Wind Turbines: More Ghosts in the Gearbox

There is a wall of silence from the wind industry regarding wind turbine reliability. But once in a while data seeps out through the wall to the general public. A little bit of new seepage has just come to my notice.

The last time I blogged about wind turbine reliability was after I had come across an obscure department within the USA government National Renewable Energy Laboratory (NREL) called the Gearbox Reliability Collective (GRC). The purpose of this U.S. government sponsored department is to address the appalling and largely hidden reliability problems with wind turbines, particularly gearboxes.

The GRC has their own website here: http://www.nrel.gov/wind/grc/ 

My first post on the GRC is On This Link 

The GRC is not alone. Clearly there are several European agencies and groups working on this problem too. Unfortunately information on them is very obscure. I am unaware of any public access to their data other than when it is mentioned by the GRC.

What has just caught my attention is a 2013 paper from the GRC. The  paper is titled: 

Report on Wind Turbine Subsystem Reliability ─ A Survey of Various Databases.

The paper is on this link: http://www.nrel.gov/docs/fy13osti/59111.pdf

If you look at the linked document above you will find a survey of many wind turbine failure databases held in Europe and the USA.

As far as I can ascertain there is no public access to any of this data except to that presented in this paper. If I am wrong I would be grateful for any links – I have found none.

The figures from Europe in this survey stop short of fully quantifying failure rates. They do though hint at a failure rate increase for larger turbines and crucially, also for direct drive turbines.

We also have the USA data in the same document. Some of the USA data goes right up to 2013. This American data is far more open and definitive. It gives failure rates for all major components not just the gearboxes.

Here is the table (see page 31) relating to expected annual gearbox and generator failure rates for on-shore turbines.

The NREL reckons for gearboxes this averages out at 5% per year for the first ten years. Notice that in year 5 it hits 10%. 

Whatever way you cut it statistically around about 50% of turbines will suffer a gearbox failure within 10 years. Remember this is for properly maintained, serviced and generally “looked after” turbines.

But also remember – that is ONLY the gearbox. The generator is “slightly” more reliable coming out at an average failure rate of 3.5% per year or 35% over ten years.

So for an onshore turbine in the USA the chances of a properly serviced and maintained turbine failing due to gearbox or generator issues within 10 years is 85%.

If you include the other potential failure areas (say the blades - failure rate quoted at 2% per annum) then statistically, it is almost surely that a properly maintained and serviced wind turbine will suffer a major failure within 10 years. It looks like most failures will occur in year 5 or 7.

All rotating machinery can (and will) break down. But wind turbines are operating in a chaotically changing and hostile environment (offshore turbines even more so). A gas plant by comparison is operating in a closely controlled and regulated environment. So per Megawatt-Hour, the wind turbine will require much more maintenance.

The energy return from a wind turbine is simply inadequate to pay for the very high demands placed on maintenance and repair. As the machine gets older more maintenance and repair will be required. Eventually the point will be reached (7-10 years?) where the maintenance/repair bills exceed the returns.

The often hyped 25 year life span for a wind turbine would appear to be hopelessly optimistic.

Currently the only way round this problem is to hugely increase the price of the electricity generated by the machine from day one. This is essentially what the current government subsidies do.

But one day the subsidies will have to fall. When this happens, or as the turbines get older and more unreliable, the wind farms will end up being be sold on - and on.

The new owners will be ever more dubious organisations. Eventually the turbines will be run until they suffer the final major failure that renders the turbine beyond economic repair. Then they will be abandoned.

When the last one fails and the payments stop, the bailiffs will arrive to claim the “guaranteed” decommissioning fund. But by then the main company office will be a post box in Belize and the decommissioning fund will be long gone.

Remember almost all of the data in the above paper is for on-shore turbines.

When you go offshore the maintainability and reliability falls off a cliff. The consequent subsidies sky-rocket.

But more on that in another post.