The fact that South Australia’s demand could fall to zero, and even into negative territory, was a possibility predicted by the Australian Energy Market Operator (AEMO), suggesting that it would be the first gigawatt scale grid to do this and said rooftop solar alone could reach zero demand.
Minimum demand is now possibly the biggest challenge for market operators like AEMO, because under current market settings it needs to have a certain amount of synchronous generation to maintain system strength and grid stability.
It does this by running a minimum amount of gas generation, and through the recent commissioning of spinning machines called synchronous condensers that do not burn fuel. It also needs a link to a neighbouring grid, in this case Victoria, so it can export surplus production.
South Australia set a new milestone for negative demand in the local distributed network for the first time in late September, and experienced this on five successive Sundays and once for more than four hours in late October.
This latest milestone is different because it includes the transmission network, which has some big mining and industrial loads, such as BHP’s huge Olympic Dam operation, that are connected directly into the transmission network operated by .
Sunday’s milestones were just the latest in a series of benchmark achievements for South Australia, which already leads the world in the percentage of wind and solar in its grid.
Wind and solar accounted for more than 62 per cent of local demand in the last 12 months, despite occasionally heavy curtailment because of the limits of a grid with a connection only to Victoria.
The state government has a target of net 100 per cent renewables by 2030, but should reach that milestone well before then, particularly after a new link to NSW is completed in 2025.
AEMO has introduced a range of new measures to cope with the growing share of rooftop solar PV, which is expected to double in size over the next 10 years.
It has introduced a “solar switch-off” mechanism, which it has deployed once so far, but is also looking at smarter and more sophisticated solutions such as creating load through dynamic response of battery storage and appliances to help soak up the excess solar.
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