In early March, one of the newest of Alameda County, Calif.'s onsite solar power systems became operational on the roof of the Castro Valley Library. The 270-kilowatt solar array is designed to supply close to 100 percent of the electrical needs for the 34,500-square-foot library.

The $22.3 million library opened in fall 2009 and is on target to receive a LEED Gold certification from the Washington-based U.S. Green Building Council. The stucco, steel and glass structure accommodates a variety of community needs and features age-specific reading areas, a meeting room, bookstore, café and public computers.

The $1.7 million solar power system was funded by a 1 percent loan from the California Energy Commission made available under the 2009 American Recovery and Reinvestment Act (ARRA). The ARRA loan will be paid back over the next 15 years with savings from the solar-generated electricity. Also over the next five years, the county will receive an estimated $500,000 from PG&E under its California Solar Initiative Incentive Program.

The solar power system consists of 880 high efficiency modules manufactured by San Jose, Calif.-based SunPower Corp. and was designed and installed by Berkeley, Calif.-based Sun Light & Power, which also is installing a monitoring system that will display the solar array's performance on a flat screen monitor in the library's lobby. In the solar array's first month of production, the Castro Valley Library's power bill dropped dramatically. The library went from a March 2010 PG&E bill of $4,400 to a March 2011 PG&E bill of $283.