Pacific Gas & Electric and Tesla have begun construction of a 182.5 MW/ 730 MWh lithium-ion storage system in Monterey County, California.

PG&E will own the facility at its substation in Moss Landing, but the design, construction and maintenance operations will be joint effort by PG&E and Tesla. The partners believe Moss Landing will be the largest utility-owned, li-ion battery energy storage system in the world.

It includes installation of 256 Tesla Megapack battery units on 33 concrete slabs. The Megapack, which was launched by the company last year and is being made at the Tesla gigafactory in Nevada, can store up to 3 MWh of electricity per unit.

Each unit houses batteries and power conversion equipment in a single cabinet. Transformers and switchgears will also be installed along with the Megapacks to connect energy stored in the batteries with the 115 kv transmission system.

This storage system will have the capacity to store and dispatch up to 730 MWh of energy to the grid at a maximum rate of 182.5 MW for up to four hours during periods of high demand. PG&E’s agreement with Tesla contains an upsize option that can increase the capacity of the system up to six hours or 1.1 GWh total.

Moss Landing BESS will participate in the California Independent System Operator (CAISO) markets, providing energy and ancillary service – such as serving as an operating reserve – to the CAISO-controlled grid.

“Energy storage is critical in achieving California’s clean energy goals, and the California ISO looks forward to working with PG&E in advancing its storage projects,” said Mark Rothleder, vice president, Market Quality & California Regulatory Affairs, CAISO.

In February 2017, PG&E deployed its first lithium-ion energy storage system, featuring Tesla Powerpack technology, at its Browns Valley substation (approximately 50 miles north of Sacramento).

CAISO serves about 80% of California and a small part of Nevada. California state leaders are mandating 100% clean energy generation by 2045, including 33% by the end of this year.