Science

The uptake of rooftop solar shows no signs of slowdown – but two states have now legislated to ‘curtail’ this power in order to stabilise the grid, a short-term solution that risks damaging investor and consumer confidence. By Jarni Blakkarly.

Why are state governments curtailing rooftop solar?

A solar panel farm in South Australia, near the Wilpena Pound mountain chain.
A solar panel farm in South Australia, near the Wilpena Pound mountain chain.
Credit: Taras Vyshnya / Alamy

Earlier this month, the Western Australian government gained the power to forcibly switch off or “curtail” household rooftop solar panels in order to protect the grid during times of surging supply in electricity.

The move follows the South Australian government’s example: they gained the power to forcibly curtail rooftop solar in the state last year.

Energy experts say the shift by these states towards mandatory rooftop solar curtailment were necessary, given the risks of excess supply to the grid, but warned that the measures should be a short-term or stopgap fix while other, longer-term solutions are implemented.

“The big end of town – the large generators – are curtailed first, and the fact that we are needing to go to small-scale rooftop solar PV [photovoltaic] curtailment shows that this really is a last resort,” says energy economist Alan Rai of the University of Technology Sydney.

“This issue has been around for a while, it’s just that the solutions have always been put in the too-hard basket in terms of remedies. Is [curtailing] the only solution? No, and I certainly don’t think it’s the best solution either.”

The new WA rules require all new solar or upgraded solar panels to have inverters installed, which will allow authorities to switch off its generation.

WA Energy minister Bill Johnston said the new rules were like using a “scalpel rather than a shotgun”.

Rooftop solar uptake, which many thought would drop off due to the Covid-19 pandemic and related economic challenges, has continued to surge around Australia. Figures from the Clean Energy Regulator show that a record 3000 megawatts of small-scale solar capacity was added to the grid in 2021, up from the previous, record-breaking high in 2020. But with added capacity comes added challenges to the supply network, including what to do during peak times when demand can’t keep up with the huge level of supply.

Australian National University research fellow Lee White says supply in excess of demand can ultimately damage the grid and needs to be managed in some way.

The WA government has stressed that curtailing of household solar will only happen on rare occasions, during emergencies in the grid, and will not be a common occurrence. White believes people will welcome the statements, but the proof will be in monitoring the use of the measure over time.

“The main thing that matters is how it’s implemented, how they’re monitoring and tracking that to ensure that it really is just an emergency measure versus being part of just regular grid planning,” White says, adding that she wouldn’t want curtailment to be “delaying investments that could move towards energy transition”.

“If it’s just an emergency shutoff twice a year, it’s not too bad. But if it becomes something that this is the main way of managing, without also putting in the resources to strengthen the grid long term, then that would be really damaging to clean energy in the long run,” she added.

Human geographer Sophie Adams, of UNSW Sydney, recently conducted focus groups with owners of household rooftop solar panels in and around Adelaide and found most had little to no knowledge or understanding of curtailment.

One of the main downsides of curtailment – along with renewable energy generation capacity simply going to waste – is the damage it does to investor and consumer confidence for those who have already installed a rooftop solar system or who are thinking of investing in one.

“People were quite dismayed to find that this was something that might be affecting them,” she says. “There’s a bit of a sense that people, when they’re putting solar systems on their roofs in Australia, it’s often for financial reasons – they’re looking to reduce their electricity bills, they also think that they’re doing the right thing environmentally.

“People certainly felt a sense that [curtailment] was like a kind of punishment.”

Adams found there was a lack of information among consumers as to when they were being curtailed and how often it might be, leaving them in the dark about their electricity usage and effectively denying them choices about what to do.

She says when the reasons for curtailment were explained to people they were more understanding. But, in general, governments and energy regulators needed to do better in informing people about the issues and reasons why they may be switched off from the grid.

“People who are investing in clean energy want a certain payback,” White says. “They also are clearly wanting to be able to make informed choices and they need that information to be provided to them.”

While rooftop curtailment is a short-term solution, she says, more investment is needed to go into things such as community, medium-scale batteries, which could help the grid cope at peak supply and demand times.

Along with batteries, White says another partial solution is to financially incentivise people to use less power during times of lower generation and more during periods when generation from solar is high.

Rai says while some segments of the Australian retail energy market had peak and off-peak rates for usage, the country was really in its “infancy” when it came to informing and encouraging people towards smart electricity usage in a way that helped stabilise the grid.

He adds that more investment is also needed for upgrading poles and wires to cope with higher voltages of electricity, and that government incentive schemes could be more directed towards batteries – to make them more affordable – instead of towards rooftop solar panels. When the cost of batteries, which continues to fall, reaches widespread affordability, households may be able to solve this problem on their own.

Until then, we need better solutions than just switching off the rooftops.

“Batteries have a huge role to play in this solution,” Rai says. “On a larger scale, but also on the community scale – batteries that are large enough to absorb energy from a handful of houses.”

There’s been investment in a number of “big battery” projects so far in both South Australia and Victoria, but more will be needed to further address long-term grid stability.

Rai says while curtailing is a short-term solution, it shouldn’t become a crutch to avoid more difficult and systemic conversations about broader grid reform.

“Hopefully some good will come of all this, and the issue of curtailments will force us as a society to have a think and invest in ways to better manage the transition to renewables in our grid,” he says. 

This piece was produced in collaboration with cosmosmagazine.com.

This article was first published in the print edition of The Saturday Paper on February 26, 2022 as "Nodes to curtail".

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Jarni Blakkarly is a Melbourne-based journalist who writes for Cosmos.

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