The Curious Case of Switching Off Rooftop Solar And Pleading For Power Consumption In South Australia

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In the past week, South Australia has seen the apparently curious situation of the national grid operator switching off itself, or asking owners to switch off rooftop solar systems in the state, even while requesting them to increase demand by switching on more appliances and other power hungry equipments. This apparent dichotomy  is easily explained, and also a pointer to the challenges many grids could face as the share of renewable power goes up.

The challenge

For AEMO( Australian Energy Market Operator), the challenge in South Australia was caused by the high share of rooftop solar in the grod in that state. When a storm knocked out grid connectivity with the rest of the national grid, it faced a unique challenge of ‘ minimum opeational demand’ as it calls it, falling to unacceptably low levels, leaving it with few tools to manage grid stability if a second storm or similar event was to strike. In an explainer  shared by it, it says ” When rooftop solar generation is high, the need for grid-scale supply naturally becomes extremely low, which displaces grid generators. At present, these generators provide a range of essential system services, including frequency control, system strength, voltage management, inertia, and so on. In periods of very low operational demand, these services need to be sourced from elsewhere or, if that isn’t possible, AEMO must intervene to keep the grid in a secure operating state”.

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That has led to AEMO pushing for better inverter standards whereby it can ‘control’ those inverters remotely, allowing it to switch off inverters if required in these situations. Besides this of course, the grid is being upgraded with more transmission lines between states that will allow surplus power to be exported to the other states by states producing too much renewable power, as in this case. Of course, if the same situation was happening in peak summer, then AEMO would have found it easier to manage the situation, as peak load, and demand would have been higher, allowing solar rooftop generation to be absorbed locally by energy guzzlers like ACs etc.

AEMO’s predicament underlines how higher renewable share in grids will shift worries from managing peak demand, to managing periods of minimum demand, when renewables would have a disproportionate impact possibly. In countries like India, we have states like Karnataka living that risk, with a very high share of renewables at over 50%, but ensuring grid stability thanks to the connectivity with the national grid.

Solutions to this issue in the future will include more large storage facilities that can absorb the higher generation, besides flexible energy consumption setups like Hydrogen electrolysers, that can switch on and off much more faster.

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