Energy Vault Holdings, a provider of sustainable grid scale energy storage solutions, and Pacific Gas and Electric Company, a subsidiary of PG&E Corporation announced on 5 January a partnership to deploy and operate a utility-scale battery plus green hydrogen long-duration energy storage system (BH-ESS) with a minimum of 293 megawatt-hours (MWh) of dispatchable carbon-free energy. 

The BH-ESS will use a hydrogen fuel cell powered by electrolytic hydrogen derived from renewable energy. It’s designed to power downtown and the surrounding area of the Northern California City of Calistoga for a minimum of 48 hours during planned outages and potential Public Safety Power Shutoffs (PSPS), which is when the powerlines serving the surrounding area must be turned off for safety due to high wildfire risk.

The companies claim the BH-ESS system’s capacity can be expanded to 700MWh, allowing it to operate for longer without refuelling. 

“We’re excited to partner with PG&E on this groundbreaking project that reflects Energy Vault’s differentiated ability to design, build and operate innovative and utility-scale energy storage solutions that meet our customers’ specific needs in achieving their grid reliability and decarbonization goals,” said Robert Piconi, Chairman and Chief Executive Officer, Energy Vault. 

“We are setting a new benchmark for what can be achieved with an innovative design that integrates the most advanced energy storage mediums in order to deliver a fully renewable green hydrogen battery energy storage system. We look forward to delivering this world-class resiliency system for the City of Calistoga, which has been an excellent partner throughout the evaluation and operational review process.”

The energy storage system, which is still subject to approval, will be owned, operated, and maintained by Energy Vault. It will provide dispatchable power under a long-term tolling agreement with PG&E.

Under the 10.5-year agreement, Energy Vault will provide “Distributed Generation-Enabled Microgrid Services” – a type of energy service that involves using grid-forming generation and storage resources, potentially in combination with demand-side resources, to provide energy, fault current contribution and to regulate voltage and frequency within the utility’s established parameters to enable the islanding of the Calistoga microgrid during planned outages.

Energy Vault’s proprietary Energy Management System will provide full system control and optimal dispatching across the multi-medium aspect of the project, including batteries, hydrogen tanks and fuel-cells.

PG&E will use and upgrade its existing distribution infrastructure to establish the microgrid.

The entire system will be developed on less than one acre of land and is expected to serve as a model for Energy Vault’s future utility-scale hybrid storage system deployments.