Friday, 1 August 2014

Australian Wind Energy Wasn't Generating 'Nothing' In July

Whilst on holiday, in Germany, I stumbled across something that filled me with instantaneous joy. It's from a columnist at the Herald Sun, named Terry McCrann, with the headline "WHEN THE WIND DOESN'T BLOW, THE POWER DOESN'T SWITCH ON":
"On Monday, all the wind farms in Southern Australia, all the hundreds of turbines scattered across South Australia, Victoria, New South Wales and Tasmania, altogether produced exactly zero — nothing, nada, zip, zilch — power for two hours smack in the middle of the day.
Indeed, right through most of the working day — from 11am in the morning until after 8pm that night — the total output of all the wind farms was effectively zero for that entire period. 
But over those nine hours they pumped out at most just 120MW, barely 4 per cent of their capacity (sic), and for most of the time much less even than that. 
That included those two hours, from 3pm to 5pm, of absolutely no power
...these wind farms are scattered from as far west as Port Lincoln to east of Canberra, from the top of Tasmania to way north of Adelaide, from coastal sites to tops of country hills, and from all of them, for those two hours not a single MW of power."
The pitiable headline writer (tasked with awkwardly cramming a hook onto an article that is largely about the fact that wind speeds change over time) didn't give much thought to the fact that the power actually did 'switch on', during the times at which wind speeds were low.

The reason this sort of thing makes me happy is because it's not very hard to make fun of. To be fair, we can't expect a piece of writing that descends instantaneously into self-parody to be hard to make fun of.

The author seems to have an awkward relationship with the concept of 'zero. He's fond of it, as evidenced by the fact that he summoned his thesaurus when describing it. But his dictionary seems to have been misplaced. This is a chart of the time period during which NEM-based wind farms produced "exactly zero — nothing, nada, zip, zilch":

It's low, but it's non-zero, meaning McCrann's assertions were wrong.

I love watching reality mercilessly trample the feelpinions regularly laid out by conservative columnists, like a giant mechanical elephant strolling over an out-of-date Kit Kat.

These articles on wind power output are particularly fun examples of where emotionally-driven ranting collides comically with the need to try and gracelessly wedge some skerrick of numeracy amongst a forest of feels.

So what about the claim that wind farms were, between 11am and 8pm, somehow simultaneously producing 'effectively zero' (wat) and 120 megawatts?

There are peaks at 126 megawatts during the time McCrann angrily insists it was no greater than 120, but hey, what's a few megawatts between friends?

The total amount of energy produced by wind farms during that nine hour period was 521 megawatt hours. Considering the average Australian home uses about 18 kilowatt hours per day, you could have theoretically powered about 521,000/18 =  28,944 homes for a day each during McCrann's nine hour period of 'effective zero' output.

At wind's minimum output during that period, 15 megawatts, you could still have powered 15/((18/24)/1000) = 20,000 average Australian homes (depending, obviously, on how much power each home was actually using).

The fact that McCrann is, quite literally, wrong about his claims, isn't all that surprising. What's more interesting to me is why he opts for the analytical approach of 'ignore nearly all data available'.

Below, we can look at Monday's total output - I've highlighted the time he's ignored, and the times he's discussed:

The probability that Terry McCrann will say things about wind power seems to increase as the wind speed decreases. No doubt, McCrann cast his eye over the output of wind farms over the previous weeks, and regarded all other data as a bizarre, hateful, green-conspiracy anomaly.

Here's wind farm output over the month of July, with the period that McCrann discussed highlighted in red:

This doesn't really give you a good idea of how often wind speeds are high, low and average. A better visualisation is a frequency histogram - this tells you how many hours that the NEM wind fleet spent at each output level. I've summarised the output levels into 50 megawatt bars:

The times at which wind speeds are low across the fleet of wind farms were not particularly common. The times at which total wind output was below 50 megawatts accounts for ~1.8% of total time. The times at which wind power output was higher accounts for the remaining 98.2% of July.

McCrann's furious focus on the small, brief periods when wind speeds are low reveal an important point - logical fallacy is a never-ending fountain of content for conservative columnists critical of renewable technology. In this instance, McCrann uses a 'straw-man fallacy' - he assumes advocates of renewables want only wind farms, and then critiques the rare periods at which the fleet has low output. Build a straw man, and gleefully tear it down.

McCrann also seems to deny the existing of the market operator's wind energy forecasting system, known as AWEFs:
"This is what we saw with Edis some weeks ago when he claimed that an analysis showed you could predict these sorts of “outages” an hour ahead of time (he originally claimed 24 hours, but corrected that); time enough to power up an alternative"
The fact that Tristan Edis followed up with market operator data showing forecasts 24 hours in advance has been, presumably, blanked out by McCrann's subconscious.

This isn't the last time that a conservative columnist will cherry-pick a short interval, and insist that they're being analytically honest. In this case, McCrann couldn't even get it right about the period he'd sliced out, making statements about 'zero output' that were quite literally false. McCrann's ability to take refuge in these brief periods is decreasing as installed wind capacity grows across the NEM. Here's one last chart - showing the percentage of time, each month, that wind power has spent at output between zero and fifty megawatts, since 2010:

The walls of the low-wind cherry-picking room are closing on its few, angry inhabitants. Soon, I suspect, I'll have to find my fun elsewhere.

No comments:

Post a Comment