Energy Vault Holdings has announced the start of construction at its utility-scale green H₂ plus battery ultra-long duration energy storage system (BH-ESS) with 293 megawatt-hours (MWh) of dispatchable carbon-free energy.

Construction of the BH-ESS, which is being developed for Pacific Gas and Electric Company (PG&E) on less than one acre of land in the Northern California City of Calistoga, is expected to be completed by the end of Q2 2024. Upon completion, the BH-ESS, dubbed the Calistoga Resiliency Center, will be the first-of-its-kind and the largest utility-scale green H₂ energy storage project in the U.S. The battery portion of the system will be used to support grid forming and black start capabilities.

The system will be prepared to power downtown Calistoga and the surrounding area for up to 48 hours during potential Public Safety Power Shutoffs (PSPS), which occur when the powerlines serving the surrounding area must be turned off for safety due to high wildfire risk. PG&E’s proposal for the system was approved by the California Public Utilities Commission (CPUP) in April 2023.

Energy Vault’s BH-ESS will replace the traditional mobile diesel generators currently used to energize PG&E’s Calistoga microgrid during PSPS events in the area. The project represents a major advance in community-scale microgrid development and a significant step toward realizing the CPUC’s vision of cleaner forms of microgrid generation.

“The timely start of construction is an important milestone in our partnership with PG&E to deliver this first of its kind microgrid solution. We greatly look forward to not only its delivery but most importantly to the sustainability benefits it will bring to the Calistoga community,” said Marco Terruzzin, Chief Commercial and Product Officer, Energy Vault. “Our partnership with California’s largest public utility is yet another example of the growing recognition that optimizing grid resiliency and economics toward achieving decarbonization goals requires innovation that leverages multiple technologies and a ‘fit-for-purpose’ customer-centric approach when designing energy storage solutions. The City of Calistoga and PG&E have been excellent partners for Energy Vault, and we are excited to bring this innovative project online in the coming months.”

“Deploying cost-effective, next-generation energy supply and long-term storage technologies is essential to ensuring grid reliability and to achieving PG&E’s goal of a net zero energy system by 2040,” said Mike Delaney, Vice President, Utility Partnerships and Innovation. “PG&E is developing a portfolio of promising new forms of electricity generation and storage technologies, and identifying the right applications that will support the further proliferation of these technologies at the lowest capital cost and highest-impact locations.”

The energy storage system will be owned, operated and maintained by Energy Vault while providing dispatchable power under a long-term tolling agreement with PG&E. The company will leverage its VaultOS™ Energy Management System to control, manage and optimize the BH-ESS operations. The system has been developed under the umbrella of Energy Vault’s H-VAULT™ suite of hybrid configurations leveraging green H₂ and batteries, to ensure continuity and resilience during PSPS events. By coupling the ultra-long duration capabilities of fuel cells using green H₂, and the fast response capabilities of B-VAULT™️ lithium-ion batteries, H-VAULT™ provides the clean, reliable, cost-effective back-up power that is critical to enable islanded microgrids during transmission outages.

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, 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 PSPS outages. The solution is designed to operate during PSPS events, serving all the load within a safe-to-energize area in the City of Calistoga, including critical facilities such as fire and police stations, and shared services in the downtown and surrounding area.