A group of researchers rethinks the stained glass window for an energy-conscious future.
There’s been a lot of talk about how much light enters buildings: depending on the time of the day or year, it can make a huge difference in their energy efficiency. For most people, this has simply led to a lot of tedious curtain-opening and closing and stuffing rugs and towels under doors to keep climate-controlled air from flowing in or out. What if that sunshine could be harnessed by ordinary household items like windows? Such a novel solution was recently discovered by researchers at the University of Michigan, who have found an alternative to the big, shiny, black solar panels that live on rooftops and give architecture critics headaches.
The colorful panels devised by professor of electrical engineering Jay Guo and his team could find their place in a variety of corners of the home. They resemble stained glass, but don’t be fooled – dyes and microstructures can blur the image behind them, leading to less light absorption. Instead, the glass is actually engineered to transmit certain wavelengths of light. This is done by varying the thickness of the semiconductor layer of amorphous silicon in the cells. In a sample piece that was made to resemble the American flag, for example, the blue parts were 6 nanometers thick and the red parts were 31 nanometers, reflecting the wavelengths of the light they’re meant to absorb.
The resulting material isn’t as efficient as the glass found on solar panels, achieving only 2 or 3 percent efficiency – a meter-square piece would power fluorescent lightbulbs or small electronic gadgets. A state-of-the-art organic cell has 10 percent efficiency. Though some of this discrepancy is inherent in the cells’ design – black solar panels are black in order to absorb all wavelengths of light, and these panels instead use those frequencies to dazzle our eyes – the idea revolutionizes how we might think of solar energy, and could one day have a wide enough distribution in the home to make up for the inefficiencies of individual pieces. The unchanging colors of the material no matter what angle it’s seen from also means that the panels wouldn’t have to pivot the way traditional solar panels do.
This is especially encouraging news considering the rising popularity of urban living. “Today, solar panels are black and the only place you can put them on a building is the rooftop. And the rooftop [of] a typical high-rise is so tiny!” said Guo. The paper about the material is titled “Decorative power generating panels creating angle insensitive transmissive colors” and was funded by the National Science Foundation.
Sources, Images: University of Michigan Engineering