IN² Spotlight: Powering Buildings with Transparent Photovoltaic Windows

Commercial Buildings

May 25, 2023—In the process of creating photovoltaic smart glass, or window coatings that also absorb light and turn it into electricity, there is no one-size-fits-all solution. NEXT Energy Technologies, Inc. COO Brenton Taylor laments that it would be easier but unfortunately, that is not the case.

“The thing about the window business,” Taylor said, “is there’s no such thing as a standard size commercial window. It’s all custom, based on the individual project. Because of the nature of customization, it’s important to be able to integrate custom-sized coatings in-line at the point of manufacture.”

NEXT Energy developed a coating for windows based on organic semiconductors that allows the window to absorb light from infrared rays and convert it into electricity. Electricity is generated by the coating which transfers the power to the edges of the window and channels it to a junction box. It then feeds into inverters to use within the building’s electrical infrastructure.

“Our objective is to design a product that looks and feels and behaves exactly like a normal window, but with an added benefit of providing electric power,” NEXT Energy Co-Founder and CEO Daniel Emmett said. “The coating is just like a normal solar panel, but we can tune it to only absorb the particular wavelengths of light that we want. It truly is an architectural product.”

The coating is printed onto windows during the fabrication process, similar to ink printing onto paper. To speed up the process, NEXT Energy looked at the window supply chain and decided they wanted to leverage the manufacturing expertise of top window fabricators.

“We want to get this out quickly around the world,” Emmett said. “It is much more efficient to work with existing window manufacturers. We print this as ink in a wet-coating process, and it doesn’t need an ultra-high vacuum, so the energy costs going into making it are much less. The coating method is well established and has been used for decades in a range of industrial products, including Kodak for photographic film. It’s a high-speed process that’s well understood—we’ve just modified it.”

NEXT Energy can also tailor the coating to allow different wavelengths of light through and change the colors of the windows.

Through the Wells Fargo Innovation Incubator (IN2), National Renewable Energy Laboratory (NREL) helped NEXT Energy calculate a key metric important to architects: the solar heat gain coefficient. Because the coating absorbs light and converts it to electricity, the calculation required a modified method to properly account for the impact of the technology.

“One of the big ‘A-ha’s’ was being able to show people the improved solar heat gain coefficient,” Emmett said. “We now have a result that is essentially not just us saying, but NREL validating, ‘this is how to calculate it, and this is an improved solar heat gain coefficient.’ We didn’t even get to tell that part of the story before, and it’s been huge.”

Construction workers install windows on a building.

Patagonia allowed NEXT to install 22 solar windows on its south façade. The electricity generated powers charging stations so employees can charge phones and other devices. Photo courtesy of NEXT Energy, via US Glass News Network

After several installations, including at the Patagonia headquarters building in the San Francisco Bay area, NEXT Energy continues to scale up the size of their windows. Currently, it produces 14×20 inch glass, and to get larger sizes requires a larger coating line. The company also works with Viracon, one of the largest window producers in North America, on installations.

The Patagonia installation uses a curtainwall framing system, which is pre-wired and integrated with NEXT Energy’s windows. That whole window section is then installed on a building, and installers can plug those sections together and into the building itself.

“It’s a really big step for us to integrate into the building and the whole framing system,” Taylor said.

NEXT Energy has at least two more installations planned for 2023 at increasingly larger sizes and with more supply chain partners. The leadership team feels the environment is right for their technology to make strides forward.

“There are some pretty important drivers for adoption of this technology that are happening in real time,” Emmett said. “The Inflation Reduction Act’s strong incentives help with the adoption of our tech. Regulations in California mandate that all new buildings have on-site renewable energy and storage. New York also has a very aggressive climate-oriented building standard. The building sector is facing a lot of pressure to reduce its carbon footprint. Europe is doing something similar. With our coating, we now have an opportunity to seamlessly leverage the façade of the building to help tackle the climate crisis.”

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