Fraunhofer-Gesellschaft_Dipl.-
summarises their work on improved redox flow batteries for electric cars (Research News October
The principle of redox and redox flow batteries is not new – two fluid electrolytes containing metal ions flow through porous graphite felt electrodes, separated by a membrane which allows protons to pass through it. During this exchange of charge a current flows over the electrodes, which can be used by a battery powered device.
Until now, however, redox flow batteries have had the disadvantage of storing significantly less energy than lithium-ion batteries. The vehicles would only be able to cover about a quarter of the normal distance – around 25 kilometers
– which means the driver would have to recharge the batteries four times as often. “We can now increase the mileage four or fivefold, to approximately that of lithium-ion batteries,” Noack enthuses. The researchers have already produced the prototype of a cell. Now they must assemble several cells into a battery and optimize them. This further development is being carried out with colleagues from the University of Applied Sciences, Ostphalia, in Wolfenbüttel and Braunschweig. They are testing electric drives and energy storage units on model vehicles that are only a tenth of the size of normal vehicles.
Thanking also
New Energy and Fuel_online website
NB.
"Keep in mind the redox electrolyte research is just now getting under way and the claim is to meet the lithium ion standards very soon. There is even room for opportunities in research at the anode and cathode. What remains of great interest is the energy per weight and volume numbers that can really enthuse or befuddle the future."
& Comment
"Vanadium liquid electrolyte batteries are well-developed, maybe don’t quite have the energy density for automotive use. Here is a good review article on vanadium batteries: http://www.scribd.com/doc/20283743/Status-of-the-Vanadium-Redox-Battery-Development-Program"
en référence à : Improved redox flow batteries for electric cars - Research News 10-2009-Topic 7 – Fraunhofer-Gesellschaft (afficher sur Google Sidewiki)
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1 comment:
VRB will have both volumetric and voltage problems with respect to automotive applications. The electrolyte will hold approximately 25Wh of energy per litre. A litre will weigh about 1.4Kg. The VRB chemistry produces about 1.4V per cell and the cells are very bulky.
Toyota Prius uses a 1.3kWh battery pack as standard. However, to extend the battery range, there have been conversions to install 9 kWh battery systems in the Prius. Excluding the weight of the VRB cells, 9 kWh of Vanadium Electrolyte will require 2 x 360 litres (two equal tanks of electrolyte are required for each half cell). This will weigh over 1,000 KG in fluid alone.
VRB is a none starter for automotive applications where space and weight are a premium.
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