When I first glanced at this graph I thought little of it; after all, it is about fossil fuel fired power stations and not renewables. But a little more thought shows that it gives us some very important information about the effectiveness of South Australia’s wind farms.
The capacity factor of a power station is the amount of power it generates in terms of what it would generate if it ran at full capacity all the time. So, for example, if a 100MW power station produces an average of 40MW over a year it is said to have a capacity factor of 40 percent.
There are several important pieces of information relevant to renewable energy in this graph.
First: The average capacity factor of Australia’s wind farms is 35 percent. Wind power opponents often criticize wind farms for this, implying that their capacity factors should be much higher if wind farms were of any real value. Note that only three of the thirteen South Australian power stations have a capacity factor greater than the 35 percent achieved by wind farms.
Second, and more importantly: The graph shows that the capacity factor of the coal-fired Playford B power station has declined to zero in the period 2009/10 to 2012/13. (It was the dirtiest power station in Australia in terms of carbon dioxide released per unit of electricity generated and has been ‘put into mothballs’). The graph also shows that the capacity factor of South Australia’s only remaining coal-fired Northern Power Station, the second biggest power station in the state, has declined from more than 90 percent to less than 50 percent in the period 2008/09 to 2012/18. The Northern is expected to only be used for the warmer half of each year before being shut down all together.
Wind farms have, in effect, replaced the dirtiest form of power generation in SA, greatly reducing carbon emissions from power generation as well as the air pollution that causes premature death and serious diseases.
Wind farm opponents have used convoluted arguments to claim that wind farms do not really reduce carbon emissions because coal fired power stations have to be run less efficiently to fill in the gaps when the wind farms are not generating. Plainly this is not so, at least in the case of SA; and if it applies to SA, why should it not also apply to other places?
Wind farms now generate 27 percent of the SA’s electricity (the state is speeding towards being 50 percent renewable). Pre wind farms, SA used to import a substantial amount of power from the eastern states, since the wind farms were built, and in spite of the declining use of coal, SA is now a net exporter of electricity.
More information is available from Ramblings.