The first wind farm Life Extension Certification to 40 years | Nabla Wind Hub - SGS Success case
success cases

The first wind farm Life Extension Certification to 40 years | Nabla Wind Hub - SGS Success case

05 May 2023

The wind farm of our success case is located in Zaragoza, Spain. Composed by 27 units of Nordtank NTK43 600kW wind turbines, it became the first wind farm in the world to achieve the Live Extension Certification to 40 years in 2018, thanks to the analysis performed by NWH and the positive evaluation resulting from the Lifetime Extension (LTE) program carried out by SGS.

This milestone marked a before and after for the company, since having obtained the certification in life extension guaranteed security and credibility to new investors and decision makers to bet on these new methodologies that were not recognized until the date.

From this moment on, the strategies and studies of life extension based on extreme loads that NWH had been developing since its constitution as a company, back in 2011, had a certified standard model to rely on, which validated the 40-year operation plans established for wind turbines.

For the obtainment of this first Lifetime Extension (LTE) certification, Nabla performed a Full Life Analysis (P90), that showed how the site-specific conditions were affecting the wind turbine components. From this P90 analysis, we are able to get an accurate life expectancy for each of the wind turbine structural components, as well as a detailed mechanical fatigue degradation model of the structures, according to the turbine morphology, site conditions, detail operation conditions, and type of materials.

This in-detail assessment was indeed the key to the completion of SGS’s LTE Certification Program, following SGS ECPR 2056:2017 procedure and IEC 61400-22 experience.

In the first instance, the complete aeroelastic model of the Nordtank NTK43 600kW TWR43 wind turbine was built, to subsequently proceed to analyze the wind conditions and operation conditions of the emplacement. The deviation between the original model and the aeroelastic model being of 10% maximum margin as per Type Certification for OEMs (thus P90 nomenclature).

The wind conditions analysis provided us with the Weibull distributions, the turbulence intensity, the inflow angles, the wind shear, and the air intensity, per sector, to better determine the wind flow conditions of the wind turbines. Which in our case of study led to general benign wind conditions for the turbines, suitable for extending their useful life up to 40 years.

In this case study in particular, the wind farm was divided into 4 different cells according to the different wind conditions of each wind turbine, for being analyzed afterwards.

Image 1: Turbulence intensity

Once this wind condition analysis was performed, we turned to examine the operation conditions, crucial to determine the real operation of the wind turbines in terms of number of annual transients, yaw misalignments, and production availability.

And to conclude, the aeroelastic simulations under design and site-specific conditions were performed in order to determine the loading map and overall accumulative fatigue damage spectra, which helped us to define more accurately the life expectancy for every structural component of the wind turbine.

Table 1: life detection analysis results

To qualify for the SGS Certification, this first instance Full Assessment is needed plus a Long-Term Maintenance Recommendations (LTMR) for ensuring the operation of the wind turbines.

SGS delivers periodic checks and follow-ups in order to maintain the certification of the wind farm.

It was not until 10 years later, since Nabla Wind Hub began studying the wind farm life extension plans, that the wind industry reached the IEC61400-28 agreement between OEM’s, ISP’s and wind farm operators on methodologies that were recognized to be certified and marketed for extending the wind farm life expectancy.

This made it possible to extend the life of wind farms from the standard 20 years to 30, 35 or 40 years, reducing operations and maintenance costs, and increasing the Annual Energy Production (AEP) of the asset. A scenario that before the certification was impossible to support and finance as ISPs and wind farm operators were not able to validate their life extension plans.

Image 2: SGS Life extension Certification

Nabla Wind Hub and SGS were pioneers in certifying the first 40-year wind farm in the world. It was a job that was done independently because there was not yet an IEC61400-28 standard that would bring the wind industry into agreement on how different levels of analysis for life extension were considered good.

As of today, Nabla Wind Hub is in charge of 2 of the most relevant working groups for IEC 61400-28 International Normative for Life Extension, leading the groups for Aeroelastic Models and Uncertainties. As of conducting the Life Extension Guidance of the Spanish Wind Energy Association (AEE).