AEMO installs early warning system for surplus solar and rooftop PV shutdowns

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The Australian Energy Market Operator says it has developed a new early warning system to give advance notice that there could be too much rooftop solar in the grid and that some installations may need to be shutdown.

The new notice system is similar to the three-tiered “lack of reserve” notices already in place, but instead of advising of a possibly supply deficit, these “contingency” or “minimum demand” notices will warn of having too much power, or at least too much rooftop solar.

Instead of LOR (lack of reserve), the new notice will have an acronym of CMSL (contingency and minimum system load).

It is yet another sign of the rapid changes in Australia’s main grid, where rooftop solar is forecast to account for up to 80 per cent of total demand at various times by 2025, and possibly up to 100 per cent of state demand in South Australia as early as the next two months.

In fact, on Sunday, rooftop solar PV met 84.4 per cent of state energy demand in South Australia in one five minute interval at 1.15pm, and from 1.30pm to 2pm it sent the level of minimum operational demand to a record low of 236MW – a 21 per cent fall from the previous record low.

This new early warning system will initially be focused on South Australia, which has the highest percentage of rooftop solar in any state grid, and has already experienced one “solar shutdown”, in March this year.

AEMO insists it will rarely occur, and if it does it will most likely happen if there is a risk of a transmission problem that isolates the state from the rest of the grid, or if there is so much rooftop solar output that it pushes out too much other generation.

The first level notice – hopefully issued a day before an anticipated situation – will invite responses from demand response providers (creating more load to soak up supply), while level 2 will advise of a possible move to shut down rooftop solar if other actions are not sufficient, while level 3 is where that takes place.

The shutdown can take place because all homes installing new solar systems in South Australia in the past year must install inverters that can be remotely controlled and an “agent” who can manage that solar system – either isolating it or switching it off – if called on to do so by AEMO.

That likely gives AEMO more than 250MW of capacity that it can control or “orchestrate” in that way – out of a total South Australia rooftop capacity of around 1.7GW. These inverters will be compulsory in the rest of Australia by the end of the year.

AEMO says there is now more than 14GW of rooftop solar spread across millions of homes and businesses across the country, making it the country’s biggest generator. But until the new inverter standards were imposed it had little control over that resource.

“We are now in the enviable position of having a surplus of solar energy, especially during spring and summer when there is an abundance of clear, sunny days and just the right temperature for solar panels to produce at their maximum potential,” an AEMO document says.

It says the electricity grid wasn’t designed with rooftop solar in mind. It was designed for energy from large power stations that would be dispatched at the request of a system operator and which would flow in one direction from generators to homes and businesses.

“Now energy is also flowing into the system independently, and in reverse, from homes and businesses. AEMO is working with industry to explore new technology, engineering, and services that will help bring more renewable energy into the electricity system and avoid these last resort situations.”

“Just as occurs today with last resort load shedding measures, when all other operating tools have not been sufficient in keeping the power system secure, it is important that emergency operating tools are available to avoid issues that risk state-wide outages, which have a far greater impact on consumers.”

It says this will happen rarely – it has happened just once this year – Switching off rooftop solar will become an important feature of a renewables grid and will only cost “a few dollars or less” for each solar system if it does occur.

It is also looking at so-called “smarter alternatives” to shutting down rooftop solar, which could include more community scale storage, demand response initiatives and other moves to “soak” up excess solar.

There is a pretty good fact sheet here if you want to learn more.


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