Let's assume a large example: trains weighing in sum 20 000 tons (e.g. 200 freight cars, each weighting 100 tons, probably distributed across a few trains), and an incline with a height difference of 1 km (which is going to be very long to be usable with heavy trains).
that's 20 000 000 kg * 9.81 N/kg * 1 000 m = 196 200 000 000 Nm or 55.4 MWh stored energy (without efficiency factors, so not the usable energy at the end).
In comparison, a stored-hydro plant typically has between 200 MWh to 3 GWh capacity.
Maybe you could stack even more trains on it? But that again adds complexity and costs (more locomotives needed). I'm not convinced it will work out in all that many locations. And how fast can you transfer power in and out, with limited train speeds and overhead wiring?
Stored hydro is simpler and at least just needs space to scale the capacity, so you can make it a lot larger, even if it also only works in selected suitable locations.
(Sorry for editing this so much, should have written it out in a text file beforehand ;))
My understanding of the idea is that they plan to move the weights up the hill by train, but then unload the weight. That way, with just one car, you can move multiple cars' worth of weight up the hill. Now, this bottlenecks you on how quickly you can store/release energy, and you have to store a lot of cargo containers in a possibly small space, but even moving 4+ cars' worth of weight per car brings the total stored energy capacity up to that of a smaller stored-hydro plant. Not to say this is necessarily cheaper than stored hydro, but it at least costs a lot less in terms of excavation.
That is greenwashing taken to anther level. They are not just pretending to be green, they are actually doing harm and wasting money that could be used in better places.
If you read the article you'll notice they refuse to compare to pumped hydro (because if they did people would laugh at them for how expensive they are). They are happy to compare to batteries though, because those are also not a usable way to store energy in bulk.
Sigh. With projects like this is it any wonder people are so skeptical of "green technology"?
There has to be some political reason this is getting built, because there sure isn't an economic or environmental one.
Then rail energy storage only works in areas with railelectric plants.
Pumped hydro works anywhere with a power source and a water source.
Dragging a train uphill for 5 miles to store energy sounds moronic. I bet the losses in this system are absurd. It also creates a 5 mile virtual chasm that's potentially unsafe to across.
Hydro storage works because water is available in huge quantities without much special work, and you don't need any infrastructure except "big hole". Neither of those are true for a train or weights.
