An abandoned mine in Finland is set to be transformed into a giant battery to store renewable energy during periods of excess production.
The Pyhäsalmi Mine, roughly 450 kilometres north of Helsinki, is Europe’s deepest zinc and copper mine and holds the potential to store up to 2 MW of energy within its 1,400-metre-deep shafts.
The disused mine will be fitted with a gravity battery, which uses excess energy from renewable sources like solar and wind in order to lift a heavy weight. During periods of low production, the weight is released and used to power a turbine as it drops.
2MW is a measure of power, not energy.
Time for something to free fall 1.4km is about 17s, so the minimum capacity is 34MJ or 9.4kWh in order to make their statements true. $1.50 in electricity.
How something be turning a huge ass generator (most likely) AND be in free fall…
You put a rope on it. The rope goes around the generator shaft/alternator as it would be with a steam/wind turbine.
It will be similar to a big pulley.
The weight will pull the turbine, the turbine will require a torque to generate current. This torque will act as an upwards force against gravity. This force will slow the fall of the weight significantly. The turbine ‘consuming’ the torque allows the weight to fall.
The higher the power output the faster it will fall. This will be adjustable. No power out = stationery. A small amount of power out, the descent speed will be tiny. A faster fall a higher power output.
This won’t be designed to fall at full speed. It’ll be designed for a long slow descent. The theoretical power will likely be much higher. It will be limited by the turbine and wiring capacity that’s rated at 2MW.
If your calculations are correct it will be able to generate $1.50 a second. It will also consume power that is below market price/free/paid to consume when it ‘charges’. It also provides the utility of stabilising the electrical grid against renewables. Increasing the capability of the grid to support more cheap renewable energy, without the lead time of nuclear or the pollution of biofuel.
The weight doesn’t have to “free fall” for this to work. It could be a huge boulder that’s lifted a few centimeters per hour. And then it can be dropped a few centimeters per hour when needed.
Run the numbers.
How heavy a boulder? 10,000kg?
Potential energy is mass x height, so 10,000kg x 1,400m which is 14MJ of energy. Sounds like a lot, right?
One Joule is a watt flowing for a second and 1,000 watts flowing for 3,600 seconds is 1kWh. 3,600,000 Joules or 3.6MJ. So our 10 ton rock up a 1.4km shaft only stores 4kWhs? 60¢ of electricity?
Everything is linear here, so even having a 100 ton rock will only get us to half a EV battery.
Edit: if you’re wondering where the other 90 cents went, this example won’t produce two megawatts. It would only produce about 700 kilowatts.
Thanks for doing the math and for expanding.
The way I see it is: if I gather all the electricity I use to power my appliances in a week and just for one home - my home (fridge, heat, washing machines, vacuum cleaner, lightbulbs, laptop), and use it to lift that rock, how high will that rock get?
Also, I wasn’t even picturing a rock that small (10,000 kgs in water can be stored half a bedroom of a midsized apartment. Let’s just assume that it would take about the same volume in “rock.”) I was picturing a rock that’s 10m by 10m by 100m tall. More like 10,000,000 kgs.
You missed a factor of ten from the gravitational field strength, but still not great. Their heat batteries work better when it comes to heating, but that is mostly limited to just that.
Isn’t this a little goofy? It presumes there will be extra electricity. Do you see any sign that we’ll be producing significantly more than we need? All i see is stupid decision after stupid decision. Can’t even build a nuclear reactor these days so barring a fusion breakthrough there are no big leaps to be made. That said, fusion does appear to be coming, but that’d also make this moot and hence silly.
On-demand (or surge) power generation like this is much different then base power generation like you get from solar, wind or nuclear (or theoretically fusion).
Long story short, any functional power grid needs both because generation has to match demand, and demand is uneven and wonky.
The most common surge power source is small natural gas plants. This is a replacement for those.
It presumes there will be extra electricity.
There’s always extra electricity. Eg. Solar generates power during the day, charges this “battery” and then powers lighting at night when demand is higher and people need to be able to see.
There’s always extra electricity. Eg. Solar generates power during the day, charges this “battery” and then powers lighting at night when demand is higher and people need to be able to see.
And this is only set to become more of an issue. Solar and wind are going to be a larger share of the energy mix, but they will still be unreliable. Energy storage, whether physical or chemical, will need to be part of the solution.
That’s so cool!
This is one of those ideas that in hindsight seem so simple and obvious that it makes one wonder how nobody thought of it prior. Absolutely brilliant.
Is it more or less efficient than a derelict mine and an unstored energy surplus?
Not if the energy would go to waste. This is a mechanical battery to store surplus power generation from things like wind and solar.
They have done this before, only instead of using a big weight, they use water. Lookup “Dinorwig Power Station” for a good example.
