Windows as power stations
Power-generating windows are no longer a dream of the future. New developments from research and industry are turning glass surfaces in façades into active energy sources without compromising the view.
One solution relies on special films that direct visible light specifically to the edge of the glass pane. There, PV strips, often made of high-performance material such as GaAs, absorb the light and convert it into electricity. Solar cells are only needed at the edge, which saves material and resources. The view is retained and the window remains transparent.
Using cholesteric liquid crystals, a research team at Nanjing University has developed a prototype that achieves an optical efficiency of over 18% and delivers stable values under real conditions. For a typical window with a height of two meters, there is a strong concentration of light at the edge zone. The coating can be produced industrially and is suitable for large façades.
Transparent tandem cells
The EU project CitySolar presents another innovation. Two combined PV layers (halide perovskite at the top, organic at the bottom) extract energy from different light spectra while allowing visible light to pass through. This means that the room brightness and view remain unchanged, the window “looks like a window” but produces electricity.
With an efficiency of 12.3% and 30% transparency, a new record has been set for transparent PV modules. The structure is suitable for office and residential buildings as well as high-rise buildings with large glass fronts.
Future and potential
Researchers and industry partners are working on even higher efficiencies and better production methods. Challenges exist in balancing transparency and efficiency and in integrating them into existing construction processes. However, projects such as those from ZEISS or the international CitySolar consortium clearly show how great the market potential is.
Transparent solar cells and intelligent glass surfaces are paving the way for buildings that partially cover their own electricity requirements. Windows as power plants are within reach and will play a decisive role in shaping the energy transition in urban areas.