According to the American Wind Energy Association, nearly $40 billion worth of wind installations in the U.S. came out of warranty in 2011, and 50% of the country’s wind turbine generator fleet is behind in original equipment manufacturer (OEM)-recommended maintenance schedules. Now wind farm owners must assume the entire financial risk and provide cost-effective operations and maintenance (O&M) programs.
Wind turbines, generally located in wide-open, stormy places where Mother Nature takes her toll, operate under tremendous stress. The unpredictable nature of weather conditions results in constantly changing loads. Wind turbines beg for a regular maintenance plan to achieve the life expectancy of the fleet. The old saying “pay me now or pay me more later” is certainly true when it comes to turbine maintenance. Good planning and scheduling will help developers and owners manage the cost of maintenance, decrease equipment-mobilization costs and improve labor efficiency.
Because half of the U.S.’ wind turbine generator fleet is behind in OEM-scheduled maintenance, wind turbine owners can expect that increased demand and limited availability for services will drive up the cost of labor and equipment.
In 2014, new turbine construction may approach 2012 levels, and the anticipated need for additional equipment and more trained crews could drive up the costs for maintenance and major component replacements. Developers need to bring their fleets into compliance with OEM-recommended scheduled maintenance guidelines. Wind turbine owners that properly service equipment according to OEM-approved guidelines and manage preventive maintenance plans can lower costs significantly, increase production, extend the life of turbines and avoid cost increases over the life of a project.
By securing equipment and trained labor for their projects through long-term agreements with fixed cost structures, owners and operators can avoid cost hikes that are a result of increased demand.
There are three broad categories for wind turbine maintenance: emergency maintenance, scheduled maintenance and preventive maintenance.
Emergency maintenance. Also known as the “fix it when it breaks” model, emergency maintenance is the least efficient and most costly because it drives up the expense of repairs that might be prevented through properly scheduled maintenance. The reactive approach to catastrophic failure of a gearbox, generator or bearing for a single wind turbine can result in very expensive removal and replacement.
Mobilization of a main lift crane onto a site to repair one turbine can exceed $200,000, and that does not include the expenses for the crew, tools and equipment. Moreover, it can take 25 truckloads to transport a big crane to a job site and two to four days to assemble the crane. The downtime is costly as well.
Scheduled maintenance. Conducted on a time frame recommended in the OEM manual, scheduled maintenance includes any kind of maintenance within the turbine manufacturer’s specs – periodically inspecting equipment, changing oil and filters, lubricating moving parts, replacing components, cleaning the turbine’s blades, identifying electrical problems, and replacing gearboxes, bearings and blades. All manufacturers have recommended maintenance programs, provide updates on identified failures and make suggestions about components that need additional inspections.
Catastrophic bearing failures can cause other damage to the hub assembly and blades and may be prevented if they are identified during inspection and replaced before complete failure. Gearboxes that are found to need repair during routine inspection cycles allow for core credits to be issued by the rebuild facility.
However, gearboxes that fail during operation as a result of neglected inspection and oil analysis typically result in no core credit being issued because they are classified as scrap and a new housing must be purchased.
Scheduled maintenance identifies unexpected major component replacements before they become critical to the turbine’s operation. This allows for a major component replacement plan that significantly lowers the cost of the repairs in comparison with unscheduled replacement. It is essential for owners and operators to follow the OEM programs and work with their O&M teams to improve these programs through their own experience. Scheduled maintenance drives down costs of labor and equipment, while it increases the production and life of a turbine.
Preventive maintenance. Also known as planned maintenance, preventive maintenance is a proactive approach to known turbine issues. An inspection checklist made during scheduled maintenance can identify problems before they result in catastrophic failure. A gearbox may show wear, and a monitoring system may exhibit problems even though the turbine is still operational. Owners and operators know from past experience that there is a limited amount of time to make repairs. They can target issues on several different turbines. In that way, the cost per repair decreases when they mobilize manpower and equipment because more can be accomplished.
In preventive maintenance, replacements can be planned. Lower costs can be achieved by making similar repairs on a number of turbines at the same time because a preventive program decreases cost and improves labor efficiency, unlike the costly reactive approach to emergencies. There can be significant cost reduction for the numerous generator and gearbox replacements that typically can be expected. This is especially important with regard to the mobilization of large cranes. For greater efficiency and cost-effectiveness, cranes can be walked from one turbine to the next and reduce overall expenditures. For example, if four turbines are serviced at the same time, the cost per turbine is reduced 25%.
In some ways, wind turbines are no different from a car. One that is well maintained will give years of trouble-free service to its owner, and when a repair is required, it will normally cost less than if performed as an emergency repair.
Recent insurance industry data further supports these findings.
Renewable energy insurance company GCube said that blade damage and gearbox failure were responsible for the greatest number of losses according to 2012 U.S. claims data – accounting for 41.4% and 35.1% of total claims reported, respectively. Poor maintenance (24.5%) and lightning strikes (23.4%) were cited as the most frequent causes of loss.
The GCube analysis states that the primary cause of gearbox failure may be poor maintenance along with design defect as a factor. Gearbox claims typically cost the industry $380,000, and turbine blade claims cost an average of $240,000 each.
The importance of a proactive approach to wind turbine maintenance cannot be underestimated. Wind farm developers and owners may find the following suggestions beneficial:
- On-site cranes can be assigned to a wind farm and become part of the project cost to eliminate future mobilizations.
- Tool innovation may drive down the cost of equipment required to perform scheduled and unscheduled maintenance. For example, our engineering staff developed a crane-less single-blade removal and replacement mechanism that can be implemented for pitch bearing replacement and blade repairs that cannot be completed up tower. By eliminating the requirement for a crane, the total cost of a repair can be reduced by 25% to 50%.
- Eliminate or lower the frequency of purchasing rebuildable parts through a good preventive maintenance program that identifies deficiencies before they become catastrophic failures.
Industry At Large: Operations & Maintenance
Turbine Maintenance: Pay Now Or Surely Pay Later
By John Clark
In addition to causing lower output and decreased run time, neglecting the maintenance on your wind turbines could lead to exorbitant costs that are likely avoidable.
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