Sunday, October 13, 2013

1000 Mile Battery

Imagine an electric car with twice to four times the driving range of a gasoline model, yet can be refueled in a few minutes time, if you want to take a long driving trip. Even better, you can also recharge it at home overnight, saving the hassle of having to find a filling station.
Sounds like a fairy tale, doesn’t it?
Well, for the moment it is, but given the amount of research into ‘flow’ batteries, including a reported breakthrough at the Illinois Institute of Technology (IIT), it could someday become a reality.
A ‘flow’ battery has characteristics of a chemical battery and a fuel cell. Two electrolyte fluids, rich in metallic ions like Vandanium or chromium, exchange those ions across a membrane, generating an electric current. Once the ions have flowed across the membrane, you either replace the fluids - which can be recycled indefinitely - or you connect the car the electric grid and reverse the process just like charging a regular battery.
Lots of research groups are working on the technology: MIT, University of Michigan, Fraunhofer Institute in Germany, Argonne Labs and IIT. The problem is the technology is bulky and has, until now, low energy density by volume. A lithium-ion battery will have 150-200 Wh/liter of energy, whereas a Vandanium flow battery might be 20-35 Wh/liter. Power density is just as miserable: 60-100 W/L versus 275 W/L for lithium.
When the University of Southampton in England experimented with a prototype hybrid car using both lithium and an early Vanadium flow battery, the concluded that they needed a flow battery that weighted 400 kg (881 lbs) and took up a volume of space equivalent to 424 liters (15 cubic ft) to accomplish the same work as a lithium battery weighing just 60 kg (132 lbs) 96L (3.3 cu. ft).
The secret to the future success of a flow battery, be it for transportation or grid energy storage, is coming up with a working fluid that can accommodate more ions and not, like water, breakdown at voltages as low as 1.2V. States a Stanford University research paper on the subject, “Truly disruptive innovation entails an order of magnitude increase in both energy and power density. A critical limiting factor is the solubility of the electroactive species in the electrolyte solution.”
That appears to be what earned a team made up of researchers from Argonne National Labs and IIT a $3.4 million ARPA-E research grant from the U.S. Energy Department. They have come up with what they call an ‘nanoelectrofuel’ that, if successful, could be the ‘disruptive innovation’ the industry is looking for.
The key piece of technology seems to be - and the press release lacks specific details - the infusion of nano-scale materials rich in ions that not only matches lithium, but significantly exceeds it in energy density, with the Illinois teams talking in terms of at least a 500 mile-range battery and maybe even a 1,000 miles.
States Argonne’s press release, “The IIT-Argonne nanoelectrofuel flow battery concept will use a high-energy density ‘liquid’ with battery-active nanoparticles to dramatically increase energy density while ensuring stability and low-resistance flow within the battery. “
From the sound of this, it appears the researchers have developed a promising fluid that would, effectively, become a high energy replacement for gasoline, yet on that would - hopefully - be safe to handle, unlike liquid hydrogen.
None of the research we found mentioned how or where the fuel would be recycled, whether it involves processing on site or at a centralized location, nor how much energy it takes to reverse the process. Presumably, whatever they have come up with will be environmentally benign, unlike other substitutes like methanol or ammonia.
The ARPA-E grant is only one of 22 grant under the DOE’s Robust Affordable Next Generation Energy Storage Systems program, all of them seeking to solve the energy storage problem. Hopefully, one or more will make the fairy tale come true.

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