When we first started planning works on the house, we had decided on using pellet heating, as we were told that with all the wood floors, the low-temperature, heat pump alternative would not be possible. Then Sace Bakan showed me wall heating and everything changed. It makes for a lovely room climate without cold spots, and much more efficient. Ok, out with the pellet boiler and all that storage, and instead, use a ground source heat pump with a horizontal collector field to the east of the barn (the green thing in the map to the right). It needs about 500 square metres, with 6 100m-long circuits buried between 1.2 and 1.4m deep (see my first draft below). But it's been tough trying to get someone to help us with digging this, and in the meantime, we've had all sorts of additional ideas from other people, including deep boring (too expensive) and diesel power/heat generators (too radical).
As a result, I've a slight pain in my arse, as I'd hoped we'd have this part done in August. So, now I'm considering one of the new, higher efficiency air-to-water pumps. Good to -20C, they say, but the efficiency varies with the temperature, ranging from 2 to 4.3 at best, the higher of which matches the ground-source heat pump.
It's a tradeoff between a quick, clean installation, with variable energy efficiency, or a longer, dirtier install process with more or less constant energy efficiency (assuming conditions are right underground). In either case, it would be nice to add a wood stove in the living room with a back boiler to help with the hot water supply in deep winter.
A friend in Ireland got an air pump thing cheap, but they've never been too happy with it. I could send you his email if you wanted to confer. Definitely put your stove in... Personally, I've always thought the water from baths, washing, showers, should go into a tank to be reused in flush toilets, thereby keeping the heat in the house as well as using grey water. Back to your field, I would get it dug over NOW, hire a digger and set to laying the pipe. You want some time for it to grow over. You can get a very narrow bucket - 6-inch =153mm - if you opt for a tiny digger which won't disturb a lot of ground (tho' this will take longer, bigger diggers, bigger buckets). There's got to be lots of Irish groundworkers who would jump at the chance if you put them up!
ReplyDeleteHi Dave!
DeleteI've heard mixed results about air source heat pumps in Ireland and the UK, mainly because the winter air is often quite humid, which leads to ice build up on the unit, which means it has to run in defrost more more often (basically, run in reverse for a while), which is not good for the efficiency, and therefore costs. Over here, the air is usually a tad drier when it gets really cold, and you hear of them being used a lot in Sweden, where it gets a lot colder. Three of our neighbours have them and are as happy as pigs in shit. One of them has had it for just over a year, so they got their first view ona year leccy bill for heating the house and water, and they're delighted.
We'd actually planned to lay pipes for a ground source heat pump in August, but the man we were talking to about the digger kept disappearing. It's 600m of pipe to be buried at least 1.2m deep in trenches lined with sand, so will definitely take time if we go that route.
I need to weigh up the investment costs. In theory the ground source, if laid correctly, should have a relatively stable efficiency, whereas the airpump goes up and down depending on the air temp. Much, much quicker to install though, and then we'd still be able to plant fruit trees in the field, which we can't if we go ground source. many pros and cons :)