An amazing new solar power technology can turn skyscraper buildings into giant solar power plants. 

Currently, these buildings use Low Heat Emission (Low-E) glass windows to reduce overheating and air conditioner costs during warm seasons. According to the U.S. Office of Energy Efficiency and Renewable Energy (EERE), such windows are in 80% of homes and 50% of commercial buildings. The National Renewable Energy Laboratory thinks this is a giant wasted opportunity because they figured out a better way to use those UV rays. They invented a glass window that still keeps heat out but also turns the sunlight into electricity at the same time.

Smart Tinting Solar Windows


NREL’s prototype changes color when the glass gets hotter; this is called being thermochromic. When the sun heats the window, methylamine molecules are pushed out, darkening it. They’re made from the energy-harvesting material perovskite and maybe in all the windows of the future.

“There are thermochromic technologies out there but nothing that actually converts that energy into electricity,” NREL scientist Lance Wheeler said in a press release.

The inner workings of this “smart window” technology. Image Credit: NREL

NREL’s team of scientists tested their prototype and published a report in the Nature Communications. It turns out this new solar window is 11.3% efficient converting sunlight into electricity. This is pretty low compared to the best solar panel at 46%, but it’s better than the 0% windows were getting before.

“There is a fundamental tradeoff between a good window and a good solar cell,” explained Wheeler, who is a lead researcher in this study. “This technology bypasses that. We have a good solar cell when there’s lots of sunshine and we have a good window when there’s not.”

Clear Future Turning Dark?

Considering a large office building has more square footage of windows than it does on its roof, the 11.3% efficiency multiplied by the large surface area can make a big difference to the building’s energy bill.  According to Electrek, 80% of facility energy costs are spent on heating, cooling, and ventilation.

While this all sounds like this may be a path to a clear bright future, things may, ironically, turn dark. So far, at least, NREL’s solar-powered smart windows stop working after 20 color changing cycles. This is a major dealbreaker and no one will install solar power windows that last less than a month. To put it in perspective, standard solar panels maintain their effectiveness for 25 years.

Again though, the potential here is huge, so if NREL figures this out, it’ll be well worth it. Besides replacing commercial building windows, these could replace car windows as well; maybe even sunglasses.


  1. NREL
  2. Nature Communications