Wind turbine failures are likely to become more important as older turbines, built before 2010, come out of warranty.
There are many unknowns about how wind turbines will weather aging, as none of the modern designs have been in operation for their full twenty years of expected life.
Undoubtedly many components have been subjected to twenty year accelerated life tests, but these can only identify the most obvious of weaknesses.
Two components seem to be most vulnerable:
- Gear boxes
Three systems appear to have the highest failure rates:
- Electrical system
- Gear boxes
The cost of repairs are affected by whether cranes are required when making the repair, which frequently means that gear boxes, generators and blades have high repair costs.
Blades are numerous and failures can be dangerous.
One estimate is that 1% to 3% of turbines require blade replacement annually.
There were 33,250 turbines installed between 2007 and 2015, indicating that between 300 and 1,000 blades need to be replaced each year.
The cost of each blade is around $150,000, according to an NREL analysis. If 1,000 blades are replaced each year, the cost will be around $150 million, not including the cost of installing the new blade.
Blade replacement costs are not a trivial matter, and have largely been covered by the manufacturer while units were under warranty. Now, the cost will increasingly shift to the owners of wind farms.
Blade failures are no trivial matter. Blades weigh around 24,000 pounds, or 12 tons.
Catastrophic blade failures have thrown portions of blades, or entire blades, onto surrounding areas, which for the most part have been rural farmland.
But communities should be careful not to have wind turbines installed near buildings, such as schools and hospitals, as a broken blade, that weighs 4 times more than a Tesla S sedan, could cause considerable damage. Potentially, these are life threatening installations.
According to an NREL report, gear boxes represent 6% of all failures, but account for the largest amount of downtime.
Gear boxes cost around $250,000. The cost of replacing a gear box is substantial when the cost of crane rental and the cost of lost production, from long down times, are taken into consideration.
As units go off warranty, owner-operators must decide whether to enter into extended warranty agreements with the manufacturer, or into warranty and maintenance agreements with third party service companies … or manage the maintenance costs themselves.
In each case, the owner-operator must contend with equipment that’s supposed to operate for twenty years, but where none of the existing equipment has ever done so.
This creates a huge unknown for the future cost of wind generated electricity.
The original equipment manufacturer (OEM) has extensive data on maintenance costs and failure rates across all of its installed base. OEMs guard this proprietary information carefully, as it provides them with the advantage of being in the best position to predict future maintenance and failure costs.
The government and some industry members are upset over this practice, claiming that the industry would benefit if all such information was made available to everyone.
Third party service companies may have data on equipment manufactured by several OEMs based on maintenance contracts they have performed, but have less information than OEMs on OEM equipment.
The owner-operator of a wind farm is at a disadvantage when deciding how to handle its maintenance and service costs after the warranty has expired. Any equipment that fails out of warranty will be replaced at a very high price if it isn’t covered by a service agreement.
The owner operator’s best alternative may be to enter into an agreement where the OEM or service company guarantees yield or output, under specific operating conditions.
Since most modern wind turbines in the United States haven’t operated for more than seven years, there is great uncertainty whether maintenance and failure costs will increase significantly over their remaining lives.
The real cost of maintenance is being absorbed by OEMs during the warranty period, and will continue to be absorbed by them when they provide maintenance contracts. As a result, the true cost of maintaining wind turbines is largely hidden from view.
If the cost of maintenance contracts increase, the already high cost of electricity from wind is also likely to increase.
Eventually, the cost of decommissioning existing units will also have to be accounted for, and it’s not clear who will absorb those costs … wind farm owners, or the land owners on which the turbines are built.
The next decade could provide a better understanding of the levelized cost of electricity form wind turbines.
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