I have a reconditioned beer cooler in my garage. I bought it on eBay a year ago and it didn’t cost a bomb and it isn’t that big, about the size of a microwave. I don’t drink much beer but that’s not what it’s for, I bought it to help warm my greenhouse. It would be nice if I could say the idea is my own, but I saw it on BBC Scotland’s ‘Beechgrove Garden’ programme. The cooler will act as a heat pump and will, hopefully, raise the temperature in the greenhouse a few degrees, just enough to prevent frosts zapping the seedlings (we get frosts as late as early June). The heat isn’t free. Like a fridge, it needs electricity. You get Owt for Nowt, as my Granddad would say (no points for guessing which county he came from).
Heat pumps have been described as fridges that work in reverse, but that’s an odd explanation. They are better described as fridges that take heat from the ground instead of from your food – and just like a fridge they put that heat into your house. As you can see in the photo, I’ve got as far as fitting two brass connectors to it. All I have to do now is to lay about twenty metres of pipe in a shallow trench in my garden and then cut through the concrete floor of the greenhouse – which probably explains why the cooler is still in my garage.
Watch this space….
I have a reconditioned beer cooler in my garage. No beer, just a cooler. It’s about the size of a microwave and I bought it on eBay after seeing one on Beechgrove Garden (BBC Scotland). They had it connected up as a heat pump to help prevent freezing in one of their greenhouses – the facts sheet is here. The principle is that you bury pipes in the garden and extract heat from the ground (I haven’t got round to that bit yet). The heat you get from a small unit like that is no big deal, but it should use less energy to run than the energy I would use heating the greenhouse to the same temperature… if you see what I mean. Just a couple of degrees would help, as we get frosts in early June and they can flatten seedlings.
Whitmuir Organics has a REAL ground source heatpump. The pipes are buried deep beneath large earth embankments, and from them they heat most of their new building. I can only bury my pipes a maximum of 18″ (45cm) beneath the surface because at that depth I reach solid rock – and I’m not sure I would be popular if I started blasting it out.
In the 1980s I was on the UK Department of Energy’s Geothermal Energy Steering Committee, and in those days heat pumps were hardly worth considering (not that ground source heat pumps use geothermal energy – they use heat from the sun that has warmed the Earth, not heat generated deep down, that’s quite different).
Things have changed a lot since the 1980s. The cost of fossil fuel has rocketed and heat pump technology has improved. I have yet to see if my little experiment will work. Trouble is, a lot of digging is involved. At present the ground is rock hard and covered by an ice sheet, like Greenland.
[Many false claims are made about heat pumps. If you are seriously thinking about installing one (not a toytown one like mine) then download the Energy Saving Trust’s .pdf file from here]