The number of interventions by the Australian Energy market Operator in South Australia jumped sharply in the second quarter – mostly because of a large number of gas-fired generators that were not available due to planned and unplanned outages.
AEMO – in its latest Quarterly Energy Dynamics report – says it had to intervene more than 60 per cent of the time in April and May, mostly because gas generators that would normally be on line were absent due to repairs.
This meant that it had to require other gas generators that might otherwise choose to switch off, because of low prices, to stay on line to ensure grid stability.
Since South Australia has exceeded more than 50 per cent renewables in the past year – and is headed to around 75 per cent by 2020/21 – AEMO has devised a couple of dozen different generator combinations that it says are required to ensure system security at times of high wind output.
But the absence for much of the last three months of the state’s biggest combined cycle gas generator – Pelican Point – and repairs to other generators such as Mortlake, severely reduced its options, meaning it had to call on other generators to stay on line when the wind output was high.
This graph above illustrates the number of directions for system strength in the last year (left), and the level of curtailment of “non-synchronous” (read wind energy) over the same period.
“During April and May, directions were in place for 62 per cent and 70 per cent of the time respectively (Figure 3) driven by high wind, lower operational demand and generator outages, including at Pelican Point,” AEMO said.
“Since September last year, there have been directions in South Australia for approximately 26 per cent on the time on average.
The amount of curtailment more than doubled in the last quarter to 4.8 per cent. It said this was driven by high wind conditions and insufficient synchronous generators being available to meet system strength requirements.
AEMO hopes to address these issues through its Integrated System Plan, which includes requiring ElectraNet to install synchronous condensers, a new transmission link to NSW, and the ability to “co-ordinate” distributed generation, which refers to rooftop solar and storage.
This latter part is particularly important, because as the state’s minimum demand falls towards zero – because much of it is being served by rooftop solar – it will have increasing system strength issues. The use of battery storage and increased links could be essential.
South Australia already has the Tesla big battery at Hornsdale, the Dalrymple battery at Wattle Point which is undergoing commissioning, and the new Tesla battery announced for the Lake Bonney wind farm.
Batteries are also planned for the Lincoln Gap wind farm near Port Augusta, for the Whyalla steel works also near Port Augusta, and the Snowtown wind farm, alongside a new solar facility.