Tomato Farm 0702

A tomato farm in Northern California. The CEC is considering a small-power-plant exemption for a proposed Amazon data center and 50 diesel generators on a working farm in Gilroy.

A tomato farm in Gilroy might be transformed into an Amazon data center with 50 diesel generators and a new 96-MW substation.

The California Energy Commission is considering granting a small-power-plant exemption that would allow installation of backup diesel generators at a proposed data center for Amazon Web Services. The data center would provide "cloud" infrastructure that is integral to California's economy, Amazon representatives said in the proposal [20-SPPE-03]. 

The CEC certifies thermal power plants with capacities of 50 MW or more that are proposed in California, but can grant a small-power-plant exemption for a facility between 50 and 100 MW if the commission determines it will not significantly affect the environment or energy resources.

The proposed diesel generation component at the Gilroy facility would consist of 50 2.5-MW generators that would supply power to data servers during a grid outage. However, previous reports showed that certain backup diesel generators at data centers in the area have been turned on at times other than grid outages or for testing and maintenance, CEC staff said at a June 25 business meeting.

The San Francisco Bay Area region currently has about 1.2 GW of backup diesel generation capacity at data centers and another 1.5 GW of proposed diesel capacity. Construction of new data centers in Silicon Valley could double the peak electricity load in the region by 2026, a previous research study for the CEC found (see CEM No. 1626).

Pacific Gas and Electric would supply electricity to Amazon's data center that would include a new substation, three new electric transmission poles and 1,000 linear feet of new overhead 115-kV transmission line. When asked if PG&E ratepayers or shareholders would fund the new electric infrastructure for Amazon, utility representatives told California Energy Markets that information was confidential.

The backup generators will be connected to the data center, not the grid, Amazon's proposal says. Therefore, the diesel facility would be different from a conventional power facility that is interconnected to the transmission grid and responds to calls from the California Independent System Operator. For the Amazon diesel generation plant, there is only one place the electricity can go: the data center, the proposal says.

Last year, state officials asked other, existing data centers to power up their diesel generators and push power onto the grid during high-demand times. Diesel power plants at data centers were useful in addressing reliability issues in the summer of 2020, CEC staff previously told CEM. The commission does not support the use of data center diesel backup generators as a long-term strategy for ensuring system reliability on hot summer days, CEC staff said.

If the CEC grants Amazon a small-power-plant exemption, the project will still need to be reviewed by local city officials and air quality organizations, staff said.

Separately, on June 25, the CEC granted a small-power-plant exemption for a 96.5-MW backup diesel generation facility at the Sequoia Data Center in Santa Clara. The CEC in September 2020 postponed its decision on Sequoia's small-power-plant exemption, in part due to air quality concerns from the California Air Resources Board and the Bay Area Air Quality Management District (see CEM No. 1607).

The Sequoia Data Center is located about 1.5 miles from an elementary school in a disadvantaged community. As part of the previous five data center applications in the area, BAAQMD asked the CEC to eliminate diesel generation in the community, proceeding expert Robert Sarvey said at the June 25 meeting. The City of Santa Clara, where the data center and diesel facility will be located, intends to be diesel-free by 2033, according to BAAQMD.

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Staff Writer

David Krause is an energy reporter covering the California Energy Commission and Air Resources Board. He writes about transportation, climate change, utilities, and wildfires. He has an MFA in Writing, an MA in English, and a BS in Civil Engineering.