Thermal store

[greasemonkey]

Getting somewhere. Not running on anything alternative yet, just good old heating oil.

The base.


With the tank. Base of the tank is 4 foot square. It's a meter high. Cut from a 600 gallon tank.


Inside the tank.


Frame work and lagging


Oil boiler, with temp controller sat on top of it.


This is down in the tank, being heated by the oil boiler.



The FPHE, giving heat to the radiator circuit. Tap is a fill/bleed valve. Plastic pipe is return to the boiler from the rad in the tank. Pipe coming off the top is out to a common header tank, which is indooors. Has boiler and rads on it.Pipe going off before the tap is supply to the rad in tank.

I don't seem to have a photo of it all closed in. The top of the tank has 4 inches of kingspan on it, and the whole top has ply on it, soon to covered in felt.

I have a temp gauge in the tank, which I can see from out side.

[greasemonkey]

This has been quite a frustrating project, not least coz most of it has been done in the pouring rain, waddling around in an ever growing quagmire.

Basically, it seems to be working. I've heated the store to 33c tonight, and the rads inside are creeping up over 20. They do seem to creep up very slowly. I've switched off now, because I think I'm getting some pretty bad heat losses from the pipe work supplying the rads. They go through the porch, into temps a 5c, before entering the mobile home. They need lagging.
I do wonder if the FPHE is working properly.
I haven't got a photo of it (prat!), but it has a short piece of pipe, picking up the hot water, where the return from the rad comes in, then a pipe to the bottom of the tank on the other side, where in theory, the cooler water should be dropping out, after exchanging the heat into the rad circuit.
I wonder would this benefit from having the thermal store water pumped through it?

I have heated the thermal store a couple of times already. I consistently heats at 1c per 10 minutes, with the boiler cutting out at 70c.
The last time I heated it to 25c, and 48 hours later, it was at 18, and thats with no insulation on top, and nothing closed up, so I'm pretty optimistic about it.
I know it needs a lot more insulation around the sides, and a few holes need stopping up, it's very much a work in progress, and probably always will be, but it is functioning.
Having said all that, i'll see how efficient it is now, and might just connect the boiler direct to the rads, in the normal fasion, until i either improve the store, or get the WMO burner going. No point in wasting heating oil if it would be better that way. It won't be difficult.
The rads have now hit 21c, and although they still don't feel warm, there is a noticeable difference in the temperature in the caravan.

[photoman290]

sloshing about in the rain. really? been dry and sunny down here. but that was some time ago. wet and windy now i have time to do all the outside stuff as usual. as i posted over at the other place. my experiments with the wmo fuel feed seem to  be going well. after a bit of reading it looks like that kit i mentioned,plus an ac peristaltic pump  seem to be the way forward. the best deal i can see if you have to buy one is the aspen air con condensation removing one. 6.5 litres an hour and 2  outputs for thermostats built in. ac 240 volt as well.

 the burner.
i think using the same design as mine with a length of steel pipe though an oil drum so it forms a tank around the flue should work. i would use about 100 litres of water and keep circulating it around so you don't totally kill the draught. that way you can vent it so you don't end up with a steam boiler explosion. that could be messy. get the burner hot first so you have a draught then start pumping water into the drum. have a an outlet about halfway up feeding into the thermal store. i am planning something simular but using the  m67 for the heat source. the m67 seems fine in a tank of cold water once the draught is established so we know having the flue in the water wont be a problem. good work, mine is still in my head.

[Julian]

Just a thought ... would additional top insulation be an advantage if it were directly on the water surface?

You can get specially moulded spheres with a lip around the equator, I've seen them on heated treatment baths, but they are probably expensive.  So how about off cuts of your Kingspan floating on the surface with as few gaps as possible?  I'm pretty sure it's closed cell so won't soak up the water.

[greasemonkey]

Good point. It may well be an advantage to put the kingspan directly on the top of the water. If not that, then put a plastic membrane on the water, then the kingspan. it would do away with the air gap. I think usually on something like this, it is a good idea to put a membrane on anyway, to stop the evaporation. It steams quite spectacularly at 30 plus.

I've been pondering the WMO burner a good bit. i could do like you say Bob, I may have over thought it a bit. i could jut let the water syphon out, heat it, and pump it back in. I have enough height.

What I would like to do, is have the burner at the bottom of a gas bottle, the bottle acting as the flue, and then have a matrix of water pipes in the bottle, so the flame and flue gases are going directly on them. i think that would be most efficient. But that is really getting into boiler making, and I'm no boiler maker. It would only take one weld to crack and I think the resulting explosion would vaporise everything within a 15 foot radius.....

What I may do is try and lie a bottle horizontal, cut it flat along the length of it, less than in half, and weld a six mm plate on it. Have the burner at one end, and the flue at the other. Then make a box to take the water.
Either that or make like a saddle tank over the horizontal bottle. At least that way there is a bit of safety if the tank carrying the water springs a leak, and it can be pulled apart to inspect it. Another thing, it needs to be drainable, so water doesn't freeze in it.
Having the water directly in contact with the flue is no doubt the most efficient, but it bothers me what would happen if water got into the burner. It's a lot of rapid and wide heat cold cycles.

