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Sunday 1 August 2010

Offshore wind turbines revisited.

Further to my post about these bird mincers, nowhere can I find actual costs of maintenance. All I find is statements such as this:

6.5.3    Serviceability

The service demand of the present generation of offshore wind turbines in terms of man-hours is in the order of 40 to 80 hours [7].� Service visits are paid regularly, (except in the more demanding first year) about every six months.� A more major overhaul will be undertaken every five years, and will take around 100 man hours to complete. [1].

100 man hours after 5 years of operation in a salt water environment. Utter Hogwash. It will take more than 100 man hours just to reach the turbine in question.


Their Scenario and assessment

Note: No hard and fast methods, just theoretical assessments.

My Scenario

Firstly you will have to open up the casing to gain access to the operating machinery. No small task if the covers are not secured by stainless steel fastenings and even then working several hundred feet above sea level has it's own risks.

Once the casing has been opened, the inspection has to be carried out.

What do you find? Oh dear, one of the main rotor shaft bearings has become damaged and requires replacing. Just by chance you have the exact spare lying around on your support vessel. Remember now you have budgeted for 100 hrs. Oh dear and now it's raining. All that water is now filling up inside the casing which houses the  machinery which comprises of a 6.6KV generator (6,600V) which abhors water. Better try and rig up a cover to protect it. Must have one in the boat somewhere. (If anyone of you have seen what a 6.6kv discharge is like, it comprises  a plasma arc at the same temperatures as the surface of the sun.)

So far we have the crew of the vessel, probably 4, at an hourly rate of say £50 per hour. A maintenance crew of 4 on average of £100 per hour. Trip to the turbine 3 hours. opening the casing 1 hour. Inspection 1 hour. Locating and lifting the bearing onto the turbine 1 hour. Securing the turbine from the effects of the weather, 1 hour. Probable time to renew bearing 24 hours. (Wildly optimistic). Insulation testing and closure 2 hours. Return to port 3 hours.

This of course does not address the problem of why the bearing failed in the first place.

And all this is in the summer months. Almost impossible for 6 months of the year.

I'm just an ex marine engineer. So what do I know?