26th October 2017

Transparent solar tech represents 'wave of the future'

See-through solar materials that can be applied to windows represent a massive source of untapped energy and could harvest as much power as bigger, bulkier rooftop solar units, scientists report in Nature Energy.

Led by engineering researchers at Michigan State University (MSU), the authors argue that widespread use of such highly transparent solar applications, combined with the rooftop units, could meet almost 100% of U.S. electricity demand and would drastically reduce the use of fossil fuels.

“Highly transparent solar cells represent the wave of the future for new solar applications,” says Richard Lunt, a Professor of Chemical Engineering and Materials Science at MSU. “We analysed their potential and show that by harvesting only invisible light, these devices can provide a similar electricity-generation potential as rooftop solar, while providing additional functionality to enhance the efficiency of buildings, automobiles and mobile electronics.”



Credit: Richard Lunt/Michigan State University

In 2014, Lunt's team pioneered the development of a transparent, luminescent solar concentrator. When placed into a window, it creates solar energy without disrupting the view. The plastic-like material can be used on buildings, car windows or other clear surfaces. The solar-harvesting system uses organic molecules to absorb invisible wavelengths of sunlight. This material can be “tuned” to pick up just the ultraviolet and near-infrared wavelengths, which are then converted into electricity.

Moving global energy consumption away from fossil fuels will require innovative and cost-effective technologies such as this. Currently, only about 1.5% of electricity demand in the United States and globally is produced by solar. But in terms of overall electricity potential, the authors note that there is an estimated 5 billion to 7 billion square metres of glass surface in the United States. And with that much glass to cover, transparent solar technologies have the potential to supply up to 40% of energy demand in the country – about the same potential as rooftop solar units. “The complimentary deployment of both technologies,” Lunt explains, “could get us close to 100% of our demand if we also improve energy storage.”

At present, highly transparent solar applications are recording efficiencies above 5%, while traditional solar panels are typically 15 to 18% efficient. Although transparent solar will never be more efficient at converting sunlight to electricity than its opaque counterparts, it can get close and be applied to a lot more additional surface area, Lunt says. Right now, transparent solar technologies are only at about one-third of their realistic overall potential, Lunt added.

“That is what we are working towards,” he said. “Traditional solar applications have been actively researched for over five decades, yet we have only been working on these highly transparent solar cells for about five years. Ultimately, this technology offers a promising route to inexpensive, widespread solar adoption on small and large surfaces that were previously inaccessible.”

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