Wednesday, 2 October 2013

Parasitic Power Consumption

There was a letter in a recent edition of the Carmarthen Journal – from one of the usual suspects – claiming that wind farms are 'parasitic' users of power from the grid.  'Parasitic' is a word chosen to give a nice negative feel to it. Wind farms still need some electricity, he said, even when the wind isn’t blowing, and they can only get this from the grid – generated, of course, by other types of power stations, usually those using fossil fuel.  As far as it goes, it’s true, of course.  And it’s equally true, but never mentioned in such letters, that nuclear, coal, oil, and gas power stations need electricity – a great deal more electricity, as it happens – to power their offices etc. when those stations are not generating electricity.
So far, so factual.  The unique element about the claim in this particular letter, however, was that wind farms draw electricity from the grid to keep the blades turning, so that we won’t realise that they’re not generating electricity at the time.  The fact that some turbines can be seen turning on “windless” days is evidence, claimed the author, that the operators of wind farms reverse the turbines and use them as motors to turn the blades.  His final ‘proof’ of the claim was that a retired meter reader had told him so.  So now we know!
It’s not a new claim.  I’ve seen it made a number of times before, and the Internet makes it easy to repeat such claims - usually cross-referencing each other as evidence.  I don’t know how and where the claim originated, although that doesn’t seem to be important those repeating it.  It suits their argument, and the extent to which the claim is repeated makes it commonplace; that’s quite enough for them.
It’s not enough for me, though.  I want more than anecdotal repetition – but there is none to be found.  It should surprise me how many people are willing to believe that the companies really would keep the turbine blades turning on still days just to try and convince us that they are working when they aren’t, but somehow it doesn’t.  It’s akin to conspiracy theories, and much of the basis for most of those is the lack of trust (sadly not without justification) of officialdom in general.  It doesn’t help progress though.


Welsh not British said...

Just because there appears to be no wind on the ground doesn't mean there isn't wind how ever many hundreds of feet up these things are.

Add in the fact that these things are designed to capture what little wind there is and it's not easy to imagine how plausible this would sound to a complete moron.

Just like back when the Sun went around the flat Earth.

MH said...

I can think of two circumstances in which grid power would be used to spin the turbine blades, John. But both are understandable.

All turbines are different; but a certain turbine might turn and produce electricity in a low wind speed of 4m/s, yet only start turning at a wind speed of 6m/s. If you knew (from forecasts or hard information from upwind sensors) that there would be a steady wind speed of 5m/s for the next few hours, it would be worth using grid power for a minute or so to overcome the initial inertia and get the turbine spinning, knowing that you would then get much more electricity back.

Another reason (and only on some turbines) would be that if the turbine was likely to be idle for a day or two, you would slowly turn the rotor every so often to prevent it remaining in one position and causing disproportionate wear. However when this is done, it happens imperceptibly slowly (maybe one turn in half-an-hour).

So perhaps it's more a case of a couple of grains of truth being exaggerated into a whole silo.