The race that stopped the nation … and electricity demand

(Note: This story has been updated to reflect the sudden fall in demand was due to outages at the Tomago aluminium smelter).

The anti-renewable lobby love to complain about the intermittency of “variable” renewable energy sources such as wind and solar, saying that it is impossible to manage on a large grid.

But there’s nothing quite so variable as demand … and the grid operator has been handling it just fine, as it has done for decades.

Just minutes before yesterday’s running of the Melbourne Cup there was a 1,000MW “cliff” in the NSW grid, as demand was suddenly lost.

It was first speculated that it was because of disappearing demand as punters took leave of their work stations and work places wound down. Turns out it was a sudden “trip” at the Tomago aluminium smelter which took three pot lines and more than  930MW of demand out of the system

As the graph shows, demand went from more than 8,200MW to less than 7,200MW in the space of five minutes, before gradually recovering over the next hour.

By the way, the big fall in demand on the previous day – though gradual – is an example of the so-called duck curve, where rooftop solar hollows out demand in the middle of the day, once one of the most profitable parts of the day for fossil fuel generators.

One of the differences between wind and solar and fossil fuels is that while the changes in output in wind and solar are quite predictable, sudden outages from coal and gas-fired plants and industrial users are often not.a