KIT prototype turns one surface into a source of power, heat and cooling

In outdoor tests, a transparent surface at Karlsruhe Institute of Technology did three jobs at once: it generated electricity, produced heat and cooled itself. The prototype reached 6.5 °C below ambient temperature, delivered an electrical power density of 60.6 W/m² and produced temperatures of up to 110.8 °C for heat use.

The device combines solar energy with passive daytime radiative cooling, or PDRC—a way to lose heat by emitting infrared radiation into space without using power. Its transparent cooling layer is made from a silica plate coated with polydimethylsiloxane, a silicone polymer. Sunlight passes through it, while heat escapes through the “atmospheric window,” a range of wavelengths in which Earth’s atmosphere is especially transparent to thermal radiation.

Below that layer, a Fresnel lens concentrates the transmitted sunlight onto a much smaller photovoltaic-thermal collector. That collector makes electricity and heat. The arrangement addresses the system’s central conflict: the solar collector must become hot enough to harvest energy, while the radiative cooler must stay cold. Keeping the two components physically apart lets the prototype do both.

The work was led by Dr. Gan Huang’s team at KIT’s Institute of Microstructure Technology, with doctoral researcher Iván Alberto Cruz García as first author and collaboration from Stanford University professor Shanhui Fan. It builds on KIT research from 2024, which produced a transparent material capable of cooling buildings while transmitting daylight. The study, “Co-harvesting universe coldness and solar energy for tri-generation of cooling, electricity, and heating,” was published in Cell Reports Physical Science (2026), DOI: 10.1016/j.xcrp.2026.103492.

So what changes in practice? A roof or facade could eventually provide several energy services without dedicating separate surfaces to panels, thermal collectors and cooling equipment. The concept may be relevant to energy-intensive sites such as AI data centers, which need substantial electricity and cooling at the same time. These are envisaged applications, not uses demonstrated by the prototype. For now, however, this is a prototype: KIT says the next steps are to improve the optical design, thermal management and solar cells.