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Nevada Startup Stores Energy With Trains (fortune.com)
An anonymous reader writes: Nevada's Bureau of Land Management has granted a land lease to a $55 million project by Advanced Rail Energy Storage, which "proposes to use excess off-peak energy to push a heavily-loaded train up a grade," according to Fortune. "Then, when the grid needs that energy back, the cars will be rolled back down the slope...that return trip will generate energy and put it back on the grid."
The company claims its solution is about 50% cheaper than other storage technologies, according to Fortune, and boasts an 80% efficency in energy reclamation, "similar to or slightly above typical hydro-storage efficiency." Citing Tesla's factory, the magazine callsthe project "further evidence for Nevadaâ(TM)s emergence as a leading region for innovative transportation and energy projects."
The company claims its solution is about 50% cheaper than other storage technologies, according to Fortune, and boasts an 80% efficency in energy reclamation, "similar to or slightly above typical hydro-storage efficiency." Citing Tesla's factory, the magazine callsthe project "further evidence for Nevadaâ(TM)s emergence as a leading region for innovative transportation and energy projects."
When I was a kid I always wondered by we couldn't store the cold air in boxes in the winter and then use it in the summer to cool us off. I was a dumb kid.
Citing Tesla's factory, the magazine callsthe project "further evidence for Nevadaâ(TM)s emergence as a leading region for innovative transportation and energy projects."
And the existence of Las Vegas is evidence for Nevada as a leading region for innovations in ways to needlessly waste energy and resources.
I read about this system and it seems interesting and it makes me wonder if there are any other forays into mechanical storage of energy, such as some kind of larger scale clockwork system of raised weights.
A lot of the locations able to generate power surpluses are in remote regions with poor access to the geography and water for pumped hydro, but generally have a lot of square footage that could be used to house some kind of mechanical storage system.
I can see this project going off the rails.
I'm sorry, but your opinion seems to be wrong.
Sisyphus
That's not the issue. The problem is that demand is highest during the day, and you end up with unused power at night. That's especially true during the summer. You still generate the energy at night but you waste some of it when it's not needed. In the case of wind, in some places the winds tend to be stronger at night. If your turbines are high enough in the central US, that's absolutely true. That's probably somewhat true out west, too. The goal is to store the energy generated at night so it can be used during the day. Otherwise you have to build more of those generators that work 24x7 to meet peak demand, and it costs everyone more money.
They should call it project Sisyphus.
I Don't Work Here
Brilliant. Think of all the #2 pencils we could make out of all that carbon.
Sounds like a variant of Electric Mountain in the UK. The same thing is done, only instead of moving trains up the hill they move water instead. There's more in the Wikipedia article - essentially though, this idea works fine.
Rube Goldberg...call for Mr. Rube Goldberg...
Grid Scale Energy Storage (complete with requisite animation)
It looks interesting, especially for places in the West of the US where water access is slowly becoming problematic. On the East coast (where there is a lot more available water) there is the Bath County Pumped Storage Station which has 3GW generating capacity.
I am Slashdot. Are you Slashdot as well?
To be fair... it does make some sense that these two things would chase each other around in circles.
I think you are correct. Necessity is the mother of invention and apparently invention can be the mother of necessity too. The amount of wasted human effort involved in making a major metropolis in the middle of a desert in a location with zero natural resources to justify its existence is astonishing. Same thing applies to Phoenix. Great examples of doing something because we can without stopping to wonder if we should.
Bill Nye had a similar idea that involved digging a large hole and raising a large weight with solar energy, then reclaiming it by letting gravity do the work. It's basically the same principle as weight driven clocks.
There's really no innovation here - they've just made the entire thing larger. we've been storing energy like this even before batteries were a thing.
BeauHD. Worst editor since kdawson.
Bill Nye proposes a similar scheme, using giant pistons lifting weight instead of driving a train uphill.
https://www.youtube.com/watch?... starting at 7:40.
ARES quotes an energy efficiency of 80% which would outperform pumped water storage (70%), so that's pretty good.
Converting CO2 into carbon is being worked on, but no large-scale efficient process has been found yet.
You spent all your time trying to get frist post!!
The basement is below a think layer of concrete you sensitive dad
Please have someone who knows basic physics do the numbers before investing in this.
