Keeping Turbines Turning for Longer: How Offshore Wind Can Address Ageing Assets Smartly to Extract Hidden Value

The following article is a guest post by John Coultate, Head of Product Development, and Evgenia Golysheva, Head of Engineering, ONYX InSight. The article discusses asset life extension in offshore wind and the benefits of a data driven approach.

Offshore wind is set for a golden age. For continued growth, the sector must plan ahead. How can the global wind fleet provide the most value for the longest time? How can wind farm owners and operators continue to improve the profitability of their asset portfolios year-on-year? Data driven life-extension strategies will be at the core of efficiency gains – but they must be considered now.

It’s common for wind farm owners and operators to consider ageing assets a liability. It’s an issue which the onshore wind sector has been grappling with for decades in established markets such as Germany and Spain. Older turbines are viewed as less reliable and more inefficient, and replacement components may be hard to source. Historically, decommissioning has often been regarded as the only viable option.

Offshore wind is a younger industry, but as markets such as the UK and the Netherlands add capacity year-on-year, they face increasing numbers of turbines aged 20 years or more. Even emerging markets such as the US will need to ensure new assets are primed for life-extension from the start.

To realise this benefit operators must ensure a clear view of asset health. A careful management strategy to boost long-term efficiency across an offshore fleet needs to be followed, using the latest digital tools to monitor assets’ health in the short-term, focusing on asset integrity in the long-term, and delivering smart operations and maintenance (O&M) from the outset.

Although turbines are often certified for a 20-year lifespan, operators are increasingly aiming to keep projects operational – and profitable – beyond the initial design life. With a solid life-extension strategy in place, useful asset life can be extended by up to 25% – which could mean five more years of revenue for owners and operators.

This is driven primarily by economics – reduced margins on wind projects incentivises investors and developers to use 25 and 30-year lifespans in financial models. But increased confidence in wind technology and the previous experience of traditional power generation or offshore oil rigs, where operation beyond design life was economically effective for operators, have also played a role.

While this strategy makes sound business sense, there can be a disconnect between long-term operational strategies and the realities faced by engineering teams on the ground, who may not be thinking about life-extension as they tackle day-to-day O&M challenges at their wind projects.

This is a missed opportunity for the industry, however, as many operational decisions taken during the mid-life phase can have significant consequences for long-term profitability.

With ageing offshore assets, the first step to life-extension is ensuring high quality, consistent data – the cornerstone of a modern life-extension programme.

While offshore turbines are equipped with vibration-based CMS as standard, other measurement systems can bring additional value by diversifying the data pool.

Two examples of data streams that can be combined with drivetrain vibration to provide more accurate insights into turbine health are oil quality and tower vibration.

Gearboxes are replaceable when viewed as one element of a holistic life-extension strategy. However, the rate and timing of replacement can make a huge difference to the economic case for the life-extension phase.

Oil monitoring can pick up unusual failure modes that may not be effectively detected using vibration, and in addition will ensure that lubrication quality is maintained at a high level to maximise the useful life of the gearbox.

It can also serve as a useful indicator of maintenance quality and the general condition of the gearbox. This can inform the long-term replacement strategy for owners and operators, reducing the risk of downtime for mid-life assets, while significantly improving operating margins post design life.  

Wind farm owners and operators have many technologies available to them for monitoring vibration, strain, displacement and corrosion of a wide range structures outside the nacelle. These systems are useful for structural monitoring, but it is not economically practical to install them on every turbine.

Instead, a combination of inspections and routine measurements using existing systems provides powerful insights for some wind farm owners, however.

For example, most turbine controllers can detect excessive vibration of the tower or nacelle, but this is primarily for the purpose of safety – stopping the turbine quickly in the event of high vibration. Where this data is available in the SCADA system, it is normally heavily averaged and only reported at 10-minute intervals, so it is not routinely used to monitor for impending structural failures.

Additional valuable information can be extracted from tower frequency data, especially during the life-extension phase. Monitoring a tower’s natural frequency, in conjunction with statutory seabed inspections and general turbine operating conditions, allows owners to build models correlating to the tower’s natural frequency with seabed condition and current operating regimes, giving insights into wider structural integrity to underpin critical life-extension choices.      

The insights generated from these analyses can inform strategic decision-making, with increased profitability as a result. Traditional models of O&M leave owners and operators on the back foot, unprepared for failures and in the dark as to when they must replace key components. Backed with data, components can be replaced as needed – not too early, and certainly not too late.

Crucially for offshore wind farms, it means maintenance can be planned for the low wind season, and grouped by proximity, reducing logistical costs and avoiding unscheduled downtime. This can deliver savings of up to 30% from O&M budgets.

These gains are maximised when a life-extension strategy is implemented early on – ideally from the start of the turbine’s lifecycle. Modern diagnostics can still have transformative effects on profitability even for 20-year-old assets, but at that point there will be greater wear and tear compared to assets maintained smartly from day one.

When life-extension is implemented from the outset, this supports financial modelling and also increases the resale value of assets by up to 12%. Since offshore wind farms are growing in scale, this will be a significant factor for assets coming online today. Healthier wind turbines with a longer projected useful life are more attractive to investors – and with good data, wind farm owners and operators can demonstrate this.

Finally, not all life-extension strategies will provide equal savings. A versatile provider with a solid engineering background can deliver an integrated approach over a mixed portfolio of assets, which may require different strategies depending on age, turbine model and available data.