Published on August 26th, 2011 | by Breath on the Wind


Eos Rechargable Zinc-Air Battery: Energy Storage “El Dorado?”

August 26th, 2011 by  


The dream of a “City of Gold” captured the imagination of a previous age. Today we search for a solution that will answer our aspirations for energy storage. We need energy storage for solar and wind resources. We need storage for peak shaving, frequency regulation. We need storage for electric vehicles. Lithium-Ion batteries are increasingly cost-effective with better energy density, however their future development is limited. The theoritical maximum energy capacity of present lithium-ion battery technology is not enough to give us the range we have come to expect from petrol vehicles. We will have to move, eventually, to a new battery chemistry to achieve increased energy density and range. Zinc-air holds a promising solution.

The Zinc battery that is non-rechargeable is what we most commonly use in our many portable devices. The anode tends to form dendrites, membranes destroyed and, when used with air, the air ports tend to become blocked by carbon dioxide. In yesterday’s 2GreenEnergy webinar, Craig Shields spoke to Steve Hellman president of Eos Energy Storage, (formerly Grid Storage Technologies) of Easton, PA about its “first ever long-life Zinc-air electrically rechargeable battery.” The secret to this discovery started in 2004 with a complete reworking of the way the battery is built.

Advantages of the Zinc-air battery start with its reduced volume. Other batteries must carry around cathode reactants where this battery needs only air. Zinc is a cheap and very common material, with the US, Canada, and Australia as primary producers. In a recent greentechgrid article, Michael Kanellos says, “The zinc/zinc oxide reaction is essentially infinitely renewable. By contrast, titanium and silicon oxide reactions can’t be reversed in the same way. Iron and lead have lower energy densities and lithium and sodium, which can pack quite a bit of energy, aren’t as stable.”

Several products are anticipated by Eos, such as the following:

The Eos Aurora 1000/6000 is designed for utility-scale energy storage and is delivered in a standard ISO 40′ shipping container (1MW/6MW-hr) for immediate deployment. There are no sub-components that need routine replacement, and the system is expected to last at least 10,000 true (full discharge) cycles, or about 30 years, with a cost of 1000/kW and $160/kW-hr. The cost does not include necessary inverters. Power supplied by this storage is expected to be less than gas turbine peaking plants at about $ .02 to $.06 /kW-hr. Product deliveries will begin in 2013.

The Eos Vista Zinc-Air Flow Battery is expected to be available after 2015. Anticipated energy density is around 100wh/kg, and 400wh/liter electrolyte can be removed and saved for re-conditioning. New electrolyte can be placed pumped into the battery and drivers can be on their way. Battery cost would be about $200/kW-hr. A Nissan Leaf with a 100-kW-hr Zinc-air battery might cost $8,000 less and have a range up to 340 miles. We could be well on our way to the city of Gold.

Photo via davidreber


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About the Author

We share this World; its past, present resources and our combined future. With every aspiration, the very molecules we use for life are passed to others through time and space so that each of us may be considered a Breath on the Wind. This part of the world's consciousness lives in NYC; has worked in law, research, construction, engineering; has traveled, often drawn to Asia; writes on Energy and Electric Vehicle issues and looks forward to all your comments.   "If you would persuade, you must appeal to interest rather than intellect." -- Benjamin Franklin

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  • sola

    Is the $200/kwh is a system level cost, including the battery management system?

    The $200/kwh cell-level cost is not really that far from 2013 lithium-ion batteries (it is said to be $400-300 for large-volume orders now) so this may not be a breakthrough from the cost perspective. Of course, this technology may have the potential for getting cheaper with mass production.

    On the other hand, the 10 000 cycle life is impressive and currently unmatched by li-ion batteries.

    Lets not forget that the automotive flow system (Eos Vista) would require electrolyte swap which requires a complete, currently non-existent infrastracture. You obviously cannot just go to a petrol station and expect to be able to swap your discharged zink electrolyte to fresh electrolyte. All (or at least a big number of) petrol stations should be eqipped with electrolyte regenerating equipment or a distribution system for continuously getting fresh electrolyte. Not unimaginable, but it will require serious investment. Now, if Better Place invested into this technology, then I could imagine a working system for this, since BP will run a huge network of recharging/swapping stations anyways.

    • Breath on the Wind

      The Vista Flow system battery is at least 3 years down the road. It will probably be a licensed technology rather than one built in house. Presently we could swap batteries or recharge them. The flow battery would simply give another option to keep the battery in place and change the electrolyte. It could be recharged but as power density is nothing special just now, a 100kw-hr battery may take 1 to 2 days to recharge. Reconditioning the electrolyte could be a similar process to simply recharging the battery and is possible locally or may be done centrally if economies of scale outweighted transportation costs.

      I assume $200 is a cell level, future projected cost. I asked about a BMS. The zinc-air battery does not require the same careful voltage regulation as Li-Ion batteries. The system would be far simpler and we can expect cheaper than present energy storage systems.

      I think that the last word is not to get too attached to li-ion technology. It may be the best team on the field today but tomorrow is another ball game. In this way battery tech is not like other electronics where we have heard vinal records, 8 tracks, cassettes, minidisks, cd, (dvd) and mp3… Many different technologies just to store and reproduce sound.

      • sola

        With a simplified BMS, the cost advantage may be more pronounced to the advantage of the Zink-battery.

        If charging is so slow do to low charging-power-density, then it is a big question whether the flow battery is capable of accepting partial recharges. If it does, than this may not be a big problem, since you can put the car on recharge any time you stop (typically at night at home but also at your workplace, parking lots…etc). With this continuous partial-recharging you may be able to keep up with your normal car use.
        Naturally, this is not an option for longer trips but if an electrolyte swapping system is sufficiently widespread (aka Better Place), this may work.

        • Breath on the Wind

          What you may find is that the power density will not be bad, and the battery could be partially charged, or topped up, but because it is so cheap and takes up so little space it will have a large capacity and take a long time to charge. On a trip that means a long time to recharge.

          Partial charges should be no problem as the battery is fairly robust and can can take complete charges unlike Li-ion that really don’t like going below 20% or more than 80 to 90% capacity.

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