And what makes you think that they haven't?
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https://en.wikipedia.org/wiki/...
There's an invention that can help with that. You may have heard of it, it's called "brakes".
Converting carbon dioxide back into carbon is a lot harder than moving mass to a higher elevation, solid or liquid, and a hell of a lot less efficient.
=Smidge=
But they take it to Vegas every weekend.
See, if you'd ever tried to get funding for a business, you'd have been asked for something called a business case that includes something called analysis...
To me it seems a bit of a time limited system. If energy is reclaimed by rolling the train down hill there are two options: Either the train has to go really slow or the ramp has to be really long if you want to reclaim that energy in a reasonable long time. I can't imagine that let's say 15 minutes is enough time to catch up with top demand, a train rolling for 15 minutes at some speed needs a long track and thus a lot of space. If the speed were 15 km/h you would need a ramp of almost 4 km, an hour would need about 16 km.
As a poster before me already mentioned, flywheels could do the same trick, take less space and are likely more efficiënt.
What person will donate an airborne act of love?
Where I live we pump water up a mountain into a lake to store energy. Seems to me a simpler solution than using trains.
I wouldn't be surprised if water would be slightly less efficient due to pumps and turbines having higher loss factor and due to water evaporating. But how many trains, tracks and difference in height would you need to have something equivalent to a small lake high up a mountain?
I hadn't the slightest objection to his spending his time planning massacres for the bourgeoisie... (P.G. Wodehouse)
Not going to work well anyplace without mountains.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
I'd be curious how much space such an installation might require and how easy it is to add capacity. I imagine adding more cars or putting more weight per car is probably pretty cheap in comparison to other options.
I wonder what argument NIMBYs will to try to shitcan it some places.
But at what capacity?
How many trains would you need to store the energy of an average tank / water tower (built at the same elevation as the upper station of the train system) and what area would be needed as storage capacity for trains instead?
Gtall already mentioned the rounding losses as the least amount of energy you can store is the amount that is needed to bring one train all the way up to the upper plateau.
Granted, it doesn't need water which may be an advantage in dessert areas, but there you could usually just build a solar thermic plant (like the one that just had a little fire accident...) to create the amount of additional electric energy that those trains could probably store and dump the excess power.
Intresting concept, but probably less practical then hydro.
bickerdyke
A thousand tonne train of railcars pulled up a slope 100 metres in height, assuming no losses (spherical cow assumptions here but bear with me) will require Mass x Gravity x Height = 1 billion joules = 270 kWhr which at commercial rates for electricity is worth maybe $20 or $30 US. That's not a lot of energy storage given the capital cost of track and equipment and recurring maintenance costs etc.
"Need" is a matter of opinion.
Incorrect. "Want" is a matter of opinion. "Need" is not optional by definition. Sometimes people confuse the needs with wants but they are not the same thing.
IMHO, concerns about storage energy losses when the source power system (solar for sure, wind mostly) is capable of generating power but for which there is no useful work for it seem to throw away useful ideas.
If a solar farm can produce 10 megawatts of power and the grid demand is 5, does it really matter much if the storage system is only able to reproduce 1 megawatt of the surplus 5? Sure, you've lost 4 megawatts, but not doing anything at all is a loss of 5 megawatts.
Obviously there are some economics in play -- if the construction and operation costs and the facility life of the storage system don't work, then it's an economic problem, but still not really an energy problem. And even if the construction costs are high, it's not hard to see some more esoteric systems with extremely low maintenance costs and long facility lives might make sense even at high energy losses.
With wind I can see arguments where braking the turbines may make more sense than high loss storage if you take into account that a turbine is a mechanical system that will wear out.
Simple - some "obvious" things aren't obvious at all.
Their brochure has more info on their proposed solution. 2 rail yards, 8 miles apart, 70 4-car trains weighing 1000 tons each, capacity 2 MWh per train. Each train is about 60 m long and ~3 m wide. Peak capacity 333 MW.
Rail cars weigh 240 tons, mostly concrete. A block of concrete 15*2.5*3 m weighs that much.
The least amount of energy you can store is achieved by parking one train somewhere up the slope. Want to store 200 kWh? Drive 0.8 miles.
