How are we going to heat our cities in the future?

Changed the title picture again. Air happened to be in such a configuration that the smoke from the hood district heating plant travelled horizontally. It uses fuel oil and isn’t in use most days. Only when it’s quite cold like today (about -10 C).

Making coal electricity and using the waste heat for district heating apartment buildings is quite effective and has a pretty low workload compared to separate houses and oil heaters or what you have.

There isn’t any really good “green” solution for this. Making district heat with wood has its problems for example, and having heat pumps everywhere is inefficient and even inelegant in many senses. First making electricity with a low efficiency and then using that to make heat again with a low multiplier. You need magnets and bearings and whatnot in both devices. Are there even enough rare earths?

Building nuclear plants close to cities isn’t nice either. If you built them far away, you’d need to build really long pipes and that gets inefficient again. It also hurts the nuke’s electricity output surprisingly much. You could probably optimize the plant for better district heat production though, and the Russians have done that in some cold cities. But you can’t have a single nuclear plant as the only thing that’s heating a city: it would be devastating if an unplanned break left a million people cold in their homes.

In the future though, buildings can be much more energy efficient, so that’s the biggest saver. That too can be overdone, and I don’t like many modern buildings which have tiny awkwardly placed windows. A human produces about 70 watts of heat, and electronic equipment produces some waste heat too. “Zero energy” houses can take the heat from the exiting air and use it to heat the incoming air (like penguins do with the blood in their feet), making large savings (and at the same time making it hard to retrofit some old buildings.)

Dividing Finland’s yearly energy consumption with all the seconds in the year and all the people, we get nine kilowatts of constant power, day and night, summer and winter, for each person. That’s huge.

One big part of that is heating. It’s also a big missing part of the discussion.

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3 Responses to How are we going to heat our cities in the future?

  1. Doug Jones says:

    Annualized Geo-solar can probably be very useful in Finland, by storing the abundant summer solar energy in warm soil under the dwellings. Don Stephens built on John Hait’s earlier work on passive annual heat storage, with solutions that don’t require the house to be earth sheltered. Some useful links for you-

    This technique can also be used to store coolness for the summer, which is important for me, working in Mojave where the summer temperatures can exceed 45 C.

  2. gravityloss says:

    Lots of people are drilling really deep holes for heatpump “cold sinks” or however you want to think about it. (Not very nice if the glycol pipes break.) They also use it in combination with heat exchangers to recover heat from discarded air and preheat incoming air. But it’s only used for houses, while the majority of people lives in apartment buildings. (Heating becomes much more efficient per person if you live in an apartment building.) It’s also costly per inhabitant and requires all that hardware that also has to be maintained.

    I think the surface area per inhabitant is so small that getting the energy from the surrounding environment directly is hard, especially being so close to the pole so that the sun facing area is even smaller. With the annual mean temperature of Helsinki being 6 degrees Celsius, about the same as in a cold room or a warm refrigerator, you’d need quite large areas of heat collectors during the short warm time to live the rest of the year.

    But there indeed have been annualized geo-solar projects, but I think they’ve used storage like hollow rock “halls” filled with water. The bedrock in Finland is easy to get at and is quite solid. Combined with rare and mild earthquakes, it could be pretty good. Though again, that’s a big and expensive solution.

    The easiest would probably be to move most of the people to the Mediterranean climate :) . The few hardy souls left can heat with firewood. I guess in the US many old people retire to Florida and in Europe to Spain.

    I’m also quite skeptical of many of these integrated ground heating solutions – because of the ground frost, a lot of stuff that can be done elsewhere, can’t be done here. Houses have to have good foundations that extend deep beyond the ground frost level so that they don’t move up and down every winter. Also you need ventilation beneath the house, at least in spring, summer and autumn. So if that “umbrella” is good enough to prevent ground frost, it might work. But it might also get messy as the top still freezes and thus expands and moves around.

  3. Doug Jones says:

    Heh, I do like the Mediterranean climate of southern California, I enjoyed a sunny day yesterday aboard the Queen Mary in Long Beach. There may housing for 5.4 million people in this area just in the form of empty foreclosures…

    Yes, the underground umbrella really has to work, but it is out of the sun and wind. Certainly the 0.6 meter or so of soil above the insulation will freeze and heave, but that apparently wasn’t a problem for Hait’s prototype house built in Montana, about as harsh as Finland. Certainly apartments are more efficient than single family dwellings, but it may be easier to introduce the annual storage technique on smaller projects, and the entire footprint of an apartment building could be used for heat storage. The high latitude does make solar heat awkward due to the low altitude and almost 360 degree azimuth of the sun (although the midnight sun would probably be too faint to be really useful). Maybe a flat solar array with an angled mirror above it to redirect the low sun downward, rotating to follow the sun?

    As I understand it, the greenershelter technique does not require deep holes, but only a shallow trench under the house combined with Hait’s underground insulation umbrella, no deep drilling or major excavation. I don’t know if anyone has tried the technique in an area with permafrost, though. According to the map at most of Finland is permafrost-free, and heat storage should be possible in soils that aren’t saturated.

    You say “Houses have to have good foundations that extend deep beyond the ground frost level so that they don’t move up and down every winter,” and that would be aided by the insulation blanket protecting the foundation from freeze-thaw cycles. The frost level would only be above and outside the insulation, not near the foundation. Installing the insulation would require a temporary excavation to a depth as much as 1.5 m, but not as much as a full basement would require, and all the soil would be backfilled. Annualized storage seems quite well suited to Finland’s needs- certainly the techniques used in cloudless low latitudes are not!

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