The device is a solar harvester on top and radiative cooler on the bottom. Shanhui Fan says the goal is to figure out how to make solar cells more efficient so it's easier for the two technologies to share roof space. Fan states, "We think we can build a practical device that does both things."
The team's article, "Simultaneously and Synergistically Harvest Energy from the Sun and Outer Space", was published November 8, in Joule. It describes how their device is able to simultaneously harvest energy from the sun, and dispel heat from the building, addressing two of the most sought after energy needs.
The sun-facing layer of the device is nothing new. It's made of the same semiconductor materials that have long adorned rooftops to convert visible light into electricity. The novelty lies in the device's bottom layer, which is based on materials that can beam heat away from the roof and into space through a process known as radiative cooling.
In radiative cooling, objects – including our own bodies – shed heat by radiating infrared light. That's the invisible light night-vision goggles detect. Normally this form of cooling doesn't work well for something like a building because Earth's atmosphere acts like a thick blanket and traps the majority of the heat near the building rather allowing it to escape, ultimately into the vast coldness of space. Fan's cooling technology takes advantage of the fact that this thick atmospheric blanket essentially has holes in it that allow a particular wavelength of infrared light to pass directly into space. In previous work, Fan had developed materials that can convert heat radiating off a building into the particular infrared wavelength that can pass directly through the atmosphere. These materials release heat into space and could save energy that would have been needed to air-condition a building's interior. That same material is what Fan placed under the standard solar layer in his new device.
The researchers believe they can build a device that is able to both harvest solar and create The team is now designing solar cells that work without metal liners to couple with the radiative cooling layer.
Read article from the theverge.com
Excerpts from Stanford News, Stanford researchers develop a rooftop device that can make solar power and cool buildings, November 2018.