I'm not as thick as you stoned I am
The world is moving towards more closely matching electricity supply to daily demand so hopefully we'll need less of these methods of shifting off peak power to peak power. Without exception they are all very lossy, some like this a lot more lossy than others. Using the power to actually do something useful instead of lossy storage, or not using resources to generate the unneeded offpeak power at all is a better idea.
If it's an ore train in no hurry moving only at night when plenty of power is available then that's a good idea if there's plenty of sidings, staff are cheap etc etc. Shuffling rolling stock around and consuming a lot of power to release only a small amount at peak times isn't such a good idea and makes me wonder if some palms were greased and kickbacks delivered.
They're both fairly pointless ideas now that we have the technology to build magnetically levitated flywheels in vacuum vessels. They have very low loss, they take up very little power, they cost very little to build, they store fairly enormous quantities of energy, and they are very efficient.
And yet nobody has found an economically viable way to make this miraculous device and deploy it at industrial scale. Perhaps they aren't quite everything you are making them out to be just yet?
Seriously the idea of large flywheels to store energy has logic to it and has been proven at smaller scales. We're just not quite there yet for industrial scale use. Maybe soon hopefully.
You don't need to store a lot of them. Assuming that you can somehow build a single strong boxcar out of lead (more likely it would be many cars, but we'll use that for the sake of argument), you would end up pushing 3.4Gg up the hill. Nevada has 10,000ft mountains at its western edge. If you could push that weight to near the top of those mountains you would be storing about 9GJ, or about 7.5GW/h (assuming 12 hours of high usage and 12 hours of low during a day). That's a similar level of production to 7 or 8 nuclear plants from pushing just one single lead box the size of a train car up a mountain.
Now I'm not saying that a single lead box, pushed up a 10,000ft mountain is the optimal way to design this system, but the fact that the maths works out to so well just for that demonstrates that you do not need to store a lot of trains at the top of your mountain.
Because pumped water storage isn't 80% efficient.
That doesn't sound right. For the entire cycle or just recovery? Electric motors are nowhere near perfect whether they are run as motors or generators.
Easy, just reduce it with a lot of hydrogen you make using ... oh damn.
Why not optimize it further so you drive freight trains uphill when the electricity is cheap and then downhill when it's expensive and feed back the braking energy to the grid?
The downside is that it would require a lot of tracks to be electrified, but that can be seen as an investment. You will also need some large holding areas at the top and bottom.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
Essentially what is already done already.
https://en.wikipedia.org/wiki/...
--Q
Is it? The write-up does not mention financing and TFA is at Fortune... Did they get any money from the DOE, like that failure we discussed yesterday, or are they financed the old-fashioned way — by people voluntarily giving them money hoping for nice payback?
In Soviet Washington the swamp drains you.
Two problems I see with this: 1. Safety. If the grid goes away, this thing will have no reaction torque to apply, and it ain't gunna stop in a hurry. 2. Scale. A quick look at Wikipedia suggests that the heaviest goods trains in use anywhere are about 40,000 t. Suppose you have a mountain where you can raise that 1,000m. The energy involved is roughly 40,000 * 1,000 * 10 * 1,000 = 4e+11 J. That's 4e+11 / 3.6e+9 = 111 MWHr. It's not small cheese, but it's also not national grid scale. As I sit at my desk, demand on the UK national grid is ~31GW. It will last 4e+11 / 3.1e+10 = 12.9 seconds supplying the whole country. That 40,000t train is about four miles long, BTW, so there's a limit to how many of them you can put on the same bit of track. As I say, it's not small cheese, but at the same time, in our renewable-powered future, being able to smooth out a few hours of low wind is going to require a lot of trains and a lot of quite large mountains to drive them up.
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Their would be wayy more than one train, hopefully dozens, if not hundreds. I imagine a triple track leading up a steep grade with a large flat switch yard at either end. Enough for doxens/hundreds of trians at either end..
At any one time they could have ten or more mile long trains on two of the tracks generating electricity. One only needs enouigh specialised three phase motor/generator 20-50MW locomotoves for the trains on graded tracks.(third track woud be used to return locomotives to the top/bottom of grade) as needed They could regulate their speed to sync with the grid, thus incurrng minimal losses..Here is a link for more details
Sisyphean Railways
Requiem for the American Dream
How does this scale compared to other technologies? The "use heavy trains" approach is easy for the lay person to see scaling issues.
