Electric boiler?

[ericmark]

Seem to remember turned to liquid at around 70°C. Sodium maybe? There must have been a problem as it was dropped.

 

[JohnW2]

Seem to remember turned to liquid at around 70°C. Sodium maybe? There must have been a problem as it was dropped.

I've just had a quick look. Sodium and potassium have much lower thermal capacities than water, and lithium about the same as water - but all three of those (particularly lithium) in that 'column' or the periodic table would come with big problems (particularly the tendency for 'spontaneous combustion'!) ... and, as I suggested might be the case, I can't find any solid or liquid which would have a higher thermal capacity than water.

However, I've just realised that you are talking about phase conversions, whereas I was talking about storing heat without a phase change. Hence, as you said, it's the latent heat of materials (not their thermal capacity) which matters - so, when I have a moment, I'll look into that.

 

[Harry Bloomfield]

The lower bath has my wife's e-bike in it, never used.

No, no, no - You are supposed to keep coal in it, not a bike!

 

[JohnW2]

However, I've just realised that you are talking about phase conversions, whereas I was talking about storing heat without a phase change. Hence, as you said, it's the latent heat of materials (not their thermal capacity) which matters - so, when I have a moment, I'll look into that.

I've had a quick look at latent heats of melting/fusion. The first table I found (here) indicates that ammonia has a similar latent heat to water but all the other substances in the list are lower than water, other than aluminium and chromium (both about 18% higher than water) - although their melting points would obviously be far too high to be useful for routine heat storage.

 

[BS3036]

Back at that time (70's) my plan was a house with a large cellar which I would fill with wax, and loads of pipes going through it. It meant the heat could be stored at a constant temperature (melting point) suitable for heating the house for a year. I found that you could choose a wax with a convenient melting temperature. It might have worked but I never got round to it.

 

[JohnW2]

Back at that time (70's) my plan was a house with a large cellar which I would fill with wax, and loads of pipes going through it. It meant the heat could be stored at a constant temperature (melting point) suitable for heating the house for a year. I found that you could choose a wax with a convenient melting temperature. It might have worked but I never got round to it.

I would think far from a crazy idea, but is not one of the problems with any such approach is that it is not very (if at all ) 'controllable'?

 

[Harry Bloomfield]

I would think far from a crazy idea, but is not one of the problems with any such approach is that it is not very (if at all ) 'controllable'?

No less controllable, than storage heaters presently are.

 

[JohnW2]

No less controllable, than storage heaters presently are.

That depends upon what BS3036 meant. It sounded as if he might well have been thinking of storing heat for a lot longer than 12h/24h ...

... the heat could be stored at a constant temperature (melting point) suitable for heating the house for a year.

 

[BS3036]

it is not very (if at all ) 'controllable'?

Assuming the whole think was encased in good insulation, which is obviously part of the plan, then you only remove heat when you run water through the pipes, which then travels on up to your radiators or underfloor heating pipes. At the time I did the calculations and it really just depended on having a decent sized cellar.
At the time, solar thermal tubes were also more prominent than PV, so it was just a case of taking the sun in the summer and using it in the winter.

 

[Harry Bloomfield]

It sounded as if he might well have been thinking of storing heat for a lot longer than 12h/24h

He said a year, but would need to be well insulated, to prevent the heat rising when it wasn't wanted, and could take a very long time to charge up. Would work well, being able to charge up at especially low prices of summer, and off-peak.

 

[JohnW2]

Assuming the whole think was encased in good insulation, which is obviously part of the plan, then you only remove heat when you run water through the pipes, which then travels on up to your radiators or underfloor heating pipes.

Yes, that's roughly what I thought you were saying.

However, I'm not clear as to what temperature you would envisage storing the wax at. If it were to serve the purpose of releasing (latent) heat when it solidified, it would presumably have to be stored roughly at its melting point, so I imagine that you would have to find a wax whose melting point was adequately high for the water travelling to the radiators - in which case the insulation would presumably have to be exceptionally good?

At the time I did the calculations and it really just depended on having a decent sized cellar.

I could perhaps have achieved that, since my my very large cellar is (at a rough guess/calculation) 150 - 200 m³ However, I have far better things to do with it (my 'workshop'!) than fill it up with wax!

At the time, solar thermal tubes were also more prominent than PV, so it was just a case of taking the sun in the summer and using it in the winter.

True - but, as above, if you were going to store the wax, for months, at a temp high enough for feeding the rads, it may have proved unrealistic to install adequate insulation?

... or am I missing something?