[HN Gopher] Gigantic heat caverns in Mustikkamaa have now been f...
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Gigantic heat caverns in Mustikkamaa have now been filled with
water (2021)
Author : iljah
Score : 133 points
Date : 2023-11-10 15:46 UTC (7 hours ago)
(HTM) web link (www.helen.fi)
(TXT) w3m dump (www.helen.fi)
| iljah wrote:
| This energy storage system near Helsinki, Finland operated by
| Helen (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), 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 degC. 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 wrote:
| 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?
| birger wrote:
| Just for one city.
| bee_rider wrote:
| If I'm reading this report correctly:
|
| 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 wrote:
| 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 60deg 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...
| dharma1 wrote:
| 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-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-...
|
| There are also some startups looking to build small
| modular nuclear reactors for district heating -
| https://www.steadyenergy.com/
| SECProto wrote:
| 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
| dharma1 wrote:
| agree, I think it could take 7-10+ years for either (deep
| geothermal or SMRs) to be viable at scale. But once they
| are, it should hopefully solve carbon neutral heating for
| good - in areas with district heating at least.
|
| Steady Energy is a spin-off from VTT (Finnish state
| technical research centre) - I haven't followed it too
| closely but they are legit. https://www.ldr-
| reactor.fi/en/development/
|
| Can't be much worse than building another large scale
| nuclear plant with the French :D (which is what we did
| with the last one - https://en.wikipedia.org/wiki/Olkiluo
| to_Nuclear_Power_Plant#... - 4x over budget and 14 years
| behind schedule)
| SECProto wrote:
| Yep, the EPR design has had major constructability issues
| with every site (except the one in China, but there may
| be a lack of transparency with any issues/solutions that
| were done with them). EPR2 looks specifically to address
| the issues they've faced at Hinkley, Olkiluoto, and
| Flamanville ... we'll see how it turns out, hopefully it
| isn't just another example of throwing out one set of
| issues for a different set.
|
| Most large construction projects suffer when there is too
| great a separation between design and construction. There
| needs to be feedback from one to the other, and when it
| takes 30 years to go from conceptual design to
| operational reactor, that feedback loop just isn't there.
| One big promise of SMRs is for components to be
| prefabricated - if you're building multiple of an object,
| the connection between design and construction will be
| much closer.
| nikanj wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| lazide wrote:
| Or they want to look like they care, while having as much
| fun as possible?
| zmmmmm wrote:
| there are other ways to look at it though
|
| Is it more or less hypocritical than someone who pays lip
| service to climate change, flies 3-4 times a year and
| _doesn 't_ go to sit ins? Their total overall alignment
| of their actions and their words are probably greater
| than vast majority of people who also don't even consider
| emissions from flying but say they care about climate
| change.
|
| It's legitimate to agitate for change at a higher level
| while maintaining individual behaviours that align with
| status quo.
| nightfly wrote:
| But "everyone and their dog" doesn't do that. About half of
| Americans never fly and a quarter fly once a year. Only 7%
| fly as much as you say or more
| dharma1 wrote:
| Aviation is 2-3% of global CO2 emissions, while not
| insignificant there are bigger fish to fry
| macinjosh wrote:
| Everyone's favorite thing is a small percentage. Frequent
| flyers need to sacrifice too.
|
| It also benefits a tiny part of the global population so
| per user it's actually not that small of an impact.
| euroderf wrote:
| > The temperature of the water in the caverns varies between 50
| and 90 degC.
|
| Presumably 50 is in April or May and 90 is in August or
| September. Or are these swings shorter-term ?
| coffeebeqn wrote:
| I wonder why they used tap water instead of seawater
| Filligree wrote:
| 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 wrote:
| (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 wrote:
| 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 wrote:
| 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 wrote:
| > 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.
| mschuster91 wrote:
| > It would be more efficient without the heat exchanger
|
| Not really, heat pumps as a transfer method can achieve
| better total efficiency and make distribution of the heat
| easier.
| lazide wrote:
| That is an interesting thought, but seems like the capex
| and ongoing electrical costs of the heat pump would be
| too high?
|
| They're looking to make cheap use of the existing waste
| heat, after all, which while 'low quality' is high enough
| quality for district heating already.
| Filligree wrote:
| Counterflow heat exchangers easily approach 100%
| efficiency. It needs to be large enough, and needs
| sensors to control the flow, but both of those are
| trivial at this scale.
| lazide wrote:
| They'll need to move 2x the volume of water, and have
| more infrastructure to maintain - even if it was actually
| 100% thermally efficient. Not counting capital costs.
| Which I'd count as efficiency issues.
|
| The water pumping and maintenance costs are likely going
| to be their largest ongoing costs, no?
| Sharlin wrote:
| Ah, on second thought you're probably right.
| Hamuko wrote:
| There is a heat exchanger.
|
| https://www.slideshare.net/HelsinginEnergia/innovation-
| and-s... (slide 21)
| onetimeuse92304 wrote:
| I don't think it is this water that is going to be fed
| directly to homes. More likely there is going to be systems
| of heat exchangers.
|
| 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.
| citrin_ru wrote:
| Why they should use seawater? Fresh water is not in shortage in
| this region - yearly precipitation significantly exceeds
| evaporation.