GP's post brought to you by: the people that sit on a hill at a light with a manual transmission and keep slipping the clutch and gunning it to hold their position.
> Why not optimize it further
because of occam's razor? Also I fail to see how that would be optimized any further.
Because it would go down on the other side of the hill taking goods with it.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
Let's see now.
suppose they have oversized axles so we'll estimate 200 metric tonnes per car, then a 2000 meter mountain difference, and 100 cars long. we'll round g off to 10.
E= mgh = 200*200E3*2000*10 = 800E9
If they could release that in 1 hour then they could have 200 megawattHr
I found an old estimate that by 2015 Las vegas would need 10,000 megawatts of power on a summer day. Thus 50 trains could power it for an hour.
Or roughtly speaking 1 train would power las vegas for 1 minute
Some drink at the fountain of knowledge. Others just gargle.
Entire cycle. Electric motors have pretty amazing efficiencies. And rail has very low friction losses.
This is just dumb. Firstly this is in Nevada. A place with precious little water to spare for a hydro system as well as a myriad of obscenely complicated water rights dating back over a hundred years. Even looking crosswise at the local rivers for use in hydro generation would cost you more money than the railroad system proposed here, and that doesn't even begin to describe the outcry environmentalists will have in the US over the construction of a dam. All said and done a new hydro system will probably cost as much as a nuclear plant.
"There are lies, there are damn lies, and there are statistics"
It doesn't have to scale. It just has to store and provide energy with enough efficiency to be commercially viable. This particular technology may not "solve all our problems", but I foresee a future in which we don't turn to just one thing to "solve all our problems". This is why we ought to upgrade our electrical grid; to allow more diverse energy sources to deliver over greater distances.
As for "mother nature's solution", it has a name: biomass. Environmentalists like biomass in principle because it forms a closed loop: carbon is emitted into the air in exact balance to carbon being taken out of the air. But there are still a lot of problematic details, such as conventional air pollution (i.e., other than CO2) and biomass crops displacing food crops. So they don't like corn ethanol, but ethanol from crops like switchgrass that can be grown in land not suitable for food crops could be a different story.
By the way I hate the "mother nature" language because it makes nature seem like Nature wants to make things nice for us. Mother nature is more like, say, a coot mom, which produces plenty of chicks in case there's a good resource year, then ruthlessly kills the excess. Mother nature doesn't care whether we suffer or die.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
Train routes through mountain passes are already pretty saturated, very expensive place to lay track, hence not overbuilt. There is no place to park trains at the top.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
Sorry but true. They're rolling out some promising early models but they have not seen widespread adoption and their economic viability is still unproven though looking better every day. Current versions are still comparatively small compared with generating capacity and are still in testing. It seems we are right on the cusp I think. Please note I'm not disagreeing with you about their potential. It think they are very promising and not far from being a really helpful tool. I don't think there are any obvious showstoppers to economic viability of flywheels so I would expect to see them getting used more and more. But widespread deployment is still in the future - probably the near future.
You speak of the Las Vegas of today, when the city was established it was known for it's numerous natural springs
The Las Vegas of today is the only one we have. Whatever local water supplies it naturally has ceased to be adequate a looong time ago in order to feed utterly pointless displays like the fountains at the Bellagio. Vast amounts of water resources have been diverted to supply a city that never should have gotten larger than a small town. I've ever heard people from Nevada talk about ideas like diverting the Mississippi or the Great Lakes to supply water to the idiocy that is Las Vegas.
Unless you use the trains to carry water and store those in some kind of reservoir at the top of the grade. Then you get a two-fer.
Many people want to live in Phoenix.
People want all sorts of things that aren't good ideas. Building a major city in the middle of a desert when you have other options available to you is the very definition of an idiotic idea. The amount of water and energy resources that have been diverted from more sensible uses to supply places like Phoenix and Las Vegas are obscene.
Civilization itself isn't a need. Neither are food and shelter.
Yes they are if you want to continue to exist. If you actually consider suicide an real option then go back to reading your nihilistic philosophy books and stop bothering the rest of us.
Since your claim that Las Vegas constitutes a needless use of power did not contain a scope, I think it is fair to say that it represented an opinion.
