Hi! I'm not sure whether this is the right place to be asking this question - but I'm sure somebody will tell me if it isn't!
A little background: I moved from the UK to southern Spain five years ago, bought a plot of land and am building a house on it - that is, my wife and I are doing all the building, block by block, which is why it's taken five years so far! And no, I'm not a builder, I'm a retired IT consultant (OK, I know, I know!).
Anyway, I am really keen to make the most of the abundant solar energy available here, but it's a waste of time for hot-water heating, because in the summer, the mains water supply is about as warm as you want it for most things, including showering. However, in the winter, the temperature can drop below zero, though there's usually a lot of sunshine.
What I really want to do is to run our underfloor central heating system almost entirely from solar power. The house is well insulated, I have located a source of evacuated tube solar collectors and done the sums, and in principle it can work. The problem I am now looking to overcome is probably a common one - how can I store the abundant heat I can collect during the day to use early the following morning - or even two days later if it's a heavily overcast day?
The first obvious solution is to have very large storage tanks for the hot water - more water, more heat stored. But that seems a pretty expensive option, and I'm not so sure just how efficient it would be; so I've had another idea.
I'd like to cast a large block of concrete - maybe two cubic metres or so (70 cu ft), and well-insulated - with two sets of coiled pipes buried in it, one connected to the solar connectors and the other to a much smaller hot water tank. I'm not sure whether the storage radiators that are popular in the UK are also popular across 'the pond', but it's the same idea - put a lot of heat into a well-insulated concrete block and take it out again when you need it.
Now the problem is that I can't find any references that tell me if this is a stupid idea or not; I guess most people don't have the opportunity to cast an insulated 70 cu ft concrete slab! So would anyone like to offer their opinions?
Am I crazy, or could this just work? Alternatively, can anyone offer a better solution so storing heat for this application? Sorry for the long post - it's hard to explain in fewer words! Thanks.
