On the outskirts of Plymouth, a china-clay mine is hosting an energy experiment that sounds almost too modest for the UK’s net-zero ambitions.
There is no dam wall. No Alpine reservoir. Instead, there are underground tanks, buried pipework, and a mineral-rich fluid designed to be heavier than water. When electricity is cheap, the system pumps the fluid uphill. When power is needed, it lets the liquid run back down through a turbine. That is pumped hydro — the oldest grid-scale storage technology — shrunk and tweaked for gentler terrain.
This week, the developer, RheEnergise,
