Advanced Rail Energy Storage

Status
Not open for further replies.

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
Seems an unnecessarily complex way to store energy compared to pumped storage.
 

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
Seems an unnecessarily complex way to store energy compared to pumped storage.

I think you have misjudged it. a) There's not a lot of water available in southern USA, and b) it tends to evaporate too. Also c) there's the occasional problem of big dams high up when earthquakes happen, plus d) the continuous problem of hills being destabilised by the pressure exerted by the weight of water at the top. There aren't really very many places where HEP/pumped storage is a goer.

"instead of relying on water in a water-stressed region it plans to make use of an inclined rail track and generator locomotive"

They wouldn't be developing it if it wasn't the best option in the circumstances.

Maybe I shouldn't have been surprised at the "not invented here" crowd's reaction!
 
Last edited:

notlob.divad

Established Member
Joined
19 Jan 2016
Messages
1,513
I don't understand the need to use a railway. Wouldn't doing the same thing lifting shipping containers full of scrap, like solid elevators do the same job without the huge area of land required. Plus the generator could be stationary removing the need for Pantographs and overhead wires etc.

But if some maverick wants to try it fair play to them.
 

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
I don't understand the need to use a railway. Wouldn't doing the same thing lifting shipping containers full of scrap, like solid elevators do the same job without the huge area of land required. Plus the generator could be stationary removing the need for Pantographs and overhead wires etc.

But if some maverick wants to try it fair play to them.

Try calculating the amount of scrap you'd need and how high you would need to lift it (then the storage area needed) if you want to store a few megaWatt-hours from midday through to midnight. I think the logistics might lead you to wonder if it might be easier by rail...
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
Maybe I shouldn't have been surprised at the "not invented here" crowd's reaction!
It's nothing to do with 'not invented here' - it's a Rube Goldberg no matter where it's designed - there are way too many moving parts, the efficiencies are going to be horrible.

Given that they are likely storing energy generated by solar, then systems like this one (not invented here, by the way) make a lot more sense.
 

furnessvale

Established Member
Joined
14 Jul 2015
Messages
4,041
At last! A use for redundant 91s.

Fit regen braking, park them at the top of Shap and send them to Tebay at times of peak electricity demand!

Repeat as required.
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
Try calculating the amount of scrap you'd need and how high you would need to lift it (then the storage area needed) if you want to store a few megaWatt-hours from midday through to midnight. I think the logistics might lead you to wonder if it might be easier by rail...
Since the system is converting electrical energy to gravitational potential energy and back again, it will be most efficient to move the densest possible mass vertically. That's why pumped storage works - water is pretty dense and it can be moved through a vertically oriented motor/generator between two reservoirs located directly above and below each other.

Moving a rail car along an inclined plane introduces losses.
 
Last edited:

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
13,118
I very much doubt the system would be anything like an actual train.
You would use a three phased corner earth supply linked to the overhead lines. Probably 50kV or more on both overhead line circuits. 50kV+50kV with the third phase at ground potential.

You would probably also use simple induction motor/generators similar to those used in wind turbines, linked directly to the final drives. No need for true variable frequency drives.
You would run up and down at rather low speeds to keep losses down, and you would probably have enormous trains with huge axle weights loaded with cast iron or crushed stone.

Could probably get 90+% if you had a sufficiently low speed with such a huge mass train.
 
Last edited:

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
I very much doubt the system would be anything like an actual train.
You would use a three phased corner earth supply linked to the overhead lines. Probably 50kV or more on both overhead line circuits. 50kV+50kV with the third phase at ground potential.

You would probably also use simple induction motor/generators similar to those used in wind turbines, linked directly to the final drives. No need for true variable frequency drives.
You would run up and down at rather low speeds to keep losses down, and you would probably have enormous trains with huge axle weights loaded with cast iron or crushed stone.

