Million cubic metre 90GWh thermal storage project in Finland could begin construction next year:
A seasonal heat storage plant which will have a capacity of about 90GWh looks set to begin construction next year in Vantaa, Finland, with water stored in underground caverns heated to 140°C using renewable energy and waste heat.
City energy company Vantaa Energy said at the beginning of this month that it has selected engineering, design and advisory group AFRY and Finnish urban development and construction company YIT as project partners. Project development begins this summer and construction in autumn next year, with the massive system expected to be online during 2026.
The project, called Vantaa Energy Cavern Thermal Energy Storage (VECTES), will involve caverns around 60 metres underground in bedrock. According to project overview documents produced by Vantaa, situating the water storage that far down means the ground water's natural pressure will prevent it from evaporating, even at temperatures above its boiling point.
Four main caverns of around 220,000 cubic metres each, adding up to about a million cubic metres in total will make up the main storage chamber. The aim is to replace the use of natural gas for heating with the plant's stored energy capacity equivalent to the annual heat consumption of an average-sized Finnish town. Thus, surplus heat from summer months can be stored and used in winter with solar, wind and geothermal energy as well as waste heat from buildings helping to feed it.
[...] Vantaa will make a decision on how to direct investment into the project and begin transitioning to implementation after the initial development phase. The contract awarded to YIT and AFRY is worth about €75 million (US$88.95 million), YIT said, with the development phase of that worth about €1.6 million. An implementation phase contract is expected to be signed in Autumn 2022 ahead of construction starting.
(Score: 2) by Phoenix666 on Wednesday July 14 2021, @02:26PM (11 children)
I don't understand this project. Heat pumps work by dumping heat/cold into coils in the ground; whatever comes out of the ground shares the constant temperature of the ground, which is 55F. That's good in the winter when ambient temperatures are colder than 55F, and good in the summer when ambient temperatures are hotter than 55F. In the winter you use that 55F to heat, and in the summer to cool.
Toronto does, for example, have a system that takes water from deep in Lake Ontario and uses it for cooling in office buildings downtown. But this project wants to dump "waste heat" into water, it seems, stored in caverns deep underground, and then bring it back up still hot. How that water doesn't come out at 55F again is what I don't understand.
Washington DC delenda est.
(Score: 0) by Anonymous Coward on Wednesday July 14 2021, @02:49PM (5 children)
The hot water would eventually cool off, this is true. It's a question of heat loss rates. Simply having a massive amount of hot water means that it acts as a sort of thermal mass which slows the rate of heat loss. if you want this to work well, not not cool off too much, I imagine you can only tap some of the hot water for use, not all of it, and you have to make sure to replenish it with hot water as well. The devil is in the details.
(Score: 4, Informative) by MIRV888 on Wednesday July 14 2021, @02:55PM (4 children)
A massive enough volume of water would contain / retain heat for a very long time with minimal insulation applied to the storage areas.
Plus you are replenishing the heat with further heated water / waste heat. Very terrain dependent, but ingenious.
(Score: 3, Funny) by JoeMerchant on Wednesday July 14 2021, @04:35PM (3 children)
Plus: Finland, Sauna... of course it makes sense to them.
🌻🌻🌻 [google.com]
(Score: 0) by Anonymous Coward on Wednesday July 14 2021, @04:45PM
Plus: Finland, Alcohol... of course it makes sense to them.
*ftfy
(Score: 1) by fustakrakich on Wednesday July 14 2021, @06:21PM (1 child)
Yeah, is it as steamy as Iceland [wordpress.com]?
La politica e i criminali sono la stessa cosa..
(Score: 2) by JoeMerchant on Wednesday July 14 2021, @06:52PM
So, I'm picturing a big cavern deep underground with a thin tube to the surface which creates the pressure that keeps the hot cavern from boiling.... then that thin tube somehow becomes dry and the whole thing erupts like Old Faithful...
🌻🌻🌻 [google.com]
(Score: 5, Informative) by Rich on Wednesday July 14 2021, @02:52PM
The surface of the water blob can be considered a heat sink that sinks a certain amount of Watt per Kelvin of temperature difference, per square meter. The surface of the blob grows with the square of the blob's diameter, but the volume of the blob with its third power. If the blob just becomes large enough, the heat sinking surface becomes so negligible that only a small percentage of the heat will be been dissipated in the timeframe desired (4 months?).
