00:00On a breezy day in Western Australia's south, something seems amiss.
00:10The blades on giant wind turbines are barely turning at all, but there's nothing wrong
00:14with them.
00:15There's just nowhere for their power to go.
00:18It's called curtailment, a little known phenomenon that's increasingly becoming a feature of
00:22Australia's power systems.
00:24Curtailment in its simplest is when an energy asset generates less than it would be capable
00:31of generating.
00:32It often happens when there's simply not enough demand to soak up all the potential
00:36supply renewable energy could provide.
00:39And it's most pronounced in the middle of mild, sunny days, when the output from Australia's
00:44vast fleet of rooftop solar floods onto the system, pushing out most other generators,
00:49including large scale solar and wind farms.
00:52And there's a lot of rooftop solar that suppresses the demand that the rest of the market sees.
00:58It is happening quite a fair bit and it's a byproduct of an ever-changing grid.
01:03At the moment, curtailment isn't a big part of Australia's electricity system, accounting
01:07for only about one and a half per cent of wind and solar production last year.
01:11But it's much more than that at times, and there are expectations it will grow markedly
01:16in the years ahead.
01:18Curtailment is something that renewable energy companies are going to have to factor in.
01:22Analysts say batteries will help soak up much of the excess supply, as will consumers
01:27who shift more of their use to the middle of the day, but they say some amount of curtailment
01:31is inevitable.
01:32The marginal cost of generating that excess kilowatt-hour off a solar system on your house
01:40is zero or very close to zero.
01:42And to that extent, no harm, no foul.
01:45From scarcity at times to abundance at others, Australia's renewable energy riddle won't
01:50be solved overnight.
01:52That's a great idea.
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