Give us more load!  Why South Australia is trying to switch off all solar roofs

Give us more load! Why South Australia is trying to switch off all solar roofs

“Give us more burden. And please turn off the solar panels on the roof.”

These aren’t instructions you hear every day, but they were the ‘cri de coeur’ this week for the Australian energy market operator struggling to cope with a South Australian grid isolated from the rest of the market by storms, and one the world’s highest penetration of rooftop solar.

AEMO has ordered local authorities to shut down as much rooftop solar power as possible and encourage as much electricity use as possible as it seeks to generate enough ‘load’ to give it control of a grid feared that it could spiral out of control if hit by another major event.

It’s quite a game changer for the state’s solar budgets.

Just a few weeks ago, SA Power Networks, the owner of the local towers and lines in South Australia, boasted a fantastic new achievement – rooftop solar panels had met all local demand for more than five straight hours in the middle of a sunny Saturday.

It was indeed an important milestone and a sign for the future: this is the state with the largest share of wind and solar of any gigawatt grid in the world – 66 percent of local demand over the last 12 months. And the solar system on the roof is an important part of it.

It’s also a sign that Australia’s grid is rapidly shifting from a centralized, fossil fuel-based system to a renewable and increasingly distributed grid. Consumers are now producers too, and rooftop solar systems are crowding out baseload coal and other fossil fuels from the grid.

This week, however, SAPN has had to temporarily change its tune and has been desperate to shut down as much rooftop solar power as possible by sending signals over Wi-Fi, triggering inverters by increased voltage, and sending public pleas for customers to turn off their rooftop solar panels and turn on everything they can.

What has changed?

When rooftop solar power reached more than 100 per cent of local demand in late October, it was not a problem as South Australia’s electricity grid was connected to Victoria and was able to send excess power to its neighbour.

This meant that there was still enough ‘load’ in the grid and AEMO could use a small amount of gas generation for grid security, relying on having enough legroom and leverage to deal with unexpected events.

Electranet fallen tower
Source: ElectraNet

The storm that swept through South Australia last Saturday afternoon changed all that. It knocked down a transmission tower, triggered a trip in multiple circuits and “disconnected” the state grid from the rest of the national electricity market.

The state is now on its own and large volumes of rooftop solar threaten to become a liability rather than an asset because if rooftop solar can meet all or most of the local demand, AEMO would have little or no leverage make available to do this Another major loss concerns the network.

For this reason, the call “Give Us More Load” was issued by AEMO earlier this week. He urged big energy consumers to turn on as much as possible in the middle of the day and urged SAPN and the state government to shut down small solar farms.

Signals have been sent to all recently installed rooftop solar arrays (approximately 100MW) fitted with new inverters that can be ‘orchestrated’ – or turned off – by remote control. SAPN’s voltage control could have triggered inverters in another hundred thousand or so homes and removed another 300 MW.

On Thursday, which is expected to be mild and sunny – a day when under normal circumstances rooftop solar power could meet almost all domestic needs by lunchtime – the remaining households (with older inverters that cannot be controlled remotely) have been called upon to switch off their solar systems.

They were also asked to turn on other things, anything – pool pumps, vacuums, electric vehicle chargers, anything that could generate new load and give AEMO the leeway to turn on other controllable generators.

Is this all the result of rooftop PV being a bad thing?

Not at all, rooftop solar and other distributed power generation and storage will be a key component of a modern power grid and will also increase reliability, especially when combined with battery storage in local communities.

But it underscores why AEMO is insisting on new inverter standards that allow it to ‘orchestrate’ rooftop solar arrays, turning them into a visible asset that can be controlled, rather than an invisible wild card that can play out its best plans can bring failure. Some are calling for measures to be taken to control older rooftop solar systems installed years ago.

It also underscores the need for more transmission lines, such as those currently under construction between South Australia and NSW, and will allow the state to surpass its unofficial target of 100 per cent (net) renewable energy within the next few years.

And, of course, it underscores the need for more storage to soak up excess solar material, to act as “shock absorbers” to power grid disturbances, and for new large loads like hydrogen electrolysers that can act as large batteries to turn power on and off when needed them off if necessary.

The irony is that if this event happened in the middle of summer, AEMO would be very happy to see the rooftop solar array feeding more power into the grid, and would probably be sending instructions to consumers to reduce the load rather than them to increase.

That’s because – with the heat – the grid would be heavily stressed when air conditioners are on, meaning AEMO would have no problem finding generation assets that it can control and use as leverage when unexpected events occur.

But the staggering growth of rooftop solar means AEMO is likely to worry less about peak demand events than trough demand events when rooftop solar output is absorbing all or most of domestic demand.

Roof solar minimum requirement aemo
Source: AEMO

“Of course, when rooftop solar power generation is high, the need for grid supply becomes extremely low, crowding out grid generators,” writes AEMO in a recent statement on the subject.

“Currently these generators provide a number of essential system services including frequency control, system strength, voltage management, inertia and so on.

“During periods of very low operational demand, these services must be sourced elsewhere, or where this is not possible, AEMO must intervene to keep the network in a safe operational state.”

Over time, battery inverters are expected to provide these essential services, but the technology is still being tested and rolled out. Meanwhile, AEMO is working with several states to offer more flexibility in the management of rooftop solar systems.

Some of the government projects, including those in South Australia and Western Australia, use relatively sophisticated technologies. Less so in Queensland, causing great frustration in the industry.

See our story: “Industry Criticizes Sunshine State’s Antiquated, Brutal Solar Shutdown Plan.”

The problem in South Australia this week is that – given the particular circumstances – not enough solar power could be shut down, forcing AEMO to resort to more brutal methods to protect grid stability and minimize the likelihood of a nationwide blackout.

Its main concern – because the state is isolated – is “trip risk” – meaning if there is another big event that triggers another transmission line or generator, then it could spill over to all the solar inverters it hasn’t been able to check.

That is why she wants to have taxable assets. Contingency plans are in place, but fingers are still crossed.

See also: Western Australia sets a new record for renewable energy at 81% – in the world’s largest island grid

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