Although the idea in itself isn’t new, a new solar harvesting device created at the Center for Nanotechnology and Molecular Materials at Wake Forest can use sunlight to convert it in both electricity and heat for the home, in a more efficient manner.
Infrared light makes up the most part of the light spectrum, but the glitch in today’s solar panels is that they can’t really harvest it for direct electricity generation, because of the long wavelengths involved. Thus, a standard solar panel misses about 75% of the incoming energy, and some of them, concentrated solar cells, need cooling to prevent damage to the silicon substrate that favors the energy conversion.
“I’s a systems approach to making your home ultra-efficient because the device collects both solar energy and heat,” said David Carroll, Ph.D., director of the Center for Nanotechnology and Molecular Materials at Wake Forest. “Our solar-thermal device takes better advantage of the broad range of power delivered from the sun each day.”
The device developed at Wake Forest has a cylindrical shape and can capture sunlight more efficiently throughout the entire daytime, not only at noon, when other flat panels do their best.
A clear cylindrical tube 5 millimeters in diameter contains an specially-designed oil treated with a proprietary dye, which captures the infrared part of the spectrum and transfers is to heat exchangers, which are in turn connected to the home’s heating system (or may as well store it in molten salts for delayed usage, etc).
The back part of the cylinder contains a thin film polymer that acts as an electricity-generating solar cell (PV panel). The researchers say their solar thermal device can harvest the sun’s power with up to 30 percent efficiency (I don’t know whether they refer to the entire energy the device captures, including the heat-derived one, or just the electricity).
A one square-meter prototype is currently being built, but there’s a long way to go until they’ll be able to license and commercialize the technology.
Just for reference, Solyndra, a U.S.-based company, already manufactures cylindrical photovoltaic solar panels with great results (no thermal harvesting, though).