Home to over 1.3 million people, Alameda County, California encompasses a land area of 738 square miles on the east side of San Francisco Bay. Alameda County has been a leader in smart energy strategies for years. The vision and leadership of the County's Board of Supervisors and General Services Agency had lead to reduced annual energy usage and costs.
The Santa Rita Jail is the largest energy user of all the Alameda County government buildings. Management faced a dilemma: How could they provide reliable, cost-effective power to such a large facility, and how would they financing such a project?
Aerial view of Santa Rita Jail
By leveraging one of California's most plentiful resources--the sun--and embracing renewable solar photovoltaic (PV) technology to generates clean, reliable power, Alameda County significantly reduced it's operating costs and helped to contributed to California's sustainability.
In Spring 2002, Alameda County completed the largest rooftop solar electric system in the nation atop the Santa Rita Jail in Dublin, California. The Santa Rita Jail is the largest energy user of Alameda County's government buildings, and this solar installation, completed in three phases, was commissioned to help Alameda County reduce and stabilize future energy costs. Clean energy is generated by a 1.18 megawatt installation consisting of three acres of solar photovoltaic panels, and helped Alameda County weather the California state energy crisis by reducing the jail's monthly electric bill and replacing pollution-generating electricity with pollution free, on-site solar power.
The Alameda County solar project offers proof that solar electricity and energy efficiency are a strong blend of technological innovations well suited to respond to California's stressed power grid. By integrating Santa Rita Jail's solar electric generation with an energy efficiency plan, Alameda County was able to reduce its peak power consumption by at the Santa Rita Jail by 30%.
The solar project goals were to reduce the Santa Rita Jail's utility costs as well as contribute to California's sustainability and environmentally sound initiatives. During the daytime, Santa Rita Jail's solar system generates enough electricity to power 1200 homes. Over 1.4 million kWh of annual electricity consumption are diverted from the utility power grid, and these savings benefit all state consumers by reducing grid power purchases. Most of these purchases occur on-peak, meaning during times of the tightest supply and highest demand. Net savings to Alameda County in its first year of operation will average $425,000. Over the 25 year operating life of the project, the net savings will exceed $15 million.
Santa Rita Jail's solar electric system was installed in three phases. The first phase consisted of a 519 kW system located on the top of six of the jail's eighteen housing units. Three months later phase II was implemented, with an additional 131 kW. In April 2002, phase III was completed, adding 530 kW to what has become the largest rooftop solar electric system in the United States. Fourteen of the jail's housing units now have solar photovoltaic systems installed on their roofs. Together, the systems produce up to 1.18 MW of clean electricity under peak sunlight conditions.
The photovoltaic systems installed at Santa Rita Jail are a lightweight building-integrated (BIPV) roofing assembly that is installed over an existing waterproof roof membrane. The PowerGuard PV system utilizes silicon semiconductor technology to convert sunlight directly into electricity.
In addition to generating electrical power, the PowerGuard solar roof system provides R-20 value thermal insulation to decrease building energy consumption and reduce heating and air-conditioning costs. PowerLight's solar roofing tiles also extend the roof's life by protecting the roof membrane from harsh UV rays and thermal degradation.
"The combined solar electric power and energy efficiency solutions we implemented through our relationship with PowerLight reflects the future of the energy industry. With solar electric generation, we reduced our overall energy cost, and in particular, reduced our purchases of expensive, peak energy from our local utility. With energy efficiency and demand side management technologies, we have maximized the value of our solar investment, while at the same time modernizing our facility."
Matt Muniz
Energy Program Manager
Alameda County
