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 km2

• 90% forest cover– Tree heights critical to model– Foliage density also required– Detailed GIS data with tree heights and species provided

20172005

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 growthof plot of trees

– Able to modify felling planbased on impact onindividual 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