Effective turbine maintenance ensures the long-term productivity of the turbines.

What it costs

About £14 million per annum for a 450 MW floating offshore wind farm.

Who supplies them

The wind turbine supplier, during the defect notification period (DNP) and for the duration of any agreed contract beyond the DNP.

The wind farm owner may seek to bring maintenance and repair capability in-house or to engage an independent service provider (ISP). This typically requires agreement with the manufacturer for the supply of spares, software systems and specialist expertise.

ISPs include Deutsche Windtechnik, James Fisher Marine Services, Swire Energy Services and Worley.

Key facts

The requirements for turbine maintenance are similar for floating and fixed offshore wind turbines. Conducting maintenance in a moving floating offshore wind turbine presents additional challenges for health and safety when moving items and motion-induced sickness. These issues are more significant at height where any low frequency movement of the floating substructure is amplified.

The initial service agreement typically covers the period of the turbine defect warranty, which is usually five years. During this period, turbine technicians are typically employed by the wind turbine supplier. The service agreement may specify that technicians’ contracts are transferred to the wind farm owner on expiry. This ensures continuity of staffing and removes technicians’ disincentive to relocate to the wind farm site. Some owners employ their own technicians to deliver a proportion of turbine maintenance from the start to build in-house knowledge and capability, in agreement with the provider of the initial service agreement.

Activity is divided into preventive maintenance (scheduled) and corrective repair (unscheduled). The bulk of preventive maintenance is typically carried out during periods of low wind speeds (usually the summer months) to minimise the impact on production. However, this is not always achievable in practice.

Corrective repair is performed in response to unscheduled outages and is often viewed as more critical, due to accruement of downtime until the fault is resolved. The primary skills required are mechanical or electrical engineering, with further turbine-maintenance training often provided by the relevant turbine provider.

Typical maintenance includes inspection, checking of bolted joints and replacement of worn parts (with design life less than the design life of the project).

Unscheduled interventions are in response to events or failures. These may be proactive (before failure occurs) for example responding to inspections or from condition monitoring, or reactive (after failure that affects generation has occurred).

Guide to a Floating Offshore Wind Farm