Edit: The company press release is much clearer: https://stateraenergy.co.uk/news/thurrock-energisation The storage is 300 MWh, but it can deliver a peak of 600 MW/h (presumably for half an hour).
The 300MW Thurrock Storage project... with a total capacity of 600MWh
> With a total capacity of 600MWh, Thurrock Storage is capable of powering up to 680,000 homes, and can help to balance supply and demand by soaking up surplus clean electricity and discharging it instantaneously when the grid needs it.
Unless they updated the original post, that all sounds correct to me. It's a 2-hour battery, rather common in the industry.
EDIT: Ah, you mean the https://stateraenergy.co.uk/news/thurrock-energisation is wrong, with the fantastically outrageous statement of "delivering its full output of up to 600MWh within seconds."
Ramp-up time for grid management is important but the value is all wrong.
Journalists are some of the worst offenders.
But they will muddle bits and bytes, nanograms and milligrams, volts and amps and they barely even seem to notice that they did it.
The Guardian refuses to write the degree symbol for temperatures, for example, and have even put this error into their style guide.
300K is too hot and I begin sweating. The Grauniad's House Style is the least of its problems.
Actually, even that doesn't make sense, you can't remove non- from non-inflammable either, that would only work if it was the 'in' removed.
Power is 300MW (300000000 Joules/second), which it can deliver for 2 hours, so capacity (energy contained in the device) is 600 MWh (or 2160000000000 Joules)