Why Solar Windows Could be the Future of Renewable Energy

Jason Lomberg, North American Editor, PSD



Jason Lomberg, North American Editor, PSD

­Solar power is growing rapidly across the globe, but it faces several roadblocks, not the least of which are aesthetic factors. And now Swiss scientists have announced an efficiency record for a type of solar cell – “dye-sensitized” solar cells (DSCs) – that could help bypass one of the average consumer’s biggest objections to photovoltaics.

To be clear, DSCs (or Grätzel cells) are a fancy way of describing the technology underlying solar windows, with the tech using photosensitized dye to convert visible light into electricity. In other words, it helps create see-through solar panels (or windows).

Of course, traditional solar power is growing exponentially across the globe – the worldwide solar market was estimated at about US $197.23 billion in 2021, and with an expected compound annual growth rate (CAGR) of 7.2% from 2021 to 2030, it could be worth US $368.63 billion in less than a decade.

The U.S. has actually seen a bit of a decline. While solar represented 50% of all new electricity-generating capacity added to the US grid in 1Q 2022, the installed capacity during that same period was 3.9 GWdc, a 24% decrease from Q1 2021 and a 52% decrease from Q4 2021 (hat tip to the Solar Energy Industries Association).

But like the rest of the world, favorable renewable energy legislation in the U.S., coupled with tax and other incentives, is driving adoption inexorably upwards. It’s merely a question of when – how soon consumers will adopt renewable energy, including solar.

And one of the biggest consumer objections is aesthetically oriented – not every homeowner and business wants solar panels on their roof. That’s where solar windows come in, with their promise of unobtrusive solar energy. In theory, you could cover an entire office building – to say nothing of a home – in these solar panels that utilize photosensitized dye.

But as with any new(ish) technology, it’s a matter of tradeoffs – in this case, better aesthetics for lower efficiency. While traditional photovoltaic panels convert sunlight at around 20% efficiency, existing solar window prototypes are only about 10% efficient.

A big part of that disparity is that most solar windows share the same limitation as normal solar panels – a reliance on direct sunlight. But a team of researchers at the École Polytechnique Fédérale de Lausanne (EPFL) have found a way to soak up light across the whole visible spectrum – direct and ambient – and that plus, presumably, the system’s ability to absorb UV light, supposedly leads to 15% efficiency in direct light and 30% in ambient.

If true, that would be a tremendous step forward for solar windows, which take up less space than traditional solar panels and blend a lot more organically into a wide variety of architecture.

According to the researchers, the DSCs’ transparency, multicolor potential, and low-cost fabrication opens a host of possibilities, and the DSCs are currently being deployed in glass facades, skylights and greenhouses.

While the DSCs aren’t available publicly, their timing is impeccable, arriving right when nations around the globe are trying to go emissions-free by 2050.