22 January 2006

Flow Batteries are a new and Revolutionary Storage Technology

The Energy Blog reported a while back on a new energy storage technology, Vanadium redox flow batteries. Flow batteries are called that because the electrolytes flow through the cells, giving up electrons to an external circuit. The redox reaction is reversible, so the cells can be charged or discharged. The significant fact about flow batteries is the potential to scale to very large storage sizes into the megawatt and multi-megawatt ranges. This is the type of storage capacity utilities have been looking for.

Performance

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The VRB has an availability of greater than 98%. Designed for unattended operation with very low maintenance costs.
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No degradation from repeated deep charges and discharges. The system can be discharged and charged greater than 13,000 times (20% to 80% SOC) without deterioration in system efficiencies.
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System round-trip efficiencies between 70% - 78%.
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The VRB-ESS has a charge/discharge window of 1:1 - allowing off-peak charging for on-peak dispatch - a fraction of the time required by other battery systems and ideal for wind generation applications.
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Cross mixing of electrolytes does not lead to contamination of electrolytes
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indefinite life of electrolyte (no disposal or contamination issues).
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Once charged, the electrolyte remains fully charged with low self-discharge.


Flow batteries are not generators, like regular fuel cells. Most fuel cells use up their fuel sources in an irreversible reaction. Flow batteries do not use up their electrolytes. The electrolytes are fully reusable, with recharging. And flow cells are not like regular batteries, since you recharge them by replacing the electrolyte. They are a new, hybrid form of chemical battery/fuel cell.

The best use for these cells will probably be as load levelers for utilities, and as backup power for large industrial facilities.

Here are more links:

Sandia
Wiki
ME
Geo

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3 Comments:

Blogger Doug said...

How rare is Vanadium?
Even a 2kw system would be great for a Solar-Eco Home.

Sunday, 22 January, 2006  
Blogger Dennis Dale said...

From the Mineral Infromation Institute at http://www.mii.org/Minerals/photovan.html :

It is estimated that the presently known world resources of vanadium total 63 million tons. There is no single mineral ore from which vanadium is recovered. However, it is found as a trace element in a number of different rock materials and is a by-product of other mining operations. Vanadium is found in magnetite (iron oxide) deposits that are also very rich in the element titanium. It is also found in bauxite (aluminum ore), rocks with high concentrations of phosphorous-containing minerals, and sandstones that have high uranium content. Vanadium is also recovered from carbon-rich deposits such as coal, oil shale, crude oil, and tar sands.

We are already importing some from Canada because (I presume) that's cheaper than mining for the relatively small quantities we need now. Of course if this technology gains a foothold that can change in a hurry. I'm completely ignorant about this stuff but it sounds like it might be a beneficial by-product of other mining operations.

Sunday, 22 January, 2006  
Blogger al fin said...

Thanks for the information, Dennis. One good thing about the vanadium redox battery is that the vanadium is never exhausted, it can be used indefinitely.

Here's a link to the University of New South Wales, where the Vanadium redox battery was invented. The information available there is of excellent quality, and should answer a lot of questions.

Sunday, 22 January, 2006  

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