That form of storage on a grid will be especially useful when volatile energy sources in the portfolio are running below average demand, as they allow energy to be brought in over the grid to grid HVDC links in off-peak periods and stored for use during peak demands.
The Wikipedia mentions that it, too, was originally planned for use with shifting nuclear generated electricity from off-peak to on-peak, and with the switch in nuclear plans a sister plant at Exmoor was never built. I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
