Look at any downtown skyline of a major city and what do you see? Glass - lots and lots of glass.
What if that glass could produce energy? There is a revolution underway to transform windows and skylights into energy that will start in commercial buildings and eventually reach residential homes.
Windows might seem like an odd place to embed solar cells — after all, they are designed to let sunlight shine through, not capture it. Windows also receive less direct sunlight than rooftops.
But because windows take up so much space on buildings, especially in cities, they're prime real estate for solar technologies.
Designers are trying to figure out how windows can produce energy while being clear enough to see through — no one wants solar energy if they're sacrificing the view.
One approach is to capture only the parts of sunlight humans cannot see. Ubiquitous Energy, a California-based MIT spinout, has designed solar cells that appear transparent because they only absorb ultraviolet and infrared light.
Solar cells that leave visible light untouched won't be as efficient as traditional solar panels because solar materials like silicon capture all parts of the light spectrum. Researchers believe that even though they may be sacrificing some of the electricity potential, it is made up for because the coating required to make it work will be transparent.
Ubiquitous Energy wants to apply their thin, photovoltaic film to every surface, from home windows to handheld gadgets, covering screens on phones and laptops so they can become solar-powered. The company is currently testing the technology.
Onyx Solar installed a 575-square-foot skylight with transparent glass solar panels at the Bejar Traditional Market in Spain. The company also created a canopy dotted with color-changing skylights for Miami's American Airlines Arena, as well as photovoltaic shade canopies for the Union City train station in California's Bay Area.
Adding solar cells to the environment comes with challenges. They may end up shaded by surrounding buildings or mounted at an angle that allows less sunlight to reach them. But researchers feel these are challenges that will be solved within a few years.