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I'm amazed at how little district heating is used in northern climates like Canada and the northern US. In dense areas, district heating using waste heat from p

• calamari4065 3y ago
  The problem is adding the infrastructure where it doesn't already exist. District heating is great when building a new city, but we don't do a lot of that anymore. Just imagine the cost of laying new pipes under an entire city. I'm sure someone smarter than me can do the math, but I'd suspect it'd take many decades to recoup the environmental and economic costs of installation.
• quickthrowman 3y ago
  > In dense areas, district heating using waste heat from power plants should really be required by urban planners Power plants generally aren’t located in dense areas… > I'm amazed at how little district heating is used in northern climates like Canada and the northern US. District heating and cooling are available in both Mpls and St Paul in the downtown core. This is the coldest large metro area in the United States. St. Paul: https://www.districtenergy.com/ https://www.districtenergy.com/ Minneapolis: https://cordiaenergy.com/our-networks/minneapolis/ https://cordiaenergy.com/our-networks/minneapolis/ > On an individual household scale, I've always wondered why nobody has come up with basic drain heat exchangers to capture most of the heat coming out of shower and washing machine wastewater before it leaves the building. (Edit: I guess they do exist - https://www.homedepot.com/p/Power-Pipe-4-in-x-48-in-Drain-Wa https://www.homedepot.com/p/Power-Pipe-4-in-x-48-in-Drain-Wa... - but I've never seen one in the wild) $851 just for the heat exchanger, not including piping and labor. It will take a lot of showers and laundry to pay that back. I’d probably add one to a new house build but would pass on retrofitting one into an existing home unless I was doing a complete plumbing remodel. Similar to daylight harvesting LED lighting, it’s possible you’ll never see a payback on the equipment and labor.
  • danjrslp 3y ago
    I was going to mention the Minneapolis system, I work across the street from this plant.
• kube-system 3y ago
  I was just about to post that same link. I suspect the reason you don't see them much is because installing one will often require more plumbing and more labor. Residential installations in the US are particularly sensitive to up-front cost, and tradespeople in the US tend to be conservative in choosing 'new' technology.
  • MattGaiser 3y ago
    And also exacerbate an already challenging shortage of trades.
• FredPret 3y ago
  This would work as a sort of energy storage - you could overheat your water reservoir during cheap power times and then transfer the extra heat to the entire city the rest of the day.
  • yetihehe 3y ago
    You would need a lake sized insulated reservoir for that to work. Too much water is used already by those systems, they don't typically want to add another storage. Typically they are gigawatt scale systems burning something because just using electricity is too much strain on grid, unless you have a power plant nearby (like cogeneration, which uses waste heat from electricity generation from fossil fuels).
    • FredPret 3y ago
      Why? Just overheat the water circulating through the district water system when you can. People's thermostats will simply turn off sooner, leaving more heat in the water. Then later, you underheat the water, and the city's various thermostats turn on a bit longer. The risk is that you underheat too much, and people compensate by plugging in their own heaters during underheating. And underheating will occur during expensive energy periods, so this will exacerbate periodic energy shortages. But overall this could work to store a ton of energy - there's a huge volume of water in a district heating system's pipes.
      • yetihehe 3y ago
        Typically water coming out of your heating plant is already at max temperature. Any more and it will start boiling.
    • adrianN 3y ago
      56 Million litres, about 2,5GWh: https://group.vattenfall.com/de/newsroom/pressemitteilungen/2022/deutschlands-groesster-waermespeicher-am-start https://group.vattenfall.com/de/newsroom/pressemitteilungen/...
    • ZeroGravitas 3y ago
• bombcar 3y ago
  I remember reading on a plumbing blog (or YouTube or something) about someone who installed one of these - high end house, massive shower, owner who liked to take hour long hot showers or something. In that case, it paid for itself pretty quickly. For "normal use cases" the cost savings over time just isn't there, when you compare the added complexity. You're better off saving heat with on-demand heaters or HVAC recirculators, etc. Places where it could make sense already use them (I believe car washes recycle water and heat in some locations).
  • hooverd 3y ago
    That someone just needs a sauna.
  • euroderf 3y ago
    So how does one keep all the showered-off gunk from clogging up the works ?
    • tempestn 3y ago
      There's nothing to clog up. The drain is a normal drain; the innovation is that the cold water source pipe winds around the drain, transferring some of the heat from the outgoing water to the incoming.
      • euroderf 3y ago
        Heat transfer requires time, which is why I've always assumed that such a system would have to use coils somewhere. In the system under discussion, all the heat-transferring parts had better be metal, and it won't be worth a damn except when handling a hot shower or a draining bathtub.
• barelyauser 3y ago
  [flagged]
• blacksmith_tb 3y ago
  The builders of my house (who were angling for, and got, PassivHaus+ certification for it), built a heat exchange for the drains on the second floor that warms the intake to the hot water heater. It works, but it's pretty limited, in practice it does pass some of the heat from a bath or shower or dishwasher run back, so that's something. Of course the timing matters, water drains pretty quickly, even from a bath, the there's no coordination to guarantee the water heater runs while that happens (other than the good chance that if we just pulled hot water out it will be running to replace it, but sometimes that isn't immediate).
