Spain-based renewable energy firm Acciona Energia has acquired a two-hour energy storage system in ERCOT, Texas, from Qcells.

The two companies have closed the sale of the Cunningham Energy Storage project in Hunt County, claiming it will be the largest project in the state’s market, operated by ERCOT (Electric Reliability Council of Texas), when it is commissioned in early 2023.

The 190MW/380MWh system, pictured above, will connect to the grid within the service territory of Rayburn County Electric Cooperative, according to Qcells’ announcement of the project’s acquisition in 2018. Rayburn is one of around 75 non-profit electric cooperatives active in the state.

Qcells USA is the solar and storage engineering, procurement and construction (EPC) arm of Qcells, the integrated solar PV and smart energy system firm headquartered in South Korea under Hanwha Group’s ownership but with its main technology and innovation facility in Thalheim, Germany where it was founded, and with offices globally.

The transaction with Acciona also includes six additional projects at an ‘advanced development stage’ but the companies gave no details about these.

Acciona’s acquisition of Cunningham comes three months after Qcells secured US$150 million in financing for the project (and a few others) from European banks BNP Paribas and Crédit Agricole CIB, as reported by

Rafael Mateo, CEO of Acciona Energía, said: “This transaction is an important milestone, as it includes the biggest BESS utility scale project in one of the world’s most developed BESS markets. With 1,214MW renewable capacity operating and under construction in Texas, this deal is a good opportunity for ACCIONA Energía to strengthen our presence and optimise the risk profile of our portfolio.”

Texas is the second-largest energy storage market in the US after California, with around 4GW of battery storage with ERCOT interconnection agreements and at least 1.2GW of that already online (as per figures from March this year).

Battery storage projects have historically made most of their revenues from ancillary services RRS (regulation reserve service) and RRS-FFR (fast frequency response) but are increasingly now trading energy, particularly around ERCOT’s most congested nodes.

Projects are therefore moving up to two-hour durations (and in some cases beyond) to increase their ability to capitalise on this, with Cunningham the largest example of that. Texas’ main renewable source is wind which is a substantially more volatile and intermittent energy source than solar (as opposed to California where solar is much larger).’ publisher Solar Media will host the 5th Energy Storage Summit USA, 28-29 March 2023 in Austin, Texas. Featuring a packed programme of panels, presentations and fireside chats from industry leaders focusing on accelerating the market for energy storage across the country. For more information, go to the website.