(Score: 5, Interesting) by fakefuck39 on Wednesday July 14 2021, @03:02PM
It sounds like there is plenty of heat loss, but not sure why that's a show stopper. Nuclear reactors work by heating water, yet they have cooling systems, so that's some heat loss there. The pressure cooker on your stove, which is what they've built here, also has heat loss. They just keep heating the water as the water loses some of the heat to the surrounding rock. To heat the water they're using waste heat and green energy - which would be just heating the outside air instead. So no real loss. What happens when you don't need the extra energy but the sun keeps hitting the solar panel? Well in their case, they use it to keep heating the water.
> How that water doesn't come out at 55F again
It comes out at 155C, because they keep heating it as it cools, and they only use energy that would otherwise be wasted. If you pump a lake uphill using solar, then use hydro to recover energy when you need it, some of that lake will evaporate - that's also energy loss. When you charge a battery it heats up - that's also energy loss. They can lose as much as they want, as long as the net result is some extra energy - since the source of the heat is energy that would be otherwise wasted.
Considering they get all fossil fuels from Russia, and have almost no renewables, it looks like they're trying to start up on renewables for base energy, and the only way to do that is shifting peak production to peak use. They got plenty of wasted power, and plenty of caverns to make pressure cookers.
wood (26% of total consumption), oil (23%), nuclear (18%), coal (9%), gas (7%), hydropower (5%) and peat (5%)
(Score: 0) by Anonymous Coward on Wednesday July 14 2021, @05:39PM
This seems to be a more advanced version of systems that have been used in greehouses for a while: https://farm-energy.extension.org/geothermal-heat-for-greenhouses/ [extension.org]
(Score: 0) by Anonymous Coward on Wednesday July 14 2021, @05:44PM (1 child)
The *average* geothermal temperature gradient https://en.wikipedia.org/wiki/Geothermal_gradient [wikipedia.org] doesn't start to rise until you get down a few hundred meters, this is the stable temp used by ground-source heat pump systems But once you go deeper, like into a deep mine, the temp goes up.
This storage system isn't that deep, but perhaps they have chosen an area where it is hot closer to the surface--like many areas with volcanic activity?
One way to check might be to look for https://en.wikipedia.org/wiki/Geothermal_power [wikipedia.org] stations nearby.
(Score: 1) by Michael on Wednesday July 14 2021, @06:19PM
Heat pumps can operate fine much closer to the surface than that, they don't need geothermal input, most of the heat they pump has come down from the surface (averaged over a year if deep enough).
But this system doesn't need heat pumps or heat coming from below, heat exchangers would do fine, and they're putting their own heat down there instead of waiting for the rocks to heat the water.
(Score: 0) by Anonymous Coward on Wednesday July 14 2021, @06:27PM (2 children)
A million cubic meters is a cube around 300 feet each dimension. Not that enormous.
(Score: 0) by Anonymous Coward on Wednesday July 14 2021, @09:15PM
I think you meant to say "One cubic football field."
(Score: 2) by FatPhil on Thursday July 15 2021, @09:38PM
But you're right, it's not that big compared to some holes: https://upload.wikimedia.org/wikipedia/commons/f/fc/Icecube-architecture-diagram2009.PNG
And of course, caverns for energy storage are nothing new:
"""
7.3.2.2 Storage in man-made salt caverns
Salt caverns are alternatives to porous storages; see Figure 7.5. The caverns first have to be constructed in the salt formation by injecting water through an access well and dissolving the salt. This so-called solution mining process generates large volumes of brine that must be disposed of in an environmentally compatible way. Because of its visco-plastic properties, rock salt is extremely tight to gases like natural gas or hydrogen—even under high pressure. The enormous open cavities which these caverns represent, with volumes from a few 10,000 s to more than 1,000,000 m3 at operating pressures of up to 20 MPa and more, are particularly suitable for flexible gas operations with high production and injection rates and frequent gas cycles. The proportion of cushion gas is typically 30%. Because of these properties salt caverns are most suitable for the future storage of hydrogen from renewable energy. Rock salt does not react with hydrogen, one key advantage compared to porous reservoirs. However, water from the cavern sump will increase the water vapor content of the stored gas.
"""
-- https://www.sciencedirect.com/topics/engineering/salt-cavern
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