That’s similar but different in a lot of meaningful ways. Hydro pumping like that requires a relatively large body of water next to a large geographical height right nearby. This new system doesn’t require any water, and it uses a man made hole in the ground that’s already been created and which otherwise would be simply unused
I read of another it was the same physics but different scenario. I think it was like excess energy moves heavy carts up a hill. When energy is needed, these carts get released and their potential energy from hill and the basic idea of regenerative breaking to repurpose it’s kinetic energy.
holds the potential to store up to 2 MW of energy
2nd paragraph and he’s already lost me. It would be nice if tech columnists had the equivalent of even a single semester of high school physics.
That’s a miniscule amount compared to PSH facilities, whether it’s 2 MW capacity or 2 MWh storage.
It’s a cool concept but practically seems limited to niche applications due to the small capacity. Granted it is a prototype, but it also seems intuitive that pumping large amounts of water would be more efficient than moving solid blocks of heavy material for a gravity battery design.
My guess is that that number is simply completely wrong. Bo one would brag about a 2 MW generator or a 2 MWh grid storage.
The thing is, moving a rock up does not need a huge reservoir. You would only (more or less) need the vertical space
I was thinking that you would need increasingly beefy motors and cables/cranes as the size of the rocks scales. But for a reservoir, you could use the same pump over a longer period of time to store much more energy. It’s also easy to utilize a body of water with a volume much greater than the volume of a vertical cylinder.
They were actually planning pumped storage there earlier, with a claimed capacity of 530MWh https://yle.fi/a/3-12593341
Alright, I’ve been to high school but never understood “Wh”. For speed we say “They are moving at 25 km/h aka 25km per hour” --> in one hour the object will have traveled 25km. per indicates division. Same for flow rate (cubic meters per second --> l/s) --> “The swimming pool of 5m³ was filled at 0.5m³/h and took 10h to fill”.
If something generates or consumes 10W per hour, shouldn’t that be 10W/h not 10Wh? If I hold an object that weighs 100g for an hour, doesn’t that mean I have been exerting myself at the gravitational force of the 100g object for 1 hour --> (100g * 9.832m²/s) / h --> (100g*9.832m²/s) / 3600s and thus the units being g * m² * s⁻² which are joules? How does that equate to “watt hours”
Can somebody explain this to me conceptually? It makes no sense to me.
What you’re forgetting is that Watt isn’t a unit of energy, it’s a unit of power, that is energy per time. So you wouldn’t say something generates 1W per hour, you’d just say something generates 1W. And if you multiply that by a unit of time, you get total energy. So an engine producing 2MW running for 5h would produce 10MWh, or 36GJ.
100g * 9.832m²/s
That should be 100g * 9.832m/s², or better yet 0.1kg * 9.832m/s² to get a number in newtons (N).
From a high school physics perspective, holding a 100g object steady for any length of time does no work, since work is force applied over a distance, measured in joules (J). What you do have is gravitational potential energy. Potential energy is the ability to do work, also measured in joules. Once you release the object, then you actually start getting numbers for work and power.
Power, measured in watts (W), is work done per unit time. So 10W/hr would be (10J/s)/hr. I guess that would be the rate of change of power consumption, if that were useful to you?
In theory, energy and work should be measured in joules. Simple as that. But this unit of kwh (kilowatt∙hour) has come into vogue, presumably because that’s what power utilities show on the meter outside your house? 1 kW∙hr = 1 kJ/s∙hr ∙ (1000J / kJ) * (3600s / hr) = 3.6MJ. So now we’re back from power to energy consumption.
I googled Pyhäsalmi Mine gravitricity "2 MW" and EVERY article covering this has also cited 2 MW.
Now, under Occam’s Razor, what’s more likely:
- Absolutely none of the article writers have any clue what the difference between a MW and a MWh is because none of them remember any physics
- Some of them could suspect that it’s wrong, but an authoritative source of the claim wrote/said 2 MW capacity when they meant “2 MW peak generation” or “2 MWh storage” (I’d presume Gravitricity, but I’m struggling to find such a source, myself)
- One writer miswrote/misquoted as per 2, and everyone is mindlessly recycling that original article’s contents with no attribution or care.
I don’t know which one it is. But I’d generally lean against 1.
#2 is certainly food for thought. So the idea is that from a journalistic fact-checking point of view, it is more important to convey the information exactly as it was presented than to verify its accuracy?
This would explain why science/engineering-based articles are so commonly inaccurate or missing in critical details. The journalist can fall back on saying “I have a recording of an interview with the expert after we downed a few pints at the pub, and I’m just parroting back what he said. Don’t shoot the messenger!”
I’d honestly prefer raw parroting in most cases, even if it’s “obviously” wrong. I don’t want people selectively interpreting the facts as have been conveyed to them, unless they’re prepared to do a proper peer review.
Just FYI, you need an escape backslant (\) preceeding the octothorpe (#) to not have your entire first paragraph bolded.
Mistakes like this could be avoided if we just used joules for energy and watts for power.
Or just joules per second for power. Eliminate watts entirely. Dumbass unit
Well, Watts are just a different way to write Joules per second. The unit we should eliminate is {k,M}W.h which introduce a 3.6 factor in conversions to/from the regular unit system
I been promoting this shit for a while now. Energy storage can be surprisingly low tech, it just needs to be built