Could probably get 90+% if you had a sufficiently low speed with such a huge mass train.
but the video shows that this is flexible. Smaller units shifting a few concrete slabs can just stop and go back down when energy surplus changes to shortage. Try that with a huge train of iron ore. Mind you, high-density concrete (Iron-ore aggregate) is a good enhancement, I've read about it being used to stop skycrapers with big basements floating, but this is a far better use.
--- old post above --- --- new post below ---
Since the system is converting electrical energy to gravitational potential energy and back again, it will be most efficient to move the densest possible mass vertically. That's why pumped storage works - water is pretty dense and it can be moved through a vertically oriented motor/generator between two reservoirs located directly above and below each other.

Moving a rail car along an inclined plane introduces losses.

The densest mass? Concrete is a lot denser than water, especially with iron-ore aggregate (even if you could find enough water in the southern USA), and I can assure you that there are a lot of frictional losses in moving water around. There are also the seismic risks which would concentrate your mind if you lived anywhere nearby.
As I said, there aren't many "reservoirs located directly above and below each other" in California or Oregon (or in the UK for that matter.)
 
Last edited:

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
13,118
but the video shows that this is flexible. Smaller units shifting a few concrete slabs can just stop and go back down when energy surplus changes to shortage. Try that with a huge train of iron ore. Mind you, high-density concrete (Iron-ore aggregate) is a good enhancement, I've read about it being used to stop skycrapers with big basements floating, but this is a far better use.

Well if you went with a huge train you would only have to move up and down at less than walking pace. The slowest speed possible is best.
So it would be quite possible to stop relatively quickly.
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
Smaller units shifting a few concrete slabs can just stop and go back down when energy surplus changes to shortage. Try that with a huge train of iron ore.
Small unit means small amount of energy stored.
The densest mass? concrete is a lot denser than water (if you can find enough of that in the southern USA), and I can assure you that there are a lot of frictional losses in moving water around.
Yes, concrete is denser than water, but it tends not to flow through turbines very well. Frictional losses in large diameter pipes are marginal.
There are also the seismic risks which would concentrate your mind if you lived anywhere nearby.
If you are storing the same mass in the same area it will have the same potential for seismic effects - a million tons of water or a million tons of concrete is still a million tons.
 
Last edited:

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
Small unit means small amount of energy stored.
Yes, concrete is denser than water, but it tends not to flow through turbines very well. Frictional losses in large diameter pipes are marginal.

I'm surprised people are so sceptical. A 40-ft container (or a bit, or a lot bigger) filled with super-dense concrete on a 1-in-10 gradient (or whatever is the limit for wheel-on-rail adhesion) would be a fair number of kW-hours if it went any distance. Just imagine the weight of a concrete slab the size of a whole big diesel loco above the frames on a steep hill and ask yourself if that's a "small amount of energy stored." My car's brakes get hot, and that's just from stopping a hollow metal shell.
--- old post above --- --- new post below ---
Small unit means small amount of energy stored.
Yes, concrete is denser than water, but it tends not to flow through turbines very well. Frictional losses in large diameter pipes are marginal.
If you are storing the same mass in the same area it will have the same potential for seismic effects - a million tons of water or a million tons of concrete is still a million tons.

But the weight of concrete in dry blocks isn't penetrating the hill and liquifying it. Remeber Aberfan? And I was actually meaning earthquakes rather than the destabilising effect of the water on the geology when I said I wouldn't like to live anywhere downhill of HEP near the San Andreas or any other geological fault.
--- old post above --- --- new post below ---
like this one (not invented here, by the way) make a lot more sense.

Maybe they both have their place, but I know which I would put my money on. A huge tank of molten salt as a heat store with a steam generating power-station run off it, versus a railway using regenerative braking. Where would you see the safest place to invest?
 
Last edited:

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
Just imagine the weight of a concrete slab the size of a whole big diesel loco above the frames on a steep hill and ask yourself if that's a "small amount of energy stored."
Okay, let's say 26 x 3 x 2 metres, that's 156 cubic metres. Google says that concrete averages about 2.4 tonnes per cubic meter, so that's about 375 tons.

