Scott wrote:

I was watching an item on TV about use of batteries to balance the
national grid. I have also heard it said that the supply is likely to
become less reliable with increased dependence on renewables.

Yes, but only journalists who can't do sums, and battery manufacturers,
see a major role for batteries in solving this problem.




I have always assumed that an uninterruptible power supply must be
energy inefficient for the same reasons as stand-by uses electricity.
Is this a correct assumption or does a UPS not consume any electricity
at all unless it is brought into use?

It always consumes some, for the electronics and for charging the
battery. And the best kind, with an inverter always online, lose power
in the inverter.



As an aside, could a power cut ever damage a modern computer (say if
you happened to be installing an update or defragmenting a disc when
it happened)?
Yes. Depending on the filesystem and luck it could damage it even if
it is not actively doing anything.

--

Roger Hayter