Study Reveals Wind and Solar Lulls May Be Manageable Yet Costly
A groundbreaking study examining anticipated wind and solar lulls in Australia’s largest state grid has found that while these events may not be as severe as previously believed, they could still incur significant costs. This report, conducted by ASL, a subsidiary of the Australian Energy Market Operator (AEMO), is part of a broader investigation into the energy generation and infrastructure requirements of New South Wales (NSW).
The findings highlight the urgent need to ramp up the number and scale of tenders to ensure sufficient capacity is established by 2030, particularly to compensate for the impending retirement of the state’s coal-fired power plants, which could occur as soon as 2034.
Understanding Wind and Solar Lulls
The study tackles the long-standing question of what happens when “the wind doesn’t blow and the sun doesn’t shine.” It assesses the potential effects of climate change on wind and solar energy output, concluding that solar lulls are expected to be less frequent and less intense than earlier predictions, while wind lulls may remain largely unchanged.
Variable renewable energy (VRE) is the term used to describe wind and solar power, with VRE lulls defined as prolonged periods where generation from these sources across the National Electricity Market (NEM) falls below the fifth percentile of historical weather data. The ASL analysis employs regional climate modelling extending to 2100, calibrated against weather data dating back to 1979.
Climate Projections and Future Expectations
The climate projections encompass 280 sample weather years across various forecast periods, incorporating two climate warming scenarios and seven global climate models. The results indicate a projected decline in the average frequency and duration of solar lulls, while the frequency and duration of wind and combined wind-solar lulls are expected to remain stable.
Over the next decade, the report anticipates that compound wind and solar VRE lulls will last between four days (for 1-in-2-year events) and twelve days (for 1-in-50-year events). However, these durations are expected to decrease over time as climate conditions evolve and the diversity of VRE sources expands.
Challenges and Resilience in the Electricity System
The report identifies that the most challenging VRE lull events for the electricity system are those that involve both wind and solar output being low across the entire NEM. Fortunately, the weather patterns that lead to solar lulls typically differ from those causing wind lulls; still, sunny days often coincide with low wind conditions, while windy days are generally overcast.
Nevertheless, certain weather events can trigger widespread compound wind and solar lulls. Modelling suggests that during such occurrences, there will be an uptick in wholesale prices in NSW and a greater dependence on hydro and gas resources. However, the report notes that this situation would result in minimal “unserved energy,” significantly below the current reliability standards.
The ASL report concludes that the outlined development pathway will ensure resilience in the electricity system over the next decade. In simulations of 15 different scenarios, the modelled VRE lulls resulted in increased wholesale prices and a heightened reliance on hydro and gas resources compared to typical weather conditions. Notably, only a negligible amount of unserved energy was recorded in one scenario, remaining well within acceptable limits.
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