Windows of the future may do more than brighten up our homes. Scientists are developing windows that can absorb solar energy and generate free electricity for our future smart homes and businesses. These windows aren’t ready to hit the market yet, but the potential is astounding for residential and commercial buildings, especially those with lots of windows.
Scientists at the Los Alamos National Laboratory are among those working to make this happen. They are creating semi-transparent double-pane windows with something called “quantum dots” incorporated into the glass layers.
Wikipedia defines a quantum dot as a very small semiconductor particle, “Many types of quantum dots will emit light of specific frequencies if electricity or light is applied to them, and these frequencies can be precisely tuned by changing the dots’ size.” Scientists have taken a great interest in quantum dots because they can be adjusted or “tuned” for a specific task, and they have a potential use for things like solar cells.
Quantum Dots for Solar Windows
For the Los Alamos solar window, scientists are using two kinds of quantum dots to separate the light spectrum. They call it “solar-spectrum splitting,” and, they say, it’s “key” for this process. Quantum dots that are “tuned” to absorb higher energy photons are being incorporated into the outer glass pane. Dots that are tuned to absorb lower energy photons are being embedded into the inner glass pane to absorb the rest of the light spectrum.
As reported by Electrek, the high-energy dots absorb the blue and ultraviolet parts of the spectrum and then re-emit them in the colors a standard solar cell can absorb. That light is then guided by a reflective material inside the two glass panes to the edge of the window and the window frame. Solar cells inside the frame are then used to collect that energy, and convert it to electricity.
Lead researcher Dr. Victor Klimov said, “The approach complements existing photovoltaic technology by adding high-efficiency sunlight collectors to existing solar panels or integrating them as semi-transparent windows into a building’s architecture.” The semi-transparency of the windows would also provide shade for the interior of the building, and the double-paned glass would provide insulation (1).
“Transitional” Solar Windows
The Los Alamos team isn’t the only one working on a solar powered window. Scientists at the National Renewable Energy Laboratory in Golden, Colorado, are also developing solar windows with a different technology.
The Denver Post just provided an update on their progress saying the team had developed a “switchable photovoltaic window.” This window will darken when hit by the sunlight and generate electricity at the same time. When the window is no longer exposed to the sun, the glass cools and transparency is restored (2).
This has been one of the big challenges in the development of solar windows. Traditional solar panels are opaque and can absorb a great amount of sunlight. Since windows are transparent, they let most of the light pass through. To increase the potential efficiency of solar windows, scientists have had to figure out a way to make them darker, without removing their ability to be transparent.
In this case, the glass is treated with methylamine gas to make it “transitional” like eye glasses that get darker when you go outside. As the glass heats up from the sunlight, gas molecules are released from the glass coating, making it darker. The molecules remain trapped in an area between two panes of glass, and can return to the coating and restore transparency when the glass cools.
The Post writes, transparent windows allow an average of 68% of the solar spectrum to pass through. When the window darkens, only about 3% of the sunlight passes through. The rest is absorbed, and can be used to generate electricity.
Solar Window Technologies
Another company, Solar Window Technologies, announced before Christmas, it’s about to start mass producing solar windows for use on commercial buildings. The company describes its technology as a first-of-its-kind transparent coating that converts ordinary windows into electricity-generating windows. That, in turn, could turn tall skyscrapers into “vertical power generators.”
This solar window technology does not require the manufacturing of new windows. The company says, the coating can be applied to existing windows as a veneer that’s cut to the size of the window. Power collected is then transferred to the edge of the window, where it’s collected by the company’s “proprietary interconnection system” and delivered into the building’s electrical system (3).
The website claims, the system is easy to install. Installation can be done by a window installer and a licensed electrician. The company also claims the coated glass will stand up to bad weather and hurricanes.
The December announcement included details about an agreement to begin the production at a facility outside of Los Angeles. It didn’t include an exact timetable however.
As you can see, it appears solar windows are about to make a big debut into the green energy realm. If they truly work as described, they could become the go-to solution for solar power generation, along with other solar solutions that don’t modify the appearance of a building, like traditional solar panels.
A blog, called Energy Sage, describes the solar window as a “building-integrated photovoltaic” because it’s a technology that’s built into an essential part of the home, like the new Tesla solar roof. They not only provide functionality, they also blend into the aesthetics of the home. The blog also lists a few other companies producing solar solutions for windows.