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Electronics & Test
Energy Storage Could Make Electric Trains More Efficient
7/5/2012

Saft's Max20 lithium-ion energy storage system can push power back into the third rail when system voltage drops.   (Source: Saft)
Saft's Max20 lithium-ion energy storage system can push power back into the third rail when system voltage drops.
(Source: Saft)

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tekochip
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Platinum
Re: Energy storage and energy recovery
tekochip   7/6/2012 2:05:42 PM
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The real beauty to this system would be pushing the energy back into the grid rather than having to carry the heavy storage media on the train.

herbissimus
User Rank
Silver
Re: Energy storage and energy recovery
herbissimus   7/6/2012 1:59:15 PM
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i worked in an open pit copper mine and the trucks we used had a gross wt 0f 300 tons loaded uphill and 150 tons empty yet their diesel-electric system included 100% retarding i.e. electric to resistance braking which was effective up to 40mph downhill to a 2-5mph stop. then you'd use the hydraulic brake. pretty cool eh ?

herbissimus
User Rank
Silver
Re: Metrics
herbissimus   7/6/2012 1:50:37 PM
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beautiful, jerry ! i love the ge loco part with the molten salt battery. per a previous comment i've heard of stationary batteries deployed in japan, presidio, tx and now philly.

we're on our way !

Rob Spiegel
User Rank
Blogger
Re: High visibility, high utility
Rob Spiegel   7/6/2012 1:23:54 PM
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Good point, Beth. It would be good to know where the funding is coming from and whether there is a reasonable return on investment with this technology.

tluxon
User Rank
Gold
Conservation of Energy ROI
tluxon   7/6/2012 12:38:17 PM
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Wouldn't time be better spent on flywheel energy balancing, which should have far less of an environmental impact?

k4man
User Rank
Iron
This idea has merit
k4man   7/6/2012 10:51:40 AM
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Certainly transit systems, Metro's in particular, are huge power users. The shorter the vehicle headways, the greater the potential benefit & ROI, methinks.  Couple this with more electrically efficient aluminum/stainless steel 3rd rail (compared to the steel rail still in use on many systems) and you could reap some significant benefits.

There may also be an opportunity for this technology with ship-to-shore cranes or intermodal facility cranes where high duty cycle,  repetitive lift & drop motions of heavy containers would make good use of energy storage & retrieval.  Slab handling or ladle cranes in a steel mill may also be good candidates for this technology.

William K.
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Platinum
Energy storage and energy recovery
William K.   7/6/2012 10:27:03 AM
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The amount of energy turned into heat in a standard braking system is very large. Most regenerative systems that store it in batteries are unable to recover very much of it because the battery can only accept so much charge. How much energy? consider that a freight train may spend ten minutes getting up to speed, and yet do a fast stop in thirty seconds or less. Think about a passenger car, possibly ten seconds for zero to sixty MPH, but in a panic stop, sixty to zero in much less time. The limitation is always in the energy conversion process, it appears. Asking an inverter that delivers up to 10KW for an acceleration to convert 50KW back into electrical power is asking for component failure unless the system is built for much more than the driving loads would ever be. 

Forcing power back into the grid is a similar situation, in that each element is only sized for driving power peaks which are usually much smaller.

DB_Wilson
User Rank
Gold
Regenerative Braking
DB_Wilson   7/6/2012 10:19:47 AM
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Railroads have used regenerative braking with energy recovery for years.  The Northern Pacific used it going over the Rockies: the downhill train was pushing energy into the overhead wire which was used by a train coming uphill.  The high cost of maintaining the overhead wire was the eventual demise of this operation.  Other locations tried this but found the ROI did not justify the expense.  Currently, I don't recall any major railroads or shortline freight railroads that use electric power as their principle energy source.

In the Northeast, the electric trains are for passenger operations.  These are either 600 Vdc for subways and other third rail operations or about 11,000 Vac, 25 Hz, for the overhead wires.  In the subways, the grades as slight and the trains relatively light.  Trains are frequent.  This may help with using regerative braking with energy recovery.  The problem is that many of the old subway cars are not designed and built to provide regenerative operation.  With the units operating on 25 Hz. power, the trains are more widely distributed.  For these trains, regenerative braking with energy recovery must have either energy storage for the recovered energy or needs the converter stations to be able to change the 25 Hz. energy to 60 Hz.  Most of the electric locomotives use dc motors and do not have inverters for regenerative operation.   The point this leads to is that the locomotives and/or infrastructure will need some substantial modifications to use energy recovery systems.

One last point, many freight railroads do use regenerative braking without energy recovery.  It is dynamic braking where the recovered energy is converted to heat and dissipated into the air.

warren@fourward.com
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Platinum
Energy Storage Could Make Electric Trains More Efficient
warren@fourward.com   7/6/2012 8:11:33 AM
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I have a friend who works with heater strips that place them on rails to keep ice from causing wheels to spin in train stations.  I could see this little bit of accumlated energy created by braking being used to power this system at the stations.  Or maybe use this energy to keep the lights on and heat/AC going in the cars while sitting in train stations rather than using the engine power.  The list goes on and on and the needs are everywhere!

warren@fourward.com
User Rank
Platinum
Re: Energy Storage Could Make Electric Trains More Efficient
warren@fourward.com   7/6/2012 7:57:53 AM
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How about piezoelectric generators under the tracks for when these hugh masses move over them?  It probably doesn't meet the ROI, but like capturing energy from the sun, waves, water, and oil, it starts somewhere!

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