Researchers at Michigan State University have developed transparent solar concentrators that when placed over a window create solar energy while still allowing people to see through the window. The device can be used on buildings and even cell phones.
Past efforts to produce energy from solar cells placed around luminescent plastic-like materials were not successful because the energy production was inefficient and the materials were still highly tinted. Or as Richard Lunt, an assistant professor chemical engineering and materials science, nicely summed up: “No one wants to sit behind colored glass. It makes for a very colourful environment, like working in a disco.”
Recognising a need for new results, the team of researchers from Michigan State University took a major step forward when they decided to make the luminescent active layer transparent and developed a solar harvesting system that uses small organic molecules to absorb specific non-visible wavelengths of sunlight.
“We can tune these materials to pick up just the ultraviolent and the near infrared wavelengths that then ‘glow’ at another wavelength in the infrared,” he explained. The “glowing” infrared light is guided to the edge of the plastic where thin strips of photovoltaic solar cells then convert it to electricity. As these materials do not absorb or emit light in the visible spectrum, they appear transparent to the human eye.
The team sees a huge market for this technology because it can be applied to almost any surface, from skyscrapers with lots of windows to small mobile devices such as a smartphone or e-reader.
Lund admits that more work still needs to be done to improve the energy-producing efficiency, which is currently just under 1 per cent. The best coloured luminescent solar concentrator has an efficiency of around 7 per cent. The Michigan researchers aim to reach efficiencies of over 5 per cent.
Photo credit: Yimu Zhao, Michigan State University.
