The small onshore fields of old was meant for small scale demand. These days and to deal with power supply the volumes are huge. For example my employer has 24/7/365 2500MW of combined cycle gas power electrical generation on our site, it needs a 3' diameter high pressure pipe line to feed it. To replace coal in on the eastern grid you need to scale this up around 6-8 times.
Gas is fine, but the amount required is huge and we have enough problems with gas supply without large scale coal replacement to add to the mix until the price and availability issue is resolved.
Solar PV is fine but limited as most useful during daylight hours and mostly midday, costs and efficiency are improving dramatically, but if you have to pay to store the power, you loose 7-10% of the energy and additional costs. Solar PV seems to economical as roof top solar on existing structures where infrastructure is cheap and you can cheaply tap into existing supply. It looses efficiency by not being able to follow the sun. For free standing PV power generation on large scale, they need to have sun trackers to make them cost effective. Issue is to make a decent amount of power, the land required is huge and frequently under estimated to replace a coal fire power station, start with the CBD of Melbourne as an example used recently to replace Liddle.
Wind, pretty much as above, however many farmers enjoy leasing their land and still using the same paddocks for cattle/sheep. The best wind farms in the world only produce 35% of their name plate capacity due to non windy days and low wind days.
For both, hydro is the best large scale battery, but again more cost to the actual generation cost for each.
Ultimately solar thermal, usually coupled to a Gas turbine is the closest we come to providing 24/7/365 supply for RE. Large scale costs are probably still 10-20 years away to be truly competitive and again land required is large and hence away from the east coast and exposed to transmission losses and support services.
So for now, for me, coal should replace coal and we should be building 10GW of generation between now and 2025. When we talk about population we are talking aging coal fired power stations with poor efficiencies, most lucky to be mid 30% range and emissions control not including SO2 removal. The time frames thrown around by the anti-coal voice is excessive, 5+ years for just one turbine to be up and running, no!!! Oh and the other excuse, you get not get finance, doesn't seem to prevent others doing the same!!!
In contract, Dubai is building a 2400MW coal fired power station, using borrowed funds in a PPP, 4 turbines, 45% efficiency, SO2 and NOX emissions very low due to sea water scrubbers. 3.5 years from project kick-off to first turbine pumping into the grid and prices lower than what the bulk energy users in Australia pay and using Australian coal.
Only reason we have this issue is because coal fire power station construction and replacement largely stopped in early 2000's as govt decided to sell their aging plants and private sector upgraded rather than either govt or private sector replace. This drove down the cost of power to below replacement cost for nearly 10 years. Also during this time the govts were funding rollout of PV solar which helped cap the peak.
The fact we are exporting coal and not using ourselves is insulting.
To throw one more into the mix, I have no issue with Nuclear, but we should be building an industry, not a power station. Full lifecycle mine to disposal.