So instead of using your brain and a little common sense you decided to waste time on some nonsensical rhetorical arguments using Reductio Ad Absurdum about the scope of my argument. I'm pretty sure you're smart enough to figure out what I meant without me explicitly explaining the entire scope of my argument. Do so.
You have a fundamental misunderstanding what siphoning is and how it works. Siphoning only works when a higher placed reservoir transfers a liquid to a lower placed reservoir, it doesn't allow for a pumping action from a lower to a higher reservoir - which is why pumps are used for that purpose.
Another piece of the puzzle is constricted transmission capacity. There is a complex relationship between the summer consumption of power in California and generation in the Northwest from spring/summer hydro. The capacity between California and the NW has always been a choke point. Recent expansion of wind generation has caused situations where there is more power available than can e used in the NW nor transported to other regions.Admittedly, this can be solved by just adding more transmission capacity but sometimes a little storage that can even out the peaks can even things out at a lower cost. BTW, California and Washington have some of the larger pumped storage facilities on the planet already.
Nevada Bureau of Land Management
Too bad there's no such fucking thing. Idiot journalists with zero reading comprehension skills; what will they think of next...
why didn't I think of this????
Because it’s been done before. The Virginian railroad used to haul coal down the hills of Virginia; it was electrified, and the engines used regenerative braking. When they slowed down, the electric motors turned into generators and sent back power through the wire. When one fully-loaded train was going downhill, it provided enough power to get two unloaded trains up the hill; the net energy consumption was pretty negligible
OK, something here doesn't "compute."
The cost and challenge of pumped-storage hydro is finding an available mountain or hilltop where you can store enough mass in the form of water. Here you are storing mass on top of the hill in the form of train cars and electric locomotives. If you had enough room on a spare hilltop to park the train, wouldn't you have enough room to put in a bunch of water tanks, or better yet, and open-air pond or maybe an underground water-storage cavern.
And if you are going to have the train make a bunch of trips to move gravel to the top of the hill and then later bring it back down, why would you not have room to store water? OK, water is less dense than gravel, but water can be pumped as opposed to loading and unloading gravel from those train cars and the attendant friction loss?
Biomass uses water and soil nutrients, so I believe it's not fit for our relatively huge demands. As an analogy we could chop all accessible wood and burn it in furnaces, or try to support a population of one billion horses and lose everything in a few years.
Looking only at carbon, we could also build a few thousand nuclear reactors and call it done (assuming we would just find untapped uranium and not care if it gets 10x more expensive). I've liked it in principle but bad shit may happen eventually - and I don't know about designs meant to be torn down cheaply.
Maybe there are ways to rape the oceans for biomass, energy and other things but it may be dangerous (even exploiting temperature differentials on a mass scale : what is the impact of vacuuming and mixing stuff from ocean layers?)
is in my basement walls. The walls not only accept heat, if they are dry, they soak up humidity.
Not enough storage between seasons, although the basement chilled in winter delays, perhaps, by a week or two turning the A/C on. But certainly enough storage to not have to run the A/C flat out in the heat of day where it consumes more electricity than running in the cool of morning.
Ahhh... nuclear shills are getting a bit shy of last. I was waiting for one to show up...
Because the potential energy in a few piles of rocks in boxcars totally eliminates the need for baseload power sources.
Meanwhile, the trackage I would build in Nevada would be to haul spent fuel rods to Yucca Mountain.
They will sell insurance. Suppose the wind suddenly drops or electric demand jumps at when everyone turns on their kettle after the end of an episode of East Enders. The utilities need power now and they can't wait for a coal plant to increase its out put.
So this company will drive their trains to the top of the hill and just park them there. They will then sell the right to by electricity from them for a specific price. Utilities will pay for this right even they only ever purchase the power once or twice a year.
This is how most of the North American water based electric storage systems work. Even with North American prices regularly fluctuating between $7.00/kwh and $-0.02 cents companies can't take advantage of this arbitrage because there maintenance costs are too high.
Why is the concept about using a relatively cube-like mass similar to a normal freight car? You could flatten the mass out and have a really huge solar panel to help generate some of its own "surplus".
Or hey. Why not just put the power plants themselves on giant long tracks. Or hey let's make the trains actually giant batteries. So they can store energy two different ways at once.
