Australia's Grid Navigates Record Demand and "Negative Demand" Peaks
Australia's National Electricity Market (NEM) faced a period of extreme electricity demand during heatwaves in early January, with substantial contributions from wind and solar generation. Concurrently, South Australia set new records for 'negative demand' on Christmas Day and Boxing Day, driven by its high integration of rooftop solar. This unique phenomenon involved exporting excess renewable energy and necessitated specific grid management interventions.
National Electricity Market Demand and Renewable Contributions
From January 7-9, Australia's NEM experienced extreme electricity demand due to widespread heatwaves. During this period, observed peak demands, which factored in demand met by rooftop solar, ranked as the first, fourth, and second highest on record.
Analysis of the ten highest demand days since January 1, 2023, including rooftop photovoltaic (PV) systems, indicates that rooftop solar reduced peak demand levels by an average of 14%.
When considering demand net of both rooftop and utility-scale PV, the average reduction was 17%. For demand net of all PV and wind generation, the average reduction reached 28%.
These trends were broadly observed across most Australian states. Tasmania stood out as an exception, where peak demand typically occurs in winter; solar energy contributed negligibly to peak demand reduction there, though wind power did play a role. Interestingly, excluding rooftop PV from demand calculations sometimes shifted peak demand dates to winter.
South Australia's "Negative Demand" Records
South Australia, renowned for its advanced adoption of renewable energy, established a new 'negative demand' record of minus 263 megawatts (MW) at 1:30 PM on Christmas Day. At this specific time, rooftop solar systems remarkably supplied 117 percent of the underlying grid demand.
The 'negative demand' condition re-emerged on Boxing Day, with rooftop solar providing 110 percent of underlying demand and the minimum grid demand registering negative 165 MW. According to the Australian Energy Market Operator (AEMO), rooftop solar met or exceeded 100 percent of South Australia’s underlying demand in nine half-hour intervals on each of these public holidays, and in a total of 78 half-hour intervals throughout the year.
Currently, South Australia is the sole Australian grid experiencing 'negative demand,' a direct consequence of its high share of rooftop solar. In comparison, Victoria recorded its lowest grid demand at 1,287 MW, while Tasmania registered 720 MW.
Renewable Energy Integration and Grid Management
On average over the past year, wind and solar accounted for nearly 75 percent of South Australia's energy generation. The state aims to achieve 100 percent 'net' renewable energy by the end of the next year.
To effectively manage periods of negative demand, South Australia exports its excess renewable energy to Victoria and New South Wales via interconnections. A minimum of one gas unit, approximately 42 MW, is maintained within the state for essential grid services.
On both Christmas Day and Boxing Day, AEMO issued directives to Neoen’s Blyth battery, the largest battery in the state, to provide minimum system load services. These directives included maintaining synchronization, a pre-agreed minimum state of charge, and adhering to dispatch targets to serve as a backstop for the system. Unlike in Victoria, where battery responses for similar services are voluntary and compensated, AEMO in South Australia issued direct instructions due to an inability to establish a comparable voluntary agreement.
The capacity to export more renewables and reduce curtailment of large-scale solar and wind farms is projected to increase significantly next year. The current export capacity to New South Wales, which stands at 150 MW, is expected to expand to 800 MW upon the completion of upgrades to the New South Wales component of the interconnector.