The California energy system – as expected – survived the stunning solar eclipse that traversed the US on Monday, but Australian grid operators are already thinking about how they will manage a similar major eclipse that will cross the Australian continent in just over a decade’s time.
While most Americans were looking to the sky to watch the eclipse, or to the NASA tracking tool, dozens of engineers at the California Independent System Operator (CAISO) were staring at screens in their operations centre in Sacramento, making sure the power stayed on.
The focus was on California because, even though it was not in the path of the total eclipse, it was deemed the most vulnerable, or at least the most interesting, due to its significant share of solar, with 10,000MW of utility-scale solar and another 5,600MW of distributed solar.
Solar can account for up to 40 per cent of demand at any one time.
The state was expecting its solar output to drop by one-half or more as the moon started to move across the sun from around 9am, which is pretty much what it did. “Things went really, really well,” Eric Schmitt, vice president of operations at the CAISO, told the Washington Post.
“If there’s any doubt about how planning pays off, we demonstrated it this morning,” Schmitt told the San Francisco Chronicle. “We didn’t have any major challenges on the system, even minor challenges. We’re very pleased with how smoothly it went.”
The graph above shows the output of solar over the 24 hour period, while the graph below shows demand and net demand, which excludes variable sources such as solar and wind.
The fact that both the German and California grids survived the eclipse without interruption should come as little surprise, given the grid operators knew the exact time of the event well in advance, and could prepare by ensuring stand-by capacity was available, such as pumped hydro and gas-fired generators, and various demand management initiatives were also in place.
The biggest challenge for these grid operators right now is dealing with peak demand in summer, and unexpected outages and system faults. In Australia, the market operator, AEMO, is facing a tough challenge this summer, with the greatest risk coming from failing fossil fuel plants that melt in the heat.
In the peak of the summer heat wave in California in June, 6,400MW of gas capacity was offline due to heat related issues – similar events occurred in Australia last summer, and are seen as the biggest risk factor for the coming summer or two.
The installation of the Tesla big battery, demand management programs in South Australia, Victoria and NSW, and the temporary diesel gen-sets in S.A. are designed to help address that.
Australia’s big day will come on July 22, 2028, when a total eclipse will draw a path from the north-west of WA across the Northern Territory, down through NSW and across Sydney.
Like the US event last night, the path of the total eclipse will be relatively narrow, but impacts of 50 per cent or more will be felt across the continent. The eclipse will begin around 9am in the north-west corner, and will arrive around midday in the eastern capitals, lasting till after 3pm.
And by then, Australia will have significantly more solar than it does now. The amount of rooftop solar may have trebled, given current installation rates, and the amount of large-scale solar will have risen at least 10-fold, possibly more depending on the course of state and federal policies.
In some states, such as South Australia and Western Australia, the amount of rooftop solar capacity, alone, may be the equivalent of minimum demand, and by that time more utility-scale solar will be installed. Depending on the weather that day, there could be significant swings in ramp rates.
California was preparing for ramp rates of twice the normal experience, from its average 29MW a minute to double that and a peak of 98MW a minute.
In the future, when California reaches its 50 per cent renewable energy target by 2030, and its 100 per cent target by 2050, those ramp rates will be even more impressive. Storage, demand management, smart controls, and back-up will play a critical role.
The eclipse “is another in a long list of examples that show that system operators are able to integrate the current level of renewables on the grid without sacrificing reliability,” David M. Hart, a professor and director of the Center for Science, Technology, and Innovation Policy at George Mason University, told the Washington Post.
Eclipses in Chile in 2019 and 2020, and another in the US in 2024, when solar capacity may have doubled, should provide some more information and experience in how to manage the events.