Storage Heaters what types are there?

[ericmark]

OK seen and used the iron laden brick type and also the water tank type even seen a central brick store and fans.

The main problem is to store energy only releasing it when required with a secondary problem with size. The small brick units are hopeless the larger brick units work well but whole house needs designing around them.

So the water type seem to be gaining ground with the added advantage can also use solar power to top them up. However the 100 deg C limit well really a little less than that does mean they become rather large.

In theroy other mediums could be used. Oil could be stored hotter and there is also the latent heat type where something often a salt changes for solid to liquid and back again to store heat. However although I know it can be done I know of no commercial system where it is done.

There is with pure heat a trade off between size and temperature the higher the temperature the more heat will leak out when not required. And the hotter a liquid the higher the danger so I can understand why we seem to have mainly brick and water systems but are there any other?

My interest is can they be used to store heat from a wood burner? Water boiling at 100 deg C is a problem as wood stoves can exceed that temperature something which could be heated to 600 deg C would be far better. Not likely to boil and smaller store required. There are FRF so fire should not be a problem with right oils. But if that easy I am sure others would already be using it. If not why not?

The wood burner has a big problem except for pellet burners there is no auto feed and so fires will go out and when running they tend to heat the home well over the temperature required. A heat store would allow the fire to go out and home still be heated and damp down the excesses.

The existing Megaflow and Willis systems will of course work but can they be filled with FRF instead of water? I would think not if main central heating was water it could boil the water. But maybe there is a way?

Power failure is one thought and likely there would need to be battery back up may be even solar power but question remains is there already a system working on between the heat used by water and that used with bricks and if so what is it called and does anyone have links to it?

 

[big-all]

have you thought about ground or air sourced heat pumps

 

[ericmark]

Yes I have. Ground not really an option in woodland with a timber framed house on stilts with really thick roots. Which if damaged could mean another tree will fall on the house.

Again as woodland humidity is high and likely air type would freeze up.

Loads of wood for stove but goes out during the night and to store some energy to release over night would seem the answer.

However after narrow boat and having problems with power failure and water boiling not so keen on water system if used would need battery back-up to ensure pump runs while stove is running.

Radiator outside to sink any excess is all well and good if one can stop if freezing. Not a problem in the narrow boat ice never more than one foot thick and heat sink below water line.

Incoming water does freeze from time to time so can't rely on running off hot water when over heated.

On narrow boat had a tank stat on the boiler outlet set to around 30 degs C so no water circulated until stove started heating or very hard to light. Clearly from this experience will need some electrical control.

Was undecided as to if to post in electric of plumbing section. The consideration was to use a large storage tank able to supply hot water to radiators when fire goes out until morning when re-lit likely only 4 hours. However a little worried about weight so putting out feelers for lighter storage medium than water.

Something like Ba(OH)2 (Barium Hydroxide) 8H2O would it would seem make a very good heat store. Melts at 78 degs C and has a latent heat of 655 (MJ/m3) that would seem a good way to store heat. So why is it or something similar not used to store heat? There must be a good reason or we would use it instead of the silly iron/clay bricks used today.

 

[ban-all-sheds]

So why is it or something similar not used to store heat? There must be a good reason or we would use it instead of the silly iron/clay bricks used today.

Toxic, corrosive and expensive?

 

[bernardgreen]

There were several projects using phase change storage ( salts in and out of solution and solid to liquid changes ) but most seemed to fail after a year or two. Stratifying of the material was one problem. The layers preventing circulation of the fluid so not all the material could be used. And as mentioned corrossive liquids made more problems. A leak in a test site was tolerable but in a domestic situation ( with no trained maintainance staff ) a leak of corrosive created an immediate safety hazard.

Recovering heat from ambient air works well and provided the control system does not allow the exchanger to go close to freezing the outside unit should not freeze. Humid air provides more heat than dry air as the latent heat can be recovered from the water vapour as it condenses.

 

[ban-all-sheds]

I'm sure that people like Daikin, Mitsubishi, Panasonic can give you an aircon unit which can be used in temperate rainforests.

 

[ericmark]

Total supply for three houses 60A I see this as a problem with electric heating. Electric control great but not all electric. The road is only big enough for a small tractor no way to get a wagon up the road so gas in in bottles in loose box on back of tractor. Hence still on wood heating. But guy now nearly 80 and getting his wood chopped is a daily chore he could do without. At the moment he burns a lot so reducing how much would mean others could cut it for him. This

is about a Winters supply that's a lot of wood to transport and if wet can't use tractor so wheel barrow job.

Hence idea of heat store. Then may be one fire could warm the two buildings which are connected by a small wood store.

 

[17thman]

insulation, insulation and more insulation! and dig a very big hole, line it with a few skins of thermal bricks, plumb some pipe work around the inner edge and line it with a more skins of bricks and burn all the logs in the pit. Use a pump to circulate the warm/hot water to whatever buildings you require. a carefully designed roof to the structure will allow minimal heat escape but allow oxygen to enter. Link it in to a geo thermal sysytem. the residents can then chop logs or use them less frequently

 

[ban-all-sheds]

This is about a Winters supply that's a lot of wood to transport and if wet can't use tractor so wheel barrow job.

That's what horses were made for. Narrower than a tractor, and better in the wet.

And with two of them you can make more - can't do that with tractors or wheelbarrows.

Anyway - that's Gandalf, can't he just do some magic stuff?

PS - the cutting may have been done, but there's a lot of splitting still to do.

 

[tangowaggon]

If you look up the latent heat capacity of water, it is very high compared to many other liquids, so 100kg water at 100'c holds more heat than the same amount of oil at much higher temperatures.
I fitted a system based on two 350 litre copper tanks encased in a 100mm thick kingspan box heated by 4x3kw conventional, thermal store immersion heaters on economy 7, the water is circulated around conventional radiators by a pump controlled by a conventional programmable room stat.
At the time the theory was sound but the system untested, the owner reports two years later that the system works well and is surprisingly cheap to run. Even at full temperature of 90'c, the system only uses 7kwh/day to stay warm with no demand from heating.
We use a combiation of wood and coal on our woodburner, wood through the day, then scrape the burning embers to one side and fill the other side with coal before going to bed, the fire slowly burns across the bed of fuel, usually leaving enough burning embers to resurrect the fire in the morning.

 

[bernardgreen]

Another option is a bio-digestor system. Rotting vegatable matter in a thermally insulated tank creates heat which can be extracted by water circulating in pipes around the tank. The flow has to be controlled to prevent the material being cooled to far and the rotting stopped. It also produces methane gas which can be collected and use as gas for cooking or in a gas engine to create electrical power for lighting and some more heat for heating.

The centre of a pile of hay that has started de-composing can create very high temperatures and in the absence of oxygen at the centre it cannot burn. I recall from my childhood seeing an iron rod glowing red hot as it as pulled out of a hay stack that had been stacked when wet. Later that day the stack erupted into flames as it was being taken down to save the outer layers.