Green Cities

The Future of Green: Solar Windows

**This is the sixth installment of our new blog series: The Future of Green. Every other Friday we will post a blog about a cutting-edge and futuristic innovation in the world of green technology. Technology is one of several barriers that stand between today’s society and a sustainable future. The innovators we highlight through The Future of Green are shattering those barriers. Make sure to tune in every other Friday for a glimpse into the future of energy and sustainability. A few weeks ago, we wrote about smart windows—windows capable of controlling the amount of heat and light that pass through, resulting in huge energy efficiency gains. Today, we highlight windows once again, this time focusing on “solar windows,” an emerging technology that allows windows to double as solar panels. Leading the way in solar window technology is a public-private partnership between New Energy Technologies (NET) and the National Renewable Energy Laboratory (NREL). Together, they’ve developed a solar window coating, composed of “the world’s smallest functional organic solar cells—“about one-fourth the size of a grain of rice. While typical solar panels use silicon, the smart window coating relies on hydrogen-carbon materials, considered “organic solar cells.” Here’s how it works: Once the solar coating has been applied to glass, the cells arrange themselves into a network connected by “invisible wires.” Electrons get knocked off of their atoms and start to move. That potential energy is eventually converted into usable electricity. So what makes this technology different? For one, it’s transparent. And two, it can be sprayed, painted or applied retroactively to existing surfaces, which means that integrating the technology into our infrastructure should be fairly simple.

Unfortunately, the technology has been too expensive and not efficient enough to be commercially-available. That might be about to change, however, thanks to the ongoing work of NET and NREL. They took a huge step forward in 2012, developing a solar window module that was larger, easier to apply, and cheaper. “Over the past few months, our researchers have unveiled a virtually invisible conductive wiring system, which collects and transports electricity on SolarWindow™ prototypes, and fabricated a large area working module, which is more than 14-times larger than previous organic photovoltaic devices fabricated at NREL. Earlier, we developed our first ever working SolarWindow™ prototype using a faster, rapid scale-up process for applying solution-based coatings,” said NET CEO John Conklin, “Together, these achievements have moved us closer to our manufacture, scale-up, durability, and power production goals—all important factors to advancing our SolarWindow™ technology towards commercial launch.” In May, the researchers revealed other important breakthroughs. The process of applying the solar coating, which used to take a couple days, can now be completed in a few hours. New developments have also allowed for a doubling in conversion efficiency and improved transparency in the glass. It’s easy to imagine the potential uses for this extraordinary technology. It could be applied to the windows in family homes and large commercial buildings. Eventually, one can imagine, the solar cells could cover nearly every glass surface, constantly generating electricity. It seems that commercial availability of the technology is on the horizon. In the meantime, we’ll anxiously await its arrival. Did you miss past entries in The Future of Green? Here they are: Record-Breaking Solar Cells, Automatic Light Switches Reimagined, Smart Windows, The Hyperloop, and Floating Offshore Wind Turbines.