Solar Cell Breakthrough and its Economic Feasibility
Posted by urjart on August 28, 2008
Solar Concentrator Innovation:
The goal of any solar concentrator is to concentrate the light that falls on a large area to a smaller one. Usually concentrators are large mirrors, lenses or other devices. The focused light increases the electrical power obtained from each solar cell “by a factor of over 40”.
MIT engineers report a new approach to harnessing the sun’s energy that windows can be used for this purpose. As a result, rather than covering a roof with expensive solar cells (the semiconductor devices that transform sunlight into electricity), the cells only need to be around the edges of a flat glass panel .Light is collected over a large area [like a window] and gathered, or concentrated, at the edges. Solar concentrators, in use today, track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain. Also solar cells at the focal point of the mirrors must be cooled, and the entire assembly wastes space around the perimeter to avoid shadowing neighboring concentrators.
Mechanism of the Window Concentrator
The MIT solar concentrator involves a mixture of two or more dyes that is essentially painted onto a pane of glass or plastic. The dyes work together to absorb light across a range of wavelengths, which is then re-emitted at a different wavelength and transported across the pane to waiting solar cells at the edges. A mixture of dyes in specific ratios, applied only to the surface of the glass, that allows some level of control over light absorption and emission. The mixture was made so that light can travel a much longer distance and light transport losses can be reduced, resulting in a tenfold increase in the amount of power converted by the solar cells.
Economic Feasibility:
Because the system is simple to manufacture, the team believes that it could be implemented within three years–even added onto existing solar-panel systems to increase their efficiency by 50 percent for minimal additional cost. That, in turn, would substantially reduce the cost of solar electricity.
Continuous Improvement in Solar Cell Efficiency:
Most of today’s solar cells are between 12% and 18% efficient. Some of the ones used to power satellites are around 28% efficient. In 1954, 4% efficiency was state of the art. In 2006 Boeing-Spectrolab managed to create a solar cell with 40.7% sunlight-to-energy conversion efficiency. Recently, just after two years scientists at the US Department of Energy’s National Renewable Energy Laboratory have developed solar cells with efficiency 40.8%. These cells are basically multi-junction solar cells and composed of several layers, with each slice capturing only a portion of the solar spectrum; this method of optical concentration is what has allowed cells to surpass the 12% to 18% efficiency barrier faced by most traditional modules.
References:
(1) http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=196602149
(2) http://web.mit.edu/newsoffice/2008/solarcells-0710.html
