9 ms·

Gigantic heat caverns in Mustikkamaa have now been filled with water (2021)

174 points by iljah 3y ago

iljah 3y ago
This energy storage system near Helsinki, Finland operated by Helen (https://en.wikipedia.org/wiki/Helen_Oy https://en.wikipedia.org/wiki/Helen_Oy) might be interesting for HN readers. Some facts from previous article (https://www.helen.fi/en/news/2020/mustikkamaa https://www.helen.fi/en/news/2020/mustikkamaa), not sure which one would've been better in url field: District heat is stored in two rock caverns in Mustikkamaa. The temperature of the water in the caverns varies between 50 and 90 °C. The effective volume of the cavern storage facility is 260000 cubic metres and energy capacity about 11500 MWh. The charging and discharging capacity is 120 MW. The discharging or charging of the heat caverns at full power takes four days. The rock caverns will decrease Helen’s carbon dioxide emissions by 21000 tonnes per year. The stored heat can be used for balancing demand peaks and that way cutting fossil heat production, for example, in cold winter days.
- Reason077 3y ago
  This is a cool project, and I'm sure it has many benefits beyond just carbon savings. But 21,000 tonnes per year is surprisingly little in the scheme of things. Equivalent of about 150 or so long-haul 777 flights?
  - cobaltoxide 3y ago
    That should tell you more about the energy intensity of a long-haul 777 flight.
  - birger 3y ago
    Just for one city.
  - bee_rider 3y ago
    If I’m reading this report correctly: https://julkaisut.hel.fi/en/reports/environmental-report-2021/environmental-indicators https://julkaisut.hel.fi/en/reports/environmental-report-202... It looks like the emissions for the Helsinki area are 2,345 kt per year, so I guess 21 kt is only a small part of that. Of course, no one project should be expected to solve everything! But it is depressing to see the scale of the problem.
    - SECProto 3y ago
      1% reduction from one project seems pretty decent to me. Especially when it's just from reusing pre-existing caverns from oil storage to decrease the district heat emissions. Heating emissions for a city at 60° North are a big challenge to reduce, and combined heat and power is a huge efficiency gain - the heat is otherwise wasted, and thermal emissions are an environmental issue in their own right. The emissions could be reduced much further if they decrease the 55% of their generation that comes from fossil fuel fired CHP plants[1], and increased their nuclear capacity from current 27% (unfortunately they had to cancel a plan to build another reactor because their partner was rosatom[2]) [1] https://fi.wikipedia.org/wiki/Helen https://fi.wikipedia.org/wiki/Helen [2] https://en.wikipedia.org/wiki/Nuclear_power_in_Finland#Reactors_2 https://en.wikipedia.org/wiki/Nuclear_power_in_Finland#React...
      - dharma1 3y ago
        Heating is perhaps unsurprisingly a large part of overall energy consumption in the Northern hemisphere. Helsinki shut down one coal plant used for district heating this spring and is shutting down the last remaining one next spring, well ahead of schedule. https://www.hel.fi/en/news/helen-phases-out-coal-more-than-five-years-ahead-of-schedule https://www.hel.fi/en/news/helen-phases-out-coal-more-than-f... I personally am bullish on deep geothermal - there was a pilot project near Helsinki which was unfortunately unsuccessful, but with cheaper new drilling tech (plasma etc) I think this can work out in the future. https://www.st1.com/st1s-otaniemi-geothermal-pilot-projects-deep-geothermal-wells-to-be-used-for-research https://www.st1.com/st1s-otaniemi-geothermal-pilot-projects-... There are also some startups looking to build small modular nuclear reactors for district heating - https://www.steadyenergy.com/ https://www.steadyenergy.com/
        SECProto 3y ago
        Yep, deep geothermal would be cool, but not as mature. Was specifically advocating nuclear as it is basically a drop in replacement for fossil fuel in existing CHP plants. SMRs might work, though I am somewhat skeptical of anyone proposing "this brand new nuclear tech!" as a solution to difficulties constructing proven nuclear tech - we have decades of examples showing they basically swap one issue for another
  - nikanj 3y ago
    That tells you how pointless all the at-home energy savings are when everyone and their dog flies to a weekend getaway every month
    - quacked 3y ago
      I know people who attend sit-in protests at Chase Bank locations over fossil fuel divestment who also fly internationally 3-4 times per year for pleasure. The cognitive dissonance and lack of engineering intuition among the general populace is staggering.
      - FpUser 3y ago
        I thought pleasure is more important than business. The only reason I do business at all is to feed my interest in doing whatever I like.
      - ForHackernews 3y ago
