Author Topic: I think I smell something.  (Read 13989 times)

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Offline Biff383

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I think I smell something.
« on: May 02, 2016, 11:37:37 am »
http://www.vox.com/2016/4/28/11524958/energy-storage-rail   

  A friend sent this out to me. Seems to me to not be a very efficient way to store energy. I suggested batteries.

  Any thoughts?
 

Offline slaterk93

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Re: I think I smell something.
« Reply #1 on: May 02, 2016, 11:51:36 am »
I don't know, the article says they're 86% efficient which is comparable to batteries, and this system should last much longer than batteries I would hope. First thoughts, I don't think this such a bad idea. The only question is how much land would this take up?
 

Online Ian.M

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Re: I think I smell something.
« Reply #2 on: May 02, 2016, 12:04:29 pm »
It stinks.  You aren't going to get a response time in seconds because the rail car has to accelerate up to speed under gravity alone before you can tap usable amounts of power from its motor/generator.  To get the claimed 86% efficiency end to end, you need to beat 92.7% efficiency in each direction.  That doesn't leave much for geartrain and rolling losses.   

I would suspect its the rail lobby trying to get pork out of the green energy barrel.
 

Offline rrinker

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Re: I think I smell something.
« Reply #3 on: May 02, 2016, 12:42:42 pm »
 Conceptually it works - on all-electric rail lines, trains doing downhill used dynamic braking to maintain speed, and the power generated was pumped back into the power system to help power trains on the other side of the hill coming up.

 Their efficiency projections though, kind of stink. Steel wheels on steel rails IS very efficient, but that very efficiency plays in both directions. It might not take a whole lot of energy to lift those blocks up the grade, but you also aren't going to get a whole lot of that back coming down.

 

Online Halcyon

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Re: I think I smell something.
« Reply #4 on: May 02, 2016, 01:48:06 pm »
I thought trains already had regenerative braking systems?
 

Offline johansen

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Re: I think I smell something.
« Reply #5 on: May 02, 2016, 02:21:03 pm »
fundamentally the project is no different than the http://gravitybattery.info/ , which is really a cable fatigue experiment.

the friction of the cable on the drum (and bending fatigue) is no different than the rail wheel on the track, except for the fact that the track and wheel can be made from a harder steel.
but with the train, you have bearing friction, bearing friction that is Multiplied according to the tangent of the slope of the track.

with the gravity battery, you have cable fatigue but low bearing losses. with a train, you have lots of bearing loss and wheel fatigue, but no cable fatigue.

in the case of a gravity battery you could make the cable drum arbitrarily large to make the cable fatigue negligible, but if you do, then the gear box friction is not longer negligible because the velocity of the cable is slow relative to the tangential velocity of the motor. so you can make the diameter of the motor larger but that increases air drag and cost.

but a train has a huge surface area and air drag. so you have to have a gear box.
« Last Edit: May 02, 2016, 02:44:15 pm by johansen »
 

Offline calexanian

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Re: I think I smell something.
« Reply #6 on: May 02, 2016, 02:33:08 pm »
Old Old news. Its been done. Here is the one that happens to be closest to me. https://en.wikipedia.org/wiki/Helms_Pumped_Storage_Plant  Pumped charges hydroelectric systems have been in use for nearly a century. Same idea. Much more practical.
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Online Ian.M

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Re: I think I smell something.
« Reply #7 on: May 02, 2016, 02:51:12 pm »
Dinorwig pumped storage hydro plant stores approximately 9 GWh in a similar land area with efficiency of 75%.  ARES Nevada uses 106 Acres of land for 12.5 MWh with claimed 86% efficiency.  Marchlyn Mawr reservoir (Dinorwig upper) is approx 50 acres area.  Add another the same size as a lower reservoir, and the rest for the turbine and generator halls etc, and the area will be very similar.    Over 700 times the storage capacity in a similar footprint, with a height differential of 500m - that's practical to install anywhere you've got a really deep open cast mine that's no longer economic or is abandoned.   Remediate the Berkeley Pit superfund site and you could put a 20GWh storage plant in it! 

The efficiency could be improved with shorter larger penstocks and tail races  + separating the pumps and turbines so each can be designed for maximum efficiency.

« Last Edit: May 02, 2016, 03:00:24 pm by Ian.M »
 

Offline ez24

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Re: I think I smell something.
« Reply #8 on: May 02, 2016, 03:07:20 pm »
California politicians are trying to save the world.  They have set high goals for renewable energy.  50% by 2030, so that will take a lot of money out of peoples pocket and place it in the lobbyist's pockets and the rich who will get the projects. 

One big problem is energy after the sun goes down.  So there are billions available (some from my pocket) to be used on projects like this. Another project will be to use molten salt.

