Washington state’s new 8 megawatt-hour flow battery is the largest of its kind

Ars Technica » Scientific Method 2017-04-07

Snohomish PUD

A company called UniEnergy Technologies (UET) has installed a new large flow battery on the grid in Snohomish County in Washington state. The 2MW, 8MWh battery system may seem like a small installation compared to recent projects in Southern California and Hawaii, but it's quite a step for the nascent flow battery industry. In fact, this installation is currently the largest capacity containerized flow battery system in the world. It's housed in 20 connected shipping containers and will be used by the Snohomish Public Utility District (otherwise known as SnoPUD), which has also invested in lithium-ion battery installations.

Flow batteries are less common than their lithium-ion brethren. But as grid-scale batteries go, they offer some interesting advantages to lithium-ion that could really pay off as some of the more obvious hurdles, like energy density and temperature sensitivity, are overcome. Flow batteries generally use two electrolyte chemical solutions stored in separate tanks, which are pumped into a common area where the solutions come in contact, often through a membrane, creating electrical charge. Flow batteries are cumbersome and much less energy-dense than lithium-ion batteries, but battery capacity is only limited by how much solution you can store. On a grid-scale level, that’s an advantage—grid-tied batteries don’t need to be portable or light, but they do need to store a great deal of energy.

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