Solar panels have been used for some time; however, the materials they’re made of render them ineffective at converting half of the solar energy into usable electricity. MIT estimates that a typical home in the sun-filled state of Arizona requires five hundred square feet of solar panel space (assuming they’re at a 15% efficiency) to satisfy its energy requirements for the day. In winter, when it’s cold and gray, the same house will require eight61 square feet in Vermont. This is a lot of panels.
That’s why MIT researchers are working with a completely new method to convert sunlight, one that uses very high temperatures to increase efficiency. If it succeeds at a larger scale, it could result in dramatically more efficient solar panels in the future, possibly changing the solar energy industry.
“With our research, we are trying to address the fundamental limitations of photovoltaic energy conversion,” says David Bierman, one of the researchers leading the project.
The technology converts sunlight into heat and transforms it into light. The process employs a light concentrator known as an “absorber emitter” or “absorber-emitter,” with an absorbent layer composed of solid carbon nanotubes that convert the sun’s rays into heat. Suppose temperatures rise to 1,000° Celsius or more ( as hot as the lava from several volcanoes, for a hint). In that case, the emitting layer, made of photonic crystal, reflects the energy to the type of light solar cells can utilize.
An optical filter can reflect away all light particles not used in a process known as “photon recycling.” This boosts efficiency significantly and makes the cells nearly double as efficient as the standard.
Fittingly, the technology has been known as “hot solar cells.” The cells have been recently recognized as one of MIT Technology Review‘s ” 10 Breakthrough Technologies of 2017.” The magazine editors have put together this list each year since 2002. The technology of 2017 includes brain implants, self-driving vehicles, to cameras that take 360-degree selfies, which “will affect the economy and our politics, improve medicine, or influence our culture,” according to MIT Technology Review. “Some are unfolding now; others will take a decade or more to develop,” editors write. “But you should know about all of them right now.”
It is more advanced than conventional solar cells at a fundamental level. The semiconductor material in the standard solar devices, which are nearly always silicon, typically can capture light from the red to violet spectrum. That means the remainder of the range of sunlight is gone. Due to this fundamental flaw, solar cells only convert around a third of sunshine energy to electricity. This upper limit, or the highest theoretical effectiveness of any solar panel, is known as the Shockley Queisser limit. Solar panels for home use generally produce less energy than the Shockley-Queisser limit because the most efficient materials are costly. However, the high-temperature solar cells that have been in effect for more than 50 years might soon become the norm.
As of now, researchers have just an idea. Seeing these solar cells for sale could take ten years or more. The materials are so expensive that it is difficult to convert them into panels with the size required to be used commercially.
“We will need to solve a whole range of issues related to scaling-up the device to actually generate powers that are useful solutions for people and their problems,” Bierman says.
Bierman and his fellow collaborators working on his project Andrej Lenert Ivan Celanovic, Marin Soljacic, Walker Chan, and Evelyn N. Wang, hope they can surpass these limitations. They also hope to find a way to store excess warmth later. This could lead to renewable energy even on the bleakest winter day, even in Vermont.