Electricity-generating windows? Swiss scientists design more efficient transparent solar panels

All that natural light streaming through your windows could one day do more than just lift your mood.

Swiss scientists have reached a new efficiency record for transparent solar cells, paving the way for electricity-generating windows that could help power our homes and appliances.

Also known as Grätzel cells, dye-sensitized solar cells (DSC) are a type of low-cost solar cell that uses a photosensitized dye attached to the surface of a semiconductor to convert visible light into energy.

Previous versions of DSCs relied heavily on direct sunlight, but scientists at the École polytechnique fédérale de Lausanne (EPFL) have found a way to make transparent photosensitizers – molecules that can be activated by light – that can “absorb” light across the entire surface. visible light spectrum.

“Our findings pave the way for easy access to high-performance DSCs and offer promising prospects for applications as power supplies and battery replacement for low-power electronic devices that use ambient light as a power source,” the authors wrote. authors of the study, published in the scientific journal Nature.

Transparent solar panels

DSCs are transparent, flexible and can be made in a wide range of colors at relatively low cost. These transparent solar panels are already used in skylights, greenhouses and glass facades.

In 2012, the SwissTech Convention Center became the first application of DSC technology in a public building.

The Swiss Tech Convention Center – © Richter – Dahl Rocha & Associés Architectes SA.

In 2017, the International School of Copenhagen opened its new building covered with around 12,000 blue but transparent solar panels that use the same DSC technology.

They provide approximately 300 megawatt hours (MWh) of electricity per year, meeting more than half of the school’s annual energy needs.

Jens Cederskjold on Flickr

Copenhagen International School – Nordhavn – Copenhagen – Jens Cederskjold on Flickr

Transparent solar technology with 30% efficiency

But despite the fact that power-generating windows have been on the market for several years, a recurring complaint was their limited ability to generate electricity compared to traditional solar cells.

The EPFL team’s new breakthrough may soon help overcome this hurdle.

Using a new design of molecules, they have increased the power conversion efficiency of DSCs – in other words, the portion of solar energy that shines on them that is converted into usable electricity – to beyond 15% in direct sunlight and up to 30% in ambient light conditions.

For reference, commercial solar panels currently have an average efficiency of around 20%.

Next-generation DSCs have also demonstrated “long-term operational stability” of at least 500 hours.

Materials that convert sunlight into electrical energy have enormous potential to meet the world’s growing need for cost-effective renewable energy technologies.

Glass windows have particularly huge potential: imagine if entire skyscrapers could be turned into vertical solar farms?

In 2017, a team of University of Michigan who developed a new type of solar concentrator that creates solar power when placed over a window estimated that see-through solar technologies could meet about 40% of energy demand in the United States.

He estimated that if combined with rooftop solar units – and the right storage technology – that share could reach almost 100%.

In Europe, solar power accounted for 12.2% of electricity generated in the EU this summer, the highest share checked in.

On current trends, it has the potential to meet up to 20% of EU electricity demand by 2040, according to the European Commission.

Most of the planet’s solar energy is currently not captured. What would things look like if every window around us could harvest it?

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Rozella J. Cook