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Comment by Animats | Hacker News Reader

This new sand battery is expected to stand 13 m (42.7 ft) tall and 15 m (49.2 ft) wide, providing an output power of 1 MW and a capacity of 100 MWh.

That's impressive. It's close to the energy density of fuel oil. Or did I calculate that wrong?

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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.

It's still pretty good though.

“Oil” is 10-15% less dense than water. So yes, “about” the density of water, for napkin purposes. This would be diesel or heating oil.

Gasoline is 30% less dense than water though.

your number is good, as it's the heavier from all oil. Don't work for all type of oil though.

https://en.wikipedia.org/wiki/API_gravity

    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)

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