While the solar energy industry is expanding — at an average annual rate of 68 percent from 2006 to 2016, according to the Solar Energy Industries Association — solar panels and solar cells still have an efficiency issue.
“Any light that is not being absorbed by your solar cell is decreasing the efficiency of your solar panel,” said Paul Leu, an associate professor of industrial engineering at the University of Pittsburgh’s Swanson School of Engineering. “Anything you can do to increase your efficiency is good.”
About 4 percent of light that comes into contact with solar panels and cells — the part of the panel that converts sunlight into electricity —is reflected off, leading to lost energy, he said. Leu has been researching new glass technology that aims to increase the light absorbed by solar panels to give them an extra energy boost.
The glass that Leu is developing is based on nanostructures about 1,000 times thinner than a human hair. Under a microscope, these tightly packed structures look like a field of clear blades of grass.
This structure’s advantage, Leu said, is that it scatters light energy at different angles, giving the light that does bounce off a better chance to be trapped and converted into useable energy.
“With these nanostructures, you can get the reflection rate close to zero,” Leu said.
Building smarter windows
Using a video simulation, Leu demonstrated another feature of his glass research: using water as a control to turn the glass from clear to hazy.
This ability for a user to choose whether the glass is hazy or clear is still in its conceptual phase, but the process could be useful in smart window applications, Leu said, allowing control over the privacy of a room or blocking glare from sunlight in homes or office buildings.
“It’s a simple way to transfer between hazy and non-hazy within a few seconds by just applying or removing water,” said Sajad Haghanifar, a PhD candidate in industrial engineering who is aiding Leu in the research along with junior mechanical engineering student Rafael Rodriguez De Vecchis. “It could replace current, costly smart glass that uses electricity.”
Leu and Haghanifar said it’s too early to say how much more efficient this glass will be for energy absorption and storage, but early tests have shown promise. The study has been conducted on small pieces of glass that can be held in the palm of a hand.
Leu and his research group currently have a provisional patent on fused silica glass that combines both ultrahigh transparency and ultrahigh haze with the application or removal of water.
The team is also developing follow-up studies to measure the glass’ durability, possible self-cleaning capabilities and the technology’s use in flexible plastics, among other aspects.
As the team continues research for the provisional patent, Leu is looking for commercial opportunities to further develop the glass and possibly make it available for homes and businesses.