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Wednesday, 4 August 2010

Bird Mincers part 2


Further to my investigation into the maintenance and lifespan of offshore wind turbines I find some disturbing information revealing that all is not as is publicised in the MSM.

The Media has been regurgitating that the lifespan of a turbine will be 20 years. Perhaps not, going by this statement.

Recently, Sandy Butterfield, a former chief wind turbine engineer at the National Renewable Energy Laboratory (NREL) in Colorado, was quoted as stating that the wind industry expects today's gearboxes to last 7–11 years. This markedly contrasts with the 20-year design lifetime of the wind turbines. And the implications for the industry are huge, since changing a gearbox is typically a lengthy and extremely costly exercise.

Replacing a wind turbine gearbox involves primarily the gearbox cost itself, which typically represents around 10% of the total wind turbine cost. On top of this expense, must be added its transportation to site, crane rental and mobilisation cost, and the man-hours spent on the replacement. It means that the value can quickly reach about €200,000 – €500,000, depending on the turbine size and the wind farm's location.

Not quite what we are led to believe. Of course they are now attempting to build direct drive turbines in order to do away with a gearbox completely.


Some manufacturers have chosen to move to direct drive to reduce the number of moving parts in the wind turbine more exposed to wear. But this has led to wind turbine specific generator designs that are usually more expensive and often come together with a long-term maintenance contract with the Original Equipment Manufacturer (OEM), which does not necessarily meet the operations and maintenance (O&M) concept of flexibility expected by customers.

So now they are going to be even more expensive to build. Though at least one manufacturer is trying a different tack to the conventional thinking on turbine design. Alstom Pure Torque system



  1. Would a direct drive be a lot less efficient than a gearbox?

  2. Well there wouldn't be any gear box losses but there would have to be radical design of the blades to give the right generator speed.

  3. So, if they do opt for direct drive, there'd have to be some sort of torque limiter to keep the blade speed constant at a certain velocity. means they wont work at low wind speeds and torque limiters are just as likely to go wrong as a gearbox. I doubt they'd use a shear pin, synchronous magnets wouldn't be strong enough, ball detents would wear away to easily and pawl and spring types would snap too easily and friction plates would just wear away in inclement weather. probably have to come up with some sort of magnetic particle type though how they'd do that dynamically is getting beyond my admittedly limited knowledge in this field.

    Oh and any torque limiter is usually a nightmare to service as well.

  4. They could maybe use a fluid clutch. We has one or two on ships.

  5. Fluid could work, but there are weight limitations and further problems in maintenance, heat problems too if under extended running, not like you can have a refrigerant system onboard as well.

  6. Well you could use a heat exchanger cooled by sea water if offshore. But would have to be manufactured from high grase alloys for long term life. More expensive of course.

  7. Gosh, you mean they've been less than forthcoming about the long term costs of the bird mincers? There's a shock, eh, though obviously not an electric shock.

  8. And I still can't find any actual projected maintenance cost figures. All I find is waffle.


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