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The hybrid system has a cooling power of 63.8 W/m2 and a photovoltaic power of 159.9 W/m2. According to its creators, the cooling capacity provided by the system can be used in buildings or refrigerators.
Researchers at Pennsylvania State University (United States) have manufactured a prototype of a hybrid energy system that integrates solar cells for energy production and radiative cooling for external cooling purposes.
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.
“The photovoltaic electricity generated in the dual system can be used to store energy or converted into alternating current using an inverter,” the scientists explain. “The cold achieved in the transparent radiative cooler can be used to cool air or liquid, which can be driven by a fan or pump, respectively, to interface with thermal systems and save energy.”
The proposed system simultaneously achieves daytime subambient radiative cooling and photovoltaic electricity generation from the same area. “At night and during the day, the radiative refrigerator works as a natural air conditioner 24/7,” explains Pramit Ghosh, lead author of the research. “Even on a hot day, the radiative cooler is cool to the touch.”
The system consists of a transparent low-iron glass radiative cooler capable of transmitting 91% of sunlight, a visibly transparent opaque infrared layer, and a 125 mm × 125 mm interdigitated back contact (IBC) photovoltaic cell supplied by the American manufacturer Maxeon. The radiative cooler does not have direct radiative heat exchange with the photovoltaic device.
Scientists tested the system in an outdoor environment at the Sustainability Expertise Center at Penn States Sustainability Institute and found that it could exceed the electricity savings of a bare solar cell by up to 30%. “We demonstrate simultaneous sub-ambient daytime radiative cooling with a temperature reduction of 5.1 °C under solar irradiance of about 1,000 W/m2 and solar power generation of up to 159.9 W/m2 from the same area,” they explained. “Experimentally, we achieved an ambient cooling power of 63.8 W/m2 under maximum solar irradiation and an ambient cooling power of 87.0 W/m2 at night.”
The research group also assumed that the energy generated by the solar cell would be used to power a cooling system with a coefficient of performance (COP) of 2.8, and found that the cooling power of the hybrid system would be five times greater than the daytime cooling power achieved in conventional solar reflection radiative coolers.
“Our work highlights the great opportunity to simultaneously harness the sun and the cold universe to obtain renewable energy at a level that can exceed the performance of using either resource separately,” the study concludes.
The system is described in the study “ Simultaneous subambient daytime radiative cooling and photovoltaic power generation from the same area ,” recently published in Cell Reports Physical Science .
Radiative cooling has recently been applied to the cooling of solar panels by researchers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, Shanghai Jiao Tong University (China), Purdue University in the United States, the Institute Catalan Institute of Nanoscience and Nanotechnology and the Institute of Materials Science of Spain, and the University of Science and Technology of Jordan and the Australian College of Kuwait, among others |
