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   23rd Feb 09

 National Semiconductor's new technology can help solar PVs to manage the shade better

National Semiconductor has commissioned a survey conducted by Greenberg Quinlan Rosner Research, to study the effect of shade on performance of Solar Photo Voltaics (PV). Survey points out, most installers of solar photovoltaic (PV) systems (54 percent) believe no amount of shading is acceptable on residential and commercial rooftop solar installations.

Due to the characteristics of solar arrays, small amounts of shade (for example, shading of less than 10 percent of the surface area of a PV system) can lead to disproportionate power losses of more than 50 percent due to mismatch in power generation. National Semiconductor going to introduce a technology later this spring, which manages the power generation differences due to shade and recoup up to 50 percent of power losses associated with partial shading.

The shades can be caused due to trees, chimneys and dormers, and intermittent debris including falling leaves, bird droppings and dust. In the case of structural shade, even correctly installed solar systems can be partially blocked from the sun at certain times of the day or during certain days of the year.

The outputs of survey are:
1. 41 percent of solar installers encounter shade when selling or installing a PV system.
2. Of those, 87 percent "frequently" or "always" design around shade.
3. Another 28 percent "frequently" or "always" tell the owner that solar cannot be installed.

The study also revealed that installers often place smaller solar arrays in order to avoid shady sections of customers' roofs. Roughly one third of installers said designing around shading increases system costs, and many said they lose time doing so. Additionally, nearly half of all installers have seen solar arrays whose performance has been impaired by shading.

"Shade happens, and customers and solar installers are picking up the tab," said Ralf Muenster, director of National Semiconductor's Renewable Energy Key Market Segment. "There is a real need to educate the market that shade does not mean 'lights out' for solar. Shade can be mitigated."

Shade need not be terminal for solar power. While solar cell manufacturers have poured millions of dollars into research and development to improve conversion efficiencies by a fraction of one percent, solving power mismatches from different panels within a single solar array, whether caused by shade or other problems, can yield improvements in system performance of more than 30 percent.

The technology named SolarMagic power optimizer from National Semiconductor is a new energy management product that will mark National's strategic entry into the photovoltaic market. The power optimizer will enable installers to embrace shade, placing PV systems on roofs previously regarded as receiving inadequate levels of sunlight to justify a solar array.

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