The wind measured by the fleet of windmills had been strong across most the country lately, rising from a low point at 20% of capacity at 9am yesterday to reach 50% at 9 in the evening, peaked near 57% at midnight and stayed over 50% to the present time (12 noon Monday). The stability of the aggregate covers wild fluctuations at many of the windmills, notably Musselroe in NE Tasmania. There are only four windfarms in Tasmania so it is easy to find.
In terms of feeding the grid, the wind provided 22% of the power required at midnight as the demand fell to 20 GW from a peak of 26GW at dinnertime to a low of 18 GW at 4am. That looks exciting for wind fanciers because 22 is a lot compared with zero a decade or so ago, but wait! At midnight while the wind tipped in 4.4GW, coal supplied almost 14 (70% of demand) plus gas 1.1 and Hydro 1.8.
What is more to the point, coal, gas and hydro can all be ramped up on demand, for example when the wind stops, not that it matters if the wind stops at present because we can do without the wind and the solar power as well.
Even more to the point, the chain in the supply of intermittent energy is only as strong as the weakest link – that is the choke point aka the lowest point of supply. Obviously the sun chokes every evening and so the wind has to be there in adequate supply 24 hours a day for 365 days a year (not to mention leap years). Clearly this is not the case if wind is supposed to replace 20GW of coal-fired power but the more immediate test of the wind supply will come with the closure of Liddell that will take the best part of 2GW out of the system. This means that we can build a lot more windmills but the old energy will still be required until we go nuclear.
Mike O’Ceirin has provided a list of the episodes when the wind supply fell to 10% or less of the installed capacity and the duration of those episodes for some recent years (he can do it for every year since 2011). I will report on this in due course but people who have been paying attention will not be surprised to find that the results are not good news for all the taxpayers and power consumers who generously contribute to the wind industry.