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High-tech energy system at Santa Rita Jail

Staff writer |
The Energy Storage North America (ESNA) recognized S&C Electric Company with an Innovation Award for their work on the Santa Rita Jail microgrid. Santa Rita Jail is one of the largest jails and among the most modern high-tech energy systems.

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Santa Rita Jail is one of the United States' largest correctional facilities, spanning 113 acres near San Francisco and with enough space for 4,000 inmates. Since jail officials need a reliable source of energy all day, every day, they turned to engineers to think about something innovative.

The jail's power infrastructure was upgraded to function as a microgrid using onsite generation. This microgrid system allows the facility to operate indefinitely without a connection to the local utility grid. Their onsite power sources include diesel generators, fuel cells, lithium-ion batteries, and renewable resources, such as a 500-kW solar array and microturbines

Santa Rita Jail needs 3 MW of power per day in average, they needed a way to store excess energy produced by onsite generation and they also needed a system allowing them to purchase power during non-peak hours, store it, and then use it during high-cost peak demand periods.

The jail's size came with an interesting price tag - $3 million in utility bills each year. Here the new energy grid helped too: The $7.7 million project was jointly funded by the state and the U.S. Department of Energy and it is saving about $100,000 per year in energy costs.

The system uses a 2-MW S&C PureWave Storage Management System to control 4 MWh of lithium-ion batteries. This energy storage system gives up to 8 hours of back-up power in case of an outage. It also provides the facility with spinning reserve and onsite renewable energy generation shifting, allowing the microgrid to maximize use of onsite renewable energy generation while protecting the reliability of the microgrid.

Through the years, along with the battery pack, the jail installed a 1.2-Megawatt (MW) peak-power solar PV array capable of meeting about 30 percent, a 1 MW molten carbonate fuel cell power plant capable of meeting 50% of the jail's electricity needs and 18% of the facility's waste heat requirements, and five wind turbines, each generating about 2.3 kilowatts (kW) at peak.

Santa Rita Jail is now able to generate the power it needs, the costs went down, and there are still two back-up diesel generators, just in case.