100 MWh is 8 tons of "oil", according to a google search. Oil is probably about the density of water, so 1 cubic meter is about 1 ton of oil, and this structure is about 2000 cubic meters, so oil has 200 times the fuel density of this battery.
Light crude oil has an API gravity higher than 31.1° (i.e., less than 870 kg/m3)
Medium oil has an API gravity between 22.3 and 31.1° (i.e., 870 to 920 kg/m3)
Heavy crude oil has an API gravity below 22.3° (i.e., 920 to 1000 kg/m3)
Extra heavy oil has an API gravity below 10.0° (i.e., greater than 1000 kg/m3)
It's still pretty good though.