For as long as wind turbines have been spinning, the phenomenon of blade failure and breakage has posed a consistent technological challenge for the developers, manufacturers and operators working throughout the industry.
Now, as wind energy expands globally, moving out of traditional growth markets in Europe and North America into newer, emerging sectors in Asia Pacific, Africa and Latin America, the issue has grown and intensified. Rapid supply chain expansion and project development in new and often highly remote territories has coincided with growing pressure to deliver cost-competitive energy through larger turbines with longer, lighter blades and to ensure minimum unscheduled downtime.
In this climate, current trends seem to suggest that the overall integrity and performance of blades has suffered. With an estimated 700,000 blades in operation in 85 countries globally, there are approximately 3,800 incidents annually of blade failure – a rate of 1:184. This rate varies significantly from country to country and from manufacturer to manufacturer.
Given this variation, it would evidently be over-simplistic to attribute blade failure to any single cause. Nor is this failure rate overly alarming in the context of wider industry expansion.
However, given that the average total cost incurred by a single incident and associated business interruption can fall anywhere between $100,000 and $1 million, there is a clear industry imperative to categorize known blade incidents and seek to mitigate associated losses as much as possible.
Furthermore, as a result of construction slowdowns in many of the traditional growth markets, the importance of securing secondary investment in operational assets has risen. These additional costs can prove an unwelcome deterrent to the pension and fund management communities; therefore, it is in the interests of all parties to minimize unscheduled downtime and the frequency and severity of turbine failure.
As such, GCube Underwriting recently undertook a comprehensive analysis of our extensive claims database and publicly documented incidences of blade failure, compiling all known root causes of malfunction and the factors influencing the cost of blade claims. This research fed into a report entitled "Breaking Blades: Global Trends in Wind Turbine Downtime Events."
Although the use of obsolete technology that is no longer in serial production pushes up repair and replacement costs for aging equipment – and it might, therefore, seem logical to point the finger at an aging asset base across North America and Europe for the prevalence of blade incidents – the report found that there was no direct causal relationship between the age of a turbine and the likelihood of blade failure.
Likewise, there is no single factor responsible for the majority of incidents. Root causes can be roughly categorized into four categories: technological fault, manufacturing defect, external incident, such as lightning strikes, and human error.
In turn, the impact of blade failure on the balance sheet and insurance claims can vary greatly in severity, depending on a number of interlinked factors. These include the following:
Nature of damage – the extent and scale of the failure, including the number of blades affected and the severity of the damage to these blades. Any consequential damage to surrounding property, such as the tower or transmission infrastructure, will elevate costs, as will any blade-related environment, health and safety incident causing temporary shutdown of the site. Additionally, costs incurred will depend on whether the blades in question require repair or full replacement, or whether damaged equipment can be salvaged.
Location – a hugely important factor, particularly given market migration into remote territories. Proximity to suitable blade manufacturing or repair facilities and access to crucial resources and equipment, such as skilled labor and cranes, make a big difference to the costs of unscheduled maintenance. Delays can be compounded if site access is impeded by poor transport infrastructure or adverse weather conditions. Likewise, country-specific permitting challenges and financial incentives will have an impact on the overall cost of blade repair or replacement.
Equipment specifications – naturally, the size and the price of the blade in question on the market will affect the overall cost of an incident. The age of the blade in relation to the extent of serial production and whether the blades are under warranty at the time of loss is also significant, as is the level of interchangeability with other blade models.
Risk management – evidence of prudent and appropriate risk management is a key requirement for an insurer when paying claims for blade breakage incidents. The availability of a spare blade and crane is the ideal way to minimize the financial impact of a breakage. An insurer will also look for evidence of scheduled, proactive maintenance post-warranty and responsiveness on behalf of the operations and maintenance team to rectify blade performance and mitigate external issues such as lightning strike before an incident occurs. Building in pre-agreed replacement times into supplier contracts is a proven means of boosting responsiveness.
An understanding of the aforementioned considerations and their influence on total claims costs is the first step toward bringing these costs down. While many of these factors may fall outside of the control of an owner/operator, knowing which risk management and mitigation options are available and implementing these will help to reduce the financial impact of technological failure and ultimately keep insurers on board.
As for the blades, routine inspections are a must. A host of examination techniques analyzing blade tolerance to defects should be used.
Visual inspection, tap tests, probing and lightning system continuity checks should be accompanied by noncontact inspection procedures such as thermography or ultrasonic testing. It is crucial that these blade inspections are conducted thoroughly and are not seen as a mere box-checking exercise.
Experienced technicians will know that, in addition to visual indicators, many of the telltale signs of blade defect are audible. Any whistling or unusual banging sounds during operation are a timely warning sign and an indication that further investigation is required.
For operators and owners, thorough knowledge and inspection of each of the constituent blade elements and factors contributing to their failure demonstrates a commitment to proactive project maintenance, promotes wider industry awareness and will ultimately help the sector bring down unscheduled maintenance costs.
Jatin Sharma is business development leader at GCube Underwriting Ltd. He can be reached at email@example.com.