Imagine if every building in the world had solar power windows that could generate a small amount of electricity from the sun. The technology exists. It has been tested and it is ready for production. In Manhattan alone, there are 47,000 buildings with over 10,700,000 windows, according to a 2013 estimate from The New York Times.
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Transparency Versus Efficiency
The first challenge for researchers is to make the solar power windows transparent. “No one wants to sit behind colored glass,” Richard Lunt, an assistant professor of chemical engineering and materials science at Michigan State University. “It makes for a very colorful environment, like working in a disco.”
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Perovskite Is A Game Changer
In 2013, Oxford University researchers did a study on how neutral colored, semi-transparent solar cells made of perovskite could be used in building and car windows to generate electricity. Perovskite is an oxide used in ceramic superconductors. The Oxford researchers said their transparent solar cells can be made up to 20% efficient using a simple cell architecture.
The university’s work is being commercialized by a spin-off company, Oxford Photovoltaics, which is planning to produce colored and semi-transparent glass that works as a solar cell. Its glass could be integrated into windows and into the facades of buildings.
Two Companies Ready For Production
Two companies say they are ready to bring solar power windows to the marketplace, according to Computer World. They say the windows will cost about 40% more than ordinary windows, but claim the extra cost will be recaptured in a year through lower utility bills.
One is Solaria, a company that currently manufactures rooftop solar panels. It uses existing photovoltaic (PV) cells and slices them into 2.5mm strips. It then sandwiches those thin PV strips between glass layers in a window. “The way the human eye works, you don’t even notice them,” says Solaria CEO Suvi Sharma.
As the PV strips absorb light striking a building’s window, they also reduce solar heat gain, which lowers air conditioning costs. Solaria is targeting its technology for windows that will be installed in newly constructed buildings. It says its windows are about 8% efficient.
Delivering The Electricity
Once solar power windows generate electricity from the sun, who is that energy connected to the building? Each company uses a different approach. Solaria, embeds its wiring in the window frame. From there, it is connected to a dedicated electrical line that conducts it to a central power inverter. The inverter then converts the direct current from the solar window to alternating current that is fed into the the electric panel for the building.
The Solar Window technology offers more flexibility. It can power a micro DC-to-AC power inverter to provide electricity for a single room. It can also be connected to a distributed microgrid inverter to power a single floor of a building. Finally, it can be fed to a central inverter that supplies elecrticity to an entire building.
New Clean Power Opportunity
Many buidings are not good candidates for rooftop solar power systems. Skyscrapers and large urban apartment buildings cannot participate in the clean power revolution that rooftop solar is bringing to many homeowners. Solar powered windows could change that dynamic by providing the benefits of electricity from clean solar power to all buildings.
Solaria estimates that a skyscraper with south facing windows could generate up to a third of its annual electrical needs from solar power windows. Apply that to buildings around the world and you have the potential for a significant new source of clean, renewable energy that will pay for itself in a matter of months rather than a period of years.