Didn't they used to have a flywheel?
To help regulate the power draw from the grid - or am I imagining it?
JET's power requirements during the plasma pulse are around 500 MW with peak in excess of 1000 MW. Because power draw from the main grid is limited to 575 MW, two large flywheel generators were constructed to provide this necessary power. Each 775-ton flywheel can spin up to 225 rpm and store 3.75 GJ. Each flywheel uses 8.8 MW to spin up and can generate 400 MW (briefly).