Solar window generates energy by reflecting light

A new type of window had been developed and tested that produces electricity and simultaneously controls heat and light for indoor comfort

This was done by researchers from the ZIEZO project, led by TNO. This window, the first of its kind, has special double-sided solar cells and built-in Venetian blinds that reflect sunlight. This directs more light to the cells’ rear side, increasing the energy yield whilst protecting against overheating.

Solar Energy Scientist at TNO: Roland Valckenborg: ‘By effectively using sunlight and solar heat this window can have a major impact on the energy efficiency of buildings. For a general medium sized office building these windows can reduce the CO₂ footprint of that building by at least 20%. It’s also commercially interesting because as far as we know this concept is not available on the market yet.’

The new solar window, called the ZIEZO (Sunshade Including Electricity-Generating Solar Window)window, consists of double-sided crystalline silicon solar cells strips and embedded Venetian blinds. When the blinds are down, they reflect sunlight onto the back of the solar cells, making more energy.

It offers three operational modes:

Users can automatically adjust the blinds to focus on either generating more energy or controlling the room’s temperature and light.

Next to TNO the research group consists of the TU/e, glass company Pilkington Nederland and W/E adviseurs. For the past year they tested 12 small versions of this window at the outdoor facility SolarBEAT in Eindhoven and installed 6 full-size windows at Pilkington’s office in Enschede.

On sunny days, it increases energy by up to 25% with the most reflective blind, compared to a window with only one sided solar cells without blinds On average, over the whole year, the energy boost is about 13%. The results of the system were recently published in the solar energy journal SolarRRL.