How a Thermal Store works
Thermal stores vary from conventional hot water cylinders in that water in the thermal store does not come out through the taps. In contrast the water going to the taps is heated by passing through a heat exchanger that transfers heat from the thermal store water to the mains water. Heat exchangers transfer heat extremely quickly a mains pressure shower can be had or a bath filled exceptionally quickly
The water in the store is also used to drive central heating, as well as heating water for taps. This allows both central heating and hot water to be run off any of the connected heat sources e g a biomass stove can be used to heat up the thermal store in the evenings and the thermal store will retain this heat to run radiators in the morning, without needing a boiler to turn on.