19 September 2012
Saving materials cost is an area researchers are focusing on to help catalyse solar technologies to commercial viability. One way to achieve this is to reduce the required amount of expensive high-efficiency semiconductor material by shrinking the physical size of the solar cell array in the panel while still maintaining the same level of performance.
This is where concentrating photovoltaic — or CPV — technology comes in. Typically, CPV technology collects a large amount of sunlight, “bundles” it through lenses or curved mirrors and directs it onto a small area of solar cells to generate electricity. CPV therefore is a quintessential technology to save cost, exactly because a smaller area of photovoltaic material is required.
The Industrial Technology Research Institute (ITRI) in Chutung, Taiwan, however, has developed an entirely new type of CPV design that functions much like a LCD display, only in reverse. The SideLighter, as the Institute dubbed their innovative optical microstructure-based CPV design, receives sunlight on a flat panel, rather than a curved mirror or lens. The light is then channeled out toward the edges where the photovoltaics are located. As its name may be intended to indicate, the flat panel design offers the advantage that the SideLighter still achieves a strong concentration of light even when the light guide plate is tilted away from the light source. In experiments using solar cells that usually operate at 17% conversion efficiency, ITRI's SideLighter achieved 25%.
Most CPV systems that use parabolic reflectors require precise tracking of the sun. ITRI’s SideLighter, however, only needs single-axis course tracking for best performance, thanks to the advantageous flat panel layout. What’s more, with a normal-incident transmittance of just 40%, the panel does not completely block the sunlight, an attribute that could open the door to opportunities for mixed solar application.
Written by Sandra Henderson, Research Editor, Solar Novus Today