        If there were less investment in fossil fuel exploration, prices for fossil fuels could rise and airfare might be priced more appropriately. They would fly less because it cost more, or trains and boats might become more competitive. Moaning about individual "cognitive dissonance" is absolute nonsense when talking about global scale problems that require policy solutions. The activists' intuitions are more correct than yours, I'd wager. Climate change is not an engineering problem.
        kortilla 3y ago
        Protesting Chase doesn’t stop investments. It just pushes them elsewhere. Those activists are morons and stopping their flights would do far more to help than to protest a single bank. If they were protesting the government to massively increase oil taxes then you might have a point. Alas, they don’t have any economic intuition.
        dylan604 3y ago
        If those protestors did not have tickets on those flights, somebody else would be able to purchase them. It's not like the plane isn't going to fly that route because of this. So whether the protesters fly or somebody else, the plane is still make the emissions you're concerned about.
  - wildzzz 3y ago
    A reduction in foreign energy dependency is always nice to have. They can also use the geothermal to generate electricity. The carbon savings aren't that much but nearly free energy sources are nice to have.
- euroderf 3y ago
  > The temperature of the water in the caverns varies between 50 and 90 °C. Presumably 50 is in April or May and 90 is in August or September. Or are these swings shorter-term ?
  - trenchgun 3y ago
    Yea that is one thing missing. Is it seasonal heat storage, or for balancing wind power?
coffeebeqn 3y ago
I wonder why they used tap water instead of seawater
- Filligree 3y ago
  Seawater erodes everything it touches. It isn’t impossible to build hardware that touches it, but it’s more expensive and needs more maintenance. Fresh water makes the entire project much cheaper.
  - Sharlin 3y ago
    (Edit: this is wrong – see comments) And this water is supposed to be fed directly into the homes of hundreds of thousands of customers through the existing district heating network which obviously isn't built with seawater in mind. A seawater storage facility would at the very least require a heat exchanger which would decrease efficiency.
    - michpoch 3y ago
      I don't think they'll be pumping that water directly into the heat distribution system. My understanding is that it'll be used as a heat reservoir and there will be some sort of heat exchanger to get the heat out of it.
      - lazide 3y ago
        It would be more efficient without the heat exchanger, but you’re almost certainly right - the reservoir water would probably be too oxygenated/mineralized for direct use if being stored in contact with the rock, at least without a lot of additional treatment. Don’t want to kill all those underground pipes with mineral buildup as things precipitate out as it cools.
        onetimeuse92304 3y ago
        > It would be more efficient without the heat exchanger, No, the only cost really is the cost of heat exchanger and maybe energy to pump water through the heat exchanger. Heat exchange approaches 100% thermal efficiency with large enough heat exchanger.
anttiharju 3y ago
"Mustikkamaa" translates to "blueberry land" or "blueberry earth" (Mustikka|maa) in case anyone's interested.
- askonomm 3y ago
  Mustikamaa in Estonian :)
  - anttiharju 3y ago
    I've heard people joke that if a Finnish person just spends enough time in Estonia they start to understand it :)
    - euroderf 3y ago
      Finns will say that Estonian sounds like some kind of really odd super-rural accent. Estonians will say they wonder why the heck it takes a Finn twice as long as an Estonian to say the same thing.
      - anttiharju 3y ago
        Haha yeah definitely! I was watching the news where Estonian people were interviewed. While there were Finnish subtitles I could understand maybe half of the sentences without them, but the words would be "really odd super-rural", which I found funny. Also, I'm not sure if it's a thing in Estonian, but I've heard in Lithuania or Latvian there's no distinction between spoken and written language. Example from Finnish: * Minä means I/me in written Finnish * Mä/Mää/Mie/... is what people typically use in spoken language Which is what some of my international friends have been complaining about the Finnish courses at my university -- that they learn the written Finnish from their 101 books, but it's not so useful since in daily interactions people just use spoken Finnish. And well maybe the minä -> mä you can see the length difference. Maybe Estonian is just more advanced in the "spoken-ness", if you will, of the language. Here you can see the different "minä"s by region in Finland: https://yle.fi/a/74-20010020 https://yle.fi/a/74-20010020. The article's in Finnish, but just scroll down and you can still very much understand the map. Here's the article Google-translated to English, but I'm not sure if it would also translate the "minä"s: https://yle-fi.translate.goog/a/74-20010020?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp https://yle-fi.translate.goog/a/74-20010020?_x_tr_sl=auto&_x...
