A major new study into anticipated wind and solar lulls in Australia’s biggest state grid – the first of its kind – has concluded that they may not be as bad as once thought, but they have every chance of being expensive.
The report by ASL, formerly AEMO Services and a subsidiary of the Australian Energy Market Operator that acts as the consumer trustee in NSW, has been released as part of a series of reports into the state’s energy generation and infrastructure needs.
It includes a call to rapidly increase the number and scale of tenders to ensure enough capacity is built by 2030, and the following five years, to fill in the gap caused by the retirement of all the state’s remaining coal fired power generators, which could happen as early as 2034.
The study – which addresses the old chestnut of what happens when “the wind don’t blow and the sun don’t shine” – looks into the anticipated impact of climate change on wind and solar output, and concludes that solar lulls are likely to be less common and less severe than previously thought, and wind lulls could be little changed.
Wind and solar are characterised as VRE (variable renewable energy), and VRE lulls are described as multi-day events where availability from wind and solar generation across the main grid, known as the National Electricity Market (NWM), is sustained below the fifth percentile of recently observed weather history.
The ASL analysis uses regional climate modelling which reaches out to 2100, calibrated to historical weather data which reaches back to 1979.
“The climate projections include 280 sample weather years for a range of forecast years, comprised of 2 x climate warming scenarios, 7 x global climate models and a 20-year rolling window.
“The results show that throughout the remainder of the century there is: A projected decrease in the average frequency and duration of solar lulls, and no projected change in the average frequency and duration of wind and compound wind and solar lulls.
“Across the next decade, NEM-wide compound wind and solar VRE lulls are projected to have a duration of 4 days (the 1-in-2-year events) to 12 days (the 1-in-50-year events),” the 2025 Infrastructure Investment Objectives report says.
“These are projected to decrease in duration over time as both the climate changes and the diversity of VRE increases.”
The report says that the VRE lull events which are likely to be the most challenging for the electricity system are compound lulls (both wind and solar at low output) when they are widespread across the regions that make up the entire NEM.
“Fortunately, the weather patterns responsible for solar lulls are typically different to those responsible for wind lulls. Still days are typically sunny whilst windy days are typically cloudy,” it says.
“However, there are weather events which can cause widespread compound wind and solar lulls.” And when these occur, modelling shows there will be an increase in NSW wholesale prices and an increased reliance on hydro and gas resources. But it says it results in minimal “unserved energy”, much less than the current standard.
The ASL report says the VRE lulls assessment indicates that the development pathway it has outlined will maintain resilience across the next decade.
Of the 15 cases simulated, the modelled VRE lull led to higher NSW wholesale prices and greater reliance on hydro and gas resources compared to cases with typical weather conditions. “There was a very small amount of NSW unserved energy observed in one case, but at an amount well below the reliability standard,” it says.
