Turning windows into see-through solar panels

What if shimmering, full-glazed façades of commercial – and residential – buildings could mean the solution to energy efficiency, rather than being the weakest link in saving energy? That’s the promise of solar windows, which could change the way we build and manage buildings. 

Scientists and entrepreneurs have been trying to make solar PV (photovoltaic) panels transparent enough to be used in windows and other visual building-integrated PV applications. There had been little success until recently when researchers turned to organic semiconductors.

Organic semiconductors can be dissolved to print like ink and spread thinly on a glass substrate to appear much more transparent than a solid silicon cell, making organic PV a suitable product for solar windows.

It is time to move beyond thinking about fields of solar panels

Early in 2023 outdoor apparel company Patagonia announced it had installed solar windows at its corporate headquarters in Ventura, California. NEXT Energy Technologies PV coating was integrated into 22 windows on the south-facing façade of Patagonia’s campus, and the power is being used to charge phones and other devices in the employee community spaces – Solar Power World reports.

„The windows are a marked departure from other building-integrated photovoltaics (BIPV), which are usually black and opaque” – Jeff Horowitz, director of business development and partnerships for NEXT told Buildings.com

NEXT’s technology consists of a printed transparent photovoltaic coating on glass, which is sealed by a second piece of glass and integrated into a traditional window glazing system. By using organic semiconductors, NEXT is able to absorb more infrared energy than traditional solar, which means fewer semiconductors are needed to produce energy, allowing the coating to be transparent.

Patagonia HQ

Windows are an underutilized assets

“You don’t realize the cells are there, it’s pretty much invisible. At the very edges of the glass are some busbars. Windows in commercial buildings have a frame system already that’s particularly good for carrying wires. You can use rapid shutoffs with power optimizers at the windows. You can connect them with string inverters, and microinverters. It’s like a normal solar installation”- Corey Hoven, chief technology officer for NEXT pointed out to Solar Power World. It is time to move beyond just thinking about fields of solar panels or solar panels on a rooftop. With this technology, any façade of a building can be counted as a solar cell. 

Windows are an underutilized asset when it comes to energy generation. NEXT estimates that, by leveraging the surface area of the building’s facade rather than relying solely on the rooftop, its windows could produce 10-40% of a typical commercial building’s energy load. 

“I want to look out and see no colour or obstructions”

Ubiquitous Energy got its start at the Massachusetts Institute of Technology 11 years ago. By discovering spectrum engineering and organic photovoltaics they developed a thin coating that is fully transparent with no colour tinting.  

Ubiquitous solar windows have already been installed at Michigan State University, a commercial building in Boulder, Colorado, and the NSG Pilkington glass development facility in Ohio and throughout Asia. The company is currently making solar windows at its R&D pilot line in California.

“I want to look out and see no colour or obstructions. We want the consumer to operate it just like a traditional window. You don’t even know that our technology is integrated in there, but it’s giving you all its benefit”- Veeral Hardev, VP of strategy for Ubiquitous Energy told Solar Power World.

Disrupting the market without disrupting the supply chain

Residentially, power could be used locally for active window features or connected back into a smart home’s energy settings. Commercial buildings have more window area, making it more logical to feed that energy back into the grid for net metering.

“The nice thing about our technology, very similar to how thin-film solar technologies behave, they perform very well in off-angle or diffused light. You don’t really need access to direct sunlight to operate” – Hardev said, adding: “We didn’t really invent or develop any new method or process that requires new equipment to be developed. It’s using what the window coating industry already does as part of their day-to-day operations. Our goal has been to not disrupt the whole flow, to not create unnecessary challenges. We want it to be something that people can easily use and get installed and integrated.”


Photos: patagoniaworks.com, ubiquitous.energy


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