sdflhasjd 3y ago
> the temperature of the water in the heat cavern will vary between +45 and +100 degrees I'm not sure if I should be assuming Fahrenheit or Celsius? The article isn't clear on the units here.
- Torkel 3y ago
  If it isn't a story from the US, it will be Celsius.
  - sdflhasjd 3y ago
    That's what I would normally have assumed, but 100C seemed a little hot for water just sitting in a big cistern
    - andrelaszlo 3y ago
      I'm no physicist but I assume that you'd need to put a lot more energy into the system before the water starts boiling, so you wouldn't have to worry about it? If the energy would just be lost otherwise, you might as well go all the way to 100℃? That's at 1 atm, perhaps the water is a bit pressurized as well? A bit further down there's this confusing quote though: > District heat is stored in two rock caverns in Mustikkamaa. The temperature of the water in the caverns varies between 50 and 90 °C.
      - SAI_Peregrinus 3y ago
        +100°C (relative to some other temperature not clearly explained, probably the rock) vs 90°C absolute temperature.
        andrelaszlo 3y ago
        That would mean that the rock baseline would be 10 degrees below freezing, which seems improbable. I think it would be close to the yearly average temperature for Helsinki (6.5°C) that close to the surface. Maybe I'm missing your point?
wbl 3y ago
One application of this technology is to economically harnessing fusion power. Sadly there are considerable engineering and political difficulties. https://en.wikipedia.org/wiki/Project_PACER https://en.wikipedia.org/wiki/Project_PACER
- switchbak 3y ago
  Not simply fusion power: exploding small fusion or fission bombs. I think some difficulties are to be expected with such a plan.
moogly 3y ago
There is also one of these in Västerås, Sweden, about 100 km from Stockholm. 3 caverns 30 m below the surface that used to store oil during the Cold War in case shit would hit the fan. 300,000 cubic meters, 13 GWh. Basically identical. Not as far along as the Finnish site though; it'll start backing up the district heating plant in 2024.
deleted 3y ago
[deleted]
cromulent 3y ago
Mustikkamaa is a recreational island about 3 kilometres from Helsinki’s center. It’s really nice. It’s a gateway island to Korkeasaari, the city zoo island.
- euroderf 3y ago
  So there must be a maze of underground pipes westward to Helsinki peninsula and to points north of Mustikkamaa. In any case the ground under Helsinki must look like Swiss cheese - Finns are tunnelers. Thru granite.
cmrdporcupine 3y ago
Got to wonder if this kind of thing wouldn't be possible here in Canada on the Canadian Shield (half-a-continent-sized slab o' granite), especially in places in Northern Ontario where there's old nickel mines, etc. Bonus points if one uses the waste heat from e.g. industrial plants to help heat up the water.
- yason 3y ago
  The municipal heating network consists of both cooling and warming networks. Excess heat from, for example, data centers will be used to heat the water. Newer apartments are cooled using cold water from the network in the summer and heated using hot water in the winter. There are also joint power-and-heat plants connected to the heating network which are quite efficient: first the generated heat is used to drive a generator turbine and the remaining waste heat is piped into the municipal heating network. Combined efficiency is way higher than with generator-only plants or heating-only plants.
  - cmrdporcupine 3y ago
    We do have buildings here in Toronto that are cooled using pumped water from Lake Ontario, which is very close to the downtown. And I suspect a heat pump could be used to provide heat by the same process. But in general I don't think it's being done at scale.
    - Scoundreller 3y ago
      The Toronto system uses heat exchangers on the incoming tap water supply. So everyone (close to that leg of the water treatment system) gets slightly warmer tap water in summer time.
deleted 3y ago
[deleted]
wayvey 3y ago
Torilla tavataan!
8bitsrule 3y ago
Great to see the perception of energy-waste leading to new ventures. In the past century wasted energy had become a blind-spot (except when it led to some environmental effects - killing fish for example). Thought was seldom given to re-using heat (let alone storing it) after its primary purpose. (I don't recall ever seeing any meta-survey of the scope of this near-blindness ... but it has to have become enormous ...) Home-heating solutions have usually been limited to the cost for consumers rather than the environment. That will have to change drastically.

