14 DAY TRIAL // A team of researchers from Japan, has been very inspired by the moth eye's microstructure and they created a new film for covering solar cells that can reduce the amount of reflected light and capture more power from the sun.
Noboru Yamada, a scientist at Nagaoka University of Technology Japan, who led the research with colleagues at Mitsubishi Rayon Co. Ltd. and Tokyo Metropolitan University, came up with the inspiration for this new technology several years ago.
At that time, the researchers started looking for a broad-wavelength and omnidirectional antireflective structure in nature, and the eyes of the moth were the best they found.
The eyes of the moth are special because, besides allowing them to see very good at night, they are covered with a water-repellent, antireflective coating, which makes them the least reflective surfaces in nature, and keeps the moths undetected from predators in the dark.
According to Yamada, the most difficult thing about making this film was designing a seamless, high-throughput roll-to-roll process for nanoimprinting it, but the solution to this problem came from Hideki Masuda, one of the authors on the Energy Express paper, and his colleagues at Mitsubishi Rayon Co. Ltd.
“Surface reflections are an essential loss for any type of photovoltaic module, and ultimately low reflections are desired,” said Yamada.
In a published paper, the team talks about the improved performance of photovoltaic modules in laboratory and field experiments, and they predict how this anti-reflection film would improve the performance of solar cells deployed over huge areas in Tokyo, Japan and Phoenix, Arizona.
These two cities have been chosen because, on one hand, Phoenix is a 'sunbelt' city, with high annual amount of direct sunlight, while on the other hand, Tokyo is well outside the sunbelt region with a high fraction of diffuse solar radiation.
These new films should improve the annual efficiency of solar cells by 6% in Phoenix and by 5% in Tokyo, and even though this doesn't seem much, Yamada said that “every bit helps,” because “the efficiency of photovoltaics is just like fuel consumption rates of road vehicles.”
The researchers are now working on improving the durability of the film and optimizing it for many different types of solar cells.
They also think that the film could be applied as an anti-reflection coating to windows and computer displays.
The paper presenting this research appears in Energy Express, a bi-monthly supplement to Optics Express, the open-access journal published by the Optical Society (OSA).