| onetimeuse92304 wrote:
| Please, take a look at the map. Even cursory inspection of it
| will reveal to you that Finland is the land of lakes.
|
| Finland has vast stores of fresh water and annual
| precipitation has nothing to do with it.
| alright2565 wrote:
| They have a massive desalination and pipeline operation to
| create lakes throughout the country?
|
| Or is it the the sun and rain that created the lakes?
| toivotuo wrote:
| https://www.geographyrealm.com/finland-many-lakes/
|
| Thanks to the last ice age and retreating glaciers...
| krisoft wrote:
| Ice age and retreating glaciers created holes. And those
| holes filled up by the melt water of the glaciers.
|
| The fact that they are still full of water is due to them
| being replenished by precipitation more than they lose
| water. If they would lose more water then what flows into
| them we would be speaking about the "land of many bone
| dry holes" in the famous Finnish desert.
| BurningFrog wrote:
| To a first approximation, Finland is on average a swamp.
| Thousands and thousands of lakes everywhere.
| hiAndrewQuinn wrote:
| The Finnish name for Finland, Suomi, literally means "Land
| of Swamps". And it is _awesome_ here.
| euroderf wrote:
| That is one proposed etymology of "Suomi".
| I_Am_Nous wrote:
| It makes sense that Finns love rally so much then, if all
| the roads are weaving around swamps!
| lazide wrote:
| Seawater is a corrosion nightmare. Even tap water is going to
| soak up minerals from the rock eventually and be a problem, but
| it will still be less of a problem than seawater will from the
| very start.
|
| 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.
| Torkel wrote:
| Sibling comments are on to this too, but I think an important
| detail here is that the water in lakes, river and ground in the
| nordics is so clean that the extra cleaning needed to make it
| "tap water" isn't really as big of a deal as it might be in
| other parts of the world.
| kwhitefoot wrote:
| The little town I live in (about 40 km south of Oslo) is
| supplied from a lake in the granite hills. They filter out
| the bugs and precipitate the solids with a little aluminium
| sulphate and that's it. It's above all the agriculture so no
| chlorine is needed and there is no chalk so no problems with
| deposits on the insides of kettles and water heaters.
| euroderf wrote:
| Finland has a small number of lakes that are basically dead
| from pollution from pulp & paper plants. The rest are quite
| clean. Helsinki's tap water comes from Paijanne, the large
| lake that basically runs from Lahti northward to Jyvaskyla.
| anttiharju wrote:
| "Mustikkamaa" translates to "blueberry land" or "blueberry earth"
| (Mustikka|maa) in case anyone's interested.
| askonomm wrote:
| Mustikamaa in Estonian :)
| anttiharju wrote:
| I've heard people joke that if a Finnish person just spends
| enough time in Estonia they start to understand it :)
| resolutebat wrote:
| Finna can kinda-sorta understand a lot of written Estonian
| with no training, because there's so much overlap in
| vocabulary. Spoken Estonian is basically incomprehensible
| though.
| euroderf wrote:
| 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.
| askonomm wrote:
| From my own experience as an Estonian, if we both get
| together in a pub and get drunk, even if neither of us
| speak each others languages, we'll have no problem
| communicating. Drunk spoken Estonian and Finnish sort of
| blend together and the use of vocabulary gets limited to
| the more common words.
| leke wrote:
| Or even bilberry land?
| JaakkoP wrote:
| Yeah bilberry land is the correct translation. The grocery
| store blueberry translates to pensasmustikka and the flavor
| is a lot less intense.
| sdflhasjd wrote:
| > 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 wrote:
| If it isn't a story from the US, it will be Celsius.
| sdflhasjd wrote:
| That's what I would normally have assumed, but 100C seemed a
| little hot for water just sitting in a big cistern
| andrelaszlo wrote:
| 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 degC.
| SAI_Peregrinus wrote:
| +100degC (relative to some other temperature not clearly
| explained, probably the rock) vs 90degC absolute
| temperature.
| andrelaszlo wrote:
| 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 (6.5degC) that close to the surface. Maybe I'm
| missing your point?
| notforviewingit wrote:
| The heat store is used in the winter when it is cold.
| euroderf wrote:
| 6.5 sounds right. Average ground temperatures down where
| they are stable are under ten degrees C. So this project
| will definitely warm up the surrounding rock, which (I
| guess) will increase its effective heat capacity.
| Reason077 wrote:
| > _" perhaps the water is a bit pressurized as well?"_
|
| I suppose in such a large storage vessel, most of the
| water is naturally pressurised by its own weight. So most
| of it won't boil, even at 100degC, except right at the
| surface?
| pixl97 wrote:
| If the water is not being heated from the bottom then I'd
| expect all the hottest water at the top/and or at the
| point of entry to the system. Heat loss into the holding
| substrate will cause rather rapid convection and surface
| boiling.
| kagakuninja wrote:
| I interpreted it as +100C compared to the temperature of
| the rock
| ceejayoz wrote:
| That would be well _above_ boiling.
| kagakuninja wrote:
| Lol, you are right...
| wbl wrote:
| 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
| switchbak wrote:
| Not simply fusion power: exploding small fusion or fission
| bombs. I think some difficulties are to be expected with such a
| plan.
| moogly wrote:
| There is also one of these in Vasteras, 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.
| cromulent wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| wayvey wrote:
| Torilla tavataan!
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