Solar Windows Power Buildings From Inside and Out

Imagine if every window in a skyscraper could generate clean energy, even at night when the office lights are still on.

Researchers at University College London just made that vision real. They've developed semi-transparent solar windows that harvest power from sunlight streaming in AND from the artificial light bouncing around inside buildings.

The 30cm square prototype converts 22% of bright indoor light into electricity, plus 14% of outdoor sunlight. That might not sound huge, but consider this: most modern buildings have massive glass facades that currently do nothing for energy production.

"Rooftops are commonly fitted with solar panels, but the vast window areas of many modern buildings remain largely untapped," said Dr. Mojtaba Abdi-Jalebi, who led the research team. His group cracked a puzzle that's stumped scientists for years: keeping windows transparent while maintaining solar efficiency.

The secret lies in perovskite, a special material the team engineered to be ultra-thin. Their solar layer is just 185 nanometers thick, about 500 times thinner than a human hair. Traditional solar cells use perovskite layers three or four times thicker.

The windows block some sunlight, letting through 30% compared to regular glass at 80-90%. But that's actually a bonus. In hot climates, the tinted effect reduces air conditioning costs while generating power at the same time.

The Ripple Effect

The technology opens doors beyond buildings. The research team is already working on flexible versions that could wrap around curved surfaces like car windshields or the iconic Shard tower in London.

Picture solar film applied as easily as window tint to vehicles, transforming millions of cars into mobile power generators. Or imagine backpacks and clothing that charge your devices while you walk around outside.

PhD student Siming Huang sees the climate benefits clearly. "By obscuring some of the sunlight it acts in the same way as tinted windows, saving a portion of the energy required to keep the building cool," he explained. That matters most in regions where air conditioning devours huge amounts of electricity.

The prototype passed durability tests too, keeping 80% of its efficiency after 300 hours of constant light exposure. The team is now focused on scaling up from their small prototype to full-sized windows.

The research received funding from multiple UK government agencies committed to clean energy innovation, including the Department for Energy Security and Net Zero. When buildings become power plants, every window becomes a step toward energy independence.