Nothing would destroy trust and raise the risk spectre faster than fleets of wind turbines suffering costly failures of key components. It has happened before and it could happen again. But there is now much less excuse for catastrophic failure than in the past. The development of sophisticated equipment for monitoring the condition of most major components in wind turbines has come on in leaps and bounds, often pushed along by the demands of insurance companies in Europe. These days, automated systems for tracking the health of vital wind components are readily available -- and provided the data they collect is analysed correctly, a stitch in time could certainly save nine.
With this in mind it is surprising to learn that wind plant owners in the United States are not more rigorous about service and maintenance of their machines. Not only is automated condition monitoring far from standard, one school of thought believes the cost of fitting the equipment and using the results properly could never pay off. Field technicians in this school readily admit when interviewed that even the streams of data spewed out by the ubiquitous wind farm SCADA systems (for Supervisory Control And Data Acquisition) are often poorly understood and little used (pages 87-94). More data from condition monitoring devices is the last complication they need, goes the argument. Yet leading consultants on both sides of the Atlantic Ocean decry the poor use of SCADA data by maintenance teams in the US. At the annual European wind energy conference last month, questions were even asked publicly about whether investors are knowledgeable enough about managing their wind farm assets, particularly in America.
Owners of any plant and equipment have a choice of "maintenance by breakdown," which speaks for itself, or "preventative maintenance," which can be as simple as visual inspections. The more advanced approach involves mounting devices on specific components, such as gearboxes, that monitor for abnormalities, storing data or alerting an operator to any severe deviations from the operational norm. At one time this "predictive maintenance" was the preserve of nuclear power stations and other sophisticated plant, but now most motor vehicles have warning lights that tell, for example, if the brake fluid level is too low. To argue against employing such equipment on wind turbines could be considered contrary.
What it comes down to, however, is cost and practicalities. If breakdown statistics show that failures are rare, detailed monitoring of every turbine in a big fleet is likely to be more expensive than exchanging the odd duff component. This seems to be GE's philosophy with its workhorse 1.5 MW turbine. As to practicalities, data has to be understood to be useful and that requires rigorously built databases over time and technicians doubling as computer boffins. Even if an owner wants condition monitoring carried out, lack of information and personnel is a serious practical deterrent. But so too is employing enough engineers to shin up the towers of thousands of machines to take a look at what is visible to the naked eye and listen out for telltale sounds of trouble. If prevention is better than cure, proper use of advanced technology has to be the better long term solution.
Cynics might be tempted to suggest that with many wind plant owners in America only in the business for the relatively short duration of wind power's ten-year tax credit, long term solutions are not the first priority. That thought aside, as wind turbines get larger and more expensive, running them in the dark makes less and less sense. The increasing availability of statistics on failures and their costs means that hard-headed accountants can do the sums. What are the likely probabilities of failure? What are the likely consequences? How much will the damage cost to rectify? How long will the turbine be out of use? What will the lost revenue be? Would the cost of buying and running automated condition monitoring be less than all the losses?
The argument that profits on wind plant operation are not sufficient to support the cost of predictive maintenance in the United States should set alarm bells ringing. Finance specialists are pointing out that for every dollar invested in a wind farm these days, 66 cents are coming from the American taxpayer in the form of one tax break or another (Windpower Monthly, March 2008). Even then, returns are nothing to write home about, as investors point out in this issue. The indication is that the market price of wind power has dropped so low that corners are being cut, at least by some, when it comes to keeping wind turbines healthy. That could be a grave error of judgement.