New materials and designs are being incorporated in contemporary wind turbines with the ultimate goal of reducing weight, controlling loads, and improving energy capture.

At the same time, there is a potential impact on reliability and other operational aspects whenever new technologies are introduced.

Considering these changes, one needs to ensure that technology risks are diligently assessed while planning and budgeting for O&M.

There is no denying that we all want new, improved technology, says Roger Hill, Principal Member of the Technical Staff, Wind Energy Technology Department, Sandia National Laboratories. And those improvements can include reliability performance as well. 

“But, after reliability and availability, we have the last two aspect of the RAMS approach: maintainability, and safety,” says Hill.

According to him, there should be plans for maintenance of any component and what is required in terms of access, tools, personnel, equipment (such as crane service), and either spare parts inventory (especially for long lead equipment) or fast delivery of parts. 

A key aspect of maintainability and safety reviews is performance analysis of these steps, and assessments of new technology can be performed given detailed information of this from the suppliers. 

One way of minimising the risk of new products is to adjust for these risks through warranty service as well, points out Hill.   

Overall, with advancements in the technology, the industry is gradually reaping the benefits.

There are definitely economies of scale and that is why the turbines and the wind plants have increased in size. 

“This is due to the ongoing maturation process of the industry,” said Hill. 

There is also a learning curve for O&M where there is a process of continuing improvement.

“However, this wouldn’t suggest that there should be a relaxation of maintaining the reliability metrics,” added Hill.

Unscheduled maintenance

Commercial wind turbines contain a variety of complex systems and failure or malfunction of a minor component will frequently shut down the turbine and require the attention of maintenance personnel.

In this context, it is imperative to evaluate which is the best way to plan for certain amount of unscheduled maintenance especially direct costs associated with labour and equipment required to repair or replace.

“This type and in fact, all types of faults should be budgeted for, both in terms of the reliability budget, and in O&M funds as well,” said Hill, who added that keeping records or tracking will be important.

Also, defined availability guarantees have been included in turbine supplier agreements when the supplier operates the wind plant during the warranty period to partially address this issue.   

Another aspect of work is related to performing tasks associated with machine maintenance, including both routine service and unplanned repairs.

The key to same is said to be performance engineering, reliability tracking, and trained staff. 

“Routine service can be scheduled and unscheduled maintenance cannot. But through condition monitoring certain predictive benefits may be realised where unplanned repairs can be forestalled or converted into planned actions.  Condition monitoring should also help to minimise cascading failures which should be a significant benefit and cost savings,” said Hill.    

One proactive approach that isn’t always seen is to schedule maintenance actions for periods of less energy value. 

If a utility has high costs of energy during peak periods then the value of wind energy is greater at that time. 

“This fact is not always recognised under operating contracts. If it were to be recognised an incentive would exist to shift planned maintenance away from peak and high energy value times,” said Hill. 

Of course that would be an additional constraint on the operation of the plant and would have impact on the O&M crews.