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.
Noted. Thanks!
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.
That’s what [sic] is for though. You fact check, and then leave the quote as the press release had it.
The problem is that most of these articles are basically reprinting of the press release without any editorial additions at all.
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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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These cursed time units remind me of the super messy imperial units. Unfortunately, the French revolution wasn’t able to fix that, but it did fix a whole lot of other nonsense.
What's even worse is that some units differ between the US and UK, such as a cup. So you can't even assume the wacky units are even consistent within themselves, you need to know which country you're talking about.
You know, there’s a reason why NASA and the US military use metric units. You just can’t afford to screw these things up because the units are a bit wonky.
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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.
They were actually planning pumped storage there earlier, with a claimed capacity of 530MWh https://yle.fi/a/3-12593341
Jiggawatts
Jay-z's preferred unit of 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.
I’m going to preface this by saying, all I know is that know about the subject was one physics class in college… The teacher mentioned Hydro Pump Storage that pumps water into a reservoir when there is an excess of energy generation then releases it through turbines when there is a surge is energy needs on the grid. Wouldn’t this idea work in a very similar way? If so it would seem feasible as about 15% of the UKs STOR requirements are met in this way.
Yeah, I was imagining it would probably work better with water instead. Sand can't be pumped (or turbined lol), and I noticed those many enormous trucks carting the sand around underground which seems to introduce an enormous efficiency loss to the system. Good to see the fundamental concept works well in practice, thank you.
Yeh, again I’m not sure how efficient using water is but my instinct says it will be a lot better than any mechanical system as they are generally very inefficient!
Right, my bad. I thought you were explaining turbines in relation to the post, which would indeed have one attempt to run sand through it if not used with either liquid or steam.
I also wrote turbine and generator separately, as, as you stated, turbines and generators are not the same. I, in turn, hope I didn't give the impression that they were.
I fully agree about the system as a whole better being described as a battery, which usually includes generators of some sort to convert the stored energy back into electricity.
And yes, this is a rather precarious article, which also is why I wrote the half-question half-joke about unnecessary conversion steps using turbines.
The illustration also showed a bucket wheel excavator. Don’t remember seeing that the last time I visited Pyhäsalmi.
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.
They’re planning to use the 530 m long secondary shaft at first. The entire mine is a lot deeper, so obviously, there are other shafts too. You gotta start somewhere.
Is it just 2 Mw or is the article wrong?
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