So appreciate that Californians are saving your world.  :-+

I like what someone said people could do - and that is save our utility bills so we can look back at them someday and think "oh the good old days"   :--
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Offline hayatepilot

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Re: I think I smell something.
« Reply #9 on: May 02, 2016, 03:44:59 pm »
This seems like a good alternative a hydroelectric storage plant for areas with little to no water.  :-+
Efficiency is probably very comparable.

One could build this train storage near solar power plants in the desert where hydro storage is simply impossible due to the lack of water and huge evaporation losses.
Certainly more durable and less toxic materials than batteries.
A "small" capacitor bank would probably still be necessary to cover the time untill the train power kicks in.
 

Online Ian.M

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Re: I think I smell something.
« Reply #10 on: May 02, 2016, 04:12:14 pm »
"Certainly more durable ... than batteries" is highly questionable.  It needs sliding contacts for the power connection the whole lengthg of the track, the rail cars are mechanically complex and will need significant maintenance, and even the track will need regular maintenance due to ballast movement.

NiFe batteries are environmentally fairly benign, don't use rare minerals, are low maintenance and have life expectancies in excess of 40 years and efficiencies up to 80%.  They don't have great energy density, but in a stationary application, that's not particularly important.  600 tonnes of NiFe cells could easily store the same amount of energy as the ARES Nevada project.
 

Online Brumby

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Re: I think I smell something.
« Reply #11 on: May 02, 2016, 04:17:18 pm »
It just goes to show you, there are many ways to approach energy storage.  I think energy generation solutions are just as important, if not more so.

So long as people keep testing out ideas, there is hope.
 

Offline wraper

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Re: I think I smell something.
« Reply #12 on: May 02, 2016, 06:00:19 pm »
Old Old news. Its been done. Here is the one that happens to be closest to me. https://en.wikipedia.org/wiki/Helms_Pumped_Storage_Plant  Pumped charges hydroelectric systems have been in use for nearly a century. Same idea. Much more practical.
Not to defend that rail thing but pumped storage have some serious issue. It can only be constructed where natural landscape allows (water reservoir on the mountain).
 

Online Brumby

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Re: I think I smell something.
« Reply #13 on: May 02, 2016, 09:54:41 pm »
Old Old news. Its been done. Here is the one that happens to be closest to me. https://en.wikipedia.org/wiki/Helms_Pumped_Storage_Plant  Pumped charges hydroelectric systems have been in use for nearly a century. Same idea. Much more practical.
Not to defend that rail thing but pumped storage have some serious issue. It can only be constructed where natural landscape allows (water reservoir on the mountain).

When you have the landscape and resources for it, it's a great idea - but extremely limited in where it can be implemented.  The rail thing is a lot more flexible in that regard, but it does have maintenance and efficiency issues.  As for the speed it's output could be ramped up - that's going to be one of the development challenges.

I don't expect it to be a silver bullet - but I'm interested to see what they can achieve.
 

Offline rrinker

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Re: I think I smell something.
« Reply #14 on: May 02, 2016, 10:57:52 pm »
I thought trains already had regenerative braking systems?

 Diesel power trains do, but the energy is simply dissipated in resistor grids. Electric railways usually do what I mentioned, feed the power back into the grid. There's an incredibly large amount of switchgear involved in an electrified railway, as the loads are constantly changing AND moving. Much automated these days, but there used to be a position of Power Director who controlled the switching of substations to keep the power where the trains were.

 

Offline john_p_wi

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Re: I think I smell something.
« Reply #15 on: May 03, 2016, 01:17:08 am »
I thought trains already had regenerative braking systems?

 Diesel power trains do, but the energy is simply dissipated in resistor grids.

Many years ago I was a manufacturing engineer involved in the testing and manufacturing of a 5500 kilo watt dynamic braking resistor being developed for the now retired EMD SD90 MAC.  It truly was an experience being on the SD90 platform and testing the resistors, and it is an amazing amount of heat generated and blown out the "hatch".
 

Offline rrinker

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Re: I think I smell something.
« Reply #16 on: May 03, 2016, 03:36:26 am »
 It's neat watching them come down a grade like Horseshoe Curve, clearly braking but the prime mover is in anything but idle - just to keep the fans turning fast enough. I've gotten chances twice to ride in the cab, no 90MAC though, an SD50M and a rebuilt GP30.
 There's a LOT of electronics on modern locomotives, and not just for engine control. Would have probably been my dream EE job, but then with the ups and down in the industry I might have ended up like my friend the microwave engineer who hasn't been able to find work in over a year.

 

Offline john_p_wi

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Re: I think I smell something.
« Reply #17 on: May 03, 2016, 03:54:46 am »
With the reduction in coal production due to EPA reasons and the reduction in transport of oil and drilling / fracking supplies (fine sand etc) the railroads are really taking it on the chin lately.  The days of lengthy coal trains and specific platforms like the SD90MAC are gone, sadly.
 

