Solar Power Systems
Cloudy Days and Solar Panels - How Well Do They Work?
By Roger Diez
Even as solar panels sprout on more and more rooftops, people still have questions about their effectiveness. One frequently asked question is how do they perform on cloudy or cold days. The answer is twofold: cold days are no different than warm ones to a solar panel, but cloudy days make a significant difference.
Solar Panels: Let There Be Light
Photovoltaic (PV) panels operate on light, not heat, so the temperature is immaterial. But when cloud cover reduces the amount of sunlight, the performance of the average solar panel is significantly degraded. A PV panel on a lightly overcast day will produce about 50 percent of the electrical power produced in bright sunlight. On a very dark, heavily overcast day, only 10 percent to 20 percent of the power will be produced. Obviously, power from rooftop solar panels is more viable in areas which have more days of bright sunshine.
Photovoltaic Science Marches On
Fortunately for the future of green energy, scientists are working feverishly to improve the energy efficiency of photovoltaic panels. One such breakthrough is a relatively new design utilizing lenses with concentric grooves which focus the sun's rays on miniaturized PV modules. Scientists at the Rensselaer Polytechnic Institute in New York estimate that this design will achieve 80 percent efficiency, compared to the 14 percent efficiency of current solar panel design. In New Zealand, researchers at Massey University's Nanomaterials Research Centre are making dye-sensitized solar cells using titanium dioxide. These cells can be manufactured for a tenth the cost of silicon PV cells and are much more effective in low-light situations. Similar experiments at the University of Colorado utilizing cadmium telluride thin film also show promise of producing efficient, inexpensive solar panels with a "greener" manufacturing process. And in the United Kingdom, researchers at Swansea University in Wales are experimenting with a method of painting photovoltaic cells onto flexible steel sheets. The technology promises a new method of capturing low-light radiation, making solar power more viable in areas with fewer sunny days.
The solar energy reaching earth in one hour can power all human activities for a year. All we have to do is to capture it.

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