174 points by iljah 3y ago

This energy storage system near Helsinki, Finland operated by Helen (https://en.wikipedia.org/wiki/Helen_Oy https://en.wikipedia.org/wiki/Helen_Oy) might be interesting for HN readers. Some facts from previous article (https://www.helen.fi/en/news/2020/mustikkamaa https://www.helen.fi/en/news/2020/mustikkamaa), not sure which one would've been better in url field: District heat is stored in two rock caverns in Mustikkamaa. The temperature of the water in the caverns varies between 50 and 90 °C. The effective volume of the cavern storage facility is 260000 cubic metres and energy capacity about 11500 MWh. The charging and discharging capacity is 120 MW. The discharging or charging of the heat caverns at full power takes four days. The rock caverns will decrease Helen’s carbon dioxide emissions by 21000 tonnes per year. The stored heat can be used for balancing demand peaks and that way cutting fossil heat production, for example, in cold winter days.

Reason077 3y ago
This is a cool project, and I'm sure it has many benefits beyond just carbon savings. But 21,000 tonnes per year is surprisingly little in the scheme of things. Equivalent of about 150 or so long-haul 777 flights?
- cobaltoxide 3y ago
  That should tell you more about the energy intensity of a long-haul 777 flight.
- birger 3y ago
  Just for one city.
- bee_rider 3y ago
  If I’m reading this report correctly: https://julkaisut.hel.fi/en/reports/environmental-report-2021/environmental-indicators https://julkaisut.hel.fi/en/reports/environmental-report-202... It looks like the emissions for the Helsinki area are 2,345 kt per year, so I guess 21 kt is only a small part of that. Of course, no one project should be expected to solve everything! But it is depressing to see the scale of the problem.
  - SECProto 3y ago
    1% reduction from one project seems pretty decent to me. Especially when it's just from reusing pre-existing caverns from oil storage to decrease the district heat emissions. Heating emissions for a city at 60° North are a big challenge to reduce, and combined heat and power is a huge efficiency gain - the heat is otherwise wasted, and thermal emissions are an environmental issue in their own right. The emissions could be reduced much further if they decrease the 55% of their generation that comes from fossil fuel fired CHP plants[1], and increased their nuclear capacity from current 27% (unfortunately they had to cancel a plan to build another reactor because their partner was rosatom[2]) [1] https://fi.wikipedia.org/wiki/Helen https://fi.wikipedia.org/wiki/Helen [2] https://en.wikipedia.org/wiki/Nuclear_power_in_Finland#Reactors_2 https://en.wikipedia.org/wiki/Nuclear_power_in_Finland#React...
    - dharma1 3y ago
      Heating is perhaps unsurprisingly a large part of overall energy consumption in the Northern hemisphere. Helsinki shut down one coal plant used for district heating this spring and is shutting down the last remaining one next spring, well ahead of schedule. https://www.hel.fi/en/news/helen-phases-out-coal-more-than-five-years-ahead-of-schedule https://www.hel.fi/en/news/helen-phases-out-coal-more-than-f... I personally am bullish on deep geothermal - there was a pilot project near Helsinki which was unfortunately unsuccessful, but with cheaper new drilling tech (plasma etc) I think this can work out in the future. https://www.st1.com/st1s-otaniemi-geothermal-pilot-projects-deep-geothermal-wells-to-be-used-for-research https://www.st1.com/st1s-otaniemi-geothermal-pilot-projects-... There are also some startups looking to build small modular nuclear reactors for district heating - https://www.steadyenergy.com/ https://www.steadyenergy.com/
      - SECProto 3y ago
        Yep, deep geothermal would be cool, but not as mature. Was specifically advocating nuclear as it is basically a drop in replacement for fossil fuel in existing CHP plants. SMRs might work, though I am somewhat skeptical of anyone proposing "this brand new nuclear tech!" as a solution to difficulties constructing proven nuclear tech - we have decades of examples showing they basically swap one issue for another
- nikanj 3y ago
  That tells you how pointless all the at-home energy savings are when everyone and their dog flies to a weekend getaway every month
  - quacked 3y ago
    I know people who attend sit-in protests at Chase Bank locations over fossil fuel divestment who also fly internationally 3-4 times per year for pleasure. The cognitive dissonance and lack of engineering intuition among the general populace is staggering.
    - FpUser 3y ago
      I thought pleasure is more important than business. The only reason I do business at all is to feed my interest in doing whatever I like.
    - ForHackernews 3y ago
      If there were less investment in fossil fuel exploration, prices for fossil fuels could rise and airfare might be priced more appropriately. They would fly less because it cost more, or trains and boats might become more competitive. Moaning about individual "cognitive dissonance" is absolute nonsense when talking about global scale problems that require policy solutions. The activists' intuitions are more correct than yours, I'd wager. Climate change is not an engineering problem.
      - kortilla 3y ago
        Protesting Chase doesn’t stop investments. It just pushes them elsewhere. Those activists are morons and stopping their flights would do far more to help than to protest a single bank. If they were protesting the government to massively increase oil taxes then you might have a point. Alas, they don’t have any economic intuition.
        dylan604 3y ago
        If those protestors did not have tickets on those flights, somebody else would be able to purchase them. It's not like the plane isn't going to fly that route because of this. So whether the protesters fly or somebody else, the plane is still make the emissions you're concerned about.
- wildzzz 3y ago
  A reduction in foreign energy dependency is always nice to have. They can also use the geothermal to generate electricity. The carbon savings aren't that much but nearly free energy sources are nice to have.
euroderf 3y ago
> The temperature of the water in the caverns varies between 50 and 90 °C. Presumably 50 is in April or May and 90 is in August or September. Or are these swings shorter-term ?
- trenchgun 3y ago
  Yea that is one thing missing. Is it seasonal heat storage, or for balancing wind power?

