AEMO hints at “staged transition” as it seeks to define limits of wind and solar

The Australian Energy Market Operator has hinted at a “staged transition” to a grid dominated by renewable energy, and suggested it would take a “precautionary” approach is it seeks to understand the upper limits of wind and solar.

In a new report released on Tuesday, “Maintaining power system security with high penetrations of wind and solar generation”, AEMO highlights where Australia is either leading the world, or is near the front, in the transition to a renewables-dominated grid.

The criteria are many, but three main areas are cited – the amount of variable wind and solar in the South Australia grid, the amount of distributed solar on household and business rooftops across the country, and the amount of new wind and solar generation being installed in weaker parts of Australia’s “skinny” grid.

AEMO seems proud that Australia is leading the world in many aspects of the energy transition, and knows that the eyes of the global energy industry are upon it.

“Australia is achieving these very high levels while at the forefront of connecting wind and solar generation in areas with low system strength,” it says.

But the view from the front, or the top, can sometimes appear vertiginous, and its biggest fear is that the system itself, dealing with issues such as frequency control, inertia, and system strength, may also get a sense of vertigo and begin to wobble.

“Australia can learn from the staged transition Ireland has taken to relax power system limits, particularly in areas where Australia is leading the world, such as low system strength,” the report concludes.

“This could include taking a precautionary approach (such as holding extra reserves as insurance) for a period (for example, one year) while the system is operated closer to its limits (for example, with fewer synchronous generators online) to build experience and confidence, before accepting those conditions as a new norm.”

The report is part of a new AEMO project called the Renewable Integration Study, which in turn is part of its Integrated System Plan that is being updated and will consider the infrastructure (storage and transmission) and market rules required for five different scenarios for the clean energy transition, from slow to “step change’, with business as usual and consumer and technology led transition scenarios in between.

AEMO says the RIS will focus on quantifying the technical limits of the NEM for a projected generation mix and network configuration in 2025, and will also identify any “ultimate theoretical limits on renewable penetration levels” in the NEM.

It seems unlikely that AEMO will impose any arbitrary limits, and will ignore the doubters’ claims that the country is already near its limit of wind and solar. But it will identify what tools it will need to manage such a high renewables system and the technology options and market signals it needs to get there.

On a broader level, managing high levels of renewables requires sufficient flexibility in dispatchable generation, including storage and demand management, adequate network infrastructure, and renewable energy zones. But it also needs different technologies and management protocols for issues such as ramping, inertia and system strength.

There is no doubt that the new technologies will work, the biggest debate is how the transition is managed and how the old technologies cope with new systems and new ways of doing things. There is a huge debate in energy circles about what is required and when.

But the buck stops with AEMO and it clearly doesn’t think it has all the necessary tools at its disposal right now, and hence its interest into what is happening overseas and what actions its international peers are taking.

The reference to Ireland is interesting because at various points it has set limits for the ratio of wind power and imports to total generation, starting at 50 per cent in 2010, to 65 per cent now and to 75 per cent from next year.

And where once Eirgrid deemed that going above 75 per cent wind penetration was not possible, it now accepts that it is and aims to relax the restriction further over the next decade.

AEMO has so far avoided such arbitrary limits, although it has imposed a complex series of requirements that effectively puts in a limit of around 75 per cent in South Australia, depending on which wind farms and gas plants are operating and available, and where.

It has gradually relaxed these constraints, and from next year, it will have little need to “intervene” in the market at all, because newly installed “synchronous condensers” will provide system strength and reduce the need to have gas generators do that job by burning fuel.

(The report notes that the amount of “directions” has already reduced significantly, falling to around 12 per cent after reaching a high of more than 40 per cent earlier last year that was caused by repairs to the biggest gas generator in the state, Pelican Point).

AEMO has also intervened heavily in the Victoria market, where concerns about system strength in a weak part of the grid in the state’s north west led it to reducing the allowed output from four of the state’s five big solar farms by 50 per cent. The Broken Hill solar farm in NSW was similarly affected.

AEMO hints that it will be cautious in its approach because “the velocity of … change means there is less time to understand and mitigate” new risks. This seems to apply to the use of synchronous condensers – and additional flywheels to deal with inertia – and relaxing localised constraints.

“Australia can learn from the staged transition Ireland has taken to relax power system limits, particularly in areas where Australia is leading the world, such as low system strength,” it says.

“This could include taking a precautionary approach (such as holding extra reserves as insurance) for a period (for example, one year) while the system is operated closer to its limits (for example, with fewer synchronous generators online) to build experience and confidence, before accepting those conditions as a new norm.”

AEMO is also concerned about the amount of rooftop solar and other technologies it groups together as “distributed energy”, and the fact that is has little visibility and even less control over these systems.

On Monday it noted that operational grid demand had fallen to a new low in South Australia, largely due to rooftop solar. See Rooftop solar pushes South Australia grid demand to new record low.

AEMO suggests it’s lack of control over rooftop solar must change. it points to the experience in Germany and Italy, which have “telemetry” over 70 per cent of their commercial rooftop solar systems, and to Germany, Japan and Hawaii, which at least have some form of feed-in management control over a large fleet of households solar systems at leat for isolated emergency situations.

It notes many of these countries have adopted higher inverter standards with improved functionality, and AEMO makes it clear it is looking to introduce similar requirements in Australia.

Finally, AEMO unveils a detailed work program, which includes initiatives such as requiring all generators to be able to provide primary frequency response, the introduction of an inertia requirement, and the management of ramping, voltage, system strength and power fault recovery.

For DER, it’s looking at enhanced inverter standards, more active management of rooftop solar and storage (via Virtual power plants, for instance, or “remote communications”), as well as the design of a “staged approach” for the exit of synchronous generation.