Rooftop Solar in AZ: Actually helping the grid

[J.P.M.]

At least one company wants to use trains on mountains. Trains come with massive motor/generators (a diesel locomotive's traction motors can output ~5 megawatts) and hopper cars full of rocks are as cheap as it gets.

I've seen that idea. Seems like a lot of dedicated rolling stock and track would be required for significant energy storage and reasonably variable e time of use capability, but any scheme would need storage containment so maybe the rail car itself is a moot point. However, part of the problem with elevated rail storage, besides lots of land and right of way issues and maybe a lot of track maint, including possible snow issues at higher elevations for example, is that unless each car's energy is discharged individually, or in groups less than the entire train, regulating the output might get messy, with something that looks like a switch yard at the top/bottom. Elevated storage and variable discharge on conveyors with for example, more vertical drops might be easier to handle and with perhaps less friction losses as the gradient becomes closer to vertical.

[bcroe]

At least one company wants to use trains on mountains. Trains come with massive motor/generators (a diesel locomotive's traction motors can output ~5 megawatts) and hopper cars full of rocks are as cheap as it gets.

5 megawatts (6700 hp) doesn't look like much next to my 2000 megawatt nuke. It would need to be electric
trains to work, not diesel. Bruce Roe

[BackwoodsEE]

1kg of anything lifted 10m has potential energy of 0.028 Wh compare to lead acid battery of 30-40 Wh/kg

Perhaps the solution is to pull several hundred tons of flooded lead acid batteries up and down mountains. Two for one!

[jflorey2]

5 megawatts (6700 hp) doesn't look like much next to my 2000 megawatt nuke.

It looks awesome next to my 2254 megawatt nuke. (Last I heard it was actually using tens of megawatts and generating nothing.)

It would need to be electric trains to work, not diesel. Bruce Roe

Yep. Would probably end up being a fairly standard locomotive (diesel or electric) modified with a new supply connection. Here in the US 25KV 60Hz is pretty common.

[bcroe]

It looks awesome next to my 2254 megawatt nuke. (Last I heard it was actually using tens of megawatts and generating nothing.)

Yep. Would probably end up being a fairly standard locomotive (diesel or electric) modified
with a new supply connection. Here in the US 25KV 60Hz is pretty common.

The Byron nuke down the road (2 towers, etc) has performing nicely for nearly 4 decades.

There is another power conversion problem. A century ago electric trains used DC motors,
with relays swapping in huge resistors for speed control, etc. Supply stations used AC to DC
rotating converters to supply the overhead line, stationed at regular intervals. If they crossed
into a different generating district, there was no sync problem feeding DC from multiple points.
Recently huge Variable Frequency Drives have allowed AC traction motors and much improved
control. But the drives need a DC supply, just what are the overhead lines supplying now? Or
is VFD that just for diesels?

So I doubt the AC traction motors would be suitable for the energy storage project, back to
the DC locomotives. And that output to the overhead would be DC, to be put back on the
PoCo line with something like a grid tie inverter, to track the variations and sync the line.
I'm betting that NOBODY has actually worked out a way to even do the train energy
storage, with any existing hardware. Bruce Roe

[SunEagle]

It looks awesome next to my 2254 megawatt nuke. (Last I heard it was actually using tens of megawatts and generating nothing.)

....

And because of people being fearful of nuclear is why you have a plant absorbing power instead of delivering it.

IMO CA has shot themselves in the foot and do not realize they are bleeding slowly to death.

[jflorey2]

But the drives need a DC supply, just what are the overhead lines supplying now?]

Depends on the system. 25KV 60Hz is common for long distance trains; Amtrak's Northeast corridor uses them. 750VDC is more common for commuter trains like the Long Island Railroad and the MAX in Portland. The Central Link in Seattle uses 1500 VDC.

So I doubt the AC traction motors would be suitable for the energy storage project, back to
the DC locomotives. And that output to the overhead would be DC, to be put back on the
PoCo line with something like a grid tie inverter, to track the variations and sync the line.
I'm betting that NOBODY has actually worked out a way to even do the train energy
storage, with any existing hardware.

Existing hardware does this now - most light rail systems regenerate into the supply line, as do modern electric AC locomotives. What is lacking are the tracks (and catenarys) on hills.

[jflorey2]

And because of people being fearful of nuclear is why you have a plant absorbing power instead of delivering it.

Well, the actual reason we have a plant absorbing power instead of delivering it was that it started leaking (specifically the heat exchanger failed.)

But long term, yes - the main reason people don't want nuclear is fear.

[bcroe]

Depends on the system. 25KV 60Hz is common for long distance trains; Amtrak's Northeast corridor uses them. 750VDC is more common for commuter trains like the Long Island Railroad and the MAX in Portland. The Central Link in Seattle uses 1500 VDC.

Existing hardware does this now - most light rail systems regenerate into the supply line, as do modern electric
AC locomotives. What is lacking are the tracks (and catenarys) on hills.

So light rail has this equipment working well on DC overheads? But "light" probably is the wrong class
for this job. And the AC traction locos have a regenerative braking feature that is working as well? So
with that existing equipment, the next questions might be what is the round trip energy efficiency of such
a system, and can it handle continuous service? thanks, Bruce Roe

[SunEagle]

Well, the actual reason we have a plant absorbing power instead of delivering it was that it started leaking (specifically the heat exchanger failed.)

But long term, yes - the main reason people don't want nuclear is fear.

Too bad that they fear nuclear energy power generation but I guess we all have something to worry about.

I would say that while I don't "fear the dark" I am just concerned of an unexpected loss of power for my critical loads. I have been in the industrial power field for too many years I guess.

[max2k]

...
Existing hardware does this now - most light rail systems regenerate into the supply line, as do modern electric AC locomotives. What is lacking are the tracks (and catenarys) on hills.

no, what is missing is high roundtrip efficiency- I doubt it can break 50% level using 'existing hardware'. Their regeneration abilities are more 'better than nothing' vs > 98%, they were never designed for efficiency. 2 98% processes in sequence give only 96% roundtrip and neither 'existing hardware' engines nor generators are in that range.

[SunEagle]

no, what is missing is high roundtrip efficiency- I doubt it can break 50% level using 'existing hardware'. Their regeneration abilities are more 'better than nothing' vs > 98%, they were never designed for efficiency. 2 98% processes in sequence give only 96% roundtrip and neither 'existing hardware' engines nor generators are in that range.

Converting mechanical or kinetic energy to electrical has never been very efficient.

[max2k]

Converting mechanical or kinetic energy to electrical has never been very efficient.

but the dream was so sweet- green hills with trains quietly (for high efficiency) going up and down up and down

[SunEagle]

but the dream was so sweet- green hills with trains quietly (for high efficiency) going up and down up and down

Hmmm. Why not an elevator to a close orbit station. Think of the distance and amount of energy it can produce on the way down.

[max2k]

Hmmm. Why not an elevator to a close orbit station. Think of the distance and amount of energy it can produce on the way down.

last time I checked there were some 'difficulties' with the ropes- they tend to break under their own weight at those lengths even using latest/greatest/etc .