slightly lower operating temperature of 0.2 ºC, which corresponds to to an increase in maximum power output of 16.8%,” the scientists stated.
The novel cooling technology was presented in the study “ Radiative cooling for vertical solar panels ,” published in iScience by academics from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, as well as from the State University of New York at Buffalo and the University of Texas at Dallas (United States).
Radiative cooling was recently applied to the cooling of solar panels by researchers from Shanghai Jiao Tong University (China), Purdue University (United States), the Catalan Institute of Nanoscience and Nanotechnology and the Institute of Materials Science (Spain). , and the Jordan University of Science and Technology and the Australian College of Kuwait. |
