Much of the discussion about the performance of wind energy during the recent heatwave over South Australia and Victoria misunderstood what happened.
First, the facts.
One of the four large 550 megawatt units at coal-fired Loy Yang A failed unexpectedly on Tuesday afternoon. It was out of action for all of Wednesday and didn’t return until Thursday morning.
As the grid is designed to do, other plants were ready to fill this gap immediately and did so.
We’ve all heard the myth that wind farms need extra backup in the system. In fact, the grid has massive amounts of backup power continually on standby for emergency breakdowns just like this one at coal and gas-fired stations.
The South Australian grid has not needed any extra backup, even with wind power supplying 25% of total demand.
There was a lull in wind on Wednesday afternoon, which by contrast with the Loy Yang outage, was accurately forecast over 24 hours earlier and replacement generation was scheduled accordingly.
By Thursday and Friday the wind was blowing again, with wind producing 22% and 25% of South Australia’s energy on those days. This reduced the need to run super-expensive gas-fired peaking plants and the wholesale price of electricity came down dramatically.
On Wednesday in Victoria, with the Loy Yang unit completely out and only a small amount of wind power, the average wholesale price was a whopping $497/MWh. On Thursday with more wind power and Loy Yang back it was $195/MWh. On Friday, with more wind power again, the price was down to $109/MWh.
When the wind is blowing, the wholesale price of electricity drops, which feeds through to household power bills. The more wind farms we have operating the greater the drop in wholesale prices.