Wind Farm Blockage and the Consequences of Neglecting Its Impact on Energy Production

Measurements taken before and after the commissioning of three wind farms reveal that the wind speeds just upstream of each wind farm decrease relative to locations farther away after the turbines are turned on. At a distance of two rotor diameters upstream, the average derived relative slowdown is 3.4%; at seven to ten rotor diameters upstream, the average slowdown is 1.9%. Reynolds-Averaged Navier-Stokes (RANS) simulations point to wind-farm-scale blockage as the primary cause of these slowdowns. Blockage effects also cause front row turbines to produce less energy than they each would operating in isolation. Wind energy prediction procedures in use today ignore this effect, resulting in an overprediction bias that pervades the entire wind farm.

[1]  Neil Adams,et al.  An evaluation of the predictive accuracy of wake effects models for offshore wind farms , 2016 .

[2]  Jan-Åke Dahlberg,et al.  A linearized numerical model of wind-farm flows , 2017 .

[3]  Niels N. Sørensen,et al.  The k‐ε‐fP model applied to double wind turbine wakes using different actuator disk force methods , 2015 .

[4]  E. S. Politis,et al.  Modelling and Measuring Flow and Wind Turbine Wakes in Large Wind Farms Offshore , 2009, Renewable Energy.

[5]  Rebecca J. Barthelmie,et al.  Analytical modelling of wind speed deficit in large offshore wind farms , 2006 .

[6]  H. B. Mann,et al.  On a Test of Whether one of Two Random Variables is Stochastically Larger than the Other , 1947 .

[7]  Niels N. Sørensen,et al.  Comparison of wind turbine wake properties in non‐sheared inflow predicted by different computational fluid dynamics rotor models , 2015 .

[8]  P. Thunis,et al.  Hierarchy of Mesoscale Flow Assumptions and Equations , 1996 .

[9]  Johan Meyers,et al.  Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions , 2017, Boundary-Layer Meteorology.

[10]  R. Willden,et al.  The efficiency of an array of tidal turbines partially blocking a wide channel , 2012, Journal of Fluid Mechanics.

[11]  B. Sanderse.  Aerodynamics of wind turbine wakes Literature review , 2009 .

[13]  Javier Sanz Rodrigo,et al.  WAKEBENCH Best Practice Guidelines for Wind Farm Flow Models , 2015 .

[14]  F. Porté-Agel,et al.  Flow Adjustment Inside and Around Large Finite-Size Wind Farms , 2017 .

[15]  Nicolai Nygaard,et al.  Wake effects between two neighbouring wind farms , 2016 .

[16]  Takafumi Nishino,et al.  Local blockage effect for wind turbines , 2015 .

[17]  Rebecca J. Barthelmie,et al.  Evaluation of wind farm efficiency and wind turbine wakes at the Nysted offshore wind farm , 2010 .

[18]  Andreas Bechmann,et al.  Evaluation of the wind direction uncertainty and its impact on wake modeling at the Horns Rev offshore wind farm , 2014 .

[19]  J. Corbett,et al.  Modeling stable thermal stratification and its impact on wind flow over topography , 2015 .

[20]  Patrik Berkesten Hägglund.  An Experimental Study on Global TurbineArray Eects in Large Wind Turbine Clusters , 2013 .

[21]  Mac Gaunaa,et al.  The flow upstream of a row of aligned wind turbine rotors and its effect on power production , 2017 .

[22]  Kurt Schaldemose Hansen,et al.  Empirical investigation of wind farm blockage effects in Horn Rev 1 offshore wind farm , 2012 .

[23]  Fred Nitzsche,et al.  An investigation of in‐field blockage effects in closely spaced lateral wind farm configurations , 2015 .

[24]  Aaron D. Smith,et al.  Wind Plant Preconstruction Energy Estimates. Current Practice and Opportunities , 2016 .