Accounting for tree growth in resource assessment: A case study using the VENTOS code on Kyle wind farm Presenter: Oisin BRADY (VENTEC) Contributors: Anabel Gammidge (AMEC Wind) J.L. Palma, F.A. Castro (CEsA-FEUP)

Summary Who are we Overview of VENTOS The site Method Results Conclusions

Who we are VENTEC-THALES –wind resource consultancy –Specialisation in complex terrain –Analysis of operational projects AMEC Wind Energy –UK-based developer, subsidiary of AMEC plc. –42 MW installed –1500 MW under development CEsA ( CENTRE FOR WIND ENERGY AND ATMOSPHERIC FLOWS ) –Porto University Engineering department –Developed VENTOS code since 1992 –Ongoing research Stand 149d

Overview of VENTOS CFD code –Terrain following grid –Fixed-constant k-e turbulence model Canopy extension to boundary layer treatment –Based on work by Svensson and Haagkvist Modification of k-e turbulence equations Models momentum sink and added turbulence –Developed in collaboration with RES –Validation Excellent results (windspeed, turbulence) with large areas of forest Not so good with narrow strips (windbreaks)

Kyle Forest Scotland – southern uplands 100 turbines over 110 km 2 90% forest cover –Tree heights critical to model –Foliage density also required –Detailed GIS data with tree heights and species provided

Tree heights

Method Significant wind directions identified Calculations run for 2005 –Results compared to measured –Modelled speedup between two mast locations within 2% of measured Re-run for 2017 Results normalised to undisturbed upstream location

Results In 2017 –wind speeds increase 2% to 7%. –Turbulence intensity decreases on average by 4% to 13% –Area of recirculation appears due to growth of plot of trees –Able to modify felling plan based on impact on individual turbines

Conclusions Energy yield for a site near forest will change over time! Forest management can potentially improve performance, without wholesale clearance Understanding of the effect of trees on turbine output is greatly improved using VENTOS