Operators on the hunt for better O&M

WORLDWIDE: Having gone through the difficult process of securing planning and finance, procuring equipment and building the installation, one would assume that - once a wind farm is up and running - most of the work is done. But the upkeep of wind turbines is a crucial issue that continues to trouble operators, despite the wind industry's long track record of servicing different makes and models over many years.

A worker braves the cold to service a Vestas V80 turbine in Germany
A worker braves the cold to service a Vestas V80 turbine in Germany

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Operations and maintenance (O&M) activities can be conducted by the original equipment supplier (OEM) or sourced from an independent service provider. Freedom of choice, however, often comes at a price. Sometimes a certain volume of work is required to ensure the ready availability of components and comparable service levels. For dedicated components such as power converters, information on specific control parameters is required, which OEMs seem reluctant to share.

The goal of O&M is to ensure turbine upkeep, with availability being a key operational parameter. When a given installation can operate all the time within a predefined wind speed range between a starting up (cut-in) and stopping speed (cut-out), availability is defined as at 100%. In reality, availability is never 100% due to technical issues, O&M visits, grid failures and other factors.

Room for improvement

In its latest service satisfaction survey (2009), German wind energy association Bundesverband WindEnergie (BWE) rated the performance of seven established OEMs and 11 independent service providers on periodic inspections, unscheduled repairs and extraordinary services - the latter covering unrequested functional improvements such as software updates. The responses were further divided into three groups depending on turbine age: warranty period, past warranty but less than six years old, and six years and over.

Six OEMs got a "satisfactory" score, with German market leader Enercon - the only supplier of direct-drive turbines on the list - achieving a "good" score. The independent service providers appeared to do better, with one scoring "very good", seven "good" and three "satisfactory".

The BWE survey, like any survey, was prone to criticism. For example, it has been observed that there were substantial differences in turbine numbers per individual OEM. But whatever the survey's faults, one clear message emerged: there is ample room for service performance improvement.

Experts have their views on why owner/operators in the wind industry generally perceive the O&M services they receive as sub-standard. At a recent wind power O&M workshop in Germany, Inge Aasheim, aftermarket business developer for Scandinavian drive specialist and bearing manufacturer SKF, said: "The wind industry has failed to take lessons from other industries which, like SKF, have been involved in installation upkeep for decades." SKF has developed specific tools for other industries that help operators to optimise maintenance, but Aasheim says such tools do not exist in the wind industry, which is still mainly driven by repairs.

The replacement of faulty bearings inside nacelles can also be difficult, explains Aasheim, as it requires adequately qualified staff. The wind industry's rapid growth appears to have outpaced its ability to recruit and train staff.

Another workshop participant pointed his finger at project developers, suggesting they typically choose the latest technology and biggest turbines available: "My experience is that project developers often don't care about proven technology." Other experts said that turbine owners, including large multinational corporations, often fail to make informed decisions.

Planning ahead

A standard warranty period is typically between two and five years. It usually covers repairs, component replacements and upgrades, as well as other planned and unplanned service activities. For owners, the time around the end of the warranty period can be a risky grey area. First, they have to decide whether or not to switch to an independent service provider.

Another inherently tricky issue is assessing turbine condition just before the warranty expires. There might be a suspicion, for instance, that a gearbox problem is developing, although it has not yet fully manifested itself. The key question in these cases surrounds legal liability when a post-warranty technical failure occurs within a given period - typically up to two years after the warranty ends.

An expert end-of-warranty inspection can minimise these risks. It is an investment that will save a lot of money if the suspected failure does occur later. Replacing a full gearbox for a 3MW onshore turbine costs an estimated EUR200,000-350,000. An extra EUR75,000-200,000 might be necessary for an offshore operation, due to additional crane-ship hire.

Incidentally, multiple independent wind industry sources indicate that the reliability of geared and direct-drive turbine models is very similar. This contrasts with a common perception that direct-drive turbines are by definition more reliable as they contain fewer components. Many failures requiring service visits are, in fact, caused by small components such as broken fuses, faulty electronic boards and connections.

Service packages

Enercon was the first OEM to offer turbine owners/operators a full-service package. The company's PartnerKonzept (EPK) includes comprehensive service and maintenance support, and financial compensation for yield losses. An EPK contract runs for 12-15 years, which corresponds to the typical term of a turbine loan. Owners contribute EPK costs of EUR0.012/kWh, but a contractual agreement stipulates a minimum annual fee depending on the turbine model.

According to Enercon, more than 90% of its installed turbines come with EPK coverage. The package is not cheap but can bring additional benefits, including lower insurance premiums and easier access to project funding, thanks to the reduced long-term investment-risk profile.

Long-term full-service contracts are gaining popularity in the wind industry. Earlier this year, GE introduced a full-service package on its new 2.5xl wind turbines in Europe, with plans to extend it globally on all turbine models. Nordex offers its premium service package for variable-speed turbines supplied from spring 2003, which are equipped with a Nordex condition-monitoring system.

Vestas recently announced that it intends to "move aggressively towards a full-service model". As part of its active output management (AOM) plan, Vestas Central Europe offers a full-service AOM 4000 package covering 5-20 years. With its new V112-3.0MW turbine, the company also introduced what it calls reliability-centered maintenance, an overall strategy aimed at lowering O&M costs.

All in all, especially for owners/developers that choose to opt for unproven technology, a long-term O&M contract covering 10-12 years seems a very wise choice that will shift some of the risk from themselves to the equipment supplier.

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