By Ritesh Gupta

The offshore wind sector in Europe is strengthening its maintenance expertise to combat hurdles associated with project operations. Overall, operations and maintenance (O&M) activity can account for 25% of the life-time cost of an offshore wind farm. The growth in this field is natural progression that has followed the commissioning of offshore assets, and more wind turbines going into operation over the past few years. Regular maintenance of turbines, towers, foundations, cabling and transformer platforms are an essential part of the operation phase. And as a result more service and maintenance contracts are in place today to secure the on-going performance of any wind farm.

Turbine Maintenance

Compared to the onshore wind segment, the importance of predictive and condition based maintenance strategies increases offshore. The main cost driver for offshore O&M is the fact that each visit to a turbine has a higher impact in CoE compared to onshore. Consequently, it is crucial to reduce the time spent offshore by increasing remote diagnostics of events; preparing visits by applying remote data analysis, and implementing timely planning and dispatching of resources.

O&M teams are increasingly well versed with the significance of a thorough planned maintenance programme. Time and experience offshore has highlighted certain aspects including addressing the time of year a scheduled outage can happen as well as a meticulous approach to carrying out the maintenance. So all parts of a planned maintenance initiative are ordered proactively, considering lead times.

Also, ongoing initiatives include material records for all turbines. This enables the staff to evaluate why components are failing if the same is happening repeatedly. According to specialists, O&M costs include spare parts, routine maintenance, repairs etc. in this arena. Therefore having analytical tools on hand to pinpoint a farm or turbine’s weak links is invaluable to avoid costly downtime.

It should be noted that unanticipated maintenance and major repair costs can provide expensive setbacks when it comes to controlling costs. Such work is carried in response to unscheduled outages. This can have a major impact on project economics, both in terms of direct costs and, also owing to lost revenues due to unavailability. So the teams have to plan for scheduled as well as unscheduled inspections and repairs diligently.

Improvement

Overall, the situation is gradually improving. In general, an increasing number of offshore wind farms are benefitting from more players and better engineering expertise dedicated to maintenance solutions, says Jürgen Hepper, Asset Manager, Trianel.

Several approaches have accelerated progress, as Siemens Energy’s Wind Power Service vice president Ken Soerensen highlights:

• Customisation: Today the industry is tailoring offshore logistical concepts for each individual wind farm. Siemens is one such entity. “A broad variety of service craft, both floating and airborne, provides safe access to offshore installations - even under challenging conditions of future far shore projects. Custom build solutions reduce turbine downtime through accelerated response times, better and safer transfer and access, and extended service weather windows,” says Soerensen.

• Sustaining high energy output: Offshore work could be unavoidably costly if not for remote diagnostic services. “Through remote monitoring and intelligent planning, we can turn unplanned repair work into planned preventive maintenance, bundle service visits and even solve problems remotely. Thereby, we reduce time spent offshore and help maintain high energy output,” says Soerensen.

• Bringing costs down: There are ways in which the industry is relentlessly focused on driving down the cost of wind energy, in the widest possible range of conditions. In Siemens’ case, member of its remote diagnostic services work closely with its turbine engineers. For instance, Siemens released its new 6 MW direct drive turbine, which is designed for the most challenging offshore sites. But service considerations were also highly important during the development of the turbine. “As a result the ergonomic nacelle interior helps technicians perform their tasks faster and more safely and with fewer moving parts it lowers the risk of component failures and helps bring down costs,” says Soerensen.

Set-up

The service set-up is tailor-made since each offshore wind farm is unique in terms of distance to shore, weather complexity, wave height, water depth, tidal variation, and number of turbines.

Based on measured and simulated weather data today entities are coming up with individual logistic concepts in order to help ensure a safe and efficient operation.

For its part, Siemens has developed a “Wind Farm Simulation Tool” that allow it to calculate the impact on costs and turbine availability of different combinations of vessels, platform and helicopters. This tool helps the team to design the optimal logistic solution for a particular wind farm.

Technical Maintenance

The availability of technicians and equipment for technical maintenance is mainly covered by long-term maintenance contracts. “Regular inspections will be carried out on the assembly parts to also take condition based maintenance into account in good time ahead and secure resources needed,” says Trianel’s Hepper.

Access is a big challenge when servicing offshore turbines. Turbines should be located at sites with strong winds. However, when operating offshore, strong winds equals high waves and often limited accessibility to do maintenance and repair.

In addition to working out optimum logistical set-up for each individual wind farm, companies like Siemens are also focused on reducing turbine downtime through accelerated response times, safer transfer and access, and extended service weather windows.

Depending on the site, Siemens applies different logistical solutions, from smaller crew transfer vessels, to service operation vessels, to accommodation platform, to helicopters. Here is a Siemens video that takes a look behind the scenes of offshore wind O&M: http://youtu.be/2vwtuA81YyM

Going by such development it is clear that there is a learning curve for O&M where this is an expectancy of sustained improvement. However, there is no room for complacency and one should strive to reach a stage where unplanned repairs can be foreseen or converted into planned actions.