Dive Brief:
- ESS Tech is launching a 1.2-MWh “building-block” sodium-ion battery system for utility, commercial, industrial and data center customers, it announced July 8.
- The modular ESS Bridge product can be stacked to deliver up to 4.8 MWh of energy in a traditional 20-foot battery container, the company says. That’s roughly the same capacity as the latest iteration of Tesla’s Megapack, one of the most popular grid-scale energy storage systems on the market.
- ESS Tech’s announcement is the latest in recent months from sodium-ion battery manufacturers and customers as they seek alternatives to the lithium-ion chemistries that dominate electrochemical energy storage today.
Dive Insight:
Other recent sodium-ion battery developments came from Colorado-based Peak Energy. Late last year, Peak said it would deliver up to 4.75 GWh of its sodium-based batteries by 2030 to an independent power producer, Jupiter Power. In June, Peak announced a manufacturing and design partnership to support General Motors’ stationary storage aspirations, saying it would build a 4-GWh manufacturing plant in Sacramento, California.
For its part, ESS Tech says it has attracted more than $1 billion in “early-stage customer opportunities” since announcing in late April that it would procure 8.5 GWh of sodium-ion battery cells and modules from Alsym Energy.
That announcement marked Oregon-based ESS Tech’s entry into the short- and medium-duration energy storage market, the company said at the time. Last week, ESS Tech said ESS Bridge could be configured to deliver “16 hours or more” of continuous discharge.
ESS Tech spent the first 15 years of its existence commercializing iron flow batteries that it says can deliver eight to 22 hours of energy capacity over tens of thousands of discharge cycles. It has struggled to develop that market since going public via a reverse merger in 2021, however, as competitors’ deployments of conventional lithium-based battery systems skyrocketed. Its stock price has fallen from nearly $300/share shortly after listing to less than $1/share today.
ESS Tech CEO Drew Buckley said in a statement that ESS Bridge would “meet the demand we're already seeing” from data centers and utilities while offering a “superior” alternative to lithium-ion batteries.
“AI workloads are reshaping what data centers need from energy storage, and sodium-ion handles those power needs more effectively than conventional technologies,” Buckley said.
Sodium-ion proponents like Buckley say the technology is ready to capitalize as utilities and large-load customers push to secure more capacity on increasingly power- and transmission-constrained U.S. grids.
Experts say sodium-based batteries are less prone to thermal runaway, a chain reaction caused by system faults or unsafe operating conditions that can cause catastrophic fires. One such fire in early 2025 destroyed most of a 300-MW Vistra energy storage facility near Santa Cruz, California.
That stability allows sodium-ion batteries to operate at virtually any temperature likely to occur on Earth’s surface, according to the International Energy Agency. It also allows air cooling systems that use less energy, require less maintenance and promise lower total cost of ownership than the active, liquid-based systems that typically cool lithium-based batteries, ESS Tech says.
ESS Tech, Peak Energy and other sodium-ion battery companies say the technology has another advantage in supply chain surety — a welcome contrast to lithium-based battery supply chains dominated by Chinese companies. Sodium is cheap and abundant in North America, reducing manufacturer and customer exposure to geopolitical risk and U.S. government restrictions on buying from “foreign entities of concern,” ESS Tech says.
Sodium-ion battery production and installed capacity lag far behind lithium-based systems, however. And in part because elemental sodium is more than three times heavier than lithium, sodium-based batteries are generally less energy-dense, requiring a larger footprint to deliver the same energy capacity as lithium.
