I don’t understand the article. It says you can have a flow battery that can run for 4 hours for $150, or one that runs for 8 hours for $100. Clearly the 8 hour model is superior, since it holds a charge longer, and costs less.
Based on your comment, I guess they mean to say that you get 2x the sustained wattage (not kWh) out of the $150 model.
The way I read it, the difference between the $150 ("4 hour") battery and the $100 ("8 hour") battery is that the 8 hour battery will be 2x in size. This would be the same KW (~volts x amps) available but 2x the hours at that power draw. The difference between $150 per KWh and $100 per KWh is the economy of scale.
The scaling of hours is going to be proportional to the tank sizes. The power (KW) rating is going to scale proportional to the electrochemical cell size. The expensive part is going to be the electrochemical cell; tanks are simple and scale well. The "4 hour" and "8 hour" examples would have the same electrochemical cell size since they have the same power (KW) rating but 2x bigger tanks for the "8 hour" version.
Ah right, so they’re limiting the tank size and volume of the electrolyte to make the comparison. And selling it as a closed system similar to a normal battery.
A "Flow" Battery's got the advantage of scale. To scale a flow battery, all you gotta do is build a bigger tank. A Lithium Ion battery requires you to build complex circuitry and chemicals throughout the whole battery.
In many ways, Lithium Ion batteries are like Solid State Drives: You got complex circuitry through and through. While Flow batteries are more like a Tape Drive: The drive is way more expensive to make, but "tape" (ie: Tank) is so cheap that the economics of energy storage eventually wins out.
Based on your comment, I guess they mean to say that you get 2x the sustained wattage (not kWh) out of the $150 model.
Is that right?