South Australia grid just one step away from operating with wind and solar only

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In the transition to a world free of fossil fuels, all eyes should be on developments in South Australia, because it is here that skeptics about wind and solar are being defied, and where the local grid is just one step away from being able to operate with no fossil fuels in the system at all.

Last weekend, as reported by RenewEconomy both here and here, South Australia set multiple new records for the share of wind and solar for any gigawatt scale grid in the world.

Wind and solar reached a peak “instant” output of 135 per cent of local demand, and over a 48 hour period grabbed a share of 108 per cent of local demand, and a 100 per cent share over a 93 hour period. The excess supply was mostly exported to Victoria, although small amounts were also stored in batteries.

The new records were facilitated by a new operating protocol that means the Australian Energy Market Operator requires only two gas units to be operating at the time – a total of just 80MW. It means that gas delivered less than five per cent of total generation when there was enough wind and solar to meet demand.

It has been expected that once the new transmission line linking South Australia to NSW – Project EnergyConnect – is built and operating at full capacity in 2025, then South Australia will be able to operate with only wind and solar generation, and no fossil fuels at all at certain times.

But it is now clear, according to a recent AEMO document, that this could happen even earlier than that thanks to new technologies and new ways of thinking about the grid.

“Project EnergyConnect (PEC), a new synchronous connection between South Australia and New South Wales, is expected to remove the need for a minimum level of synchronous generation online in normal system operation, subject to network support and control requirements being met,” the document says.

“AEMO continues to study the capability of the South Australia power system to function with fewer than two synchronous generating units online, prior to PEC operation.”

This is groundbreaking stuff. South Australia already leads the world in the share of wind and solar in its grid – an average of more than 62 per cent over the last 12 months – and the penetration of rooftop solar in particular, which has delivered up to 92 per cent of local demand at times.

Other grid reach 100 per cent renewables, but they do this with more traditional “renewable” technologies such as hydro and geothermal. South Australia has neither geothermal nor hydro, and it closed the last of its coal generators in 2016.

No other grid is this far down the track with just “variable renewable energy”. Critics say that wind and solar can never power a modern economy. But here they are, doing just that.

The state government has set a target of “net 100 per cent renewables” by 2030, and will likely get there much earlier, thanks to the new link to NSW which will encourage more wind and solar to be built.

But the key figure there is “net”. It’s one thing to build enough wind and solar to deliver the equivalent of annual demand over a year, another to be able to operate the system with no fossil fuels at all. It occurs on smaller, mostly off-grid systems, but not at a gigawatt scale grid like South Australia’s.

That’s where AEMO is headed. It warns that it is yet to decide exactly how that will operate, because it has not been done before.

“The operating envelope for the South Australia power system with no synchronous generating units is yet to be determined,” it says,

“Neither AEMO nor any other grid operator has proven whether a gigawatt-scale power system with the configuration of South Australia can be operated with no synchronous generating units.”

It is likely, however, that much will depend on the deployment of grid scale batteries that have what are known as “grid forming inverters”.

It’s complicated technology, but the main difference is that rather than following the signals from the rest of the grid, these inverters have the capability of creating their own lead, and act as “virtual synchronous machines” that replicate the system strength and other grid services delivered by spinning machines.

In South Australia, there are already two big batteries that can operate in this mode – Dalrymple North and the expanded Hornsdale Power Reserve. But their total capacity for these services is relatively small, and may not be enough for AEMO to allow the last gas units to be switched off.

That, however, could change when the new AGL battery at Torrens Island, which at 250MW and 250MWh will be bigger than the combined capacity and storage of Hornsdale and Dalrymple, begins operation by early 2023.

At the moment, the only reason AEMO requires two synchronous gas units operating as a minimum is because one is needed as a backup in case the other fails.

“To cover the credible loss of a unit, a second unit must be online. It is either zero or two,” AEMO says. “One unit may provide the requirements, however AEMO must cover the credible loss of that service and hence a second unit is required.”

AEMO is also making sure that a couple of others issues that have emerged, mostly as a result of the rapid growth in rooftop solar PV, are also dealt with.

These are reactive control, RoCoF (the rate of change of frequency), and ramping support. This is mostly to do with the rapid change in output from rooftop solar, either as the sun goes down or because of cloud cover.

“Will AEMO be looking into operating South Australia with fewer than two synchronous generating units?” AEMO asks itself in the document. “Yes,” it says.

More information is expected to be released in a new document in early December. What is quite clear is that South Australia is at the edge of the innovation envelope and doing things that many thought was not possible. And shining the light towards a totally renewable future.

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