The Monterey County Planning Commission approved the Tesla portion – known as the Elkhorn Battery Storage Facility – of four energy storage projects last week. The projects, totaling between 567 MW / 2.27-2.655 GWh, are part of a plan to replace the gas facilities located at the Moss Landing power plant located in California’s Central Coast near Monterey.

Other than the Tesla facility, are three other projects – the 300 MW/1.2 GWh Vistra Energy battery, Hummingbird Energy’s 75 MW/300 MWh facility, and the Micronoc 10 MW/40 MWh facility. The Tesla portion, per official documents, is still listed as a 4 hour, 182.5 MW facility – putting its capacity at 730 MWh. However, during earnings calls Tesla has communicated that there is a 6 hour option that will seemingly be exercised putting the capacity at 1095 MWh.

Tesla and PG&E hope to break ground on their project within a month, with hopes to complete construction by the end of the year.

The system layout found in the county documents show the Tesla Megapack locations on the left. Documents state approximately 268 Tesla Megapacks will be installed atop 37 concrete slabs. Each Megapack unit measures approximately 23.5 feet in length, 5.3 feet in depth, and 7.9 feet in height.

Per Tesla’s website, each Megapack is described as having 3 MWh of capacity – suggesting 804 MWh of capacity. It is probable that since these documents are aged, the sizing of the Megapack has been refined. If the site does end up offering a 6 hour, 182.5 MW/1.095 GWh, Tesla battery – approximately 365 individual Megapacks will need be deployed.

The particular value of the site is the existing electrical infrastructure for the gas facilities. The transmission lines coming into the area will allow for wind and solar to be wheeled in during high production periods, and saved for local high demand periods.

This energy will be received through the existing 115kV transmission line at the Moss Landing Substation. Documents noted that project components necessary to receive and re-distribute electricity to and from the electrical grid include:

Medium-voltage switchgear units (3)

75 or 90 MVA 115kV/21Kv transformers (3)

115kV high-voltage circuit breakers (3)

115kV disconnect switches (5)

Dead-end structures (3)

Approximately 200-foot-long 115kV electric interconnection line

A traffic analysis between the construction site and the local highway suggests that the project will result in approximately 180 daily trips.

The project’s O&M will occur on three levels. System Level Preventative Maintenance, Megapack Maintenance, and Equipment Enclosure Maintenance.

System Level Preventative Maintenance is anticipated to occur annually with an estimated work time of 2 hours per inverter block. System level preventative maintenance activities include: visual inspection, torque checks, and calibration checks of all components; cleaning of all components; coolant-level, battery and meter checks; transformer, switchgear, protective relay, and fire alarm testing; and touch up, repair, and/or replacement of necessary components.

Every five years, Megapack Maintenance – refrigerant refill and pump replacement – will require an estimated work time of 1 hour per unit.

Every ten years, for 1 hour per enclosure, Equipment Enclosure Maintenance will occur. Activities include coolant refill, fan replacement, and pump replacement for the inverters and coolant refill and replacement of fans, bypass valves, and door gaskets for the units.

The batteries have an expected lifetime of 15 to 20 years, and at end of life will be returned to the Tesla facilities in Nevada for recycling.