National Semi Innovation Recoups Over 50% of Solar Power Lost Due To Shade

March 08, 2009 by Jeff Shepard

National Semiconductor Corp. announced that test results reveal that a new technology from the company can recoup up to 57% of the power lost due to temporary or partial shading of photovoltaic (PV) solar panels. The SolarMagic™ power optimizers are said to improve the energy harvesting of solar panels in real world conditions, where shading and other issues can significantly reduce the performance of solar systems.

In tests conducted at National’s Santa Clara, Calif. facility, a screen representing typical rooftop obstructions shaded a portion of a conventionally wired solar PV system. Although 8 to 16% of the array was shaded over the course of a day, it resulted in average power losses of between 35 and 40%. However, an identical solar array fitted with National’s SolarMagic power optimizers produced on average between 30% and 37% more electricity in the same conditions – effectively recouping up to 57% of the lost power.

"SolarMagic power optimizers have the potential to transform the solar market," said Ralf Muenster, Director of National Semiconductor’s Renewable Energy Segment. "This new technology tackles several problems that have long faced rooftop PV systems--shading and panel mismatch--and provides a viable solution to commercial customers and homeowners worldwide. Enabling the installation of solar arrays on roofs that were previously deemed unsuitable will also help the United States reach the ambitious renewable energy goals set by the Obama administration."

National developed SolarMagic technology to improve the energy harvest of solar arrays. Because of the characteristics of solar modules, shading – which can be caused by a range of real world problems such as trees, chimneys, guardrails or leaves – can lead to disproportionate power losses. For example, shading of less than 10% of the surface of a solar panel can slash power output in half thus undermining the return on investment for homeowners.

For the testing, the test array and the reference array were each comprised of two strings with 12 PV panels per string. Both strings were attached to a Xantrex GT5.0-NA-240/208 inverter. The performance data was collected using Xantrex’s software, and had a measuring accuracy of +/- 5%.

According to a recent market survey commissioned by National, 54% of solar installers in the United States believe that no level of shading is acceptable, while 41% say they encounter shade when selling or installing solar systems. SolarMagic power optimizers will be available starting this spring.