RE: California - mandatory solar panels8 May 2018 09:09
Sanchez - whilst VRFBs are claimed as low energy density it is interesting to speculate on how big a VRFB might be for a residential application.
If we take a typical yearly consumption per household of 4000 KWh per year that works out at 11 KWh per day, or if you took this energy at a smooth rate that would work out at 11/24 = or just under half a KW.
If you are trying to run this from a PV array that is only illuminated 1/4 of the day then you need a 2KW Array - the first 1/2 KW provides the power you need to the house, the remaining 3x 1/2KW is used for charging the battery.
Thus the battery you need is around 1.5KW power and 9 KWh energy storage.
We know that 1GWh takes 5,000 Tonnes Vanadium - so if call our house battery 10 KWh, 100,000 smaller, requires only 50 Kg Vanadium.
How much does this cost at 70 USD/Kg - answer 3500 USD. Overall, for a small battery the other costs, plumbing, pumps, assembly, testing etc are all relatively significant so instead of Vanadium accounting for 50% of the cost of this battery I think it would be lower - around 30-35% so perhaps the whole battery could be made for 10,000 USD.