UK-headquartered battery storage investor-developer Gore Street Energy Storage Fund (GSF) has completed energisation of the 200MW/400MWh Big Rock battery energy storage system (BESS) project in California, US.
GSF acquired Big Rock from developer Avantus in 2023, at a construction-ready phase. In November 2024, GSF secured a US$80 million increase in debt facilities for its battery storage projects, including the Big Rock BESS project.
System integrator LS Energy Solutions partnered with GSF on Big Rock, located in Imperial County, Southern California. The BESS project secured a 12-year fixed-price Resource Adequacy (RA) contract worth over US$165 million with J. Aron & Company LLC, a subsidiary of the global investment bank.
As announced in October 2024, the RA contract will start in Summer 2025 and is fully ‘stackable’, meaning that GSF can combine it with other revenues from wholesale trading and ancillary services.
Try Premium for just $1
- Full premium access for the first month at only $1
- Converts to an annual rate after 30 days unless cancelled
- Cancel anytime during the trial period
Premium Benefits
- Expert industry analysis and interviews
- Digital access to PV Tech Power journal
- Exclusive event discounts
Or get the full Premium subscription right away
Or continue reading this article for free
The RA contract will account for 40% of the project’s revenue over its lifetime and support raising project-level debt due to its guaranteed revenues. Big Rock is also expected to receive an investment tax credit (ITC) of up to 30% of qualifying capital expenditures under the Inflation Reduction Act (IRA).
GSF says the project represents a 47% increase in its energised capacity, bringing the total to 621.4MW/792.1MWh, with Big Rock representing the largest portion of that capacity.
The project is composed of 137 of LS’ AiON-ESS all-in-one solutions (Premium access article), including integrated DC and AC components and LS’ modular 140 kCA string inverter AiON-SIS. LS Energy brought the first container to be deployed at Big Rock to the 2023 RE+ 2023 trade show.
The Big Rock BESS also marks GSF’s first project in the California Independent System Operator (CAISO) market. The investor-developer owns projects in the UK, Ireland, Germany and Texas.
Included with the announcement of Big Rock’s energisation, GSF noted that construction is progressing well at the 75MW/75MWh Dogfish project in Texas, with an expectation of energisation in February.
However, the company is facing delays in energising the 57MW/57MWh Enerby BESS in Great Britain. GSF says this is due to last-minute transformer inspection requirements from the National Grid Electricity Transmission (NGET).
GSF originally only invested in projects in GB but expanded into international markets. In 2023, the company’s results for the first half of its financial year showed this strategy to be successful. The revenue/MW/hour in ERCOT for GSF was five times higher than GB.
This was the same year that market analytics firm Modo Energy recorded the lowest average revenue levels to date for UK BESS projects. The result of a heavily saturated BESS market and as the firm said, a continuation of frequency response revenues falling since the launch of the enduring auction capability, a mechanism designed to help deliver co-optimised procurement for the day-ahead frequency response and reserve products.
GSF is also using Germany-headquartered provider ACCURE’s cloud-based battery data analytics software in two projects in the UK. GSF says the predictive analytics solution is able to reduce operational issues and the risk of fires caused by thermal runaway events.
Implementing this software in US projects could increase confidence among investors, with fire risk and thermal runaway becoming a growing concern across the country.
In Van Zandt County, Texas, where the grid is managed by ERCOT, 20 residents have filed a lawsuit seeking damages and an injunction (Premium access article) against the renewable energy investment arm of Finland’s Taaleri Group and the US arm of UK-based RES Group over the construction of a lithium-ion BESS.
This followed the October news that council members at Katy, Texas voted to deny a Special Use Permit for a 500MW standalone BESS proposed by IPP Vesper Energy (Premium access article). Concerns of fire safety were listed as a top concern in both of these instances.
California, where the grid is managed by CAISO, is the US’s leading market for battery storage deployment—with Texas a close second and catching up—but has just this past week also been in the headlines for the wrong reasons.
On 16 January, a fire at the Moss Landing facility in California, which houses what was once the world’s largest BESS broke out. The reasons for this fire are currently unknown.
Specialist renewable energy insurance company kWh Analytics also considers thermal runaway to still be the single most important risk that energy storage system developers must consider. GSF implementing this software and providing a track record of its reliability could help to assuage potential holdups in future projects and potentially help other developers in mitigating fire risks.
Alex O’Cinneide, CEO of Gore Street Capital, said of the Big Rock BESS:
“I am pleased to announce the energisation of the Big Rock project in California, marking our successful entry into a fifth energy market and a more than doubling of energised capacity across the portfolio on a MWh basis.”
“With the recent 12-year Resource Adequacy contract secured, the portfolio now benefits from significant contracted income and has surpassed 620 MW / 792 MWh of energised capacity. This achievement reflects our commitment to executing against our mandate, made possible through leveraging our in-house expertise with dedicated teams for construction, asset management and route-to-market/optimisation.”
