What role is large-scale battery storage playing on the grid today?
A ‘breakout year’ for storage
“Last year was a breakout year for the sector, to prove that on a utility-scale basis, battery storage is a viable, resilient and dependable source of energy,” Thomas Cornell, senior VP Energy Storage Solutions at Mitsubishi Power Americas tells PV Tech Power in a recent interview.
At the time of writing, around 6,500MW of grid-connected battery storage has been deployed in the most advanced markets in the US, UK and Australia, detailed in the table below. Around two-thirds was deployed last year.
But most interviewees agreed that despite these high deployments storage is still mainly being used for its power and not for its energy.
“Right now storage is mainly being a backup system. There’s hope it will start to do more load shifting of renewables but with the amount out there, it’s limited,” says Haresh Kamath, director of distributed energy resources and energy storage at Electric Power Research Institute (EPRI), the R&D and demonstration project organisation.
Shifting renewables-produced energy from periods of higher production to high-demand periods is the big long-term benefit of storage, but the ability to do this profitably is at a relatively early stage. And even where load shifting is happening, as in California, it’s not necessarily shifting renewables.
California ISO (CAISO)
As by far the most mature market on deployment, the California ISO (CAISO) grid is the ideal place to start with over 2,700MW of grid-connected storage on the system. Storage has taken off in response to a number of CPUC directives obliging utilities and other load-serving entities to procure new flexible capacity.
Gabe Murtaugh, storage sector manager for CAISO, tells PV Tech Power that energy storage is now regularly shifting as much as 6,000MWh of energy from low-price periods in the middle parts of the day to high-price periods later in the day. This goes a long way to helping dampen the so-called ‘duck curve’ in demand for power throughout the day in California.
But, Murtaugh adds, this load shifting is mostly shifting low-price but high-polluting gas resources: “There are some periods of overproduction of renewables and storage is certainly absorbing some of that energy but there will be some transition years before storage is charging primarily from renewable resources.”
CAISO recently revealed the role of storage during the Oregon Bootleg wildfire in July 2021, when it dispatched around 1,000MW to help keep the lights on after three transmission lines connecting the regions were disabled.