Fossil gas pared back to its bare bones in South Australia’s renewables grid

The South Australian grid has witnessed yet another step change in its world-leading transition to 100 per cent renewables, with the market operator dialling the output of the state’s gas generators down to unprecedented low levels.

South Australia often runs at more than 100 per cent renewables, with the excess supply sent to Victoria and, in smaller amounts, stored in one of the state’s three big batteries or the thousands of household batteries.

Some gas generation – even when there is enough wind and solar generation to meet all local demand – is usually required to provide “synchronous generation” considered essential to maintain system strength and keep the grid in a secure state. (South Australia has no coal, and no pumped hydro).

But the amount of gas needed for this task is shrinking rapidly. Until recently, a minimum of 240MW was considered essential for the task, but the installation of spinning machines known as synchronous condensers, and which do not burn fuel, has meant less gas generation is needed.

As we reported last week, the minimum gas output at times of high renewables was halved to around 120MW as the syncons came on line, and now it has fallen again – to around 80MW, meaning fossil fuels were accounting at times for less than five per cent of total generation in the state.

See: South Australia takes another big leap towards 100 per cent wind and solar

As this next graph shows, South Australia started running at the new low for fossil gas at 8pm (AEST) on Thursday night, and was still operating in that mode until after 1030 AEST on Friday.

Only two units at the Torrens B gas generator were operating (at about 40MW each), and gas accounted for less than five per cent of total demand over the 24 hour period. Wind and solar accounted for 112 per cent of local demand, with the rest stored or exported.

As energy expert Craig Fryer noted in a Facebook post, South Australia now has four syncons and two grid scale batteries (Dalrymple North and Hornsdale) that can provide system inertia and grid stability.

“While synchronous condensers provide a form of short term spinning inertia like a traditional generator, they don’t burn fossil fuels to provide this service. They obtain their required energy from the grid, which is normally going to be renewable energy,” he writes.

“The development of grid forming inverters to provide synthetic inertia means that grid inertia and stability services can be provided by grid scale batteries, wind and solar farms.

“To date AEMO has only approved grid scale batteries with grid forming inverters to provide synthetic inertia, but in time this service should be able to be provided by wind and solar farms. This means there is no longer the need to keep burning fossil fuels just to provide grid inertia and stability.”

AEMO has yet not stated what the next stepping point will be in the phasing out of fossil gas based generation for grid inertia and stability services in South Australia.

But, as RenewEconomy reported exclusively earlier this week, a new $100 million funding round from the Australian Renewable Energy Agency will encourage more grid forming inverters to come into the market at scale to demonstrate what they can do.

See: New ARENA funding round to help plug one of last gaps to 100 pct renewables grid

And as Fryer notes, the lowering of the minimum requirement of fossil gas based generation in South Australia from 240MW to 80MW will have a significant impact on the level of fossil fuel used for electricity generation in South Australia.

Over the last 12 months South Australia has obtained 62% of its electricity needs from renewable sources including wind and solar farms plus rooftop solar.

But in the last month that share of renewables has jumped to nearly 80 per cent. And in the last 24 hours, the average share of wind and solar in the South Australia grid was more than 112 per cent of local demand, with the rest being exported, along with a soupçon of gas.