Offline Stonent

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Re: I think I smell something.
« Reply #18 on: May 03, 2016, 08:54:19 am »
Diesel trains tow batteries.  The engines are always running when the batteries need to charge but the motive force is electric motors.  To add more capacity, they just add more battery cars and more engines.
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Online rx8pilot

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Re: I think I smell something.
« Reply #19 on: May 03, 2016, 03:04:23 pm »
86% efficiency end-to-end is HILARIOUS. No way. No way in hell. Not even close. This should be on KickStarter.

I hope they make me eat my words (I will gladly).
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Offline hayatepilot

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Re: I think I smell something.
« Reply #20 on: May 03, 2016, 03:44:44 pm »
If we can achieve 80% efficiency (end-to-end) with pumped hydroelectric storage then I think the claimed 86% of the train storage is certainly not impossible. :-/O

The train rails have less friction than the long water pipes and a geartrain has also less losses than a pump. Not by much but they can certainly make that 6% difference.
« Last Edit: May 03, 2016, 03:46:55 pm by hayatepilot »
 

Offline NANDBlog

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Re: I think I smell something.
« Reply #21 on: May 03, 2016, 11:41:41 pm »
"A body of 1000 kg is elevated 10 m. The change in potential energy can be calculated as 0.027 kWh"

"That project, called ARES Nevada, will consist in a 5.5-mile track traveling up an 8-degree slope, covering 106 acres of public land near the delightfully named town of Pahrump, Nevada. It will boast 50 MW of power capacity and be capable of producing 12.5 MWh of energy. The company expects to start construction early next year and finish by 2019."

So that is about 1 KM height. The weight must be 4600 tons. Also, trains dont like going uphill.


Pardon the bad math in the video, it is still true.
Sooo, it doesnt scale. Also, compare the mass of some stone to the massive amount of water in a dam.

Also, might as well lift the weight with a cable. Take an abandoned underground oil well, make a continuous cable attach the stones, make automatic stone attachment detachment and done.
« Last Edit: May 04, 2016, 12:21:31 am by NANDBlog »
 

Offline CatalinaWOW

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Re: I think I smell something.
« Reply #22 on: May 04, 2016, 12:15:11 am »
Dinorwig pumped storage hydro plant stores approximately 9 GWh in a similar land area with efficiency of 75%.  ARES Nevada uses 106 Acres of land for 12.5 MWh with claimed 86% efficiency.  Marchlyn Mawr reservoir (Dinorwig upper) is approx 50 acres area.  Add another the same size as a lower reservoir, and the rest for the turbine and generator halls etc, and the area will be very similar.    Over 700 times the storage capacity in a similar footprint, with a height differential of 500m - that's practical to install anywhere you've got a really deep open cast mine that's no longer economic or is abandoned.   Remediate the Berkeley Pit superfund site and you could put a 20GWh storage plant in it! 

The efficiency could be improved with shorter larger penstocks and tail races  + separating the pumps and turbines so each can be designed for maximum efficiency.

All of which is true, and works as described anyplace you have ample supplies of water and appropriate elevation differences.  Where you can afford the evaporative losses from yet another large reservoir.  Which is not anywhere in the American Southwest.  A later post raises issues with the vertical rise described finding 1 km implausible.  True that it is implausible in many parts of the world, and many parts of the US.  But not at all implausible in the American Southwest.

This solution might make sense in some parts of the world.  Just like wind and solar whose effectiveness varies widely based on local conditions.  Things like the cost of power lines to reach regions where pumped storage does make sense will factor into the decision.  The answer will not lie in the first significant figure of the analysis, and will probably come down to single digits in the second significant figure.  Which will probably not exceed the error limits in the analysis.
 

Offline Delta

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Re: I think I smell something.
« Reply #23 on: May 04, 2016, 12:31:24 am »
If they have got an electric locomotive system with 93% efficiency (93% of the electrical energy fed into the overhead lines or third rail is used to move the mass of the train) then they should be contacting train operating companies and getting rich, not messing around with energy storage!
 

Offline jolshefsky

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Re: I think I smell something.
« Reply #24 on: May 04, 2016, 12:40:24 am »
To be fair, this project is at least founded in real physics that can be measured. The key part that I appreciate is that it can be scaled up to sizes that are practical at costs that are, well, high, but not insane. Batteries, no matter what kind you use, just aren't practical that way, and at some point will need to be wholly replaced. Rail cars, electric drive motors, and generators can all last for many decades with decent maintenance—and unlike batteries, their lifespan can be extended nearly indefinitely with good maintenance.
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