Another thing, I'm pretty sure it is more efficient to heat a rad, and then heat the store, as in what I have done. I was heating the water with the boiler, and pumping it straight back in, but that wasn't working at all well. having said that, the boiler is pretty feeble, most the heat is going up the flue. The oil burner is more like forge temperatures, should be a lot hotter and quicker.

I'm thinking of having the oil tank actually in the thermal store, so that should keep the oil nice and thin. Maybe have a 2 gallon tank.

[photoman290]

Just a thought ... would additional top insulation be an advantage if it were directly on the water surface?

You can get specially moulded spheres with a lip around the equator, I've seen them on heated treatment baths, but they are probably expensive.  So how about off cuts of your Kingspan floating on the surface with as few gaps as possible?  I'm pretty sure it's closed cell so won't soak up the water.

you could use astrofoil kingspan is closed cell but as it moves around bits will rub off and block the pipework.

[greasemonkey]

Just a thought ... would additional top insulation be an advantage if it were directly on the water surface?

You can get specially moulded spheres with a lip around the equator, I've seen them on heated treatment baths, but they are probably expensive.  So how about off cuts of your Kingspan floating on the surface with as few gaps as possible?  I'm pretty sure it's closed cell so won't soak up the water.

you could use astrofoil kingspan is closed cell but as it moves around bits will rub off and block the pipework.

Apart form the FPHE, no water leaves or enters the thermal store. The stuff will float on top, so shouldn't go up the FPHE pipe.

[julesandtash]

Something I learnt from a site about thermal stores and incoporated on mine is putting a thermostatic mixing valve (tempering valve) in the return line from the store to the boiler.

The water from the store connects to the cold port, the mixed port of the valve connects to the boiler return and the hot port of the mixing valve is Teed into the hot pipe between the boiler and store.

This means that there is still a clear and open line from the boiler to the store (and therefore atmosphere) so no risk of pressurisation but the system is more efficient.

Basically, without a mixing valve, whenever the boiler is firing and the pump running, cold water is drawn from the store, and warm water (raised by whatever amount the boiler can manage in one pass) flows to the store.

That means that the boiler slowly brings the whole store up to temp evenly, but very slowly. The large flow destroys any stratification so the whole store is just like one big tank.

With the mixing valve, the boiler initially just circulates around the loop made of the hot pipe, the valve, pump and return line.
As the temperature in that circuit exceeds the set point of the mixing valve, the valve starts to open and allow cold water from the store to start joining the hot water return to the boiler.
As it does, hot water will start to enter the top of the store from the hot pipe to replace the cold drawn off.
That way, only hot water (whatever the valve is set to) enters the store and at a fairly slow rate so it heats the store from the top down, maintaining a degree of stratification.

I have this setup running with my boiler and thermal store (which is only a 250 litre one) and it works really well.

You just need to make sure that the pump is between the mixing valve and the boiler return port for it all to work.

If I find the site I found it on I will post a link up.

[julesandtash]

It was on heatweb.com - have a look at the diagrams of their stores.

Slightly complex as they show the valve and pump strapped to the side of the store cylinder but once you work out the flows, port positions etc it is as I described above

[greasemonkey]

Something I learnt from a site about thermal stores and incoporated on mine is putting a thermostatic mixing valve (tempering valve) in the return line from the store to the boiler..........

I can see the logic in that.
Initially, I tried heating the store, just by taking the cold water out, through the boiler, and back in. This was a total failure, so I fitted a valve on the outlet, to hold the water in the boiler for longer. By the time  the water was too hot to put your hand under, the flow was feeble. That's why I put the rad in.

The thing is now, the water returning to the boiler is hot. You can still comfortably put your hand on the return pipe, but it could do with staying in the rad a bit longer, in my mind. I have no valves on the rad, so can't turn it down any, not that I fancy trying to do that with my head plunged in two foot of water anyhow.

The rad heats the store evenly, I was amazed at how little difference there was between top and bottom, and the far corner from the rad. Dropping the heated water straight back in at the top, i had the bottom at 12c, and the top at 30.

It is all vented by the way, out to a header tank, which you can't see, because it's in the porch.

[greasemonkey]

It was on heatweb.com - have a look at the diagrams of their stores.

Slightly complex as they show the valve and pump strapped to the side of the store cylinder but once you work out the flows, port positions etc it is as I described above

Cheers, I'll have a trawl through that.

Blinking 'eck its 'ot in 'ere. The rads are barely warm.......

[photoman290]

i cant find the vid  anymore but i have seen an idea i want to try. you have the same set up as mine but rather than having the flue coming straight out the top the flame goes though a cylinder about 4 inches highj and 18 inch diameter. the flue goes on the other side to the burner. that gives  you  a 16 inch diameter plate that gets very hot. a gas bottle on top with plenty of insulation around it should work like a big kettle.

[Head Womble]

GM, you should have added some insulation underneath the tank, you'd be amazed how much heat is lost without it.

[greasemonkey]

I can't see any reason why the flue gasses wouldn't move horizontally, so long as the flue is well sealed along to the outlet, providing it has enough height above the burner to function properly.

[greasemonkey]

GM, you should have added some insulation underneath the tank, you'd be amazed how much heat is lost without it.

I have, the pallets are full of it. You can't see it.