One of the first things you see when you visit the headquarters of ESS in Wilsonville, Oregon, is an experimental battery module about the size of a toaster. The company’s founders built it in their lab a decade ago to meet a challenge they knew grid operators around the world would soon face—storing electricity at massive scale.
Unlike today’s lithium-ion batteries, ESS’s design largely relies on materials that are cheap, abundant, and nontoxic: iron, salt, and water. Another difference: while makers of lithium-ion batteries aim to make them small enough to fit inside ever shrinking phones and laptops, each version of the iron battery is bigger than the last.
In fact, what ESS is building today hardly resembles a battery at all. At a loading dock on the back side of the ESS facility, employees are assembling devices that fill entire shipping containers. Each one has enough energy storage capacity to power about 34 US houses for 12 hours.
The company, which last year became the first long-duration energy storage company to go public and has ambitions to open factories around the world, will soon begin work on a battery that will dwarf even these truck-size versions. In partnership with the utility company Portland General Electric, ESS plans to construct one that will fill a half-acre building on land adjacent to its factory. It’s expected to have almost 150 times the capacity of the biggest batteries the company ships today.
ESS’s key innovation, though, is not the battery’s size—it’s the chemistry and engineering that allow utilities to bank a lot more energy than is economically feasible with grid-connected lithium-ion batteries, which are currently limited to about four hours of storage.
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