Can windows work as solar panels?

Engineering researchers at Michigan State University argue in ‘Nature Energy’ that the widespread use of transparent solar materials that can be applied to windows, along with roof units, could satisfy the demand for electricity in the United States, drastically reducing the use of fossil fuels.

“The highly transparent solar cells represent the future trend for new solar energy applications” says Richard Lunt, associate professor of Chemical Engineering and Science of Materials at MSU.

“We analysed its potential and demonstrated that, by harvesting only invisible light, these devices can provide an electricity generation potential similar to that of a rooftop solar panel, while providing additional functionality to improve the efficiency of buildings, cars, and mobile electronic devices” he explains.

Lunt and his colleagues at MSU were pioneers in the development of a transparent luminescent solar concentrator that, when placed in a window, creates solar energy without disrupting the view. This thin, plastic-like material can be used in buildings, car windows, mobile phones, or other devices with a clear surface.

The sun collection system uses organic molecules developed by Lunt and his team to absorb invisible wavelengths of sunlight. Researchers can “adjust” these materials to collect only near-infrared and ultraviolet wavelengths to later transform this energy into electricity.

Shifting the world’s energy consumption away from fossil fuels will require innovative and cost-effective renewable energy technologies. Only about 1.5 percent of electricity demand in the United States and the world is produced by solar energy.

However, in terms of overall electricity potential, the authors estimate that there is 5-7 billion square metres of glass surface area in the U.S. With that amount of glass, transparent solar technologies have the potential to supply about 40% of the energy demand in the United States, approximately the same potential as that of solar units on the rooftop.

“The supplementary deployment of both technologies could bring us closer to 100% of our demand if we also improve energy storage,» says Lunt.

Lunt states that highly transparent solar energy applications register efficiencies above 5%, while traditional solar panels typically have 15-18% efficiency. Although transparent solar technologies will never be more efficient in converting solar energy into electricity than their opaque counterparts, they can approach such efficiency and offer the potential to be applied to a larger additional surface area, he said.

Right now, transparent solar technologies only represent about a third of their realistic global potential, Lunt adds, “That’s what we’re working for. Researches on traditional solar energy applications have been actively carried out for more than five decades. However, we have only been working on these highly transparent solar cells for about five years. Ultimately, this technology offers a promising route for low-cost solar energy on surfaces that used to be inaccessible.

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