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.
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
[2] https://en.wikipedia.org/wiki/Nuclear_power_in_Finland#React...
Estonians will say they wonder why the heck it takes a Finn twice as long as an Estonian to say the same thing.
I'm not sure if I should be assuming Fahrenheit or Celsius? The article isn't clear on the units here.
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.
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.
Bonus points if one uses the waste heat from e.g. industrial plants to help heat up the water.
The only advantage seawater usually has is it’s ’free’ if you’re on the coast. But in many habitable climates, freshwater is ‘free’ too. Like most of Finland.
Finland has vast stores of fresh water and annual precipitation has nothing to do with it.
Or is it the the sun and rain that created the lakes?
Fresh water makes the entire project much cheaper.
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.
They mention they are recovering heat from waste water. Obviously, they aren't pumping waste water into the system but rather use heat exchange to extract energy.
https://www.slideshare.net/HelsinginEnergia/innovation-and-s... (slide 21)
My favorite so far has been Vienna - I would describe it as similar to Evian.