  • thinkcontext 3y ago
    The DoE quoted a figure of 30% savings on showers, which is pretty impressive. All houses should be built so this is standard. It's so much more expensive to retrofit it later especially if the layout doesn't have the shower over the water heater.
  • hinkley 3y ago
    The water heater is always refilling. Otherwise you’d have no hot water pressure. It’s just that the new water goes to the opposite end of the tank from where the output is attached. How twin heating element water heaters work: https://youtube.com/watch?v=Bm7L-2J52GU https://youtube.com/watch?v=Bm7L-2J52GU
    • blacksmith_tb 3y ago
      Hmm, good point, I guess I hadn't thought about it, but that does mean whatever residual heat is in the water draining does get transferred to the water coming in to the tank, which if anything means the heater is less likely to come on.
      • hinkley 3y ago
        For showers definitely. But as someone astutely observed, washing machines (clothes and dish variety) pull a bunch of hot water, and then dump it out a half hour later, and then may or may not pull more hot water afterward, but never while they are draining. I guess there's an expensive reservoir for that and that sounds like more water damage waiting to happen. So the only heat transfer you'd get there would be whatever heat capacity the exchanger has. And since the thermal conductivity is high, all it's probably done is heat up the air inside of your walls a little bit. The best alternative to me seems like heat pumps, although you might also be able to scavenge heat to feed into your radiant heating system, or the cold air exchange on your furnace. The former seems more likely not to cause problems on hot days.
• tvb12 3y ago
  $851?! Well, at second glance, it's definitely larger than it appeared to be in the picture. Home depot says 35 pounds, so ~$100 worth of copper.
• elric 3y ago
  > I'm amazed at how little district heating is used in northern climates like Canada and the northern US. District heating is very expensive to build and difficult to retrofit. Doesn't seem very surprising to me. Any time a piece of road has to be dug up, costs skyrocket and people are inconvenienced for what seems to be an eternity. As far as I can tell, this is universally true among western nations.
  • mschuster91 3y ago
    > Any time a piece of road has to be dug up, costs skyrocket and people are inconvenienced for what seems to be an eternity. Former trench digger here. The cause are usually two problems... first, the "underground line maps" ("Leitungskataster" in German) are usually not up to date because not everyone bothers to update them. Quite the "fun" if you suddenly hit a cable at 50cm when the map says you should be clear up to 2m! The second problem is that Western societies almost always choose the cheapest bidder, which means no work on weekends or, heaven forbid, 24/7 as that would be too expensive. That means everything is slow as molasses.
    • Tarball10 3y ago
      Why is it cheaper to have one shift work on a road project that takes months, compared to three shifts working around the clock making the project take 1/3rd of the time? I've always vaguely wondered that when driving through construction zones that are seemingly devoid of workers most of the time. I assume the workers are paid hourly, so wouldn't the cost be the same? Are second and third shifts more costly?
      • sokoloff 3y ago
        Overtime is more expensive. Shift differentials (paying more for 2nd and 3rd shifts) makes those shifts more expensive. There are more workers willing to work in the 7A-4P window than in the 9P-5A window.
      • mattmaroon 3y ago
        Second and third shifts are more costly, yes. Many fewer people want to work them, so supply is much lower, so prices are higher. Also in evenings, road crews have extra safety precautions (there’s a higher chance of running one over in the dark) and that’s labor too.
• miketery 3y ago
  It's a cost thing. Prices for energy have been so cheap that investing in recapture capex didn't make sense. With energy prices going up, it does make sense. A funny anecdote (or sad?), after gas prices spiked in much of Europe due to the war many manufacturing facilities were looking to cut energy use, they found a lot of waste. Many places were able to reduce their gas usage by as much as ~33% if I recall correctly. I can't find the original source, but here's [1] one that claims 23% lower consumption across Germany in 2022 adjusted for temperature. 1 - https://www.nature.com/articles/s41560-023-01260-5 https://www.nature.com/articles/s41560-023-01260-5
  • philwelch 3y ago
    Reducing consumption as a response to increased prices doesn’t mean the difference in consumption was originally “wasted”; it only means it was not worth the higher cost.
    • fragmede 3y ago
      From the POV of capitalism, yes. From the POV of the environment, noooo.
      • ZeroGravitas 3y ago
        Or even from a non-fossil capitalism point of view, a carbon tax that equaled the externalities would lead to higher efficiency and give people a permanant financial incentive to find these efficiencies.
      • philwelch 3y ago
        If people can’t afford to heat their homes and freeze to death in the winter, is their continued survival wasteful from the POV of “the environment”?
        • fragmede 3y ago
          I think you're misreading me. The fact that there was that much waste that could have been found and eliminated earlier is an affront to the health of our planet. At no point did I suggest freezing people in their homes in the middle of winter to die.
