A Rooftop Device That Can Make Solar Power and Cool Buildings
November 9, 2018 | Stanford UniversityEstimated reading time: 2 minutes
Stanford electrical engineer Shanhui Fan wants to revolutionize energy-producing rooftop arrays.
Today, such arrays do one thing – they turn sunlight into electricity. But Fan’s lab has built a device that could have a dual purpose – generating electricity and cooling buildings.
Image Caption: Professor Shanhui Fan and postdoctoral scholar Wei Li atop the Packard Electrical Engineering building with the apparatus that is proving the efficacy of a double-layered solar panel. The top layer uses the standard semiconductor materials that go into energy-harvesting solar cells; the novel materials on the bottom layer perform the cooling task. (Image credit: L.A. Cicero)
“We’ve built the first device that one day could make energy and save energy, in the same place and at the same time, by controlling two very different properties of light,” said Fan, senior author of an article appearing Nov. 8 in Joule.
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.
Holes in the Blanket
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.
Zhen Chen, who led the experiments as a postdoctoral scholar in Fan’s lab, said the researchers built a prototype about the diameter of a pie plate and mounted their device on the rooftop of a Stanford building. Then they compared the temperature of the ambient air on the rooftop with the temperatures of the top and bottom layers of the device. The top layer device was hotter than the rooftop air, which made sense because it was absorbing sunlight. But, as the researchers hoped, the bottom layer of the device was significant cooler than the air on the rooftop.
“This shows that heat radiated up from the bottom, through the top layer and into space,” said Chen, who is now a professor at the Southeast University of China.
What they weren’t able to test is whether the device also produced electricity. The upper layer in this experiment lacked the metal foil, normally found in solar cells, that would have blocked the infrared light from escaping. The team is now designing solar cells that work without metal liners to couple with the radiative cooling layer.
“We think we can build a practical device that does both things,” Fan said.
Suggested Items
Indium Corporation, Industry Partners to Showcase Products “Live@APEX”
03/26/2024 | Indium CorporationIndium Corporation®, in cooperation with its industry partners, will feature its proven solder solutions live on the show floor throughout IPC APEX Expo from Apr. 9‒11 in Anaheim, Calif., U.S.
Dymax Will Exhibit Light-Cure Solutions for Today’s Electronics at IPC APEX 2024
03/26/2024 | DymaxDymax, a leading manufacturer of rapid and light-curing materials and equipment, will exhibit at the IPC APEX EXPO 2024 in Anaheim, CA, April 9-11.
Ventec to Launch New Bondply Dielectrics and Value-Added Services at IPC APEX EXPO 2024
03/26/2024 | Ventec International GroupVentec International Group is to reveal new products for advanced signal integrity and thermal performance, and introduce services, during IPC APEX EXPO 2024, April 9-11 on booth # 4309.
Electra Polymers Ltd Expands Manufacturing Capacity, Invests in New Facilities and Talent
03/26/2024 | Electra Polymers LtdElectra Polymers Ltd, a leading provider of coatings for the electronics industry, proudly announces a significant expansion of its manufacturing capacity for inkjet materials. The company is making substantial investments in new facilities, talent acquisition, and cutting-edge laboratory equipment to meet the increasing demand for high-performance functional inkjet materials in the market.
I-Connect007 Editor’s Choice: Five Must-Reads for the Week
03/22/2024 | Nolan Johnson, I-Connect007This week's news feed contains a bunch of big money items, as well as some interesting industrial and technology puzzles to be solved. There’s even some down-home people news from the Dallas SMTA conference held this week. Don’t overlook the latest issue of PCB007 Magazine, either. The topic is sustainability, which is becoming an ecosystem of its own.