Ruminating on and idea about power generation on trains
There are thousands of trains criss-crossing the country daily, most of them freight carrying with many times over a hundred cars between engines. All of those cargo cars have at least 4 axles and 8 wheels each. My thoughts are regarding the potential to use the solid axle of the train as the spinning part of a power generator. I am thinking of the way a generator is designed by having a spinning shaft inside a stator. So the idea is to turn the axle into the rotor and mounting a stator closely around the axle. Then when the axle is spinning it will generate power with little detriment to the engine's performance.
I have found a few things in my searches for any developments along this line but only found a single patent so far for an axle end design.
Railroad car with axle-mounted electrical generator
This would be mounted to the outside of the wheels where I would like to use the inside of the wheels and axle shafts.
It really seems like there is a gargantuan amount of potential power generation just going to waste as these trains roll the tracks. There is regenerative breaking on subway cars but they are stopping and going constantly which would give more credence to the braking generators working well in that situation. But when the freight trains are plugging along for hours in the middle of the plains states for instance, they should be producing power with some of the movement.
Why would this not work?
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The problem with that is the power input from the locomotive would usually far exceed the gains from the axle generators. That said, there may be room for additional regenerative breaking beyond that of the locomotive itself when descending mountain grades. But that also requires a storage method, and batteries are heavy.
An idea that may uave more meritnis using the flexing rails as the cars pass over them to generate power. I don't know whatbthe cost/benefit analysis would be, but that is a potential source of energy that adds no burden to the transportation system.
Would essentially just be replacing ties with ones that are generators. It would probably be a bit tricky to build something that could withstand the stress and not need a ton of maintenance.
Maybe something like a flywheel in a tie shaped container that is spun with every flex of the rail, spinning it up so that it is able to produce power a while after the train has passed until it's momentum runs out and it waits for the next train to spin it up. It would not be a constant supply to a network unless there was a constant run of the ties.
But that would be interesting to have since a train traveling across country would help put power into the local grid as it moves.
There are also materials that generate an electrical charge when flexed. I heard there were experiments a while back, but I suspect the cost was prohibitive or distribution back into the grid was a pain.
Piezo. The flex of a crystal makes an electrical charge. It just doesn't make a lot of power.
I am running down the line of the fly wheel in my head though. Since most times the engines are in the lead on the freight trains there is a large weight but I am not sure if that out weighs a fully loaded cargo car. But that heavy weight at the start of a strain with 100 cars and 4 engines would be able to start a fly wheel moving. Then there would be a total of 432 axles adding speed to the fly wheel which would then be able to spin. With the width of a track there could even be 4 or 6 fly wheels all powered through gears or fluid.
Hmm... a hydraulic system... That could provide a means of reducing maintenance.
I keep coming back to fly wheels because they are essentially a battery in themselves as long as they have rotational momentum. Since the tie would be solidly on the ground it would be able to handle the spin of the fly wheel inside. Plus having fly wheels rotate opposite directions could counteract the croc roll effect.
hmmm....
Hydraulics are a good option for ease of assembly and maintenance. Perhaps pushing a fluid through a turbine-like device to generate power would be feasible, too.