Evolving system

[2807]

Hello list

A bit of background.  I live in SW France & have a 4 bed house with a floor area of around 200 square metres, when I bought the place, heating was provided by electric under floor heating and wall mounted electric radiators supplemented by 2 wood burning stoves, one at each end of the house.  We used the electric heating only in the first year we were here, it was very expensive and ineffective.

In winter, there are just 2 of us, in summer as many as 8 or more on a regular basis. 

I currently have 120X47mm tubes facing due south.  These were originally installed to heat a swimming pool and have subsequently (after I got round to changing the tank) been used to heat a 300-litre DHW tank to 60 deg each day. 

When the DHW gets to 60 deg, the controller switches the solar flow through a couple of radiators I have installed & this (so far) has meant that we have not had to light the wood burners (much to my wife's dismay..).  On a sunny day, the radiators have been too hot to touch.

Even on cloudy days, the radiators have been on for a couple of hours, I don't know how much of the 300 litres of hot water we use each day, but I suspect not very much of it - however we do need it all in the summer.

Having hot radiators is nice, but obviously they go cold as soon as the sun nears the horizon and that time is getting earlier every day for the next 7 weeks or so.

I have another 80X47mm tubes sitting in my shed, but no available south-facing roof on which to install them.  I do have a west-facing roof and was considering putting them on that and making a crude thermal store out of a 1000 litre IBC in order to capture the energy produced by the panels during the day & allow me to turn on the radiators in the evening.

My plan would be to build an enclosure in blocks around the IBC at the rear of the house.  The structure would be large enough for the IBC to be surrounded by some 100mm thick insulation boards with vermiculite poured into any gaps between the IBC & the insulation boards. On top of the IBC I was planning to maybe double insulate with the 100mm boards and add a further layer of vermiculite.

A couple of heat exchanging coils would be dropped into the IBC, one for the new 80 tube set and one for the heat dump from the DHW, I could then suspend a heat exchanging coil at the top of the IBC to extract the energy in the evenings by pumping in through the radiators.  At this point in time, I was planning to use the existing controller to power the circulation pump for the new bank of tubes, I am aware that the circulation pump will not be operating on an optimal basis, but feel that the additional expense would not be worth it.

I am aware of the energy losses caused by having top exiting pipes and was intending to counter this by routing the entry & exit points of all 3 heat exchangers over the edge of the IBC and then down the side of it inside the insulation, exiting through the blockwork at or near ground level.

Do you think it would work???

2807

[KenB]

2807

IBCs may start to get a bit soft at temperatures above 65C.  You would most certainly need to keep them in their cages and perhaps adopt some means of preventing them sagging.

Ken

[2807]

Hello Ken

2807

IBCs may start to get a bit soft at temperatures above 65C.  You would most certainly need to keep them in their cages and perhaps adopt some means of preventing them sagging.

Ken

I did suspect this might be the case, hence I was going to leave it in its cage & pack around it with fine grade vermiculite, before the 100mm insulation board, inside the block built enclosure, hoping that would give it some lateral support.

2807

[rt29781]

Hi 2807, we live in SW France and have 150 ET tubes.  It heats our pool and our domestic hot water and our house through underfloor heating.  More details are on our blog.  see footnote.  We use a 500 litre rain bucket (in a concrete box) as a storage tank so your IBC idea sounds feasible as long as the structure can take the force if the IBC ruptures?

[mick]

2807 (good name!) and all,

Could you pour concrete, of appropriate mix, between the IBC and the insulation, perhaps with some mesh reinforcement, to make an effective 'tank' with the IBC acting mainly as a liner?

Mick.

[2807]

2807 (good name!) and all,

Could you pour concrete, of appropriate mix, between the IBC and the insulation, perhaps with some mesh reinforcement, to make an effective 'tank' with the IBC acting mainly as a liner?

Mick.

Hello Mick

That could be an idea, but I was hoping that the vermiculite would support the sides of the IBC.

Is concrete a good insulator?  I suppose it will increse the thermal mass whatever, but I was hoping to be able to control the size of the thermal mass by increasing or reducing the volume of water in the IBC in order to regulate the temperature.

2807

[djh]

I have another 80X47mm tubes sitting in my shed, but no available south-facing roof on which to install them.

Any south-facing wall? That's good for winter.

[2807]

Hello DJH

Any south-facing wall? That's good for winter.

Hmmmm - yes I do have a south facing wall, but the collectors could not stay there all year round, so I was thinking that it would be too much hassle to move them, twice a year with the risk of breakage etc...

Something to think about though.

2807

[Farside]

2807

IBCs may start to get a bit soft at temperatures above 65C.  You would most certainly need to keep them in their cages and perhaps adopt some means of preventing them sagging.

Ken

I have a similar idea to use an IBC container as a thermal store and found some info on the properties of HDPE. It will withstand 110C forever and 120C for short periods. The sagging issue had occurred to me, as I've seen some abused ones that had been overheated and pretty sad they looked
What I intend to do is simply use some saddle clamps around the top bars and bolt through the top of the container with stainless bolts, sealing with silicone as necessary. The idea of inserting tightly coiled copper is interesting and I may use that - previously, I'd thought of removing the top entirely and inserting SS shelving/bracketry to hold flat coiled copper at various heights. Sealing the top back on is slightly problematical, but nothing insurmountable.
I'm going for at least 8" of rockwool around the cube, probably 4" of Kingspan on top, simply because of its easier handling as a removable lump. I'll throw in a couple of gallons of cheap bleach to the mix, as I've seen what happens with fungus and algae around here if you don't do this.