How long shall we make the track - 1 mile? At what gradient is reasonable for a rail vehicle? Let's go with 3% (make it a little steeper than Lickey). So that's a rise of what, 50 meters vertically? So, a little e = mgh math gives us - 5MW/h - which isn't actually that much in the grand scheme of things.

I'm not saying it doesn't have merit, but it's a small-scale energy storage method. As HSTed says, to make it utility-grade it needs to be scaled up considerably.
--- old post above --- --- new post below ---
Maybe they both have their place, but I know which I would put my money on. A huge tank of molten salt as a heat store with a steam generating power-station run off it, versus a railway using regenerative braking. Where would you see the safest place to invest?
Molten salt, every day of the week. Very few moving parts once it's up and running, and thermal electric generation is a mature technology.
 
Last edited:

Lurpi

Member
Joined
13 Jul 2015
Messages
77
Maybe they both have their place, but I know which I would put my money on. A huge tank of molten salt as a heat store with a steam generating power-station run off it, versus a railway using regenerative braking. Where would you see the safest place to invest?

The fact that hundreds of millions of euros of private money, and billions of euros of development bank money - all of it on low-risk terms - have already been invested in the Moroccan thermal solar plant to which you refer and its two sister plants suggests that thermal solar is not considered an unsafe bet by the infrastructure finance market.

But personally, what I think could be a more viable alternative to this project is utility-scale battery storage. Battery storage projects with a capacity of up to 40 MW are currently being built in the US.
 
Last edited:

notlob.divad

Established Member
Joined
19 Jan 2016
Messages
1,513
Try calculating the amount of scrap you'd need and how high you would need to lift it (then the storage area needed) if you want to store a few megaWatt-hours from midday through to midnight. I think the logistics might lead you to wonder if it might be easier by rail...

If it is gravity based storage, you want as much of the movement as possible to be in the Vertical Plane. As soon as you introduce a gradient you are already less efficient than optimal. Reactionary forces on wheels and bearings will be the main frictional forces to overcome, proportional to both force at the contact point and speed.

With the rail based solution friction between the rail and wheels needs to be as high as possible whilst friction between the axle and bearing wants to be as low as possible, this is already creating a compromise as you cannot have both. The mass and angular speed of rotation being the same, you have a lower reactionary force between wheel and rail on an inclined plan because the force is not perpendicular to the rail whilst because the bearing is cylindrical the reactionary force on the bearing would be the same, just in a different location.

With a winched vertical weight solution, so long as you could fix the cables to the drums instead of running them back to a counter weight (which would defeat the purpose of the system), you have eliminated the equivalent requirement of High friction between rail and wheel. So you are just down to minimizing friction on the pulley bearings. This would then be a much simpler trade off between Mass with the corresponding cost of supporting this at height, vs the rate of change of height (proportional to the angular speed of rotation)

The real question is not the amount of scrap you would need to lift as the more you lift in either case the more storage you get but the cost of structures to support the weight in a vertical solution x the efficiency of the vertical system vs the cost of structures to support the weight in a rail based solution x the efficiency of the rail system. Where you accept that the rail system maybe less efficient. but maybe more cost effective.

What would be a perfect test bed for the theory would be a couple of old mines. You could test a vertical mine shaft v's an inclined drift mine. Assuming all things being equal you would be able to calculate each methods equivalent efficiency and use those against the estimated cost of a scaled up system. It is certainly an interesting engineering question.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
13,118
It should be noted that whilst you need high friction between the rail and wheel this does not actually disperse any energy if the vehicle is not slipping.
This is because the point on the wheel contacts only a single point on the rail per revolution and does not slip along it.

Energy is force x distance after all, and in this case distance is zero.

It should be possible to generate very high efficiencies if the air friction losses and the like can be kept low by using a very heavy train moving very slowly. 50kV would also be advisable in the corner-earthed arrangement.
 

Philip Phlopp

Established Member
Joined
31 May 2015
Messages
3,004
It's a solution looking for a problem - generate electric, step it up to 400kV and send it somewhere wet that can do pumped storage or other water related things.

