Wind resource assessment over a complex terrain covered by forest using CFD simulations of neutral atmospheric boundary layer with OpenFOAM Nikolaos Stergiannis nstergiannis.com nikolaos.stergiannis@vub.ac.be
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 1 Wind Energy Ø One of the fastest growing industries Ø EU Strategy on Climate Change for 2020 and beyond Ø 2015 a new record year: annual installations crossed the 62 GW Global cumulative installed wind capacity 1997-2015 (GWEC Report 2016)
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 2 Industrial Challenges Wind Turbine Design ü rotor aerodynamics ü mechanical loads ü incoming flow field Wind Farm Design ü wind resource assessment ü wake interactions and losses ü CAPEX & OPEX Wind Farm Optimization ü terrain effects ü wake effects ü power output Wake Effects deficit of wind speed increasing turbulence
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 3 Total duration: 4 years Aim of the project: Develop a non-deterministic CFD software for wind energy Key points: Improved mathematical model for the wind turbines Atmospheric Boundary Layer over complex and flat terrain Uncertainty quantification on the wind conditions Open-source software (OpenFOAM) Final goal: Accurate and fast simulations of onshore and offshore wind farms
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 4 Wind resource assessment a crucial process for the successful development of a wind farm project Motivation growth of wind sector scarcity of available land wind energy installation on complex terrain is expected to increase low-cost industrial models fail in very complex sites inaccurate energy estimation
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 5 Site under investigation 70% covered by thick forest trees of 15 to 20 m height mainly neutral stratification unidirectional wind from ESE
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 6 Site under investigation
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 6 Site under investigation Wind Mast 2 Wind Mast 1
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 6 Site under investigation Wind Mast 2 Wind Mast 1 NW Wind direction
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 7 Computational domain generated with blockmesh snappyhexmesh final mesh characteristics 18 blocks 7.7Mi cells 6km x 6km x 3km 3 layers 1st cell height = 0.9m
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 7 Computational domain generated with blockmesh snappyhexmesh final mesh characteristics 18 blocks 7.7Mi cells 6km x 6km x 3km 3 layers 1st cell height = 0.9m
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 7 Computational domain generated with blockmesh snappyhexmesh final mesh characteristics 18 blocks 7.7Mi cells 6km x 6km x 3km 3 layers 1st cell height = 0.9m
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 8 Governing equations & boundary conditions assumptions* neutral ABL stratification homogeneous flow local equilibrium of k and ε * Richards, P. J., Hoxey R. P. Appropriate boundary conditions for computational wind engineering models using the k-ε turbulence model. 1993
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 9 Initial conditions terrain surface characteristic* forest canopy: z0 = 0.8 m * Troen, I., Lundtang Petersen, E.: European Wind Atlas. 1989
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 10 Numerical modelling Incompressible steady state solver simplefoam Turbulence modelling RANS modified k-ε turbulence model 2nd order numerical schemes 5000 iterations in total solution converged in 1500 iterations 10 hours on 16 CPUs of 3.3GHz Model coefficients * * Prospathopoulos J. M., Politis E. S. and Chaviaropoulos P. K.: Modelling wind turbine wake in complex terrain.
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 11 Preliminary results and discussion WM-1 at 78m height WM-2 at 78m height WM-1 CFD simulations WM-2 CFD simulations 120 80 WM-2 2.545 WM-1 2.698 WM-2 CFD 3.603 WM-1 CFD 3.759 Height [m] 40 0 Velocity difference CFD: 0.156 m/s Observations: 0.153 m/s 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Axial velocity [m/s]
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 11 Preliminary results and discussion WM-1 at 78m height WM-2 at 78m height WM-1 CFD simulations WM-2 CFD simulations 120 80 WM-2 2.545 WM-1 2.698 WM-2 CFD 3.603 WM-1 CFD 3.759 Height [m] 40 0 agreement in the absolute values is much less Velocity difference CFD: 0.156 m/s Observations: 0.153 m/s 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Axial velocity [m/s]
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 12 Conclusions Test case over a very complex site Terrain covered with dense forest canopy Neutral stratification and constant roughness have been assumed CFD simulations were capable to predict the velocity difference between wind masts Absolute values were not correct since the profile of WM1 used at the inlet Challenge Impose the correct inlet conditions to derived the desired profile at the WM1 location use a flat terrain before? use mesoscale models?
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 13 Future work Simulate over different wind sectors and compare with observations Include the local roughness map with non-uniform roughness length z0 Use mesoscale model to predict the inlet conditions Compare with MeteoDyn
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 14 QUESTIONS? A person who never made a mistake never tried anything new Albert Einstein nstergiannis@gmail.com Nikolaos.Stergiannis@vki.ac.be
Wind resource assessment over a complex terrain covered by forest using 27/04/2017 - slide 14 QUESTIONS? A person who never made a mistake never tried anything new Albert Einstein nstergiannis@gmail.com Nikolaos.Stergiannis@vki.ac.be