Solar window film estimated to pay off in less than a year and provide 30-50% of electricity for new skyscrapers

By Jocelyn Timperley 12 August 2016 Cross-posted from Business Green

In these highly scrutinised days of climate risk task forces and green policy obstruction rankings, firms of all shades are under growing pressure to show they are making efforts to boost their environmental transparency.  But some green companies are challenging themselves to deliver transparency of a rather more literal kind – namely through the race to develop a see-through solar window capable of generating economically viable levels of electricity.

Clean energy firm SolarWindow is a principal contender in this race. The South Carolina-based start-up is pushing the boundaries of organic solar cell technology in a bid to create a transparent photovoltaic coating which can be added onto ordinary glass panels.

The firm’s process involves applying a paper thin layer of the its specially developed coating to an ordinary piece of window glass. This carbon-based coating, which becomes more or less transparent when applied to the glass, is in fact made up of several separate layers of materials, including a central active polymer layer capable of producing electricity.

“When light energy hits our coatings, electrons mobilise from that active layer and through what we call transparent conductors, which are transparent layers that conduct electricity,” said John Conklin, chief executive of SolarWindow. “Then we generate the electricity right on the surface of glass.”

This electricity is then moved across the glass using what SolarWindow refers to as its “invisible wire system”, and is fed in at the pane’s edges to real wires connected to the building’s electricity network.

The firm is keen to make clear this method of producing electricity is significantly different from some other solar window technologies, which generate electricity at the edges of the window by bending the light to reach it.

SolarWindow transparent solar cell. Copyright SolarWindow

The technology, which the firm plans to rollout out commercially before the end of 2017, will be available for installation in two ways: either by applying the coating directly to already-installed windows, or adding it to new windows before installation. “They would be replaced exactly as any ordinary window in today’s construction industry, the only thing you would need is an electrician to connect those wires,” says Conklin.

Importantly, Solar Window insists that applying its veneer will result in only a small percentage increase in the overall price of the windows. “Affordability is an essential element of how we want our window coatings priced out, and we expect that anybody that wants to put in a window for just a slight increase in the price should be able to install these windows,” says Conklin.

Advocates of building integrated solar technologies have long argued that they will soon be able to compete effectively on costs, as the solar cells represent a small premium on roofs or windows that the customer has to install anyway.

While the new solar windows could be installed in houses as a way to offset some of the electricity used inside, the obvious market for SolarWindow’s technology is the vertical real estate market. The firm estimates installing the technology in a next generation commercial skyscraper would allow between 30 to 50 per cent of its power to be generated onsite. Crucial for the company’s financial vision is the payback time, which its models indicate will be less than one year for a 50-story building, and Conklin claims the glass panels would generate 50 times more energy than a rooftop PV array at the same site.

Central to the high levels of anticipated generation is the ability of the technology to generate electricity from releatively low levels of light. “Because of the way this technology is engineered, we can actually generate electricity using artificial light or very, very low, shaded and reflected sunlight,” says Conklin. “We don’t need the sun to generate electricity, so imagine the opportunities that now become available on the north, east and west sides of a building, or home for that matter.”

However, there is still a major sticking point for SolarWindow’s technology to overcome: producing a solar layer capable of harnessing a significant amount of energy without obstructing the transparency of the window in any way has proved extremely difficult.

Even after seven years of work SolarWindow is currently only aiming to produce a maximum of 80 per cent transparency, with even this level coming with a significant reduction in the amount of power produced. Ultimately, the firm hopes to make fully transparent product, although there is still a big question mark over how long this would take and how much it would cost. “We do expect as we advance the technology to push the boundary even more, and our goal ultimately is to be completely transparent,” says Conklin. “But that enters us into a new area of science as it relates to organic photovoltaics, and its an area that really hasn’t developed yet.”

Transparent solar window. Copyright Solar Window

With the firm on the cusp of commercial deployment, it has come a long way from its initial aim back in 2009 to simply prove the concept of the technology alongside its partners at the University of South Florida. It is now working with the US Department of Energy and the National Renewable Energy Laboratory to speed up commercial rollout. Most recently, it raised over $4.3m in capital, which is being dedicated to both operations and further development of the technology. For now the firm wants to make sure it can rollout a viable product, with near-term plans to install the technology on one or more buildings in order to monitor its performance – it even intends to put this information on a portal on its website so that anybody can view a solar window producing energy in real time.

Meanwhile, long-term ambitions for the company are a lot bigger. “We very much want to see our technology installed in the UK, in other areas of Europe, the Middle East, Asia, and of course North, Central and South America,” says Conklin. “Without question we’re looking at global deployment.”

But SolarWindow is coming into an increasingly crowded market – several other firms, including the UK-based Oxford PV, American start-up Ubiquitos Energy, Spain’s Onyx Solar and Ohio-based DyeTec Solar, are also developing technology that could be used in the “untapped market” for skyscraper solar windows.

Conklin argues the main distinguishing factor for SolarWindow is its exclusive focus on developing its coatings for windows, with some other solar glass firms having more broadly targeted developing products for electronic devices such as tablets and e-readers, as well as windows. “Everything that we’ve done has had the idea of how to make glass, how to apply coatings to glass, how to take those pieces of glass and actually install them in a window frame, and then installing that window in a building,” he says. “We understand that full supply chain.”

As global attention increasingly focuses on the need to generate clean electricity wherever it can be done economically, Conklin sees SolarWindow as a clean energy company poised to assist with the dual challenges of climate change and resource depletion while also satisfying an increasing need for energy. Now it remains to be seen whether the company’s innovative technology allows it to slip into a potentially multi-billion dollar new market as surreptitiously as it hopes its windows will one day provide an unnoticed energy-generating sheen to the world’s skyscrapers.