Where I live every other house is heated by either air-to-air, air-to-water or soil-/ground-to-water heat pumps. -20C a large part of winter isn't uncommon, some places go even lower.
So to me it looks a little bit insane when people confidently claim that heat pumps are unfeasible in rather cold climate.
The best conditions for heat pumps are places with hard rock just below the soil, so you can drill a heat well and use it for heat storage during summer months, i.e. AC/cooling. In my opinion that's the main drawback with air- and soil-based heat pumps, can't recycle heat from cooling in the summer.
Is the kind of well that you'd typically drill for a single family dwelling capable of storing enough heat to make that worth it?
I know that underground heat storage is popular with district heating, where you've got a hollow mountain storing heat for the whole city, but the square-cube law means that there's a size below which it doesn't make sense. I had only assumed that that size was bigger than was feasible for a typical homeowner.
Don't need to use cooling to make it work, I live in a fairly large house without cooling and a bore down into the mountain below is good enough even though we have -15 to -25C for weeks during winter. It's in a small town so not an isolated location. Most people around here have air-to-water or air-to-air, because it's good enough and cheaper to install.
And it's not a hollow, it's a plastic ~1 decimeter pipe with ethanol going through stone some distance down from the surface. Not sure how long this collector is, but 70-200 meters is common depending on how large the house is and conditions in the ground.
Ethanol is an interesting choice... lower specific heat when compared with water. Is that to discourage things like tree roots from making a home in your well?
It's stable, cheap, carries heat OK enough, so it gets pumped through the pipe in the ground to collect heat and bring it back up to the heat pump.
If there's a leak it's bad since it's quite toxic to organic life. If you collect in soil rather than drilling into rock tree roots might push around the collector pipe a bit over the years but I've never heard about that being a problem.
So to me it looks a little bit insane when people confidently claim that heat pumps are unfeasible in rather cold climate.
The best conditions for heat pumps are places with hard rock just below the soil, so you can drill a heat well and use it for heat storage during summer months, i.e. AC/cooling. In my opinion that's the main drawback with air- and soil-based heat pumps, can't recycle heat from cooling in the summer.