Heliophage


Copenhagen: Urban turbines, and puzzling maths
March 15, 2009, 5:44 pm
Filed under: Uncategorized
dsc00530-vestas-crop

From the top:MWhrs, number of households that total could serve, tons of CO2 avoided, and number of new installations

Travelling around Copenhagen you can’t help noticing a lot of wind turbines: not measly little numbers like the ones outside my local Sainsbury’s, but serious, grown up 500kW+ turbines. To British eyes these are still quite a novelty, and not an unwelcome one. While opposition to wind turbines in the countryside is often misconceived, it is sort of understandable; but what Ballardian urban landscape would not be enhanced by such imposing, impersonal machinery? Greenwich Peninsula and Gallions Reach surely cry out for such things.

Right outside the Bella centre where the climate congress was held (and where COP 15 will be taking place in December) there’s a 52m circumference Vestas number, rated at 850kW. Inside the centre we had the chance to gawp at one of the blades for a Vestas 3MW machine, a singularly beautiful object, and also to see inspiring  displays like this one to the right. They use the fact that Vestas monitors all its turbines in real or near-real time, I was told, though the internet; their engineers can see how every one of the things is working at any given time.

This display though is a little puzzling. The picture was taken about 18:00 on March 12th, and so its figure of 821,202 MWh generated in the 282 hours since  the beginning of March suggests that Vestas turbines are generating power at a rate of about 3 gigawatts. But Vestas says that it has an installed base of over 33 gigawatts. If that’s right, the turbines are working at under 10% of their theoretical capacity, which seems very low.

I’m also a little surprised by the figure of 204,471 tons of CO2 saved. If you use this converter provided by the EPA, 821,202MWh of clean electricity works out at 589,757 metric tons of carbon dioxide avoided (the conversion rate used is 7.18 x 10^-4 metric tons CO2/kWh). That’s three times more than Vestas is claiming.

My best guesses for what is happening here are a) I’m adding things up wrong, b) the Vestas display is missing a digit (1,821,202MWh would translate as a utilization rate of about 20% and would give savings of 1,307,921 tons of CO2, which is not that far off 1,204,471) or c) something more complex. If the answer is b) I suppose that would be slightly embarrassing — but it would also be kind of cool if Vestas itself didn’t appreciate just how fast the numbers were growing and had thus failed to provide the number of digits necessary…

I’ll ask one of the people I met from Vestas if she can clear up what’s going on.

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