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Groundwater systems are much better. My parents house in Ottawa has one, and it works fine through -30 C nights. There's a source well about 30' deep with a pum
by tlb 8y ago
Groundwater systems are much better. My parents house in Ottawa has one, and it works fine through -30 C nights. There's a source well about 30' deep with a pump at the bottom, and a return well some distance away. That provides a constant supply of water around 5-10 C for the heat exchanger.
It is a complicated system -- lots of valves and reservoirs and so on, but very efficient and doesn't need much maintenance.
- SketchySeaBeast 8y agoI wonder how we could work this for an urban setting - could we use the water lines?
- tlb 8y agoIt consumes a lot of water, so it'd be expensive if you send the outflow down the drain. If you pump the outflow back into the fresh water supply, you have to worry about contamination from everyone's heat exchanger. In a dense urban setting, you can heat homes with water heated at the local power plant, either fossil or nuclear. https://en.wikipedia.org/wiki/Cogeneration https://en.wikipedia.org/wiki/Cogeneration
- SketchySeaBeast 8y agoIf we think insulating a single home is bad, image trying to build the infrastructure for that throughout a city.
- maxerickson 8y agoThere's closed loop ground source heat pumps. It's all very situational as to whether they are practical to install. The vertical ones are more expensive but don't need a whole lot of ground area to be installed.
- jabl 8y agoIn my city, about 10% of the district heating load is covered by heat pumps where the heat source is municipal waste water.
- Scoundreller 8y agoToronto does this for district air conditioning with incoming city water. I don’t think they’ve bothered to calculate the effects of pumping warmer water into everyone’s air conditioned home...
- upofadown 8y agoYou normally have to drill one of more well holes. If you can't go horizontally you have to go vertically.
- yungchin 8y agoYou could do some heat recovery from the sewer, but it would be a yucky affair - they already tend to clog even without heat sink fins in them :) Here are some calculations suggesting that the numbers simply don't add up for ground-source heat pumps at urban population densities: https://www.withouthotair.com/c21/page_152.shtml https://www.withouthotair.com/c21/page_152.shtml
- henrikschroder 8y agoA similar idea that's somewhat popular in Sweden is to add a heat-exchanger between outgoing sewer water and incoming tap water. You don't need to put fins into the outgoing water, it's simply a piece of regular straight copper pipe, but it's thicker, and the incoming water pipe coils around it a bit. No need to muck around with fins in the sewage, or trying to convert to electricty, simply heating the incoming water a degree or two saves energy for your water heater.
- yungchin 8y agoYes, we've got this on our shower drain. In this configuration it does better than a degree or two, recovering some 50% of the heat, in fact.
- jfee 8y agoI grew up just outside of Ottawa and we had a system like this 20 years ago. I don't think you can get a permit for them anymore because they don't like you moving water from one water table to another because of contamination reasons. Nowadays, it's mostly ground loops being installed. In rural settings where natural gas isn't available, and you have the space to run the horizontal loops, they're a good option.
- Scoundreller 8y agoWorse than that, they won’t allow direct expansion systems. So you need a glycol loop going through the ground which has another heat exchanger to the refrigerant loop.