September 15, 2013 – Vol.18 No.27
FLOW BATTERIES FOR ELECTRIC CARS?
by Bruce Mulliken, Green Energy News
Electric vehicles are too expensive. They don't go very far. They're are not selling as well as they should because of those problems. The culprit is mostly those lithium-based batteries car developers are in love with.
Electric car developers live in a land of wishful thinking; hoping for a breakthrough that may never come. They dream of the day when lithium battery prices drop like a set of car keys. They pray for the day when those same batteries quadruple in their capacity to store energy. Since they don't how to slice costs or juice up capacity themselves, they're waiting for someone else to provide those miracle breakthroughs.
There are some fundamentals about lithium that will never change. Though some say there's plenty of lithium on the planet with which to do what we want, it's not exactly easy to extract from resources and many of those resources are too small be money makers, thus may never be developed.
And that's just a simplistic explanation of raw material supply problems.
Once you've got your lithium it's an absolute pain to work with. As soon as your metal is open to the air it begins to oxidize. Immediately. Rapidly. So your battery electrochemistry or your manufacturing process has to deal with that instant oxidation problem. Extremely difficult to work with in a manufacturing sense translates into high productions costs. Battery cell makers combat productions costs with cheap labor. That's not a great solution.
At the end of life it's technically possible to recycle lithium batteries, but it's a tedious process that's different for every type of battery pack and cell. Technically possible doesn't always mean economically possible. Right now, I don't think the economics are in favor of recycling lithium batteries. So when they're cooked beyond a useful life they're headed to the toxic scrap heap.
There is of course an upside to lithium. In thousands of examples, those lithium batteries that all of us use and enjoy have changed the world. They've been the breakthrough that's driving nearly all the of personal electronics craze from smart phones to tablet computers. Even if lithium batteries don't pan out for electric cars, they have a strong future in electronics. With a new model smart phone coming out every week it seems, demand for lithium-ion batteries will remain high, like forever.
But for cars, I just don't think its going to happen. Electric car developers, and the battery makers themselves, need to start looking around for other electrochemistries.
Already this year there's been the announcement of aluminum-air swappable batteries from Phinergy of Israel that could run for 1000 miles before swapping out.
This technology deserves attention as a lithium replacement.
Now there's another possibility just starting up in the development stage: flow batteries for cars.
Scientists from General Electric and Berkeley Lab are working on this and plan a prototype in the next year or so.
And they're not alone. The Illinois Insitutue of Technology (ITT) and Argonne National Lab will share a $3.4 million award from U.S. Department of Energy's Advanced Research Projects Agency to develop a prototype of their "nanoelectrofuel" flow battery.
If you've never heard of a flow battery it's a type of fuel cell where dissolved electroactive elements in liquid electrolytes flow on either side of a membrane within a cell. A charged ion exchange takes place as the electrolytes pass each other on either side of that membrane to generate electric current. The chemical make up of the electrolytes determines the voltage in each cell. Building a stack of cells, and adding each cell's voltage together, increases the voltage available for work. The cumulative area of the reactive portions of the cells, where the membrane is, determines the amount of electric current available. And the runtime of the flow battery is determined by volume of stored electrolytes. Electrolyte is held in tanks and pumped through the cells. In an electric car runtime means range and the bigger the tanks the farther the car will go, just like fueling with petroleum.
Much like fueling a gasoline car, fueling a flow battery means replacing the electrolyte mixtures in those tanks. Or alternatively flow batteries can be electrically recharged. The flow of electrolyte can be reversed while current is applied to the cells thus recharging the system. This architecture is called a redox (reduction-oxidation) flow battery. In a car or truck a redox flow battery would likely use the fledgling charging network to recharge the electrolyte.
The scientists working on the GE/Berkeley Lab project say a range of 240 miles should be easily obtainable, and the cost of the flow battery systems should be a fourth of cost of current lithium-ion batteries.
The project at IIT and Argonne could yield a flow battery providing at least 500 miles of range (maybe as much as 1000) between refuelings of charged electrolyte.
With these two battery programs underway, there's evidence that flow batteries are moving onto the radar screen as an alternative to lithium.
Yet the most compelling hope for flow batteries isn't what could be the future, it's about what's available today. Flow batteries are already available in the marketplace, at least for stationary backup power applications. While these devices are too big and bulky for vehicles, the manufacturers of these units will be watching GE/Berkeley and IIT/Argonne's progress to do a little reverse engineering and be ready to pounce with their own flow batteries for cars.
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