Recently I have learned of "installable storage heaters". Those are fairly heavy devices which consist of a ceramic brick stack and electric heater. The brick stack is heated during the off-peak electricity hours and gives back heat the rest of the time.
This made me think: the density of bricks is at best twice the density of water. Heat capacity of bricks, on the other hand, is closer to being 4-6 time smaller than heat capacity of water.
A simple calculation thus shows, that device with exactly same dimensions as those available on the market but featuring a drainable water tank as a heat accumulator instead of bricks:
- Will be able to store more energy
- Will be light and portable when water is drained
- Will have better efficiency transferring heat from primary heater to accumulator
So the question is: why offerings on the market mostly consist of immovably heavy, brick filled devices?
Best Answer
The better-made storage heaters will use materials optimised for the task
Feolite has
Water has
Footnote
These things are heated up using half-price electricity overnight. You have to have a dual-rate meter and dual-rate tariff (e.g. "Economy 7" in UK). The heater's core is surrounded by insulation so that most of the stored heat is retained until needed. When heat is needed, air is blown through the core to extract the heat.