Glad I finally have a name (flow battery) for a concept that I've been wanting to be made for a long time (liquid batteries).

• pjc50

  today at 12:42 PM

  The idea has been kicking around for a while because it's superficially appealing.

  Benefits:

  - you can store huge amounts of energy in relatively cheap tanks

  - because the + and - storage are physically separate, self discharge can be very low

  - those two make it appealing for long term storage

  Downsides:

  - reagents end up being some combination of expensive (vanadium), poisonous, corrosive, etc. resulting in safety overhead

  - requires specialized plumbing. This is very expensive. Ultimately this is the issue with nuclear as well, every joint requires careful inspection

  - does not scale down nicely to house sizes

  - ultimately likely to get economically lapped by incremental improvements to lithium or sodium battery chemistry

  - the charge/discharge cell requires a liquid/liquid membrane separator which can exchange charge; these tend to have lifetime issues.

• somat

  last Wednesday at 2:49 PM

  Flow batteries specifically are liquid, or more accurately fluid, there can be gas flow batteries, where the chemical sub-products are pumped in and out of the cells.

  They tend to be large utility scale things that look like a chemical plant, correction, are a chemical plant with electrical storage as the product.

  Liquid electrolyte batteries have been a thing from when batteries have been invented. But not much work has been done to really scale it up.

• sfn42

  last Wednesday at 2:28 PM

  It's not a new idea, they already exist.

  A huge redox-flow battery is currently under construction in Switzerland https://www.swissinfo.ch/eng/climate-solutions/switzerland-b...

  • meindnoch

    today at 12:33 PM

    "We will be able to inject or absorb up to 1.2 gigawatt-hours (GWh) of electricity in a few milliseconds"

    1.2GWh in a few milliseconds? I'm pressing (X) to doubt.

  • gilleain

    last Wednesday at 2:45 PM

    A vanadium one, which (as mentioned in the piece) is symmetric.

    The 'Just Have a Think' channel did a video on the Swiss battery here - https://www.youtube.com/watch?v=CPAFeTvjVzY

    • pfdietz

      today at 12:49 PM

      The advantage of vanadium batteries, as I understand it, is that leakage does not corrupt the system. The vanadium gets converted to the right chemical species on either side.

• tveita

  last Wednesday at 2:27 PM

  You might find the home made batteries of this guy interesting as well https://www.youtube.com/watch?v=eq7fR9ISuCw

Thank you for this, as somebody with almost no background in chemistry, I can now appreciate just a bit more the complexity that goes into battery development. Where does one learn about this?

Cyanide batteries... hmm..

• philipkglass

  last Wednesday at 4:11 PM

  Ferrocyanide is not dangerous. Sodium ferrocyanide is used as an anti-caking agent in table salt. It's considered safe for this use in both the US and the EU, e.g.:

  https://ec.europa.eu/food/food-feed-portal/screen/food-addit...

  • pjc50

    today at 12:35 PM

    Yes, but as the article points out, the process likes to evolve free cynanide in operation.

• BenjiWiebe

  last Wednesday at 4:00 PM

  *ferrocyanide Less toxic than cyanide.

  Potassium ferrocyanide: 1.6g/kg LD50 Potassium cyanide: 5mg/kg

  So cyanide is approx 320 times more toxic.

To give the answer its the cyanide part... which I knew already when looking at the title, without having much clue about underlying chemistry.

Good luck selling batteries full of some variant of cyanide to general public, i can almost imagine it working till people hear that keyword.

• jjk166

  last Wednesday at 10:46 PM

  Yeah, just like no one would ever buy a lead-acid battery.

  I don't think many people are concerned about their batteries being safe for ingestion.

• jillesvangurp

  today at 12:27 PM

  That's pretty much what the article states:

  > When using ferrocyanide, also consider that while this salt is relatively safe in its unaltered state, subjecting it to electrochemical abuse WILL generate free cyanide and it’s likely to pose a significant danger to you and others. For this reason, I would recommend to stay away from testing ferrocyanides in symmetric systems entirely, unless you are a trained professional and professionally well equipped to handle both the potential operational hazards and wastes generated from its decomposition products.

• fch42

  today at 12:18 PM

  Well they sell that liquid explosive terrorists use to make molotov cocktail firebombs, at every fuel station without particular volume limits at all. It's also sufficiently toxic that care is taken at salespoint to limit customer exposure to the vapours.

  (these things are "all relative, if the value, measured in "convenience to the customer", is high enough, ways will be found to permit sale)

• psd1

  last Wednesday at 2:12 PM

  Somewhat true, but consumers are buying vast quantities of lithium batteries and carrying them in their pockets. Those things are eager to catch fire and emit hydrofluoric acid.

  You can have safe battery chemistry or useful battery chemistry. (Not an expert, open to correction.)

• somat

  last Wednesday at 2:35 PM

  The public is not going to buy a flow battery anyway.

  Or perhaps they will, but only when public is taken in the context as in public utility or public city. But individuals are not going to buy a flow battery, it is a chemical plant.

• BenjiWiebe

  last Wednesday at 4:00 PM

  Have to abbreviate it as FCN. Cyanide is ~320 times more toxic than ferrocyanide.

• greenavocado

  last Wednesday at 1:49 PM

  There are plenty of battery customers besides the usual suspects

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