RE: Avalon Article1 Apr 2020 07:27
Slinkyfink - I have been in touch with the author of that article to complain about the very poor coverage that they have given VRFBs and you can be confident that this situation will be very different in future.
1. Pumped Hydro - to call this 'promising' is like saying your grandmother has 'promise'. Nuff said.
2. Stacked blocks - an absolutely nonsense idea, never tried at any scale, very poor energy density and very low power, absolutely destroyed here:- https://www.youtube.com/watch?v=NIhCuzxNvv0
3. Liquid air - this should really be liquid air and hot rocks because when you compress the air you generate large amounts of heat and if you do not store this in some hot rocks then you are simply back to the sub 35% Carnot efficiencies of heat engines. Even if you do store the heat you always end up with efficiency losses due to irreversibility in any kind of heat engine. Overall it probably ends up at less than 60% of the energy put in being recoverable at the end of the overall compress, liquify gas +heat rocks, store in thermally insulated vessels, boil the gas by bringing into contact with hot rocks, decompress through a turbine to give electricity. As a result it is not a device that you've going to want to be charging-discharging on a daily or bidaily basis, not if you've got higher efficiency alternatives like VRFBs (80% efficient).
4. Underground compressed air - well it doesn't have to be underground, more precisely it is 'storing compressed air wherever you have a naturally occurring freely available large space that can contain millions of cubic metres of air at a few bars pressure without risking breaking'. Because it does not involve a fluid phase change or such extreme changes in temperature the irreversibility losses of 3 are not so bad. But it does not get around the basic problem of 1. that this is not a readily locatable technology.
5. Flow batteries - the only argument for non Vanadium flow batteries is that it does not contain Vanadium, in all other aspects they are only as good as or less good than VRFBs. You will note that apart from the Australian Redflow the manufacturers of non-V flow batteries (ESS, Vizn) are based in the US, which is notoriously unaware that Vanadium is more abundant than common metals such as Zinc, Nickel, Chrome and Copper. This is how we can mine Vanadium in an open pit instead of having to send anyone into much more dangerous underground mines.