Smart windows that generate power, cool rooms and heat water 

Sunlight pouring in through windows on a bright summer morning can deliver an invisible, unwelcome guest: heat. Despite the widespread adoption of double glazing, windows remain very leaky to heat, adding significantly to the energy needed to keep buildings comfortable.  

Globally, buildings consume more than one-third of total energy production, much of it for cooling—especially in hot regions. A smart window developed by researchers at Khalifa University promises to flip this situation, turning windows from energy sinks into significant energy sources by synergistically combining two energy-harvesting technologies.  

“Our multifunctional window provides multiple benefits from one integrated design,” says engineer Mohamed Hassan Ali, who led the work. 

“In our [window] design, as well as [the solar panel] filtering out the undesired solar radiation, the water cools the solar panel.” 

Mohamed Hassan Ali 

The first benefit is electricity generation. Encapsulated between two panes of glass is a thin layer of a semi-transparent photovoltaic (STPV) material that absorbs most of the visible light passing through the window. The STPV layer provides some shading while generating electricity to help power the building’s cooling system.  

Although power-generating solar PV windows have been trialed before, they had a major drawback. The STPV materials unavoidably generate some heat as they turn light into electricity. In previous designs, that heat radiated directly into the room, exacerbating the building’s cooling demand even as the window trapped in-coming solar energy. 

To overcome this limitation and bring a second benefit, Ali and his team incorporated a second technology called selective liquid filter (SLF) into their windows. The SLF consists of two glass sheets that sandwich a transparent film of flowing water. The SLF harnesses water’s natural capacity to absorb ultraviolet and infrared radiation, intercepting heat flowing into the room and generating a useful stream of warmed water, while letting visible light pass through.  

The KU window prototype combines the SLF and STPV technologies in a multilayer assembly.  “In our design, as well as [the solar panel] filtering out the undesired solar radiation, the water cools the solar panel,” Ali says. “The heat that the water absorbs could help to meet the building’s hot water needs.” 

The multifunction window prototype generated 350 watts (W) of electrical power—comparable to a typical solar panel—and 700W in hot water. Once incorporated into a computer model of a building, the windows also lowered the need for cooling, providing an overall net electricity benefit 80% higher than seen in a building that only incorporated STPV windows. 

Reference

Abdelsamie, M. M., Ali, K. & Hassan Ali, M. I. Enhancing building efficiency: Multifunctional glazing windows with integrated semitransparent PV and selective liquid-filters.  Appl. Energy,  377, 124723, 2025. | Article