I'd personally generate hydrogen, which can be burned in a fairly conventional power station or pumped into a grid and delivered to car fuelling stations.

I can't imagine the extra cost to offset transmission losses would run to anything like train, track and OLE maintenance, given the low cost of solar panels these days.
 

broadgage

Member
Joined
11 Aug 2012
Messages
1,091
Location
Somerset
I cant forsee this being viable, apart from the losses and the maintenance requirements of the many moving parts, has anyone considered the NIMBY factor ?
Look at the hysteria surrounding HS2 or even the electrification of an existing route.
And now consider the public reaction to building dozens of heavy rail lines up inclines in national parks. With a large and conspicuous OHLE remembering that with corner grounded 3 phase at 50KV, that each line will need TWO overhead wires, each with larger clearances than present main lines.
If each line stores 5MWH as suggested, then dozens will be needed.
Will have to be built in hilly places, most of which are either national parks or otherwise protected.
Despite the slow speeds, noise and vibration might be problematic.
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
I cant forsee this being viable, apart from the losses and the maintenance requirements of the many moving parts, has anyone considered the NIMBY factor ?
One thing the American south-west has going for it is a *lot* of space with nobody to complain about their 'back yard' being ruined. See this population density map of Arizona from Wikipedia. Note how much is less than ten people per square mile:
[IMG="Population Density Map from Wikipedia"]https://upload.wikimedia.org/wikipedia/commons/f/f4/Arizona_population_map.png[/IMG]
 
Last edited:

GRALISTAIR

Established Member
Joined
11 Apr 2012
Messages
5,810
Location
Dalton Georgia USA
One thing the American south-west has going for it is a *lot* of space with nobody to complain about their 'back yard' being ruined.

- and other places - the Midwest, the great plains etc. I live here, and just driving from Dayton to Chicago I have to drive through miles and miles and miles of wind-farm in Indiana. Americans also tend not to be as NIMBY as the UK. Most of Nevada apart from Las Vegas, Henderson, Reno and Carson City is desert.
 

HSTEd

Veteran Member
Joined
14 Jul 2011
Messages
13,118
It's a solution looking for a problem - generate electric, step it up to 400kV and send it somewhere wet that can do pumped storage or other water related things.

I can't imagine the extra cost to offset transmission losses would run to anything like train, track and OLE maintenance, given the low cost of solar panels these days.

The scale of the South West is sufficiently large that 400kV is probably not going to cut it. 735/765kV is probably the bare minimum.
Or probably a (U)HVDC system.
 

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
- and other places - the Midwest, the great plains etc. I live here, and just driving from Dayton to Chicago I have to drive through miles and miles and miles of wind-farm in Indiana. Americans also tend not to be as NIMBY as the UK. Most of Nevada apart from Las Vegas, Henderson, Reno and Carson City is desert.
That's good to hear... except that you need to be able to engineer the energy-storage railway up a steady steep-ish gradient over a few miles or more.
--- old post above --- --- new post below ---
I cant forsee this being viable, apart from the losses and the maintenance requirements of the many moving parts, has anyone considered the NIMBY factor ?
Look at the hysteria surrounding HS2 or even the electrification of an existing route.
And now consider the public reaction to building dozens of heavy rail lines up inclines in national parks. With a large and conspicuous OHLE remembering that with corner grounded 3 phase at 50KV, that each line will need TWO overhead wires, each with larger clearances than present main lines.
If each line stores 5MWH as suggested, then dozens will be needed.
Will have to be built in hilly places, most of which are either national parks or otherwise protected.
Despite the slow speeds, noise and vibration might be problematic.

This is the SW of the USA, not the home counties or the heart of a national park, and therefore fairly "empty" of expensive homes etc., so the hysteria surrounding HS2 is pretty irrelevent in this case. Noise and vibration are probably irrelevant too. If you want a utility to have grid-scale power storage available then a certain amount of industrial "hum" is inevitable.

