Rooftop solar throws massive curve ball to world’s most isolated grid

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The growth of rooftop solar in W.A. means the world’s biggest isolated grid could be a blueprint for the planning of a distributed energy system.

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The main grid in Western Australia, known as the South West Interconnected System, is possibly the most isolated grid of its size in the world, and it’s being watched with keen interest – along with Hawaii, Ireland and California – on how it deals with the shift to renewables.

The SWIS is at the pointy end for these transformations, not necessarily due to a huge uptake in large-scale renewables – although that is growing – but for the accelerating switch by households and business to rooftop solar, which now totals more than 1,100MW and which collectively has already become by far the largest generator on the grid.

For the last few years, the influx of rooftop solar has been mostly a positive.

As the latest 10-year grid outlook – known as the Electricity Statement of Opportunities, and published earlier this month – identifies, rooftop solar has helped lower average peak demand (usually around 3,700MW, but significantly lower), and has pushed the peak from the early to mid afternoon into the early evening.

It has also cut operational consumption, so much so that average demand is predicted to fall at an average rate of 0.4 per cent over the next 10 years, compared to 0.9 per cent growth previously, and consumption per capita is falling by a stunning annual rate of 3.6 per cent.

But the good news may stop soon. AEMO predicts that rooftop solar is tipped more than double again over the next 10 years to around 2,500MW, and could even triple to around 3,500MW. Most analysts and observers – noting the current rates of installation – favour the latter prediction.

There is a simple reason for this: electricity prices are high in W.A. and not likely to come down anytime soon. And the state has a lot of sun, and solar offers a way for consumers, big and small, to slash bills.

AEMO’s general manager in W.A., Cameron Parrotte, describes what is happening in the state as a “paradigm shift,” causing authorities to rethink the way they manage the grid.

More immediately, AEMO and the local grid owner Western Power are concerned that, sometime over the next few years, the growing amount of rooftop solar will force operational demand below 700MW – which is being drawn as some sort of Maginot Line across the SWIS, below which it says it cannot guarantee system security if there are not enough synchronous generators in operation.

And what to do about this has become a big debate in W.A. There appears to be no question about slowing down the uptake of rooftop solar, and nor should there be.

But there is a divergence of views of about what should be done, and there are numerous studies underway to consider the options.

These include a distributed energy plan (that includes rooftop solar, battery storage, demand management, and electric vehicles), and there is a “whole of system” plan, which is broadly comparable to the Integrated System Plan in the eastern states combined with a re-think of the market rules and operation of the type being considered by the Energy Security Board for the NEM.

AEMO has already indicated what’s at stake if the regulations don’t keep up with the pace of transition, including the security of the grid, the number of pricing events going negative, and even the “house full” sign being erected for new projects.

Hence the sense of urgency. The options are numerous, but the final solution will be guided by politics as much as technology. Coal, for instance, and managing the exit of ageing generators at Muja, for instance, is such a sensitive issue that plans to put up a solar farm in the coal town of Collie were canned, and a bike track proposed in its place, so as not to offend the locals.

Some grid-scale options may be to introduce synchronous condensers where some of the coal generators are now, to ensure the system strength that taxes the concerns at AEMO.

A greater focus on demand management is another option, as is added storage (both battery and pumped hydro), continuing the success of “community-scale” batteries, or even seasonal controls over rooftop solar (such as limiting exports at those times when that 700MW threshold is reached).

This graph below indicates some of the scenarios being considered by AEMO, and how quickly they may appear, and the impact on rooftop solar disconnections should the issue not be addressed.

The longer term plan probably involves a complete re-think about the way the grid is managed and the market designed. There are reviews over grid access, the nature of the capacity market (which now excludes demand management and heavily underwrites coal, and appears to ignore flexibility), and attempts to put together a long-term plan that can manage the transition.

In the meantime, AEMO is dealing with increasingly difficult ramp rates, and warning of “cascading failures” if nothing is done, more negative pricing periods, and the need to impose the sort of directions that have been seen only in the South Australia market.

It is looking at ways to gain more visibility, and some control, over the rooftop solar. This could come through even higher, and more stringently enforced, inverter standards, or it could come through what is being called “orchestration”, which may mean the ability to curtail, or store, rooftop solar out when grid demand approaches that Maginot Line.

But who should do this, and how? And what happens to the data accumulated by the introduction of new smart inverters, is up for debate, as it is in the eastern states.

  • On the large-scale front, things are looking better. After a three-year investment drought happily enforced by the previous conservative government, large-scale wind and solar projects are being built apace.
  • Recent additions total 400MW, and additional renewable generation capacity totalling 515MW is expected to connect by October 2020, including Yandin Wind Farm (214 MW), the Warradarge Wind Farm (184 MW), the Merredin Solar Farm (100 MW) and a solar upgrade (17.5 MW) to the Badgingarra Wind Farm.

But it appears to be the rooftop solar – and anticipated growth rates of 7.3 per cent and 13.7 per cent respectively – that bothers AEMO the most. It says that levels of 65 per cent non synchronous generation levels could occur by 2024, ranking with the highest in the world that has occurred in Ireland and Northern Ireland.

(It should be noted that this level was reached in Ireland last year, and the Irish grid operator was immediately looking at the next level, of 75 per cent.)

  • One idea being suggested to address the “duck curve” and protect that 700MW line is using various forms of storage, but not just batteries in households and community level, such as the one at Meadow Springs, but also hot water systems.

The irony here is that W.A. has very little in the way of electric hot water systems, firstly because it was one of the first to adopt solar hot waters, and then because the discovery of the massive north-west gas shelf reserve inspired the government to support the uptake of gas heaters.

Now the thinking is that W.A. should think about electrifying its hot water, both to use as a form of storage by re-directing the output of solar PV, and because it will be the cheapest avenue to decarbonising more than just the electricity grid.

  • Electric vehicles could also be a focus, although while the forecast uptake is around 49 per cent, it is from a very low base and EVs are only forecast to contribute 150GWh, less than one per cent, to operational consumption by 2028-29.
  • However, if the uptake of EVs follows the high scenario mapped out by CSIRO, and trebles to 120,000 in a decade rather than 40,000, then EVs will be soaking up around 500GWh from the grid each year, which may be something to play with.
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