if Coal is free then Solar and Wind are also free
The reason I said coal is free is because you and your mates say the wind is free.
Theoretically, SH2 will pump off Renewables and/or excess fossil.
There will never, as long as your aole points to the ground, be excess wind/solar and, until we build a lot more pipelines, nor will there be excess gas so all pumped storage will be reliant on coal.
it's electrical efficiency (estimated) is 75%
Who are you quoting? Vertical tunnels have efficiency of about 80% and Snowy 2 pipes are not vertical.
The comparison should be between the energy generated by burning the Coal and the electricity output at the generator.Not sure what that is, but It's probably below 75%
I think you will find alternators have efficiency >90%. If it were only 75% then pumped storage could not even be 50%
BTW a wind generator will have lower efficiency because they also need rectifiers and inverters and heaters, and oil pumps etc.