coffeebeqn 3y ago

I wonder why they used tap water instead of seawater

Filligree 3y ago
Seawater erodes everything it touches. It isn’t impossible to build hardware that touches it, but it’s more expensive and needs more maintenance. Fresh water makes the entire project much cheaper.
- Sharlin 3y ago
  (Edit: this is wrong – see comments) And this water is supposed to be fed directly into the homes of hundreds of thousands of customers through the existing district heating network which obviously isn't built with seawater in mind. A seawater storage facility would at the very least require a heat exchanger which would decrease efficiency.
  - michpoch 3y ago
    I don't think they'll be pumping that water directly into the heat distribution system. My understanding is that it'll be used as a heat reservoir and there will be some sort of heat exchanger to get the heat out of it.
    - lazide 3y ago
      It would be more efficient without the heat exchanger, but you’re almost certainly right - the reservoir water would probably be too oxygenated/mineralized for direct use if being stored in contact with the rock, at least without a lot of additional treatment. Don’t want to kill all those underground pipes with mineral buildup as things precipitate out as it cools.
      - onetimeuse92304 3y ago
        > It would be more efficient without the heat exchanger, No, the only cost really is the cost of heat exchanger and maybe energy to pump water through the heat exchanger. Heat exchange approaches 100% thermal efficiency with large enough heat exchanger.

anttiharju 3y ago

"Mustikkamaa" translates to "blueberry land" or "blueberry earth" (Mustikka|maa) in case anyone's interested.

askonomm 3y ago
Mustikamaa in Estonian :)
- anttiharju 3y ago
  I've heard people joke that if a Finnish person just spends enough time in Estonia they start to understand it :)
  - euroderf 3y ago
    Finns will say that Estonian sounds like some kind of really odd super-rural accent. Estonians will say they wonder why the heck it takes a Finn twice as long as an Estonian to say the same thing.
    - anttiharju 3y ago
      Haha yeah definitely! I was watching the news where Estonian people were interviewed. While there were Finnish subtitles I could understand maybe half of the sentences without them, but the words would be "really odd super-rural", which I found funny. Also, I'm not sure if it's a thing in Estonian, but I've heard in Lithuania or Latvian there's no distinction between spoken and written language. Example from Finnish: * Minä means I/me in written Finnish * Mä/Mää/Mie/... is what people typically use in spoken language Which is what some of my international friends have been complaining about the Finnish courses at my university -- that they learn the written Finnish from their 101 books, but it's not so useful since in daily interactions people just use spoken Finnish. And well maybe the minä -> mä you can see the length difference. Maybe Estonian is just more advanced in the "spoken-ness", if you will, of the language. Here you can see the different "minä"s by region in Finland: https://yle.fi/a/74-20010020 https://yle.fi/a/74-20010020. The article's in Finnish, but just scroll down and you can still very much understand the map. Here's the article Google-translated to English, but I'm not sure if it would also translate the "minä"s: https://yle-fi.translate.goog/a/74-20010020?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp https://yle-fi.translate.goog/a/74-20010020?_x_tr_sl=auto&_x...

sdflhasjd 3y ago

> the temperature of the water in the heat cavern will vary between +45 and +100 degrees I'm not sure if I should be assuming Fahrenheit or Celsius? The article isn't clear on the units here.

