What do you think?
Now, I don't want to be negative and I wish them all the very best of luck...BUT I do hope it never rains on that 7.5% gradient track! Things might get VERY interesting.
Ned Ludd writes...
Find a hill, Great dividing range is ideal
I think your train will have problems making it up the hill, especially with a heavy load.
Metros and pure commuter railways often also allow higher gradients, up to 4%, for the same reason. High speed railways commonly allow 2.5% to 4% because the trains must be strong and have many wheels with the power to reach very high speeds. For freight trains, gradients should be as gentle as possible, preferably below 1.5%.
Let's be ambitious and say that you can use a 2% grade. You then are allowed to take your rocks UP 1m for every 500m you travel horizontally. Cunninghams Gap (in QLD) has an elevation of 787m. Ipswich (where a lot of the power generation assests are around) has an elevation of 50m. The difference is then 737m. At a grade of 2% your horizontal track then needs to be 37km long. That's not that long (it's about double that from Ipswich to Cunninghams Gap by road), but it needs to be a steady grade, so what you effectively need to do is build a MASSIVE 37km earthen ramp from Ipswich to the Range. Of course you would try to follow a route that included natural hills and other features that could be included in your slope so their is less work for you to do (but then you introduce curves, which have their own problems). I have no idea how wide a base you need to have on your ramp at the end that is 700m in height. Perhaps it wouldn't be earthen all the way, but I doubt you could build an elevated track on any height that would carry the weight without some massive engineering either.
The amount of energy you can store is also interesting. Moving a 150 tonne car (loaded with rock, steel, whatever) to a height of 737 gives a potential energy of 300kWh. Not sure how many cars you'd need to satisfy peak demands, but I believe it would be in the order of GWh's ? To store 1GWh would then require 3333 cars (that's a fair number, I think you're going to need a big loop at the top).
The other factor is how quickly you can generate the power. If it's a 10MW loco then that's what it will both consume as an instantaneous value when it's going up the hill and also what it will generate coming back down. So if you want to generate 350MW of capacity (the equivalent of one of the coal fired generation units at Tarong) then you would need 35 trains coming down the track at the same time. To give 1GW of capacity you need 100 trains in full flight.
Water is good because you can pump it. It doesn't care if the grade is 90% (almost straight up) as long as your pump is powerful enough. But to use pumped hydro you need a location that has space for a massive reservoir at the top, another at the bottom, a large volume of water that you can replenish (ie. a dam on a river) and also significant height differential between the two of them. This is what we're very short on in Australia (and the world in general).
Living in southern California you might get some of your water through the same type of plant used for the aqueduct.It's similar to existing power storage systems that pump water up to a higher reservoir at night, and then use it for power during the day. There is one in Wales that we always went on school trips to.