This liquid coating turns windows into solar panels

SolarWindow Technologies says it can harvest energy from sunlight by applying a transparent film to glass or plastic.

A Maryland company has been moving slowly and steadily for 20 years toward a very ambitious goal — turning windows into transparent solar panels that harvest energy from the sunlight that passes through.
SolarWindow Technologies is among the many energy companies looking for ways to harvest solar power on a large scale. But SolarWindow's proposition is to turn windows into solar panels by way of a thin transparent coating applied to standard glass and plastic windowpanes.

The coating might not generate much power when slapped on your living room window, but SolarWindow is aiming higher — quite literally. The company hopes to eventually deploy the technology onto office buildings and skyscrapers, generating energy from the acres of glass soaking up the sun.

The technology behind SolarWindow is proprietary, but it goes something like this: SolarWindow has developed a liquid “organic photovoltaic solar array” (OPV) made from a mixture of carbon, hydrogen, oxygen, and nitrogen, that can be applied to transparent surfaces.

The liquid coating produces ultrasmall solar cells formed in groups, or arrays. Sunlight passing through these arrays generates an electrical charge. That electrical charge is then harvested by a grid of very fine wires, each thinner than a human hair, running through each pane of glass. The wires shuttle the power to a larger output wire, which is then jacked into any existing power system, as with traditional solar panels.
To generate maximum power, the transparent coating is applied multiple times to the glass or plastic surface. The coating and the grid can be applied at ambient temperature and pressure, which makes large-scale manufacturing easier.

“Conventional solar panels are inherently opaque and thus impossible to see through,” said SolarWindow CEO John Conklin. “You’re not going to build windows from those panels. SolarWindow is being developed to maintain the architectural beauty and transparency of a window while generating electricity.”

According to the company website, the SolarWindow system can outperform a traditional solar by as much as 50 times when installed on a 50-story building, largely because of the greater surface area covered by windows. By comparison, typical rooftop solar panels occupy a far smaller footprint.

Despite nearly 20 years in operation, the company's product has yet to hit the market. But it has posted research on the amount of energy the system could potentially produce, if deployed on a wide scale in major cities.

To that end, SolarWindow announced this week that it has partnered with California-based Triview Glass Industries, which manufacturers specialty glass panels for architectural firms and commercial developers. It's an important first step for finally getting the technology out of the labs and into the sun, Conklin said.
“We believe that our agreement with Triview establishes a very important strategic relationship that is a prerequisite to reaching our goal of commercial production of our products,” Conklin said.

SolarWindow isn't the only company pursuing see-through solar panel technology. The California-based startup Ubiquitous Energy is working on a similar system that harvests light invisible to the human eye – infrared and ultraviolet – while letting visible wavelengths pass through. Last year, Elon Musk unveiled his SolarCity solution, which includes options for solar rooftop cells made from tempered glass.

Conklin said that the company intends to work with glass manufacturers to find the most efficient method for integrating SolarWindow technology into new windows in both residential and commercial buildings. The company is also working on a method for applying its solar film to existing structures.

“We hope to be able to retrofit existing glass structures as we work on new construction projects,” he said.