Transparent solar technologies

Transparent solar panels could harvest as much power as rooftop panels, study suggests

Image credit: Michigan State University

Researchers at Michigan State University claim that widespread adoption of transparent solar materials mounted on windows, combined with rooftop panels, could almost meet US electricity demand.

The US team who carried out the Nature Energy study were also responsible for developing plastic-like luminescent solar concentrators that are capable of harvesting solar power, while being as transparent as glass. They can be mounted on windows of buildings and cars, as well as on screens of devices such as smartphones that have clear surfaces.

This system uses organic molecules to absorb sunlight. They can be ‘tuned’ to absorb only light outside the visible part of the electromagnetic spectrum to generate electricity, while allowing visible light to pass through.

“Highly transparent solar cells represent the wave of the future for new solar applications,” said Professor Richard Lunt, associate professor of chemical engineering and materials science at Michigan State University.

“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.”

Standard solar panels currently achieve efficiencies of 15 to 18 per cent, while the transparent solar concentrators developed by Professor Lunt’s team work at efficiencies of just above five per cent. Due to absorbing just invisible light, the efficiency of the transparent systems will always be limited, although their transparency means that they can be applied to more surface area than standard solar panels.

The near-universal adherence to the Paris Agreement – which aims to minimise the rise in global average temperature to below 2°C in order to prevent the most catastrophic effects of climate change – requires governments to look to alternative to fossil fuels in order to reduce carbon emissions drastically.

At present, just 1.5 per cent of electricity consumed globally is generated from solar energy. However, in the US alone, there are five to seven billion square metres of glass surfaces that could be covered with these solar concentrators.

Widespread use of these transparent solar panels, in addition to rooftop solar panels could nearly meet total US electricity demand by cost-effective means, the researchers found. Covering glass surfaces with these systems could generate 40 per cent of US energy demand; approximately the same as rooftop solar panels.

“The complimentary deployment of both technologies could get us close to 100 per cent of our demand if we also improve energy storage,” said Professor Lunt, who believes transparent solar technologies are at approximately a third of their potential.

“That is what we are working towards. 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."

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