IMO the point to AGS is that you do not need to go to great lengths in super insulation, air tightness details, large arrays of solar panels or specialist tradesman! it is about combining or balancing the most cost effective (money & energy) aspects of each element.

Using standard building practices with a little extra thought in the design (& simulation) stage should result in maximum benefit for minimum input, that is sustainable and market ready on a large scale.

Thanks Terry,
Your point illustrates exactly why I am building my own house and doing most of the work myself.
After reading Sue Roaf's Ecohouse book a couple of years ago, I dared to raise a couple of issues (such as nylon wall ties) with our then architect only to be told not to be so silly and to be happy with the generic box he was designing.
If some architects are so stuck in the mud, you can hardly expect builders to be worried about the finer points of keeping cavities clean and properly installing insulation.

Stephendv

From what I can gather, metal rods most certainly will contribute to thermal bridging, especially the larger ones needed for wide cavities.
There are alternatives. Im looking into reinforced Basalt wall ties right now. They are called the Teplo tie and distributed by Magmatech over here.

I think "collector area" is the key here.
In order to do away with insulation / airtightness etc you will be talking about a LOT of collector area which will have to be south facing (in the UK)
if something sounds too good to be true, it usually is ......

And I said "at the logical extreme", just to illustrate the point that truly inter-seasonal storage (which the sand idea is not) allows you to relax a bit about extreme, perfect insulation and airtightness, which Passivhaus etc relies upon.

Posted By: BenjMy argument is about the amount of collector area that would be required to make this viable

This requires Dynamic Thermal Simulation to quantify. It remains to be seen at present how big the thermal store needs to be

Posted By: BenjAll im suggesting is the cost / benefit is not going to make this method useful to more than a handful of dwellings.

We shall see - if we don't try new things - how will we ever progress

Damn ! Ive just planted 4000 of them - I should have put something else in the ground!!

Sorry for being pedantic, but whats the difference between a "very well insulated, very airtight house" and a passive house.

Fostertom, what caused me to say this is that I live in a house with 24" rock and rubble walls, so a lot of material here. When the sun shines the walls get hot on the outside and some of this heat is conducted into the room, a lot of heat is also conducted into the ground. When the sun goes in, the heat in the ground is then conducted up the walls and into space. So the effectiveness of using walls as a thermal store is the ratio of the time its getting pumped up with heat and the time the walls are pumping out heat. Idealy the interseasonal store should be totaly insulated so you can heat your rocks up to 90 deg C and regulate the heat output so the house only gets 20 deg C. For an existing house this is not really practical. Or at least very expensive. So I was thnking of getting the best bang for my bucks!
On the subject of the copper pipe and the insulation around the inner pipe, I feel that as this is the sole or perhaps one of two pipes getting the heat in and out of the ground, that its thermal efficiency should be good. With GSHP systems they use 10m of 22mm pipe per kW output. Another point brought up which I have thought about but not mentioned. Once the main pipe in installed a cutter is put on it to cut a 8" diam hole concentric with the pipe and say, 3 m deep. The cutter is withdrawn and insulation is then slipped over the main pipe. This is to minimise the heat input into the ground too close to the surface and its subsequent loss. No doubt an engineer would rebuild this as a 4" copper tube say 4 m long terminating in two plastic pipes sitting in a 4" diam rigid plastic pipe with insulation around them. So the pipe has only the copper heat exchanger bit in its active area.
As clear as mud?
Frank

I like your idea's frank,
but where do you source 4" copper pipe and at what cost ? the food industry uses 4" stainless steel pipe and its available second hand ! not as good a conductor but does that matter ?.
tom

Hi all, My first post here, so be kind :)

I'm very interested in inter-seasonal storage, as a result of wanting to build a zero-heat house that doesn't rely completely on passive thermal mass. That is, I want to be able to turn on extra warmth when I want to! But I have a bit of trouble getting my head around the various possibilities such as the type and size of thermal store and likely performance.

So I've read various publications such as the Tokyo paper but haven't seen much in the way of numerical detail. And I expect I could "do the calculations" but I also expect I'd make at least one mistake in either the analysis or the computation (numerical integration of PDEs as I understand it?). But something confirmed by experiment would make me feel more secure. So if anybody could provide any references to papers that provide models and/or quantitive analysis of actual houses, I'd be very grateful.

David, your 2000 m3 sounds a lot larger than David Mackay's 6 m radius in six months?
(<http://www.inference.phy.cam.ac.uk/sustainable/book/tex/cft.pdf> page 289)
I suspect that's telling me that it's impossible to store 5 MWh in the ground with only a 5 K delta T?

Tom, I'll be interested to see how a collector in the sunspace works out for you. I currently think that separate but fairly low-temperature facade collectors (a la Solarnor) are the way to go. It seems to me that the more decoupling there is, the better - between the collector, the storage and the building - but who knows what I'll think tomorrow.

Cheers, Dave

Blimey - 14MB! but worth the wait, at first glance. A whole book - thanks djh.

Posted By: djhI expect I could "do the calculations"

That's cool - what is your trade, profession of background?

Posted By: fostertom

Posted By: djhI expect I could "do the calculations"

That's cool - what is your trade, profession of background?

Well, I'm a computer geek by trade and a mathematician by training (back in the days when we used to count I, II, III, IV ...)

So, do you know of any AGS or other interseasonal storage papers with numbers? It's a nice idea but I haven't had much luck finding engineering data.

Cheers, Dave

Fostertom,
I am a bit puzzled by the idea of letting the heat into the room. If you could conduct it away instantly so that the room never heated up, great. But if the heat transfer was somewhat slow, the room would overheat quickly. Using Chukey's solar panels is fine (doesn't matter if they overheat a bit) or a greenhouse, but the main house? Have i missed something?

Hmm, cruddy forum software! Again! It says "attachments" but it will only let me make one "attachment". Here are the figures for a water tank.

Reading this thread and others like it with great interest.

Building two "Earthship" lodges in central Scotland,

Plan on storeing lots of seasonal energy in the mass of the structure as well as the ground around it.

Clarification; The one meter per month rule average soil conductivity, Don Stevens (AGS) seems to suggest that 18' feet equals 12 months in one of his house diagrams!

Tom and Mike, do you have any further up to date information and data regarding your AGS studies?

Thanks