Most of the energy to heat the water comes from Power Plants(Gas, Coal, Wood) which is almost all wood now. Thats why Danish power plants are about 90% energy efficient.
Simon Quvang
2019-03-30 00:51:30 +0000 UTC
The efficiency as a battery for electricity is about 50%. But when there's enough free power the quest must be to store as much as possible, as this will mean better balancing our grid and less fuel consumption for power plants. It will not compete with electrochemical batteries for the second-time frame but will act as buffer for weeks, kinda like hydro. But Denmark is flat so we can't use hydro as batteries for our wind power. So we must be creative 🙂