• joeyo 3y ago
  David MacKay discusses this in Sustainable Energy Without the Hot Air. He concludes that, while it's on first glance appealing to want to use waste heat from power generation, heat pumps are strictly superior to combined heat and power except for in a few specialized circumstances (e.g. industrial uses that require high temperatures). The book is fifteen years old now, so I suspect the math even more strongly favors heat pumps than when it was published. See the section, "Heat pumps, compared with combined heat and power": https://www.withouthotair.com/c21/page_147.shtml https://www.withouthotair.com/c21/page_147.shtml
  • renhanxue 3y ago
    But district heating is a distribution mechanism, not a heat generation mechanism. Cogeneration plants are one way to power it, but you can also use waste heat from industrial processes, very large scale heat pumps, or burning household waste. All of these are in common use in places where district heating is common. The public district heating utility in Stockholm claims to have the world's largest heat pump installation, which has the capacity to extract 225 MW of heat from treated sewage, in the process generating both heat that's sent into the district heating network, cooling that's sent into the district cooling network, and finally a small amount of electric power by releasing the treated water into a lake via a turbine. This facility opened in 1986. The utility also has various other facilities, both cogeneration plants that burn biofuel (mostly byproducts from the lumber industry) or household waste, as well as other heat pumps that extract energy from seawater. District heating/district cooling has three advantages: you can change the heat source centrally without having to refit every single dwelling, there are economies of scale in the heat generation, and you can take advantage of heat or cooling that's just in the wrong place and transport it to where it's needed.
    • tadfisher 3y ago
      Seems to me like the electric power grid is an already existing, efficient energy distribution mechanism. Converting waste heat to electricity is probably a lot cheaper to retrofit than adding a new distribution network to places that don't already have one.
• lucumo 3y ago
  > On an individual household scale, I've always wondered why nobody has come up with basic drain heat exchangers to capture most of the heat coming out of shower and washing machine wastewater before it leaves the building. I have had one of those installed in my home recently. A QB1-16 from Q-Blue https://www.q-blue.nl/en/products/q-blue-showersave/ https://www.q-blue.nl/en/products/q-blue-showersave/ Supposedly it saves about 50% of the loss heat. Since I dislike hasty showers, I figured that would save me plenty. > I'm amazed at how little district heating is used in northern climates In my country we can pick our own electricity and gas provider, but for district heating you're tied to the provider for your area. Consequently, people with district heating get fleeced. When buying a house, I gave preference to the ones without district heating.
• wenc 3y ago
  > I'm amazed at how little district heating is used in northern climates like Canada and the northern US. It is used on most if not all Canadian university campuses. Canadian university buildings are also far less sprawling because they're all connected to a steam generation plant. Toronto has district heating. https://www.toronto.ca/services-payments/water-environment/environmentally-friendly-city-initiatives/district-energy/ https://www.toronto.ca/services-payments/water-environment/e... In the reverse direction, Lake Ontario is part of a cooling system as well. https://en.wikipedia.org/wiki/Deep_Lake_Water_Cooling_System https://en.wikipedia.org/wiki/Deep_Lake_Water_Cooling_System
  • chefandy 3y ago
    Similarly, I know Harvard and MIT, and also parts of Boston have centralized steam heat systems. Harvard uses theirs extensively still, at least in the old buildings, but I'm not sure about MIT. Boston's is fed by an old commercial steam plant on the outskirts of Chinatown. I think it covers a pretty limited area though. I never lived anywhere with it.
• jstsch 3y ago
  When I renovated my house, I installed such a heat exchanging pipe. It reduces hot water usage (=fossil gas) by about 40% and with my usage payed itself back in about two years. It's not a drop-in replacement, since you should use it only for the shower drain.
  • megak1d 3y ago
    So the shower drains through it and the 'wrap around' pipe is the input to your hot water tank?
    • pg314 3y ago
      No, it preheats the cold water connected to your shower. Warmer cold water means you need less hot water to achieve the same temperature in the shower.
      • megak1d 3y ago
        Ah yes, that’s much neater and more localised. Thanks
• ed_balls 3y ago
  The nice thing about district heating is the extra space you get and no fire/Co hazard.
• btbuildem 3y ago
  I guess if everyone did that (residential heat exchangers on your house drain), there could be a real risk of the sewage cooling and congealing in the downstream pipes, causing a blockage.
• seabrookmx 3y ago
  Atleast in BC, our power plants are hydroelectric dams far from the urban center so there's no waste heat to collect.
• DanielHB 3y ago
  In Sweden most of the population is covered by district heating. I think it is mostly a matter of population density, in Sweden most people live in 3-6 floor residential buildings clustered together close to public transport hubs. In Canada and US you have urban sprawl and a lot of rural population, so running district heating pipes to every single house is just not worth it. To be fair people who live in detached houses in Sweden often don't have district heating either, but the % of the population living in detached houses is tiny.