Operations and maintenance (O&M) are the combined functions which, during the lifetime of the wind farm, support the ongoing operation of the wind turbines, balance of plant and associated transmission assets. O&M activities formally start at the wind farm construction works completion date.

The focus of these activities during the operational phase is to ensure safe operations, to maintain the physical integrity of the wind farm assets and to optimise electricity generation.

What it costs

About £32 million per annum for a 450 MW floating offshore wind farm. This includes insurance, environmental studies, compensation payments and other internal asset owner costs (not itemised in sections below).

Who supplies them

The wind farm owner oversees and fulfils overall site operations activities.

In terms of wind turbine planned maintenance in response to faults, wind turbines are typically under warranty for the first three to ten years of operations and the wind turbine suppliers offer a service level agreement during this period to provide turbine maintenance.

After this initial warranty period, the wind farm owner may maintain the wind farm using an in-house team, contract to a specialist company, or develop an intermediate arrangement where turbine technicians transfer to the wind farm owner at the end of the warranty period.

Key facts

The focus of O&M is to maximise the financial return from the owners’ investment. Owners aim to optimise the balance between operational expenditure and turbine yield. By scheduling downtime during the low wind speed summer months, owners can secure high availability during the winter months when wind speeds and energy outputs are typically higher. Contractual arrangements which award energy production are increasingly common.

Turbine availability is the percentage of time the wind turbine is ready to produce power if the wind speed is within the operational range of the turbine. Modern onshore turbines have a technical availability of around 98%. The performance of offshore wind turbines has improved with optimised design, and offshore turbines often have availabilities in a similar range to onshore. The planning of logistics and access is vital to securing high availabilities. Where there are access restrictions then availability may be in the range 95 to 98%.

Operational support is provided to the wind farm 24/7, 365 days a year including responding to unexpected events and turbine faults, weather monitoring and live turbine monitoring. Outside normal operating hours this support is provided from remote control rooms which monitor wind farm SCADA data.

Maintenance includes scheduled and unscheduled activities and requires the regular transfer of personnel and equipment to the wind turbines and offshore substation. Safe access to the turbines is a critical area for further focused innovation.

Repairs and replacement of major turbine components, including the blades, are carried out by the turbine supplier or, less commonly, by specialist 3rd party providers.

In the UK, transmission assets (substations and export cables) are transferred to an Offshore Transmission Owner (OFTO) within 18 months of wind farm commissioning. The OFTO may contract some maintenance functions to the wind farm owner because it has onsite personnel and has a strong interest in minimising transmission downtime. In other European territories, typically a transmission operator is responsible for building the offshore transmission.

Guide to a Floating Offshore Wind Farm