DUBLIN, Calif. -- The nation's largest roof mounted solar array, being installed atop Alameda County's Santa Rita Jail in Dublin, California, was previewed this week by Alameda County's Supervisors and the county's General Services Agency.

The solar deployment, together with energy efficiency improvements, was commissioned to help Alameda County reduce and stabilize future energy costs. Once the Santa Rita project is complete, it will reduce the jail's use of grid generated electricity by about 20 percent through solar power generation and energy conservation.

Clean energy will be generated through a giant 500 kilowatt solar installation consisting of 4,000 roof tiles. The solar panels will help the county weather the state energy crisis by reducing the jail's monthly electric bill and replacing pollution-generating electricity with clean, on-site solar power.

The overall need for electricity at the facility will be cut by a combination of added insulation from the solar roof tiles and an upgrade of the jail's central plant with state of the art cooling equipment and controls.

The solar array is already partially up and running. When completed in late July, it will generate over 650,000 kilowatt-hours of clean energy annually, and reduce the jail's yearly electrical need by 890,000 kWh. This project is the first of many solar installations planned for Alameda County buildings.

"Over the past several years, Alameda County has reduced electricity use by more than 30 percent, and we save more than $4 million every year by doing so," said Alameda County Supervisor Scott Haggerty, president of the Board of Supervisors.

The Santa Rita jail houses male and female prisoners from communities on the eastern side of San Francisco Bay in more than 900 cells and several dormitory units.

"We estimate that Alameda County will save millions of dollars in electricity costs as a result of adopting solar power," said Alameda County General Services Agency Director Aki Nakao as he toured the partly completed facility.

"It's great to be part of a project that's environmentally friendly and saves taxpayers money. When it's completed, the Santa Rita project will be the largest rooftop solar electric installation in the United States, and, we believe, in the entire Western Hemisphere," said Tom Dinwoodie, CEO of PowerLight Corporation of Berkeley, the company that designed, manufactured and installed the solar array.

"Alameda County is taking a leadership role in energy conservation," said Haggerty. "We are extremely committed to adopting smart, innovative technologies to reduce our energy consumption and save taxpayer dollars. Deploying solar power and making county facilities more energy efficient are key components of our overall energy strategy."