There’s a shift change to the wind industry’s convention of ‘end of life’. Lifetime is now based on a balance of economics and engineering risk of failure, rather than a pre-determined certified number. But can we extend operating wind farms to 30, 40 or 50 years? Keir Harman provides his expert insight in the latest issue of Wind Energy Network Magazine.
Life of an asset can now be considered a moveable point in time that will change based on market conditions, a chosen operating strategy and evolving technology. Untapped value is replaced with smarter operations as its catalyst, driven by innovation in dynamic control and data analytics.
Gains
There have recently been instances of owners’ portfolio net asset value increasing by over 5% through a change in asset lifetime approach. As well as monetary gain, a new angle is that owners reap ESG (Environment Social and Governance) benefits with significantly more carbon offsetting by producing 50% more energy than originally expected from the same raw materials – relying on extended lifetime as an alternative to decommission or new build.
Extending the life of renewable energy assets where capital expenditure is high, operating costs are relatively low, and the “fuel” is free, is not new. Some hydro-electric plants have now operated for a century with strategically managed refurbishment and retrofit programmes. So, can we extend operating wind farms to 30, 40 or 50 years? The answer is most likely yes, depending on how operational risks are managed and the extent of the refurbishment programme.
Investor confidence
Wind farm owners have already started to assume that they will operate their wind assets for longer and are changing their financial models to reflect this, with 30 or more years lifetime becoming common place in mature markets. Investor confidence is typically assured by assessing fatigue ‘headroom’ arising from the process of selection of type certified turbines. The ‘headroom’ is coupled with accurate operational measurements and refined load calculations to significantly increase life expectancy.
Extending asset lifetime is an integrated methodology and addresses two fundamental questions...”How much fatigue capacity remains in my asset?” and “How can I best utilize it?” Cost models to evaluate a range of lifecycle strategies are based on a data-driven framework.
“So, can we extend operating wind farms to 30, 40 or 50 years? The answer is most likely yes, depending on how operational risks are managed and the extent of the refurbishment programme.”
Options
Turbine control modifications, farm-wide control policies, operations & maintenance approaches and retrofit programmes are all input options. Simulation modelling and advanced data analysis are complemented with targeted inspections of components.
Managing the operational risks is at the centre of this methodology. For example, on a wind farm where each turbine is of identical design, some turbines will experience higher fatigue loading than others. Smarter control upgrades mean that loading can be more evenly distributed over a wind farm. Techniques such as wake steering, where a turbine is actively yawed to steer the wake away from a downwind turbine to limit loads, are being developed and implemented (today).
Smarter approach
A smarter approach to maintenance may see the operator swapping higher loaded components between turbines to distribute loading more evenly. Swapping the blades from the most loaded turbines at midlife with blades from the least loaded will reduce the extremes of fatigue life. Also, as the risk of component failure increases with time, implementing intelligent risk-based inspection and maintenance programmes mitigates risk.
As an added complexity, during the energy transition to high renewables penetration and lower electricity prices, wind farms will no longer operate in a passive, pre-determined way on our grid systems. They will instead be required to be more flexible and dynamically controlled to help balance and maintain system integrity, and to respond to market conditions with part load operation becoming frequent. Such changing operating strategies will lead to a need for fatigue life projections to be continuously re-evaluated.
New era
This new era is seeing the emergency of wind farm digital twins that model and project the impact of operational changes on lifetime assumptions. The wind industry must now challenge convention, follow a risk management approach and embrace innovation to get investors’ confidence for lifetime far beyond the original certified lifetime.
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