US-centric, but applies to wind turbines in general.
Looks at factors such as location, blade strength, mechanical stresses, height, the cost of building and shipping turbines, the economics of wind power etc.
Includes some surprising figures:
Presumably to maximize the FIT payments they optimise for power transfer rather than efficiency? See Jacobi's Law ...
En el artículo , Andy Burns escribió:
well, the article is US-centric, so FIT payment schemes, if any, will presumably be different. But the reason given for the poor efficiency was:
"most turbines extract around 48-50 percent of the available wind power after accounting for aerodynamic and mechanical losses and other considerations"
No, that's often misunderstood.
NT
That's actually pretty good considering the Betz limit is around 60%
The problem with wind turbines isn't that they could be better, its that the wind could hardly be worse, as a source on concentrated reliable energy.
Correct.
The laws in play are similar to those in play for heat engines: Basically you cant slow the wind to an absolute stop and get all the energy out of it, any more than yu can still extract useful power out of luke warm water at the outflow of a condenser.
Typical thermal engines peak out with a CCGT at about 60% thermal efficiency.
And that's because you start with white hot gas, and end up with warm water.
In a straight steam plant 37% is about as good as it gets - a bit more with supercritical steam
It looks like it's windpower-centric too.
All interesting stuff.
The really key figures (that cripple wind-power) aren't explained, but they are shown in the graph without further mention. For example, if you want to know what the Weibull Fraction is, you have to go elsewhere to find an explanation. Further, there is no mention of the fundamental limit to the efficiency of a windmill, due to the pressure build-up after the wind has passed through the blades.
But the killer fact is shown by the green line in the graph, labelled AEP but again not explained in the text, with the legend Power Fraction and peaking at 6076 kWh at a wind speed of about 12 m/s.
If the wind changes by +3 to -5 m/s, the 'AEP' falls to half its peak value, while that lovely orange Rotor Power peaks at 2000 kW and holds that from 12 to 26 m/s, after which it falls off a cliff due presumably to safety shutdown.
I got the impression that this is another 'blind 'em with science' article from a pro-windmill lobby.
Why is that suprising? You can't take all the energy out of anything.
What it is missing is that from that 50% of total energy is that on average a wind turbine will only produce less than 1/3 it's rated capacity. So potential input to actual output is more like 15% ...
Then they never seem to be running all the time. We have four identical massive ones near here, and to see them all turning at the same time is a rarity. If one can run, why don't they all? And then there are those days when the wind is too weak, or too strong......
well thats another story. No a wind turbine will extract about 50-60% of all the energy there IS in a moderate wind, less in a gale as it will exceed the rating of the turbine, and of course none at all when wind drops below a threshold value (light breeze generally)
Its really all a bit irrelevant which is why those who are actually interested in what wind can do, talk about the average watts per square meter of wind farm, and the peak watts per square meter of te farm, or their ratio (the capacity factor) and the grid planners have to look at worst case wind generation in tens of minimum and maximum in order to size the backup and grid size respectively.
The rest of us are concerned over the cost and emissions reductions elsewhere, of course, but that doesn't concern the government or indeed the renewable industry who have guaranteed returns on all this malarkey, which need not result in any emission reductions at all, or indeed even emissions increases, to still get paid.
En el artículo , Dave Liquorice escribió:
Boilers and PC power supplies manage to be ~80% efficient.
mean time between failures of a moderately middle aged turbine is generally about 6 weeks. Yes. 6 weeks.
At which point they are generally feathered and shut down pending maintenance.
Bearing failure is very common, but control gear failure and inverter failure are not unkown. And there's the slew gear the feathering mechanism and the brakes..and if the brakes fail and the feathering fails you can get runaway rotation which can lead to bearing failures and fires, or explosive destruction of the turbine. With a tip speed of
250mph + bits of blade can fly a long way...It is also likely that lightning strikes can and have destroyed turbines by vaporising a carbon fibre blade. Certainly at least one mill was destroyed and only 2 of the three blades were found... and they are rather big for 'travelling folk' to nick, and of little resale value..
getting heat out of anything is pretty efficient.
An electric fire is 100% efficient
We seem to have several bands around here, always leaving a huge mess behind them; they might get a little more sympathy if they disappeared one of these things!
BTW, there was a woman on TV recently representing travellers and hoping that there would be more understanding of them. If they behaved more responsibly, that would be easier.
Presumably because the wind is that variable locally.
Electric heaters manage to be 100% efficient or very close to that.
I can't say 'No', but as this is on the site of an old WWII airfield, I think it unlikely. There are no hills anywhere near. This is East Anglia.
No, its because half of them are at any given time broken.
Don't they have an ally strip built in as a lightning conductor?..
I've just been and looked. The dozen or so I can see in the distance all seem to be running. I'm honestly surprised; there's usually at least one down.
And that's on the days when the wind is right.
They looked a bit odd this morning though - I don't think any 2 were pointed in the same direction. The wind must have been a bit odd just before it stopped completely.
Andy
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