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Posts Tagged ‘onshore wind’

I’m talking about this Herald article.

SSE’s renewables arm have applied for an offshore wind turbine testing facility near Hunterston power station. Planning was applied for as usual and was granted.

According to the article, though, the villagers are worried that although planning is granted for five years it was simply a sneaky corporate scheme to get a wind farm approved through the back door. Which is simply paranoia: SSE renewables are an enormous developer of onshore and offshore wind energy, with SSE recently announcing that they have more wind generation capability than the Hydro power which gave them one of their operating names of Scottish Hydro Electric. If they’re going to build a wind farm that’s what they’ll apply for in planning. They’re far too big a company and far too reliant on their own good name to be able to risk that in underhanded tactics. Also, if they wanted an onshore wind farm, why on Earth would they claim they wanted an offshore testing facility on land? It seems a bit paranoid to suggest this duplicity. Certainly there can be no evidence for it as the facility hasn’t been built yet: I’m sure if the turbines are erected and then duly either removed or planning permission re-applied for in five years time, SSE will get a heartfelt apology from the villagers for their accusation.

Quoted in the article:

    But Mr Telford said: “The inhabitants of the village of Fairlie will have our homes and our home environment blighted, our population made ill by noise and coal dust, our local climate altered, our property devalued.

    “We are being made unwilling guinea pigs as a part of this extremely dangerous experiment.”

Coal dust? From a wind turbine? (OK, fair enough, three wind turbines.) “Our local climate altered”? I assume the gentleman doesn’t mean that it’ll be slightly less windy as some of the energy will be producing electricity so we can all watch Corrie. Property devaluation… well, yes. I’d maybe accept that as an issue if we weren’t talking about land a bare 3 miles from a large (and incidentally incredibly ugly) nuclear power station. If you’re interested, the photomontage showing what the turbines will look like from Fairlie is available online. It’ll look like:
Photomontage of the proposed facility as seen from Fairlie.

There do remain people who fervently believe, despite no scientific evidence, that wind turbine noise can make people ill. The interaction between health and belief and the environment and the mind is a complex one, and not one I’m going to go into here. But really, the rest of his argument is a bit of a storm in a teacup. Not only that but since planning has been granted, isn’t it all a bit late as well?

The most ludicrous part, to my mind, is the opening sentence, though: “Residents on the Firth of Clyde claim their human rights are under threat from the giant structures – thought to be the second-highest of their kind in the world.”

Their human rights? To a sea view?

That’s easily the most middle class argument I’ve ever heard. The article quotes the clause in question: “Everyone has the right to respect for his private and family life, his home and his correspondence. There shall be no interference by a public authority with the exercise of this right…” However it is not clear to me where exactly the public authority is interfering. No homes are being knocked down, no forced evictions; the land in question is currently sort of industrial wasteland so there’s little could be done to make it worse. No, I can’t see a single part of this clause which is actually relevant to the proposed development. It reads like that middle and upper class assumption that owning property gives you inherent rights to all developments within eyesight of said land. And where have we heard that one before?

No wonder the court of human rights gets such a bad press.

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Last Thursday, December 8th, was a particularly windy day across most of Central Scotland. You might have heard about it, it trended on twitter as #hurricanebawbag. It was the windiest day across Scotland at least since 2006 with gusts of over 100mph.

It’s often said rather disparagingly by people who don’t like wind turbines that they need to be switched off when it’s windy. And of course that’s true, and for a very good reason. The amount of energy available in the wind which a turbine could potentially extract is proportional to the cube of the wind speed — so when the wind speed doubles, the energy available is eight times as much. Theoretically we could design wind turbines which operated in the sort of wind speeds that we saw in Scotland, but most of the time they’d be useless. We need to choose the energy range we want to work in, and we choose the one, unsurprisingly, which lets us harvest the most energy.

It was extensively reported, in Scotland at least, that a turbine caught fire during the storm. Dramatic pictures captured by amateurs went viral on the web; you can see them at the stv news site linked above. Infinis have released a statement (pdf), and New Scientist attempted an explanation on their blog, but it’s clearly been tackled by someone who is a scientist rather than someone who works with wind turbines. So I thought it was worth looking at it in more detail.

