Researchers Develops World’s First Bifacial Solar Window Concept

The ZIEZO Window

A research team coordinated by the Netherlands Organization for Applied Scientific Research (TNO) has developed the world’s first bifacial solar window concept. This next-generation multifunctional window not only generates clean energy by producing electricity but also enhances indoor thermal and visual comfort by preventing overheating.

Simona Villa, the lead author of the study, explains, “The ZIEZO window consists of a unique insulated glass unit (IGU) featuring bifacial crystalline silicon solar cell strips and an integrated blind system.” The blind system directs sunlight to the rear side of the solar cells when in use, boosting energy production. Villa notes, “Currently, there is no bifacial PV window available for building integration.”

According to the research, the system operates in three different modes. When the blinds are fully closed, maximum energy gain is achieved, while partially open blinds allow for moderate energy production. Users can automatically adjust the position of the blinds, prioritizing either energy generation or thermal and visual control.

World’s First Bifacial Solar Window Installed

This research was based on a patented window technology developed with the contribution of glass manufacturer Pilkington. Twelve small-scale prototypes were tested with different variations at an outdoor research facility, and six full-sized windows were installed in Pilkington’s office building.

After one year of outdoor monitoring, the results highlighted the potential of this innovative product. According to Villa, with the most reflective blinds in use, energy output on sunny days can increase by up to 25%, while the daily average increase is around 13%. The angle of the blinds, the sun’s position, and radiation conditions play a key role in energy production.

Looking ahead, Villa mentioned that the focus will be on enhancing visual comfort and indoor thermal control. Pilkington is preparing to bring this product to market, and further research will explore the benefits of active shading devices in buildings.