If one can actually make a useful economy out of replacing flow battery fluid at a station, sure. But I’m making a different point:
A Li-Ion battery can charge and discharge in something like an hour. If you double the number of cells in a battery or installation, you can store twice as much energy and you can draw twice as much power. (You don’t have to provision twice as much power circuitry, but you do need to purchase that extra power worth of electrodes in the cells.)
If you’re building something for which a roughly predetermined power to energy ratio (i.e. hours of use at a reasonable rate of discharge for the technology), this is fine. Similarly, if overprovisioning power or energy is not a problem for cost or weight, also fine.
But for grid use, wide differences in the duration of energy storage for different purposes can make sense. And a flow battery can separately provision power and energy. This gives a possible cost benefit to flow batteries.
A Li-Ion battery can charge and discharge in something like an hour. If you double the number of cells in a battery or installation, you can store twice as much energy and you can draw twice as much power. (You don’t have to provision twice as much power circuitry, but you do need to purchase that extra power worth of electrodes in the cells.)
If you’re building something for which a roughly predetermined power to energy ratio (i.e. hours of use at a reasonable rate of discharge for the technology), this is fine. Similarly, if overprovisioning power or energy is not a problem for cost or weight, also fine.
But for grid use, wide differences in the duration of energy storage for different purposes can make sense. And a flow battery can separately provision power and energy. This gives a possible cost benefit to flow batteries.