News and analysis about energy in California with an eye toward renewables.

Can Electricity Be Stored Safely and Effectively? Firm Gets Big Money for Big Goal

Like this, only much, much bigger | Photo: Mick O./Flickr/Creative Commons License

Here's yet another contender in the push to find ways to store electrical power efficiently and effectively: the East Coast firm EOS Energy Storage just announced it's raised $15 million to develop affordable, scalable power storage for the grid using zinc-air battery technology. The company announced a plan to test its grid batteries on Con Edison's grid in New York City earlier this month.

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The new infusion of funding comes from a consortium of more than two dozen companies, NRG Energy the largest among them.

As we've mentioned here before at ReWire, the grid's inability to store power is usually seen as the biggest obstacle to getting out power entirely from renewable energy. Without a way to store power, the grid must be hooked up to active generating capacity at all times to meet power demand. Though renewable sources such as hydro, geothermal, and biomass can conceivably provide power 24/7, solar and wind are the fastest growing sources of renewable electrical power, and both are intermittent. When the sun goes down and the wind stops, solar and wind power stop flowing into the grid.

If the grid had storage capability, we could just save up energy during sunny days and use it later. We do have storage technology, but it's generally too expensive or too toxic, or both, to use on the massive scale the power grid would require.

EOS Energy Storage's batteries may offer at least a partial solution. EOS uses a zinc-air technology for its batteries. Perhaps more properly called "zinc-oxygen-water vapor batteries," zinc-air batteries store power chemically in the form of metallic zinc particles mixed with an electrolyte paste, usually potassium hydroxide. When exposed to oxygen in the presence of water vapor the zinc oxidizes, giving up electrons.

Small zinc-air batteries are in common use today in applications such as camera and hearing aid power packs. For use as grid storage, zinc-air batteries would not only need to be made far larger, but also rechargeable, which has historically proven somewhat difficult.

EOS keeps more or less mum regarding its approach to those challenges, describing that approach in rather vague terms:

Many challenges have prevented the rechargeability of zinc-air batteries. Eos' Znyth technology has achieved electrical rechargeability through proprietary innovations that address battery architecture, electrolyte composition and management, materials, systems and manufacturing processes.

GreentechMedia's Jeff St. John reports that that essentially means EOS is using salt water as an electrolyte.

Vague descriptions aside, EOS claims its forthcoming grid storage battery the EOS Aurora will provide 6 megawatt-hours worth of storage, enough to provide 500 average American homes with six hours worth of power. The unit will fit into a standard shipping container and be good for 10,000 charge cycles, about 30 years. EOS goes so far as to project that its batteries, which will cost about $160 per kilowatt-hour of capacity, will be cheaper than new gas-fired turbines as a way of putting power into the grid.

If EOS can make its zinc-air technology work, there'd be a couple of distinct advantages. Though it's far from completely non-toxic, zinc is actually significantly less poisonous than the lead used in lead-acid batteries now used for small-scale power storage, and it's safer to work with than the corrosive lithium found in current lithium-air batteries. Zinc is also far more abundant than lithium, and the United States holds about a third of the world's known reserves.

Zinc-air batteries also have a much lower likelihood of overheating, catching fire, and burning up your electric car.

We'll definitely be keeping an eye on EOS.


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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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