The body that runs WA's main electricity market wants the ability to remotely dump excess solar power from households — cutting the bill rebates people receive — to safeguard the grid from surging levels of renewable energy and avoid rolling power cuts.

Key points: Too much solar power in WA is threatening the stability of the electricity grid

Too much solar power in WA is threatening the stability of the electricity grid The market operator wants the ability to control households' solar power input

The market operator wants the ability to control households' solar power input The alternative is potentially rolling power cuts to avoid the grid overloading

Audrey Zibelman, the chief executive of the Australian Energy Market Operator (AEMO), said so-called smart inverters would be crucial to ensuring the rise of rooftop solar did not overwhelm the stability of the power network.

The call has been backed by the WA Government and Energy Minister Bill Johnston said having a better insight into and control over the output from rooftop solar was vital.

It comes following warnings from AEMO that WA's biggest power system — the wholesale electricity market — risked becoming unstable within a few years because of the runaway take-up of solar panels.

Ms Zibelman said the switch to renewable energy by growing numbers of households and businesses was unlikely to stop and it was incumbent on authorities to ensure the transition was managed carefully.

Almost one in three homes on the south-west grid have solar panels. ( Pixabay: MariaGodfrida )

A key part of this process was smart inverters, which would enable AEMO to "spill" excess power generated from rooftop solar panels at times when the network was coming under stress.

It is understood the devices have been progressively rolled out thanks to an industry agreement in 2017, but Ms Zibelman said their integration should be fast-tracked.

At the moment, households can freely export any surplus power produced from their solar panels into the grid, with state-owned power provider Synergy paying a minimum subsidy of 7.1 cents per unit.

But AEMO has warned such uncontrolled input of solar power placed great stress on the coal- and gas-fired power stations responsible for keeping the grid stable.

Problem arises from solar's success

Ms Zibelman said the arrangement was not a problem back when there were relatively small numbers of solar panels on the system.

But she said it had become a significant liability for the security of the electricity system now that almost one in three homes on WA's south-west grid had solar panels.

There are almost 300,000 households in the network with photovoltaic (PV) cells, which have a combined capacity of more than 1,000 megawatts.

By comparison, the biggest generator on the system is the 854MW Muja coal-fired power station at Collie in the state's South West.

The biggest generator on the system is the Muja coal-fired power station. ( ABC News: Eliza Borrello )

"When you had maybe 1 or 2 per cent of the population putting on rooftop solar, we don't really worry if there are solar units there or not," Ms Zibelman said.

"But when you have as many as we have, we need to be able to see it.

"We need to be able to anticipate how that solar is going to respond, and where it's going to respond, so we can be ready as a real-time system."

When high solar output meets low demand

Central to the technical challenge posed by solar is its effect on demand from the grid during the middle of the day.

These challenges tended to be most acute when high levels of solar output coincided with low levels of demand — typically on mild, sunny days in spring or autumn when people were not using their air conditioners.

In such circumstances, AEMO has warned solar was hollowing out demand from the grid to such an extent that base-load generators such as coal-fired plants were struggling to operate safely.

Experts say it is crucial to ensure rooftop solar does not overwhelm the stability of the electricity network. ( Pexels.com )

Authorities were managing the situation by requiring base-load generators responsible for the stability of the grid to scale back or even switch off production, but AEMO said this was increasingly a risk to the security of the system.

AEMO warned allowing demand from the grid to fall below 700MW could trigger widescale blackouts by 2022.

Rolling power cuts to keep system stable

Alternatively, AEMO warned it may have resort to "load shedding" — or rolling power restrictions across entire areas — to avoid production from solar panels overwhelming the grid.

Ms Zibelman said batteries, including large-scale storage facilities, would help balance the system in the future, but AEMO needed other short-term options at its disposal.

"Our operators need to be able to act and they can't act if they don't know," she said.

"And if we don't know we have to be very conservative, which means we can't take the best advantages [of renewable energy].

"But the good news is when you do that, you're taking full advantage of this free energy coming from the sun and using it to the best advantage of consumers."

Electricity distributor Western Power, the utility that runs the poles and wires, noted "smarter" inverter technology had been the industry standard since 2017 and now accounted for more than 40 per cent of the stock.

Under the standard, the inverters are required to automatically disconnect when there is a fault on the grid, and reduce output when the grid becomes unstable or when voltage rises occur.

They also have to help with a household's voltage control.

Rolling power restrictions would be the most drastic option if the grid can't be controlled. ( ABC News: James Carmody )

A Western Power spokesman said although the utility did not have the capacity to control the individual or collective energy produced by solar panels, balancing supply and demand was done at a "whole of system level".

The state-owned group would not be drawn on what it thought was a safe demand floor, but it is believed Western Power takes a less conservative approach than AEMO.

"We have always had strategies in place to manage the high and low extremes of demand on the grid throughout the day to avoid any impact on the customer's energy lifestyle," the spokesman said.

"While the grid was not originally envisaged to support two-way power flow, Western Power has been managing the new opportunities and challenges that residential rooftop solar generation has created over the last decade."

Clean Energy Council supports move

Darren Gladman, the Clean Energy Council's distributed energy director, fully backed AEMO's push, saying the difficulties posed by solar panels were largely technical and smart inverters were needed to help overcome them.

He said if people wanted to see ever growing rates of renewable energy on the grid, they needed to accept the role the market operator would play in regulating the system.

"The really important thing that relates to smart inverters is that it's able to understand what's happening on the grid and provide support to the grid when it needs it," Mr Gladman said.

Smart inverters are seen as key to managing any excess of power from solar panels. ( Reuters: Mike Blake )

"As we move to a future where there's more solar and storage on the network … you have to have systems that are smart enough to support the network.

"It's just the price we have to pay if we want to get to a stage where a really large proportion of our power comes from solar and batteries."

Bigger solar systems, more batteries

Mr Johnston said the WA Government wanted to encourage the uptake of renewable energy and batteries were a key part of allowing this to happen.

But the security of the system was paramount and he said the ability to "curtail" solar generation was an important tool for AEMO.

This would likely spur the adoption of household batteries — allowing people to hold on to their excess power — and would also allow people to have bigger solar installations.

There are currently "hosting limits" that restrict household installations to a maximum of 5 kilowatts, but as smart inverters would make it easier to control the market, households would be allowed to generate more power if they wanted.

Rooftop solar systems could have greater capacity in the future. ( ABC News: Briana Shepherd )

"It's not about having people install solar panels and not be able to use them," he said.

"It's if you remove hosting limits and therefore the average size of the installations will go up, how do you then manage that into the system?"

Shadow WA energy minister Dean Nalder said while it was undesirable for any resource including solar power to be wasted, the security of the network had to take precedence.

But he said the Government had failed to do enough to encourage the adoption of batteries, which could absorb excess solar power.

"We're approaching the fourth year of the term of government and so my criticism is why has it taken so long?" he said.

Among the projects Western Power is leading, to deal with the surge of solar power, is a series of grid-connected "community batteries" that can soak up surplus production from a neighbourhood's solar panels and provide it for later use.

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