Hey what about this idea: we can do away with the mountains entirely. You can just have a really, really long track with Bill Nye's patented weight-lifting system at either end. You lift the end with the train on it up during peak hours and release the car's brake when the energy's needed. When the car gets to the other end, the lifting piston is dropped and the track goes flat again.
See at that point, you could actually use the train to transport people, too. As long as they're not in a hurry or anything. Well why not put an office space inside of the train and run a business from there. You could cross a state line and pay lower taxes during peak hours.
Hey you could build the track all the way around the world. It would come back to right about where it started, and so it would be really efficient to reclaim a little tiny little bit of precious energy from the piston doing the dropping of the track (which you have to admit would probably be a really heavy track) and distribute it directly to the other piston lifting the other end.
With the solar panels on the top of the large, flat office building full of internationals who jump on to buy stock where it's lower and then jump off to sell stock where it's higher, and with the track going all the way around the world, and considering the very low resistance of the two pistons being just inches apart, it'd be really efficient guys. Let's kick start this bitch.
"Stratigraphically the origin of agriculture and thermonuclear destruction will appear essentially simultaneous" -- Lee
I'm not sure if you're joking or are honest here. The idea of storing off-peak energy is to save up energy that is being created when there isn't demand. Which is exactly what you are saying, and exactly what is being done here. I'm curious how nuanced this is. Other systems push water into higher reservoirs, which they later flow through turbines to create electricity.
I'm not sure if you're joking or are honest here. The idea of storing off-peak energy is to save up energy that is being created when there isn't demand. Which is exactly what you are saying, and exactly what is being done here.
He's suggesting deploying it on commercial rail links through the mountains, not a dead end line that's literally pushing rocks up a hill. So something useful happens as a side effect of temporary energy storage (goods arrive at their destination).
The train on the north east corridor already do this. They use dynamic braking by reversing the polarity of the motors during down hill descents, sending the 600 to1200 amps back into the grid. It is not all abput energy savings though. This keeps the cars bunched up when traveling down hill as opposed to using regular brakes which leave the cars stretched, thus causing a rough ride once the territory flattens out. It is too bad all the other trains in the country dont the run solely on electricity, so they energy produced by dynamic braking is just turned into heat.
Only a few of the people living within the geographical boundaries of Nevada have any claim of "birthright" to the land. For the rest of you, there's this: the United States government stole that land from the birthright holders, so you're lucky to allowed any sort of title to any part of it. The government stole it, the government gets to keep it, just like the casinos.
You seem to think you can get water to flow uphill if you take it in small enough steps. With a siphon?
[HankHill] I'm going to have to ask you to leave [/HankHill]
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
How can someone, who has obviously never actually siphoned anything, think it's a good idea to post such shit?
I blame his parents. He shouldn't have unfiltered internet access.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
Surely transmission losses getting to the train power network and then out to where the locomotives are is non-trivial. That's part of the entire cycle.
"Surely transmission losses getting to the train power network" was meant to mean transformer losses since trains run at a different voltage to the interconnections of the electricity supply network.
It's a bit of a Rube-Goldberg machine with losses at each step IMHO, and the amount you can generate from a locomotive (around 3MW each) is not very much either. At a power station I worked at the standby generator (for getting conveyors etc going for a cold start) which was built around a jet engine from the 1950s could output 20MW - in terms of electricity generation locomotives are tiny and could be replaced with only a couple of windmills each.
I'm beginning to suspect that this is just another example of someone taking advantage of government money for a project designed to fill their own pocket with little or no benefit for anyone else. Something like this has been possible for a century - why no takers until now?
net energy consumption was pretty negligible
As long as you have infinite empty cars uphill :)
-Bucky
net energy consumption was pretty negligible
As long as you have infinite empty cars uphill :)
Um, it's the same cars. Two trains,one coasts down making power to run the other(s) up. Then the empty one loads, the loaded one empties and they switch.
Actually it was lots of trains. The only time they bought power was when a train came through that did not run off the wires. Net power from the coal starting high and ending low. Worked for decades.
The OP is about a somewhat different arraingement. One train, fixed load. Goes up when power is cheap, goes down when power is expensive. As in: every day and night. Not far-fetched at all. Assuming the maintanance is not too expensive.
I think that would slow down transport too much.
But with some really powerful scheduling computers, it might be practical.