Image sourced from: extremetech.com
Your home windows or electric car windows, or simply your smartphone, could easily turn into power generators thanks to transparent solar cells. At Ubiquitous Energy, MIT startup co-founded by researchers Barr, Lunt, Bulović, and Bart, they are continuing development work to optimize their transparent PVs. These new solar cells selectively absorb only infrared and ultraviolet light, which are invisible to the eye, while “visible light passes through the cells unimpeded, so our eyes don’t know they’re there” (Stauffer).
This is very innovative as scientifically, a transparent solar panel is something of an oxymoron. Solar cells make energy by absorbing sunlight, but, by definition, all of the light would pass through a transparent material. This is why previous versions of transparent cells have only been partially transparent (Lendino). Hence, the challenge of a solar cell that is actually transparent and actually generating energy. “We use a combination of molecular engineering, optical design, and device optimization—a holistic approach to designing the transparent device,” says Barr (Stauffer).
Current versions of the team’s cells transmit more than 70% of the visible light, which is within the range of tinted glass now used in the windows of buildings. But their power-conversion efficiency is low—only about 2%. Getting to a higher efficiency comparable to commercial PVs is the challenge, but the researchers are optimistic. Lunt says that, by simply “stacking” their transparent solar cells, they could potentially reach an efficiency of 10% while still maintaining the ability to transmit light (Stauffer).
Besides the aesthetics that come with transparency, one big advantage of transparent PVs is significant cost savings during installation:
“The PV layer would be encapsulated between the panes, well protected from weather, window washing, and other outside threats. More important, the glass, framing, and installation costs would be included in the overall cost of the construction project—the same with or without the PV coating. In contrast, when using a conventional PV system, those costs can make up half to two-thirds of the total” (Stauffer).
They estimate that using coated windows in a skyscraper could provide more than a quarter of the building’s energy needs without changing its look. Another possible application is electric cars, where solar panel windows could be used to power the vehicle on the go. Bulovic says, “they could be on everything around you—including all your windows—and you wouldn’t know it” (Stauffer). Indeed, this is a very exciting prospect for the future of solar photovoltaics, and it could be the perfect way to optimize for efficiency and aesthetics at the same time, which is difficult to do with current commercial PV technologies. It also opens a whole new idea of deploying solar energy in a non-intrusive way, while remaining affordable.