Underground Hot Water storage

[Countrypaul]

https://www.bbc.co.uk/news/business-65098792

[Mr Gus]

Quite a lot of interesting youtube videos on Swedens prepper families (bear in mind how they are located & have modern shelters in place for many thousands of citizens before anyone applies the term "prepper" as overzealous emergency contingency hillbilly type survivalist tropes.

[Fueltheburn]

I shall have a trawl this later for an article.
BP were sponsoring house builder in C
Ada I think to build there house atop a large thermal mass. The underground water storage took in all the heat during the summer months and was stored in the massive water storage under the house.

As the heat was removed, the water became stratified and showed different temperatures at different depths.
I seem to remember the key to it working was some kind of netting sock as the siphon which allowed the water flowing into the house to remain hot.

Was an interesting read.

I had been contemplating doing something similar in Scotland but burying a 20ft insulated container full of sand as a heat storage.

[Mart]

I had been contemplating doing something similar in Scotland but burying a 20ft insulated container full of sand as a heat storage.

Good luck if you go down that route. It's an idea I find fascinating. When reading up on the sand battery idea I loved the factoid (that was so obvious once pointed out) that for small domestic storage you need about 1m of good insulation, whereas for a giant city storage facility you need ..... about 1m of good insulation!


Have you heard of Caldera? It's more for industrial scale and industrial processes like brewing, but the idea is interesting.

How One Invention Could Decarbonize 25% of All Energy

[Moxi]

who was it at the other place who made "gravy" with a hot water storage system made from a sump and some old radiators ?

Moxi

[Fintray]

who was it at the other place who made "gravy" with a hot water storage system made from a sump and some old radiators ?

Moxi

Gravyminer?

[Moxi]

oh yeah, that would be he , what was he before he changed to gravy miner tho AND more importantly is he now here with his wealth of experience ?

Mox

[spread-tee]

oh yeah, that would be he , what was he before he changed to gravy miner tho AND more importantly is he now here with his wealth of experience ?

Mox

AKA noelsquibb and I think "Heidi" at the old place, I think he did pop in here in the early days to say hallo but I can't remember his new moniker.
His Gravy mine was indeed an epic tale of fun and disaster along with brilliance and buffoonery, I wish him well if he lurks.

I did the numbers on an underground store when we did a big extension at Cactusville and it certainly added up favourably, I figured on a store some 2*6*1.5M under the extension which would have been easy to bridge over, digging out was pretty easy with a mini digger, a couple of grab loads to snatch away, and a small amount of drain re routing which was relatively trivial. The big problem I couldn't resolve was our ridiculously high ground water table and how to stop it from stealing our heat or creating a 30 tonne gravy pit under the house

Desp

[Moxi]

Noelsquibb yesssss that brings back memories top marks to you Desp!

As with many things its got a certain appeal and logic to it but when applying the sanity check of "if its that good and that easy why doesn't everyone already have it?" it falls over - thats not to say that its not worth another look but generally these simple ideas have some sort of Achilles heel that stops them dead in their tracks its only on the rare occasion that something is reconsidered and on that occasion is found to be of its time.

Moxi

[Mart]

Hi Desp, I was also wondering about water flow. Not a day to day problem for say GSHP, but would add up for longer term storage. Might even be a benefit for GSHP carrying away cooled water, during the heating season.

I wonder if placing layers of PIR overlapping (perhaps 5 x 200mm sheets), then filling with sand/gravel/stone dust, would be enough. Not trying to stop water flow completely, but just slow it down enough to make it a non-ish issue. Or just lagging the inside with dpm layers.

Just thinking out loud, perhaps you want the sand wet, to increase total mass, so long as there is little to no flow allowing heat to escape. Perhaps minimal damp proofing is all that is needed, v's the cost of making it water proof?

I live on quite a steep hill, and water leachs through the ground, so in my case, I assume I'd need the store to be pretty well sealed. Are there giant plastic tubs you can buy, something like a cheap version of a hard plastic pond liner, but without the high expense of say a giant rainwater collection tank?

Presumably someone has already thought through most of this?

[Just to say, not something I think I'd do, as heating needs are approaching minimal now (with A2A units), but ideas I am fascinated by, especially for new builds. And over 10yrs ago, someone on the MSE forum had bought a house with a large 'proper' rectangular swimming pool, and was looking to fill it in. I always wondered if it would make for a decent and cheap GSHP source, be it water, sand or both. Funny what you remember.]