Jon Norton

@Dan Pagan

Have you also thought about controling the temperature of the water?   I think boiling the water and it turning to steam will have a big energy transfer and waste.  Where as heating to say 70-80c would probably be plenty.   But doing this over time with decreasing heat available in the heat bank is tricky.

I'm probably over thinking it and it looks like you are further forward than me in planning.

Jon

Phil Stevens wrote:Jon, a heat sink is *exactly* what you want here. A body of thermal mass that absorbs as much heat as possible from your burning wood, and in so doing becomes warmer than the temperature in the building.

In my situation I would prefer not to shock the thermal mass or allow it to seep out, but give it a chance to heat water for a longer time, as it won't be in a building.   That way I can do short high temp burns and heat a high temp thermal bank to continue to heat the water after the fire is out.

I think alot of the principals you mentioned still apply, just the slow release of heat to water rather than a building.

Thanks
Jon

Hi Dan, please post your findings as well.

I have quite a few storage heater bricks which are I believe are rated for 250c, that might be enough heat for a short hot burn, used in combination with sand or other material.

Safe water heating is a bigger issue with that model.

I had thought about running coiled pipes through a larger mass of open vented water, but my feeling is it would be inefficient and act as a giant heat sink.

Thanks
Jon

Peter van den Berg wrote:Water heater... I seem to have a link to the design of Tim Barker. His water heater is reliable and can't go boom.
Ahh... here it is. http://permaculturenews.org/2012/11/23/rocket-stove-hot-water/

Thanks for the link

I will have a good read, my only reservation on a cursory glance is in my experience trying to heat up a large amount of water in one go can be miserable.   I would like to be able to do short burns as time allows, to just heat up the top of the thermalstore if needed.  But I know very little about this subject  and any new knowledge is welcome.

Thanks again
Jon

Fox James wrote:Good luck with your project, I think you need to re think your sand idea though.
Sand is neither a ‘good’ insulator or a ‘good’ mass, the grains trap air and air is a good insulator.
So sand is sort of in between  and is pretty neutral.
Any form of pipe longer than a few feet, filled with water and then heated can become a dangerous design, so think through very carefully.
I look forward to your progress…..

Thanks Fox
I have been reading alot about sand being used commercially for heat storage.   It maybe the news reports have used the word sand rather than sand like substance, maybe some more research is needed.

I have seen a couple of long form YouTube clips of people using sand as a heat battery successfully, but they may in reality be horribly inefficient.

I will read around the subject.

Thanks again
Jon

AMENDMENT.
I've just been reading this which broadly agrees with your assessment.   https://protonsforbreakfast.wordpress.com/2022/07/21/a-sand-battery-not-obviously-a-great-idea/

Thanks John and Timothy for your welcome 🤗 and links, I will look through them tonight!

Thanks
Jon

I'm thinking about making a rocket mass heater with a water heater and was looking for some wisdom on my idea.

Its going to be outside, here in the UK we can't have them indoors.  So the mass heater is not for space heating but to continue heating the water for a prolonged time.

My idea is to line the outside of the first chimney/burn chamber with sand as a thermal mass with water pipes embedded in it running round the chimney, then pass the hot gasses into a highly insulated barrel(or possibly a gas bottle as mine will be probably be smaller) and out to a chimney.

The idea is to heat the sand up so I can capture more heat and have it continue to heat the water after the fire has gone out therefore requiring a shorter burn.  

Possibly also running the chimney horizontally as described on this site to recapture more heat with water pipes in as a preheater befor going to the primary burn chamber.

I will try to upload a diagram later when I've got home.

Any thoughts welcome

Thanks
Jon