A Spectrum of Efficiency: Solar Skylight Illuminates the Future

Deep in the heart of Silicon Valley, an office building home to Google is about to become a prototype for a cleantech product that’s capable of harvesting the sun’s power in a whole new way.

The product in question is EnFocus Engineering’s Diamond-Power panel — a high-tech module that’s one part skylight, one part solar panel.

Offering building occupants a real alternative to artificial lighting, the Diamond-Power panel can control the sun’s power more efficiently than any skylight on the market while utilizing the sun’s full range of light better than the average solar cell.

“In many situations people have plenty of daylighting, but they don’t switch the electrical lights off so there’s no savings,” says EnFocus’ President and Chief Technology Officer Jason Lu. “The point of our product is to provide a good lighting source so people actually can leave their electrical lights off.”

The Power of Daylight

Even when it’s not being used to create power, sunlight still has an abundance of potential. After all, what better source of free, nonpolluting lighting is there than natural daylight? Plus, there are tangential benefits: studies have shown students perform better, shoppers stay longer and buy more, and workers tend to be more productive.

Still, streaming sunlight into a building can lead to a host of cleantech conundrums. Solar heat gain is the primary one, and it’s why many glass-walled office buildings need air conditioning even in the winter.

“What this system does is take that hot light and efficiently transport its power to the grid,” explains Stan Sutton, President of Inland Metal Technologies, a provider of the skylight’s materials as well as an investor in the company. “What you get as a byproduct of it all is light that isn’t directly from the sun. This means the light coming through the skylight is cool. One advantage you have is you’re not adding heat load to the building.”

A second advantage is that the remaining spectrum of light is similar to what you’d experience standing under a tree on a sunny day — there’s plenty to read by, but it’s not hot and glaring.

“The reason the light is better distributed is that we select a portion of the sunlight that is already diffused,” he explains. “It’s much more comfortable, and also it doesn’t change that much when you’re under a cloud.”

The Ultimate Multitasker

Its ability to make the full spectrum of light useful is what makes the Diamond-Power panel stand out in the realm of cleantech. “We’re using what is typically the waste light that photovoltaic technology can’t use well,” Lu says.

Using triple junction solar cells, the panel captures roughly 80 percent of sunlight, converting close to 40 percent into power while allowing 20 percent of waste light into the building for illumination.

These highly efficient cells, coupled with the glass and the aluminum structures that hold it together, make the Diamond-Power skylight quite the multitasker in solar power use.

“With the solar skylight, what you have is daylight passed through — and it’s not glaring, it’s not hot,” Sutton explains. “And because it’s putting power back into the grid, it’s offsetting the cost of consuming the power for artificial [lighting]. You’re attacking both sides of the equation. You’re powering up the grid a little bit, and you’re also reducing the heat load, thus consuming less power from the grid.

Lu points out that using daylight as interior lighting first is actually the most efficient use of solar energy there is.

“Normally when energy is converted into electricity, we lose a lot of energy in that process,” Lu points out. “Conversion, unfortunately, is low-efficiency. And when you use electrical lighting, you have to convert that power back into light. That process is also, unfortunately, very inefficient.

“If you look at it that way, when we directly use sunlight, we are actually using the light much more efficiently than electrical light.”

Designer Style

Although traditional skylights present myriad cleantech challenges, they’re still a favorite for many businesses due in part to their visual appeal. There’s hardly a high-end hotel that doesn’t have a glass atrium; newer government buildings sport them; even shopping malls have enough foresight to know shoppers would like a patch of sun here and there as they stroll through.

“Humans in general do better in daylight — we are an animal that needs the blue light of daylight,” Sutton remarks. And certainly, there is an element of beauty associated with the look of a skylight and simply getting that sunshine from the outside into the inside that all the physics and chemistry and engineering out there might never be able to quite pin down.

The Diamond-Power skylight antes up on this quotient, too.

“We were at the annual solar show in San Francisco, Semicon, and we had probably 500 people come by,” Sutton says. “The comment most everyone had is that this is a beautiful piece of sculpture.”

Says Sutton, “It’s highly attractive; it’s cool-looking. It has an aesthetic and it doesn’t need to be hidden or covered up. One of the reasons Google liked it is the aesthetics. People look at it and say it looks awesome.”

Illustration by Chaz Russo.

Layla Bellows is a writer and editor based in Atlanta. She focuses on sustainability in the built environment, including materials and design, as well as its relationship to renewable energy and resources.

This article was originally published on ecomagination and was republished with permission.

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