The hotter solar cells become, the less efficient they are at converting sunlight to electricity, a problem that has long vexed the solar industry. Now, Stanford engineers have developed a transparent overlay that increases efficiency by cooling the cells even in full sunlight.
Stanford engineers have invented a transparent material that improves the efficiency of solar cells by radiating thermal energy (heat) into space.
Every time you stroll outside you emit energy into the universe: Heat from the top of your head radiates into space as infrared light.
Now three Stanford engineers have developed a technology that improves on solar panel performance by exploiting this basic phenomenon. Their invention shunts away the heat generated by a solar cell under sunlight and cools it in a way that allows it to convert more photons into electricity.
The work by Shanhui Fan, a professor of electrical engineering at Stanford, research associate Aaswath P. Raman and doctoral candidate Linxiao Zhu is described in the current issue of Proceedings of the National Academy of Sciences.
The group’s discovery, tested on a Stanford rooftop, addresses a problem that has long bedeviled the solar industry: The hotter solar cells get, the less efficient they become at converting the photons in light into useful electricity.
The Stanford solution is based on a thin, patterned silica material laid on top of a traditional solar cell. The material is transparent to the visible sunlight that powers solar cells, but captures and emits thermal radiation, or heat, from infrared rays.
“Solar arrays must face the sun to function, even though that heat is detrimental to efficiency,” Fan said. “Our thermal overlay allows sunlight to pass through, preserving or even enhancing sunlight absorption, but it also cools the cell by radiating the heat out and improving the cell efficiency.”
A COOL WAY TO IMPROVE SOLAR EFFICIENCY
In 2014, the same trio of inventors developed an ultrathin material that radiated infrared heat directly back toward space without warming the atmosphere. They presented that work in Nature, describing it as “radiative cooling” because it shunted thermal energy directly into the deep, cold void of space.
In their new paper, the researchers applied that work to improve solar array performance when the sun is beating down.
The Stanford team tested their technology on a custom-made solar absorber – a device that mimics the properties of a solar cell without producing electricity – covered with a micron-scale pattern designed to maximize the capability to dump heat, in the form of infrared light, into space. Their experiments showed that the overlay allowed visible light to pass through to the solar cells, but that it also cooled the underlying absorber by as much as 23 degrees Fahrenheit.
For a typical crystalline silicon solar cell with an efficiency of 20 percent, 23 F of cooling would improve absolute cell efficiency by over 1 percent, a figure that represents a significant gain in energy production.
The researchers said the new transparent thermal overlays work best in dry, clear environments, which are also preferred sites for large solar arrays. They believe they can scale things up so commercial and industrial applications are feasible, perhaps using nanoprint lithography, which is a common technique for producing nanometer-scale patterns.
“That’s not necessarily the only way,” said Raman, a co-first-author of the paper. “New techniques and machines for manufacturing these kinds of patterns will continue to advance. I’m optimistic.”
Zhu said the technology has significant potential for any outdoor device or system that demands cooling but requires the preservation of the visible spectrum of sunlight for either practical or aesthetic reasons.
“Say you have a car that is bright red,” Zhu said. “You really like that color, but you’d also like to take advantage of anything that could aid in cooling your vehicle during hot days. Thermal overlays can help with passive cooling, but it’s a problem if they’re not fully transparent.”
That’s because the perception of color requires objects to reflect visible light, so any overlay would need to be transparent, or else tuned such that it would absorb only light outside the visible spectrum.
“Our photonic crystal thermal overlay optimizes use of the thermal portions of the electromagnetic spectrum without affecting visible light,” Zhu said, “so you can radiate heat efficiently without affecting color.”
The Latest on: Photonic crystal thermal overlay
via Google News
The Latest on: Photonic crystal thermal overlay
- Camera Sees Electromagnetic Interference Using An SDR And Machine Visionon January 28, 2020 at 4:00 pm
This heat-mapping EMI probe will answer that question, with style. It uses a webcam to record an EMI probe and the overlay a heat map of the interference on the image itself. Regular readers will ...
- Hackaday Prize Entry: Raspberry Pi Thermal Imagingon January 28, 2020 at 4:00 pm
mlxd is a driver daemon for the module, and mixview.py is a Python graphical overlay script that places the thermal array output over the camera output. A run-through of the device and its results ...
- AR Headset and Glasseson January 26, 2020 at 4:00 pm
AR glasses and headsets provide the user with the ability to overlay virtual objects in the user’s direct field of view through transparent glass. Unlike VR (Virtual Reality) where the user’s vision ...
- Well-designed substrates make large single crystal bi-/tri-layer graphene possibleon January 23, 2020 at 7:15 am
Researchers of the Center for Multidimensional Carbon Materials (CMCM) within the Institute for Basic Science (IBS, South Korea) have reported in Nature Nanotechnology the fabrication and use of ...
- UCSD creates flexible photonic crystal from liquid thin-film metasurfaceon January 6, 2020 at 1:47 pm
Shimon Rubin and Yeshaiahu Fainman from the Ultrafast and Nanoscale Optics Group at the University of California San Diego have shown how it might be possible to create a flexible yet durable photonic ...
- Flexible photonic crystal from liquid thin-film metasurfaceon January 2, 2020 at 9:10 am
Controlling the fabrication of photonic crystals is more difficult. Each tiny structure has to be manufactured and precisely replicated and placed. Once made, a photonic crystal is unchanging ...
- Azobenzene-containing polymers for photonic crystal materialson March 7, 2017 at 4:00 pm
Photonic crystals have attracted great attention because of their potential applications in optical materials. When an optically birefringent liquid crystal is incorporated in photonic crystals ...
- Photonic Crystals Keep Solar Cells Cool While Still Catching Lighton May 5, 2016 at 7:05 am
About the Presentation The presentation, “Radiative cooling of solar absorbers using a transparent photonic crystal thermal blackbody,” by Linxiao Zhu, Aaswath P. Raman and Shanhui Fan will ...
- Scientists develop transparent cooling coating for solar cellson September 21, 2015 at 2:27 pm
That's because the perception of color requires objects to reflect visible light, so any overlay would need to be transparent, or else tuned such that it would absorb only light outside the visible ...
- Capture of a terahertz wave in a photonic-crystal slabon July 19, 2014 at 5:00 pm
Here, we utilize the in-plane resonance of a thin, planar photonic-crystal slab with negligible absorption loss to successfully demonstrate and visualize terahertz-wave trapping. We artificially ...
via Bing News