Quick numbers on renewables & nuclear

I'm in favour of Ben Heard's plan to start phasing out the smaller and dirtier power plants in SA with nuclear options while simultaneously building up our renewable energy infrastructure.

I can't really follow all the arguments for/against nuclear and renewable power without some sort of reference to the costs and energy requirements behind them. Since I'm from South Australia, here are some numbers that make sense to me:

The South Australia government has the target for 20% renewable energy by 2010, which is around 2.5 times what we current have.

Were SA to be given a blank cheque to immediately replace its carbon-producing power stations with possible alternatives, it could follow some combination of all the following: (it seems unlikely that renewable energy can provide consistent-enough power)

  • $24B for four nuclear plants
  • $11B for 27 solar plants
  • $8B for forty wind farms

Have I got those numbers even close to right? I'm actually surprised that the solar and wind options even come in at a rough order of magnitude equivalence to nuclear. Solar and wind farms clearly are not 100% operational all of the time, so you'd need many more of them to cope with continuous and transient-spike power requirements. And logistically it is far more difficult to build ~50 wind farms/solar plants than four nuclear plants.

Geothermal power is another base-load energy possibility that I haven't considered above. SA is listed among the suitable regions around the world for large-scale geothermal power, but it's not clear whether it (nor its required infrastructure) can be developed quickly enough and in a large enough scale to be a serious alternative. Current developments in the area indicate ‘hundreds’ of megawatts would be feasible.

Perhaps geothermal is indeed a viable option to take up some of the base-load slack. But otherwise I find it hard to see an alternative to nuclear that can handle our base-load energy requirements.