Solar exports face shutdowns as rooftop PV lays siege to world’s most isolated grid

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The Australian Energy Market Operator is calling for the urgent introduction of rooftop solar shutdown mechanisms in Western Australia as part of new reforms to ensure the stability of the grid, as rooftop solar takes an ever bigger share of the energy market.

A new renewable integration study from AEMO – the first in two years – outlines a series of major initiatives, some of them urgent, that it says is needed within the next couple of years because the rapid growth of rooftop solar will present major challenges to grid stability.

The growth of rooftop solar in WA is similar to that in many of the eastern states, but the particular challenge of South West Interconnected System, as the local grid is called, is that it is the world’s most isolated multi-gigawatt grid, with no connections to other states or countries.

This has caused the state government and key institutions to take a more conservative approach than many in the market would like. A Whole of System Plan released last year disappointed many because of the lack of ambition in the uptake of renewables, many of which already face considerable system constraints.

AEMO now wants to replicate the “solar shutdown” mechanism it has recently instigated in South Australia, starting with the introduction of new inverter standards that will ensure it has enough capacity to control if it needs to dial down the amount of rooftop solar being exported to the grid at certain times.

“Urgent action is now required to enable the capability to manage DPV (distributed PV) output to the grid as an emergency fallback,” it says in the new report, entitled “Renewable Energy Integration – SWIS update.”

“Action must commence as soon as practically possible to implement capability for all newly installed and upgraded DPV to be managed in respect of their output on instruction from AEMO to another agency or entity.

“Specifically, action is needed to provide for reduction or curtailment in the output of DPV where required to maintain power system security and reliability in emergency operational conditions. This includes during extreme low system load conditions and as part of System Restart procedures.”

There is already more than 1.7GW of rooftop solar in WA, it’s growing quicker than expected and it has resulted in penetration rates of more than 65 per cent (and 70 per cent for all renewables, on September 7 this year).

The growing rooftop capacity pushes out other generation and AEMO is concerned about diminishing levels of “operating demand” which is the amount of operating large-scale generation over which it can exert control.

In 2019, it feared that problems could emerge as early as this or next year, and set a 700MW floor for the amount of operating capacity it needed.

It has now lowered that floor to 600MW and says any issues will most likely not emerge until 2024, but says even then minimum demand could fall to 232MW, and it needs the ability to either create demand or switch off solar to deal with it.

AEMO CEO Daniel Westerman said in a media statement accompanying the report that analysis now indicates that the timeframe in which AEMO may no longer be able to operate the SWIS securely, in all periods, has been deferred to 2024.

“AEMO has identified a number of actions to provide greater resilience to extreme events in the short term as well as recommendations that would enhance the WA government’s announced reforms to address emerging challenges over the medium term,” he said.

“As part of AEMO’s recommendations, additional operational tools, new standards, system services, and regulatory arrangements are needed to address priority actions that will provide increased resiliency to the power system beyond 2024.”

Apart from the ability to control and “orchestrate” rooftop PV, AEMO is also looking to inverter-based technologies such as battery storage, utility-scale solar, demand response and, to a lesser extent, wind to provide new fast frequency response services.

It says storage will be needed to support the grid and the new conditions brought about by the switch to renewables. WA’s main grid currently has no big battery installations, although two are planned by Synergy and Alinta, and there is a growing number of “community” scale batteries.

AEMO is also looking to other urgent measures, including boosting the UFLS (under frequency load shedding) scheme, providing more incentives for “flexible” load, and a “ramping” service to deal with the ever deepening solar “duck curve” in the middle of the day that could include batteries, demand response and fast start diesel generators.

It also recommends changes to allow hybrid facilities – wind or solar plants combined with battery storage – to more easily offer each of their components separately into the market, opening up additional revenue streams for these facilities.

AEMO says it is possible that further challenges may arise as the power system further transitions that will required additional actions to those identified in this report.

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