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Kevin Bullis is Technology Review’s energy editor.

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Flow Batteries For Fast Electric Car Charging

New batteries could make recharging EVs much faster.

By Kevin Bullis

Electric vehicles can take hours to recharge, making cross-country road trips a challenge. But researchers at the Fraunhofer Institute for Chemical Technology in Germany say they've got a potential solution: flow batteries.

This type of battery uses two electrolytes rather than the solid electrodes used in lithium ion batteries. Recharging them is as fast as pumping out depleted electrolytes and replacing them with fresh ones--it wouldn't take longer than refilling a gas tank. One of the problems with flow batteries, though, has been that they only store about a quarter of the energy as lithium ion batteries--you'd have to recharge a lot, making them impractical. The Fraunhofer researchers say they've improved the energy storage to match lithium ion batteries--still not as good as with gasoline, but a great improvement. Some lithium ion EVs get over 200 miles on a charge.

But here's the catch: one of the reasons hydrogen fuel cell vehicles have come under fire recently is that you need to install a large infrastructure for distributing and dispensing hydrogen. A flow battery system would have a similar problem. You'd need to install special refueling stations where the spend electrolytes can be recharged and dispensed.

Tags: energy, electric vehicle, flow battery, lithium ion battery, recharging

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Interesting

The question is, which is more efficient/cheaper in terms of infrastructure costs: replacing the electrolyte in the batteries or exchanging the entire battery pack for a charged one?

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Mapou
10/15/2009
Posts:65

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Re: Interesting

I think the question is more like:

"Should we even build infrastructure around a technology (batteries in general) that store only 1/200th to 1/100th the energy of chemical fuels?"

To be useful we'd probably only use these for very local traffic. Cities need to be redesigned around small electric vehicles in areas to be useful. You'd still have large cars but like pedestrian malls there'd be areas for small silent vehicles. They wouldn't be expected to go long distance, just to your local stores, college, etc.

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erbium
10/15/2009
Posts:110

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Re: Interesting

wow! I completely disagree. You are ignoring the fact that an electric motor is vastly more efficient than an ICE engine. Couple that with the fewer drive train losses in an electric drive train, and some aerodynamic modifications and we can have highway capable vehicles that get 200 miles on a single charge today. Look at the tesla. Okay, the tesla is expensive, but there are many companies working on cheaper ev's with the same range or better right now. Aptera motors has several prototype ev's with the fit and finish of a production vehicle that go over 100 miles on a charge and an expected price of mid 20K. If these flow batteries from the Fraunhofer really are as energy dense as standard lithium ion, then this is huge. 100 miles a charge and a 5 minute fill up? Sign me up! In addition, from what I have read, these flow batteries do not suffer from the hysteresis problems of lithium ion. That is, lithium ion batteries can only reliably be discharged down to 30% or so, to maintain decent cycle life. If that is true and flow batteries can go to 99% discharge, and have the energy density of lithium ion, then we are talking about 150 miles on a single charge for an aptera like vehicle and about 300 miles on a single charge for a tesla like vehicle.

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nowhereman
10/17/2009
Posts:1

Flow batteries and ultra caps

The question is how effective this technology becomes if combined with other battery extension technology such as ultra-caps. The ultimate success is most likely to be a blended solution and not a single technology breakthrough.

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nomad23
10/19/2009
Posts:1

What if?

What if you could have an engine that burns any liquid fuel, has 30% more efficiency than the ICE and much lower emmissions? It would use the present infrastructure and other fuels could be added as wanted.
Well, check out Turbine Truck Engines (TTEG), Axial Vector (AXVC) and Cyclone Power (CYPW). All three meet this now. Why go to electric charging or hydrogen. A PHEV with one of these engines may be the best solution.

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JustaGuess
10/19/2009
Posts:5

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