>You can imagine the storage tank as a large thermos flask, but it never gets empty. The hot water with a temperature of 98 degrees Celsius is at the top, cooler water layers at the bottom, with the cold water still having a temperature of about 50 degrees. A pipeline of about 400 meters connects the storage tank to the pump house where four pumps ensure that hot water reaches the tank. It is pumped into the top of the storage tank and is also taken out here when needed. If hot water is added at the top, the same amount of cold water is taken out at the bottom. So only the quantity ratio between hot and cooler water in the storage facility changes but not the total amount of water. At maximum output of 200 Megawatt thermal, the storage facility can provide heat for about 13 hours.
It appears to be resistive when the electric part is being used, but looks like it also takes waste heat from a coal combined heat and power unit, and some other industrial heat sources.
I think the electric heat part is to help provide load balancing so theyre probably aiming for cheap and simple as it'll be used intermittently.
It is possible to have heat pumps at the other end of district heat systems, to let individual units pull heat from the shared source and also feed it back im when in AC mode.
> 3. How does the storage facility work?
>You can imagine the storage tank as a large thermos flask, but it never gets empty. The hot water with a temperature of 98 degrees Celsius is at the top, cooler water layers at the bottom, with the cold water still having a temperature of about 50 degrees. A pipeline of about 400 meters connects the storage tank to the pump house where four pumps ensure that hot water reaches the tank. It is pumped into the top of the storage tank and is also taken out here when needed. If hot water is added at the top, the same amount of cold water is taken out at the bottom. So only the quantity ratio between hot and cooler water in the storage facility changes but not the total amount of water. At maximum output of 200 Megawatt thermal, the storage facility can provide heat for about 13 hours.
[1] https://group.vattenfall.com/uk/newsroom/News/2021/vattenfal...