There are a few comments that can be made about this. Firstly, wind turbines very rarely catch fire. There are currently over 2.5GW of wind turbines generating in Scotland. Since the current onshore wind turbines only really go up to about 2.5 MW that’s at least 1000 turbines. That means that in the wind conditions experienced last week, only 1 turbine in a thousand caught fire. So it’s not a high risk event; if you’re near a turbine and it’s very windy, chances are you’re pretty safe. That’s what those unnamed “experts” quoted in the media as calling it a “freak event” were probably getting at. Although I would still recommend that you don’t stand near a turbine if it’s very windy.

So what went wrong with this one? Well, Infinis, who own the site in question, don’t yet know what happened but shut down the whole site and notified the grid operator, Scottish Power, immediately. They will be slow to comment as they go through the data from the turbine. There are a few things we can think about though:

  • What components are there in a wind turbine that involve naked flame?
    Well, none, as a matter of fact. Turbines don’t use fire.
  • What components are there in a wind turbine that can generate heat?
    Now we’re on to something. Just about any moving component can generate heat if there’s excess friction involved. Brakes slow down moving parts with friction, which releases most of the energy as heat. So there’s the brakes. Any other moving components could be a risk if there’s not enough lubrication on the joints. And then there’s the electricity itself in the generator; there could be a fault or a short circuit.
  • What was happening to the turbine immediately before it caught fire?
    In this case we’re rather lucky because someone video’d it. Without that, we would have no way to narrow down the list of things which can cause heat and potentially start a fire.

It’s this third point that I want to look into in a bit more depth. Notice in the photographs, how this turbine is pointing a different way to it’s neighbours? That’s not a good sign. Smoke trailing out in front of it, horizontal in the wind, is also a bad sign. Wind turbines (of this 3-blade design, at least) are only designed to harvest energy from the wind if they’re pointing at it. Unless they’re completely switched off (rather than simply under shut down through the automatic control system) the turbine should be tracking the wind direction. From the video you can see that the turbine in question is turning its head, so to speak — the technical term is yawing — away from the wind. That means something crucial has failed.

I’m not going to say that I know what caused the fire. But you’ve got a turbine that can no longer control its direction, and a hurricane. You’ve got gyroscopic forces from the rotor spinning at relatively high speed (because it’s windy), you’ve got a turbine facing the wrong way which means the blades are very likely trying to spin in the wrong direction, putting forces on the wrong components in the wrong way. The brakes, if they haven’t failed already, are under tremendous forces. So you’ve got an event which is the culmination of a number of unusual circumstances contributing to a fire.

How dangerous is it if wind turbines can catch fire?

This is an important question. But actually it’s not as bad as it might seem. Generally hot air from a fire spreads upwards more easily than downwards and most of the moving parts of a wind turbine are already at the top. Turbines need to be placed in clear air, so generally they’re well spaced out. Unless a turbine is in an urban area or a forest, both of which are comparatively rare for a turbine of this size, the chances of the fire spreading beyond the one turbine is very small. There are also generally no people inside a turbine except for maintenance.

Scotland’s Right to Roam laws mean that the general public are allowed to walk within wind farm grounds. So although wind farms are generally remote that doesn’t mean that general members of the public are completely safe. However, risk from falling debris is very small if the distance is further than tip height (the total height of the turbine including the top blade).

There are warning signs that dangerous failure is imminent, and to be honest they’re fairly obvious. If you’re near a large turbine, you can generally hear a sort of low-pitched “whoosh” as the blades go by. Even in a high wind, the rate of the blades passing is generally less than a fast heart beat. If a turbine is freewheeling, something critical has failed. Get away from the turbine as fast as you safely can, and if you can get in touch with the operator to let them know (although by that point there’s not much that can be done — the safety systems have already failed and it’s far too dangerous to approach the turbine until the wind drops. Still they can at least close access). A turbine that is turning and isn’t facing the wind direction is also a danger, as we saw in this case.

The thing is that catastrophic failure is incredibly unlikely to ever happen when the wind speed is low. What risk exists is at its maximum when the turbine is being bombarded with lots of energy from gale force winds. It bears saying that no general member of the public should be within the height of a turbine from its base when the winds are that extreme. If you are, then keep away from any turbine which is behaving differently from its companions. Do this and you’re pretty much as safe as you can be.

If you live near a turbine, the risk of debris is very small if you’re further away than the total height of the turbine, generally somewhere between 100 and 150m. In the conditions seen last week, obviously the biggest risk is downwind, and in any other direction you will most likely be fine. There is no harm in leaving your property if you feel at risk, however. Nor in confirming with your insurance company that you’re covered in the event of a problem with your nearest wind turbine.

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