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A row of nondescript buildings in the dry brown hills of Northern California, Alameda County's Santa Rita Jail became a national model for energy security in March 2012, when the facility switched on a "smarter" electrical grid. This microgrid, which incorporates simplified controls and large-scale renewable and clean energy generation with a 2-megawatt-capacity battery, was designed and built by Chevron Energy Solutions (CES), Chevron's subsidiary for energy efficiency and renewable energy solutions. One of the country's largest microgrids, this is a first-of-a-kind project involving multiple technologies and partners, including Chevron, the U.S. Department of Energy (DOE), the California Energy Commission and the California Public Utilities Commission.

Securing Power at a County Jail

Solar panels, wind turbines, a fuel cell and energy storage allow the Santa Rita Jail to generate and store its own power off the regional utility grid.

Video Transcript (38 KB)

"The grid's large onsite battery is charged during off-peak times and discharged during peak times. It has a very fast switch that enables it to respond to grid outages in milliseconds and separate the jail from the utility," explained Dave Potter, CES senior project director for Western Region operations. "This provides the facility with a self-sustaining grid that integrates all of the jail's onsite generation with energy storage for uninterrupted power—a critical factor in such an environment."

In the event of a disturbance to the utility grid, the jail can automatically disconnect from the grid and operate under its own power until reliable power from the local utility is restored.

The completion of the microgrid is the culmination of several projects involving Chevron and Alameda County that date back to the 2001 California energy crisis.

In 2002, Chevron's energy efficiency work enabled the funding of a 1.2-megawatt solar photovoltaic system—one of the largest of its kind at that time—on the jail's rooftop. Three years later, Chevron installed a 1-megawatt molten carbonate fuel-cell cogeneration plant at the jail, providing ultra-clean energy and waste-heat recovery while saving local government more than $260,000 a year and benefiting the environment. That project was followed by the implementation of energy efficiency and water conservation measures and the installation of five small wind turbines, further adding to the jail's renewable energy capacity.

Meanwhile, Chevron's partners provided funds for Chevron to build on this remarkable facility by designing and installing a 2-megawatt battery and automatic disconnect switch. This enables the facility to run under a platform based on a simplified control scheme, allowing the facility to seamlessly remove itself from the main utility grid and independently generate and store energy for its own use. This development advances the DOE's goal to deploy an interconnected energy network.

"This project is comparable to the computer-industry shift from the main frame to desktop," said Eduardo Alegria, Chevron senior engineer for power systems. "In this case, we switched from a centralized grid system to a decentralized one enabled by distributed, renewable generation and large-scale energy storage."

Through this project, CES is gaining valuable experience that can be applied to Chevron facilities as well. "Microgrid projects like this one may have applications for Chevron operations in other regions of the world," Alegria added.

Its ability to deploy new technologies in innovative ways is one reason why CES remains among the top energy services companies in the United States.

"Over the past decade, we've applied our experience to improve operations at our own facilities, too, and we expect to add even more value in the future," Alegria said.

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