See-through solar windows see promise

Buildings equipped with 'power windows' could bring solar energy to new heights, and researchers from MIT are aiming high. They have created a translucent photovoltaic cells that can still capture enough light to generate electricity.
Written by Melissa Mahony, Contributor

One criticism that large utility-scale solar power plants encounter is the amount of land they need. But placing solar cells on existing structures could harness the sun's energy shining down in smaller yet more abundant places—and not just on rooftops.

Researchers from MIT recently developed a translucent solar cell that they hope could one day turn windows into small power stations. The organic photovoltaic cells allow visible light to pass through window glass while they capture the sun's nearly infrared light for the purpose of generating electricity.

Such solar cells have been created before, but the efficiency of see-through solar cells has always been a problem. It still pretty much is, though the researchers have improved upon it, publishing their work in Applied Physics Letters. Their prototype cells have reached 1.7 percent efficiency, compared to the less than 1 percent of previous attempts at the tech. Opaque cells of the same kind achieve around 2.4 percent efficiency.

Still, the developers know they need to go higher if their solar glass is ever going to adorn the sides of skyscrapers. By tweaking the materials within their solar glass, they say, they might be able to achieve efficiencies around 12 percent. This would be equal to some commercial panels.

Depending on location, the vertically-set solar windows would work best as the sun is rising or setting.

The photovoltaic material could either coat the glass or a flexible substrate that could then be applied to existing windows. The researchers don't know at this stage what the coating might cost. Overseas, a similar effort to energize windows is in the works. Last August,a Norwegian companyand a British university announced plans to create a thin-film-solar coating based on metal nanocrystals. Their goal is to reach 20-percent efficiency.

Another issue is how long these solar windows will work. Protecting the material from the elements and window washing by placing it within the inner surfaces double-paned windows is one suggestion. Max Shtein, professor of materials science and engineering at the University of Michigan, adds in a statement:

The lifetime of organic PV cells is a bit of an unknown at this point, though there is some hope...The potential of this technology is good if projected far into the future.

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Images: Flickr/swisscan and Geoffrey Supran

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