Torkel 3y ago
If it isn't a story from the US, it will be Celsius.
- sdflhasjd 3y ago
  That's what I would normally have assumed, but 100C seemed a little hot for water just sitting in a big cistern
  - andrelaszlo 3y ago
    I'm no physicist but I assume that you'd need to put a lot more energy into the system before the water starts boiling, so you wouldn't have to worry about it? If the energy would just be lost otherwise, you might as well go all the way to 100℃? That's at 1 atm, perhaps the water is a bit pressurized as well? A bit further down there's this confusing quote though: > District heat is stored in two rock caverns in Mustikkamaa. The temperature of the water in the caverns varies between 50 and 90 °C.
    - SAI_Peregrinus 3y ago
      +100°C (relative to some other temperature not clearly explained, probably the rock) vs 90°C absolute temperature.
      - andrelaszlo 3y ago
        That would mean that the rock baseline would be 10 degrees below freezing, which seems improbable. I think it would be close to the yearly average temperature for Helsinki (6.5°C) that close to the surface. Maybe I'm missing your point?

wbl 3y ago

One application of this technology is to economically harnessing fusion power. Sadly there are considerable engineering and political difficulties. https://en.wikipedia.org/wiki/Project_PACER https://en.wikipedia.org/wiki/Project_PACER

switchbak 3y ago
Not simply fusion power: exploding small fusion or fission bombs. I think some difficulties are to be expected with such a plan.

moogly 3y ago

There is also one of these in Västerås, Sweden, about 100 km from Stockholm. 3 caverns 30 m below the surface that used to store oil during the Cold War in case shit would hit the fan. 300,000 cubic meters, 13 GWh. Basically identical. Not as far along as the Finnish site though; it'll start backing up the district heating plant in 2024.

deleted 3y ago

[deleted]

cromulent 3y ago

Mustikkamaa is a recreational island about 3 kilometres from Helsinki’s center. It’s really nice. It’s a gateway island to Korkeasaari, the city zoo island.

euroderf 3y ago
So there must be a maze of underground pipes westward to Helsinki peninsula and to points north of Mustikkamaa. In any case the ground under Helsinki must look like Swiss cheese - Finns are tunnelers. Thru granite.

cmrdporcupine 3y ago

Got to wonder if this kind of thing wouldn't be possible here in Canada on the Canadian Shield (half-a-continent-sized slab o' granite), especially in places in Northern Ontario where there's old nickel mines, etc. Bonus points if one uses the waste heat from e.g. industrial plants to help heat up the water.

yason 3y ago
The municipal heating network consists of both cooling and warming networks. Excess heat from, for example, data centers will be used to heat the water. Newer apartments are cooled using cold water from the network in the summer and heated using hot water in the winter. There are also joint power-and-heat plants connected to the heating network which are quite efficient: first the generated heat is used to drive a generator turbine and the remaining waste heat is piped into the municipal heating network. Combined efficiency is way higher than with generator-only plants or heating-only plants.
- cmrdporcupine 3y ago
  We do have buildings here in Toronto that are cooled using pumped water from Lake Ontario, which is very close to the downtown. And I suspect a heat pump could be used to provide heat by the same process. But in general I don't think it's being done at scale.
  - Scoundreller 3y ago
    The Toronto system uses heat exchangers on the incoming tap water supply. So everyone (close to that leg of the water treatment system) gets slightly warmer tap water in summer time.

deleted 3y ago

[deleted]

wayvey 3y ago

Torilla tavataan!

8bitsrule 3y ago

Great to see the perception of energy-waste leading to new ventures. In the past century wasted energy had become a blind-spot (except when it led to some environmental effects - killing fish for example). Thought was seldom given to re-using heat (let alone storing it) after its primary purpose. (I don't recall ever seeing any meta-survey of the scope of this near-blindness ... but it has to have become enormous ...) Home-heating solutions have usually been limited to the cost for consumers rather than the environment. That will have to change drastically.