Arpa-E's $85-Million Plan to Build a Battery the Size of the Grid

The US Department of Energy's technology Incubator, ARPA-E, is working on a number of high risk but high reward solutions for energy storage. They see a need for a large increase in storage capacity as the electricity grid in America increasingly switches to solar and wind power.

ARPA-E are not satisfied with the top three solutions currently used - pumped hydropower, lithium-ion batteries and "flow" batteries.

Pumped hydropower is the pumping of water uphill so that it can flow through turbines at a later time. APRA-E estimates this accounts for approximately 95% of storage in the US. However, it requires large water supplies, large land use, careful compliance with environmental regulation, and hills. It's a reliable and cost-effective method but not applicable everywhere in the US.

Lithium-ion batteries, on the other hand, are relatively expensive and on a large scale potentially very dangerous. Lithium-ion batteries are flammable.

Flow batteries store energy in vats of electrolytes and, while scalable, are also expensive.

APRA-E are working on grid-scale battery storage, investing $85m in 73 projects at different universities and private companies since 2009. Of these projects, 8 are grid energy storage solutions. The main challenges are to make storage cheap and durable i.e. reusable after many cycles.

Their main goals are:
1 - $100 per installed kilowatt-hour of grid storage
2 - 5000 charge-discharge cycles (approx. 10 years of working life)
3 - Efficiency of 80 percent or greater per charge-discharge cycle

Arpa-E sees the flow battery as their best prospect, but development is still in early stages.

It's curious where inspiration comes from sometimes - a team from Harvard are exploring the use of quinone compounds, similar to a compound found in rhubarb, for improving the prospects of flow batteries.

As the electric grid is increasingly powered by renewables, it will need energy storage for when the wind isn’t blowing and the sun isn’t shining. But the three top grid-scale energy storage technologies today—pumped hydropower, lithium-ion batteries and “flow” batteries—arguably, aren’t up to the challenge.