Cryogenic storage can be switched on very quickly – it’s literally as easy as turning on a tap. So the specs are probably as good as diesel generators, but without any on-site pollution.

The way it would work is as follows: the data centre invests in some more backup cryogenic storage than it would need in a power cut, and charges the system up during off-peak hours. Hours of peak demand for electricity probably coincide with peak demand for data centre services (in business and leisure hours, people do a lot of Facebook and social media).

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