Storage heater bricks - max temp?

Yes but then you have a pressure vessel and the possibility of releasing all the energy suddenly.

That is why it is usually the melt from solid to liquid that is used for energy storage or eutectic molten salt energy transport. A few candidates online in this paper:

compared

Phase change is the way to go *if you can handle it*. B-)

lots of great replies and info - too many to thanjk individually. so thaanks all.

In practice it isn't, because its much easier to do than when using water, essentially because there is no possibility of a leak.

And let's say you do

That doesn?t happen and it is trivially easy to ensure that it doesn?t.

creating a

No it can not.

Just because the insulation is more practical/economic at the lower temperature.

Mine are.

Some storage heaters have metal 'boxes' full of granular ceramic material such as bonded magnetite. Yours may be this type.

Mine aren't boxes of anything, they are clearly cast 'bricks' of some sort of metal that are fairly irregular on the outside to provide channels for the air that is used to get the heat out of the pile of 'bricks'

There is no way that can ever fail catastrophically, the worst that could happen is one cracks and that crack would be completely harmless.

There are fusible links that handle a failed thermostat so it doesn't heat forever. The heating elements and fusible links are easy to change if they do fail and I have changed a couple in the 40 years I have had it.