[decimalenough]

The article mentions that they heat the sand to 500°C, which is not possible with water (well, at least not without turning into steam along the way).

[Cthulhu_]

To be pedantic, yes you can but you'd need to pressurize it to uuhh... According to this calculator [0], you can get water to 370 degrees C if the pressure is 207 atmospheres, which is about the pressure of the ocean two kilometers deep.

[0] https://www.engineeringtoolbox.com/water-vapor-saturation-pr...

[killingtime74]

Interestingly that's also about the pressure of gas in scuba tanks. Can't imagine how much energy to pressurize water to that

[trhway]

Due to incompressibility of liquids, pressurizing a liquid is very cheap energy-wise - orders of magnitude cheaper than pressurizing a gas. The issue is that pressurized liquid also requires correspondingly strong and expensive vessels and pipes.

[sfn42]

You don't need to pressurize it. You just put it in a tank and apply heat, the water evaporates and creates pressure. Like a pressure cooker.

[nick49488171]

How many kiloton of TNT equivalent?

[grues-dinner]

Well, if you say the energy stored is the 100MWh from the headline figure, and say you can arrange release every joule of all at once by flashing high-pressure water to steam at 1 atm that's about 0.1kT.

So quite a bang - allegedly this is 200lb, so about the same: https://www.youtube.com/watch?v=ZDgvar7ON54