See-Through Solar Windows Turn Ordinary Buildings into Climate Heroes

Glass windows are notorious for leaking energy in and out of buildings, but the latest development in solar cell technology is about to flip the script. New see-through solar windows enable glass to fill its normal function of allowing daylight into buildings, while also harvesting energy from the sun and converting it to electricity. That may seem impossible, but the technology’s mature commercialization is just around the corner.

The thin film solar cell difference

See-through solar cells are a sharp contrast with conventional solar cells. Typical solar cells are made with silicon. They do an excellent job of harvesting solar energy. However, silicon solar panels are heavy, thick and rigid. They are obviously unsuitable for use as windows.

Because of their weight and rigidity, silicon solar panels are also less than ideal for cladding and other building applications.

See-through solar cells are different. They are formed in a liquid solution. They form a thin film when painted, printed, deposited or sprayed onto glass, plastic or other materials. They can also be applied to curved, flexible or irregular surfaces.

In terms of converting sunlight to electricity, thin film is not as efficient as conventional silicon solar cells. However, their relatively low cost, light weight and range of applications provides thin film solar cells with opportunities to step in where silicon is too expensive or impractical.

From thin film to see-through solar

Thin film solar is not a new technology, but balancing the thin film solution to harvest solar energy while allowing light to pass through has been a challenge. While tinted, semi-transparent thin film solar cells are already on the market, fully transparent, see-through solar cells have proved elusive — until now, that is.

One company on the verge of a breakthrough to the mass market is Ubiquitous Energy. It was co-founded by Michigan State University Professor Richard Lunt, who holds the Johansen Crosby Endowed Professor of Chemical Engineering and Materials Science at the school’s College of Engineering.

Ubiquitous Energy’s see-through solar looks no different from ordinary glass. It enables ordinary light to pass through, just like regular glass. The difference is that it collects energy from non-visible ultraviolet and infrared light at the far reaches of the spectrum.

The company is planning for mass production of its “UE Power” thin film solution in the form of 1.5 x 3.0 meter see-through solar windows, or about 9.8 feet. The windows would provide ample floor-to-ceiling coverage for a typical building with 9-foot ceilings. 

The 2024 timeline for mass production of these solar windows seems well within reach, thanks in part to an investment and R&D partnership with the window maker Anderson Corporation, announced last year.

Last fall, Ubiquitous Energy was also named 2022 Green Company of the Year by the crowd-sourced award organization Business Intelligence Group. In addition, co-founder Miles Barr earned a position in the top 100 Environmental Energy Leaders list compiled by the media organization Environmental & Energy Leaders, and Entrepreneur magazine featured CEO Susan Stone in its 100 Women of Influence in 2022 list.

Solving the building emissions problem

Another U.S. firm, Next Energy Technologies, is also gearing up for mass production. In 2017 the U.S. Department of Energy awarded $2.5 million in matching funds to the company, to help it commercialize organic thin film technology.

Over and above the ability to generate electricity, Next also aims to demonstrate that solar windows can prevent excess heat gain. The company has been conducting a multi-year comparative study through the Wells Fargo Innovation Incubator. Last July the company announced results indicating that their solar windows can achieve a median energy savings of 10 percent across various regions of the U.S. compared to conventional windows, with a savings of up to 50 percent in sunny states including New Mexico, Texas and Arizona.

Next also emphasizes the need for a new, game-changing generation of energy-producing window technology in the context of global efforts to decarbonize.

“Buildings are near half the carbon problem driving climate change and representing nothing less than an existential threat to humanity,” Next points out. 

The company also cites an estimate that the global stock of buildings will double by 2060, which is equivalent to “adding an entire New York City to the planet every 34 days for the next 40 years.”

On a more optimistic note, Next notes that buildings have evolved from energy-sucking structures to showcases for energy conservation. Solar windows will help buildings take the next step, and become platforms for energy generation.

See-through solar windows, from cities to farms

In addition to stepping buildings up to the energy generation level, transparent solar technology also has the potential to transform the agricultural landscape. One US firm that sees the potential is SolarWindow. The company’s “LiquidElectricity” technology can be tinted to fit various applications. 

The company is aiming at automotive uses in addition to residential windows and skyscraper glass. They are also paying particular attention to the emerging field of agrivoltaics, which refers to the co-beneficial of agricultural activity within arrays of ground-mounted solar panels.

Studies have shown that solar panels perform more efficiently in the cooling microclimate created by vegetation. In turn, solar arrays can help conserve soil and water. They can also enhance crop yields in some cases.

Initial versions of agrivoltaic systems involved raising conventional silicon panels farther off the ground than usual, to allow for grazing livestock and planting pollinator habitats. More recently, the agrivoltaic field has expanded in new and different directions, partly due to its overlap with the regenerative agriculture movement. Solar manufacturers are beginning to tailor their products for agrivoltaic applications and SolarWindow is among them, with a particular focus on greenhouse crops.

The renewable energy whack-a-mole

The emergence of see-through solar is yet another indication that the fossil energy industry is experiencing the last of its ability to dominate the global energy profile, especially considering parallel activity in the field of advanced bio-based products.

Wood and whale oil once powered the economies of the world before fossil fuel pushed them aside. Now, Mother Nature is taking over again. Fossil energy is not going quietly, but go it will.

Image credit: Ubiquitous Energy via Business Wire