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.
this post was submitted on 07 Feb 2024
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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!"
Just FYI, you need an escape backslant (\) preceeding the octothorpe (#) to not have your entire first paragraph bolded.
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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.
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Or is all just LLMs summarising the same badly translated source.
Though btw, I also think it's fascinating the difference if you look up Pyhäsalmi Mine gravitricity "2 MW" vs Pyhäsalmi Mine gravitricity "2MW"
You'll get different articles entirely
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How many horsepower is your car's gas tank?
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
My fave has gotta be kwh/yr/ft². I came across that while researching the lighting requirements for hydroponics.
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It's the independent 🤷♂️
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.
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2MW of energy 🤦♂️
Just walked the distance of 1.8 km/h.
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.
They have done this before, only instead of using a big weight, they use water. Lookup "Dinorwig Power Station" for a good example.
Banks Lake in the US has been doing it for quite awhile too.
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
It's what we call a double whammy. Paid to remove the metals and then paid for the hole you've made.
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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.
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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.
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.
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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.
How something be turning a huge ass generator (most likely) AND be in free fall...
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Very interesting, and good to hear.
Though, I'm not sure why they would drive a turbine to drive a generator, instead of just driving the generator directly. Their illustration doesn't show any turbines either.
Just guessing here but I think they are playing with gear ratios. A large turbine with high resistance being slowly turned by a heavy weight could generate power for an extended period of time.
EDIT: Maybe the shaft is the turbine. Like a big rotating corkscrew.
And that's my confusion, why use a turbine (connected to a lift) to turn the heavy weight into a flow of steam or liquid, presumably to convert this flow to electricity using another turbine with a generator connected to it, instead of simply converting the heavy weight to electricity using a lift (or corkscrew) to turn the generator?
This is, of course, assuming that a turbine only is a turbine when it is driven by steam or liquid.
I guess the publishers of the article either got the definition wrong, or there's a less used definition of turbine which I am not aware of.
The turbine is the part that turns potential energy into rotational energy. The generator turns that rotation into electricity.
But isn't the definition of a turbine "a type of machine through which liquid or gas flows and turns a special wheel with blades in order to produce power" with the "power" (aka. rotational energy) going to a generator?
Where does the liquid or gas come from? Isn't this battery supposed to lift heavy, solid objects?
It doesn't outright state that it uses solid weights, but their illustration looks more like they'd use a lift with sand or weights, and not a turbine with liquid or steam:
I wasn't suggesting that a turbine could be used (directly) for sand, I hope you didn't get that impression, I was just trying to address that commenter's point of confusion about generators and turbines.
To your question, a flow is cause by a difference in energy potentials between two connected points in a system; Potential energy causes the gas or liquid to flow through a turbine. The more potential energy, the higher the speed, or pressure (depending). Also, not all turbines drive generators. The output could drive anything where you need rotational input, including a vehicle's transmission. For a lot of reasons, that isn't usually done.
If I understand correctly, the idea is to store something heavy up top, send it down below using the weight of the sand to somehow (unspecified?) generate electricity, then send it back up when there is an excess supply of energy generation, leaving it available to use again when energy production is reduced. Battery really describes this system better than generator, because it's only a hole in which to dump excess energy and then pull it out (which, in a roundabout turn of events, the "hole" in this instance is above ground, and then you "pull it out" of the hole by sending it back down.).
All that said, this seems like a boondoggle. I think there's a lot in this press release that is unsatisfactory, and I'm extremely skeptical that this makes good sense until I see definitive independent proof otherwise.
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Interesting. Earlier they were planning pumped storage there, with a claimed capacity of 530MWh https://yle.fi/a/3-12593341 Seems like that fell through https://www.epv.fi/en/project/a-pump-storage-station-for-pyhasalmi-mine/
Every source I can find says "2MW" of capacity. I assume they meant 2MWh, though that doesn't sound like that much.
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Is it just 2 Mw or is the article wrong?
Either way its wrong.
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