Rooftop solar delivers 80 pct share of generation in landmark moment in world’s biggest isolated grid

Rooftop solar continues to defy conventional wisdom, and many engineering assumptions, with its dramatic growth in Australia main electricity grids.

The latest milestone has been achieved in Western Australia, where rooftop solar has accounted for a record 80.5 per cent share of generation in that state’s main grid, the South West Interconnected System.

That is not as big as the 112.9 per cent share of demand recently achieved by rooftop PV in South Australia, but that state has the ability to export excess power to Victoria, something that the W.A. grid is unable to do.

The huge impact of rooftop solar in W.A. has already caused the market operator and the state government to sign contracts with a fleet of big battery developers to soak up rooftop solar in the middle of the day and reinject it into the grid in the evening peak demand periods.

That is needed because as the share of rooftop solar grows – and consumers are still adding around 200 megawatts a year – it pushes down what is known as “operational demand” to levels at which the grid operator fears will leave it without the resources to respond to any disruptions, such as network, generator or load outages.

Those contracts will see half a dozen new batteries built, including two 2 GWh batteries at Collie, the town that hosts the state’s last coal fired power generators. One of those batteries, the 560 MW, 2240 MWh Neoen facility, will be the biggest in the country, and has already commissioned its first stage.

At the time of the rooftop solar peak on Monday, at 1.30pm local time, distributed PV (almost entirely rooftop solar) was accounting for 2,118 MW of output, with gas and coal both reduced to shares of 8.6 per cent and 8.3 per cent respectively.

Wind was contributing 1.8 per cent (in Perth it tends to blow more regularly later in the day with the Fremantle Doctor, while solar was negligible, probably because of economic curtailment.

That appeared to have sent operational demand to a new record low of 474 MW, according to a LinkedIn post from the state’s co-ordinator of energy policy Jai Thomas.

But by a quirk of the way things are measured out west, that does not include the demand created by the first of the big battery solar soakers, at Kwinana and Collie, which will have pushed scheduled operating demand higher, and to a level where the market operator could be satisfied protects system security.

Either way, it is a fascinating insight into the direction of Australian grid, both isolated as is the case in W.A., and integrated in the country’s main grid.

In W.A. the addition of another gigawatt of rooftop solar by the end of the decade, another 2 GW of battery storage and the closure of the last coal fired power stations should complete the transition away from the old “baseload” paradigm that dominated energy market thinking half a century ago.

And even as the UK has discovered as it lays out its 2030 Clean Power Plans, adding nuclear into the mix – as the federal Coalition says it wants to do across the country, including at Collie, makes no sense at all. A very square peg, in a much smaller round hole.