If solar thermal ever works this will be the case, but with solar photovoltaic cells and batteries it cannot be done in quantities large enough to power trains.
How many battery packs have you come across which can put out an average of 6 megawatts (with a peak capacity of over 9MW) for over 12 hours at a time? That (plus extra to account for transmission losses) is what is needed to power one regular freight train across the Trans-Australia Railway, but at this moment in the night there are 12 freight trains between Port Augusta and Kalgoorlie, all of them close to 1800 metres long and most of them being in that 1690km segment for the whole night.
Large battery storage can be done (flow batteries, etc) but it isn't the most economic solution to what is a complex problem. There are various other solutions for national networks which are often cheaper including:
- fast start backup/standby generators (networks need these anyway)
- dynamic demand management of industrial consumption.
- aggregation of energy sources.
- pumped storage hydro/tidal
-aggregate supply from mix of sources, long periods of low irradiance generally coincide with higher windspeeds.
Australia also has a good wind energy resource along the south coast, and density of population looks to be coastal focused so there should be potential for wave and tidal energy also.
Signals, communication nodes and point machines in remote areas with appropriate local climate conditions are already solar/battery powered here, and they work quite well. But that's because the power demanded is in the order of a hundred watts, not up to ten megawatts.
There are lots of homes and businesses that have solar photovoltaic cells on the roof, but they don't actually reduce the need for other power stations as they aren't of much use when the peak electricity demand is typically in the evening.
not quite true, every Wh generated by solar or wind is a Wh which doesn't need to be generated by thermal plants, the interaction is usually by frequency control. Law of conservation of energy.
The electrified railways in all five mainland capital cities do already benefit from solar power - by way of the PV cells on building roofs feeding power not used by that building back into the electric grid, which in turn powers (among other stuff) electric trains.
As great as our climate may be for them, PV cells are not sustainable. Solar thermal (if it ever works on a large scale) might be, but with our plentiful uranium supply nuclear is more likely as a long-term solution. If the other infrastructure issues (e.g. double-stacked containers, wind conditions, maintenance) get sorted out, with nuclear power we could quite happily put up with the transmission losses of electrifying the Trans-Australia Railway in the event of the oil supply drying up.
PV cells are sustainable, the energy used in manufacture is recouped in a matter of years for a sensibly designed system. Uranium is not sustainable, there are finite reserves which would soon deplete if developed countries continue building more nuclear generators.
Do you have a respository for nuclear waste? that seems to be the elephant in the room in many places using nuclear (eg the UK).
