Solar sends South Australia grid demand to zero in a world first

Solar panel close up

South Australia became the first gigawatt-scale grid in the world to reach zero operational demand on Sunday, when the combined generation of rooftop and small-scale solar met all customer load requirements. 

The new milestone saw solar energy producing more than enough power for the entire state, with the South Australian grid receiving more energy than it needed to send out into homes. 

According to energy analysts, the grid saw two negative demand events on Sunday, the first lasting a period of 30 minutes, before a period of 25 minutes followed less than an hour later. The negative demand events included the transmission network of the grid, which includes a number of big mining and industrial loads.

While a minimum demand event means the grid is barely required above operational levels in order to produce power, negative demand events mean the grid is receiving more excess energy into the system than it needs to distribute, and will need to send that energy to grid partners to be stored or discharged.

The Australian Energy Market Operator (AEMO) had earlier predicted that South Australia could become the world’s first gigawatt-scale grid to reach zero operational demand, with an increase in rooftop solar systems installed across the state.

Australia now ranks first in the world in terms of solar capacity per person, with South Australia equal first among Australian states with 40% of homes featuring a rooftop solar system. 

Negative demand events can be damaging for grids

Providing enough solar power to keep the whole state of South Australia connected would mean a drastic fall in carbon dioxide emissions over that period. However, negative or minimum demand events can damage market operators and the grid as a whole. 

The AEMO must constantly run a minimum amount of gas generation in order to maintain system strength and grid sustainability, and the market operator also recently commissioned a number of spinning machines called synchronous condensers to provide the same services. These machines do not burn fuel.

In order to export any excess energy production, in the case of minimum or negative demand periods, the grid needs to be linked with a neighbouring grid. South Australia’s neighbouring grid is in Victoria. 

The further the grid reduces in demand, the more energy that the AEMO is forced to export to a neighbouring grid to ensure the stability of the system. The AEMO is looking to improve infrastructure to ensure the grid is ready to handle 100% renewables by 2025, which would see a reduced impact on the grid in minimum or negative demand events.

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