A hybrid energy system for heating, cooling and generating electricity
New concept exploits both the heat of the Sun and the coldness of outer space The post A hybrid energy system for heating, cooling and generating electricity appeared first on Physics World .
Researchers from the Karlsruhe Institute of Technology (KIT) in Germany and Stanford University in the United States have developed an innovative energy-collecting device capable of simultaneously cooling, generating electricity, and producing heat. The prototype features a radiative cooling layer that drops to 6.5°C below ambient temperature, while a solar collector generates electricity near 111°C.
Gan Huang, head of the Hybrid Solar Technologies lab at KIT, explains that this system could be installed on buildings’ roofs and facades to provide all three energy services at once. It could also benefit AI data centers requiring significant power and cooling simultaneously. With the increased heat in northern hemisphere summers due to climate change, there is a growing demand for air conditioning, which consumes a lot of electricity and releases large amounts of CO2.
Passive daytime radiative cooling (PDRC) offers a potential alternative, allowing objects to cool down during the day by exchanging heat with different temperature objects through thermal radiation.
The key to PDRC is reflecting sunlight strongly at solar spectrum wavelengths and emitting heat strongly in the long-wave infrared wavelengths where the Earth's atmosphere is more transparent to infrared radiation. While researchers have developed various PDRC materials, conventional systems cannot harvest both coldness from space and solar energy from the same surface.
In their new work published in Cell Reports Physical Science, the researchers created a hybrid PDRC and photovoltaic-thermal collector. The device's transparent emitting layer consists of a silica substrate coated with a silicone polymer, allowing sunlight to pass through while emitting heat as LWIR radiation. Beneath this layer, a Fresnel lens concentrates sunlight onto a gallium arsenide-based photovoltaic-thermal collector, generating electricity.
During outdoor experiments, the prototype achieved cooling up to 6.5°C below ambient temperature, an electrical power density of 60.6 W/m², and heated up to 110.8°C. The main challenge was ensuring the solar collector became hot while the radiative cooler stayed cool, which they achieved by concentrating transmitted sunlight on a smaller solar collector, reducing thermal interference between the hot and cold parts.
The team is now focusing on improving the system's efficiency, optical design, thermal management, and solar cell efficiency. Huang believes there are many exciting possibilities for a new generation of energy systems that can effectively manage both solar energy and coldness from outer space.
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