The U.S. Department of Energy’s (DOE) Office of Electricity has released a comprehensive report on the costs of various long-duration energy storage (LDES) options. According to the report, redox flow batteries offer the best cost-performance ratio.

The 51-page document (Fulfilling the promise of cost-effective long-term energy storage contains cost comparisons between 10 LDES technologies, from electrochemical energy storage to chemical energy storage, mechanical energy storage and thermal energy storage.

The 10 evaluated LDES technology areas span several energy storage families: redox flow batteries (FB), lithium-ion batteries (LIB), lead-acid batteries (PbA), hydrogen storage, sodium-ion batteries (NAIB), electrochemical double-layer capacitors (supercapacitors/EDLC), zinc batteries, compressed air energy storage (CAES), pumped storage hydropower (PSH) and molten salt energy storage (TES).

As of today’s state of the art, flow batteries have the best cost-performance ratio, at only $0.06/kWh, which is close to the Department of Energy’s target of $0.05/kWh. Lithium-ion batteries come in second at $0.07/kWh, followed by zinc battery variants, e.g. ZnMnO₂at 0.08 USD/kWh and the first rechargeable battery, the lead-acid battery, at 0.09 USD/kWh.

Sodium-ion batteries are still in their early stages at $0.26/kWh, but their commercial potential is high if new electrolytes and even anode-less batteries are developed, the report says. Supercapacitors suffer from low energy density and a high self-discharge rate. From a cost perspective, they are expensive at $0.34/kWh.

The DOE introduced the Long Duration Storage Shot in 2021 to achieve a 90% cost reduction by 2030 for technologies that provide energy storage durations longer than 10 hours.

It also evaluated the top three potential innovations for each technology to reach the $0.05 level, as well as the cost of research and development for 10 years, ranging from $90 million for supercapacitors to $1 billion for lithium-ion batteries.

On average, the top 10% of innovation portfolios can reduce LCOS by 12-85% across all storage technologies to $0.03-0.26/kWh, the report says. New materials, electrolytes, membranes and other components must be brought into production quickly to achieve critical mass and reduce overall system cost targets. Standardization is a key element in reducing development and deployment costs for lead-acid, flow and zinc batteries.

Photo: Invinity VS3-022 flow batteries in Soboba, California. infinity