Heat bank for under a kitchen worktop

Good point!

Aah yes - that's the word I was looking for! ;-)

Just think, you could make a direct contact boiler with 99% efficiency.

NT

Out of interest, what would happen if one used a thin oil as the primary fluid, storing it at upto perhaps 150C? Tank size would be smaller, and the same volume of insulation would give thicker insulation, perhaps offsetting the greater heat loss.

Think I'd be inclined to avoid soldered joints though!

A bit more seriously, if there isnt enough space under the worktop, it would be poss to use a small secondary tank as well, hooking it up to work as the lower temp end of the setup. This would also be ripe for the later addition of solar heat if ever wanted.

NT

And of course a drain heat exchanger reduces hot water requirement for showers.

You may have trouble getting the boiler to heat it to that temperature (without modifications to its sensors and software etc)

Also the specific heat capacity of oil lower than water...

.. and other components made from plastic would likely melt

And where mains water met the heat exchanger suddenly you'd be handling superheated pressurised steam.

Thinking about SHC, the storage tank need not store oil necessarily, it might have a fill of lumps of some higher shc material, with the oil run through it. Water sure is cheaper though, and has a very healthy shc.

NT