I was surprised to see the 3-phase in the pictures (the 2 OLE wires were why I deduced they were considering it.) Given that the the whole point is in moving the heaviest / highest power units practicable around quite slowly, I wonder how the OLE would cope with the pair of pans going slowly (over neutral sections?) at junctions?
--- old post above --- --- new post below ---
It's a solution looking for a problem - generate electric, step it up to 400kV and send it somewhere wet that can do pumped storage or other water related things.

I'd personally generate hydrogen, which can be burned in a fairly conventional power station or pumped into a grid and delivered to car fuelling stations.

I can't imagine the extra cost to offset transmission losses would run to anything like train, track and OLE maintenance, given the low cost of solar panels these days.

You don't seem to be able to accept that it's quite difficult to find the right place to put in a pumped storage system... and you also want to take on the cost of a new high-voltage line just to get the power to your storage somewhere suitable and wet?
--- old post above --- --- new post below ---
The fact that hundreds of millions of euros of private money, and billions of euros of development bank money - all of it on low-risk terms - have already been invested in the Moroccan thermal solar plant to which you refer and its two sister plants suggests that thermal solar is not considered an unsafe bet by the infrastructure finance market.

But personally, what I think could be a more viable alternative to this project is utility-scale battery storage. Battery storage projects with a capacity of up to 40 MW are currently being built in the US.

The Moroccan desert set-up (primarily a generating facility with some storage added in) may be the right tool for the job there, but this is being promoted in and for a different environment.
Anyway, when I read up on those molten salt systems I think it said that there is a fairly massive oil- or gas-burning support system to start it up and keep it going at the end of the night. Perhaps they are really conventional-thermal-with-solar-support?
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
23,989
Location
Scotland
The Moroccan desert set-up (primarily a generating facility with some storage added in) may be the right tool for the job there, but this is being promoted in and for a different environment.
I'm not really seeing the major differences. Could you expand on that comment?
Anyway, when I read up on those molten salt systems I think it said that there is a fairly massive oil- or gas-burning support system to start it up and keep it going at the end of the night. Perhaps they are really conventional-thermal-with-solar-support?
That's the nature of any storage system - you can only store so much. Your salt is going to get cold or your trains are going to reach the bottom of the hill.
 

Philip Phlopp

Established Member
Joined
31 May 2015
Messages
3,004
You don't seem to be able to accept that it's quite difficult to find the right place to put in a pumped storage system... and you also want to take on the cost of a new high-voltage line just to get the power to your storage somewhere suitable and wet?

I've never argued about pumped storage.

You would need a high voltage power line to get your electricity to market, routing it to the market with small deviations to reach storage would happen with this railway system, just as it happens with every other storage and distribution system.
 

AndrewE

On Moderation
Joined
9 Nov 2015
Messages
3,704
I'm not really seeing the major differences. Could you expand on that comment?
That's the nature of any storage system - you can only store so much. Your salt is going to get cold or your trains are going to reach the bottom of the hill.

The Moroccan desert has lots of sun and no consumption, so is primarily a generator... except that it doesn't match the greatest export demand so needs some storage... I'm sure that I read that they (or somewhere in the middle east) start up and guarantee their output with fossil-fuelled boilers.

If you run out of storage then by definition another system has to start generating to maintain the supply. This storage-only system is relatively local, looks as though it requires almost nothing other than maintainance after commissioning and, as it mops up surplus PV and wind electricity, no CO2 is released when renewables haven't got the required output...
What's not to like? Doesn't demand long-distance power lines, or water for HEP lakes at altitude...
 

Class 170101

Established Member
Joined
1 Mar 2014
Messages
6,646
The Moroccan Desert also has one big advantage. Lots of land and no NIMBYs. I cannot see this changing anytime soon.

For the UK pumped storage may have uses in Scotland and Wales and maybe the spine of England but I cannot see it happening elsewhere.

I reckon its going to be Fracking, Wave power, wind turbines (mostly out at sea given the political climate) and small scale solar on household roofs.

I would be interested to see if Hydrogen could be made to work but aren't there issues about its stability as a fuel source?
 
Status
Not open for further replies.

Top