Abstract
Wind-turbine-wake evolution during the evening transition introduces variability to wind-farm power production at a time of day typically characterized by high electricity demand. During the evening transition, the atmosphere evolves from an unstable to a stable regime, and vertical stratification of the wind profile develops as the residual planetary boundary layer decouples from the surface layer. The evolution of wind-turbine wakes during the evening transition is examined from two perspectives: wake observations from single turbines, and simulations of multiple turbine wakes using the mesoscale Weather Research and Forecasting (WRF) model. Throughout the evening transition, the wake’s wind-speed deficit and turbulence enhancement are confined within the rotor layer when the atmospheric stability changes from unstable to stable. The height variations of maximum upwind-downwind differences of wind speed and turbulence intensity gradually decrease during the evening transition. After verifying the WRF-model-simulated upwind wind speed, wind direction and turbulent kinetic energy profiles with observations, the wind-farm-scale wake evolution during the evening transition is investigated using the WRF-model wind-farm parametrization scheme. As the evening progresses, due to the presence of the wind farm, the modelled hub-height wind-speed deficit monotonically increases, the relative turbulence enhancement at hub height grows by 50%, and the downwind surface sensible heat flux increases, reducing surface cooling. Overall, the intensifying wakes from upwind turbines respond to the evolving atmospheric boundary layer during the evening transition, and undermine the power production of downwind turbines in the evening.
Highlights
Introduction1.1 The Evening Boundary Layer and Turbine Wakes
1.1 The Evening Boundary Layer and Turbine WakesDaily electricity demand typically increases in the early evening, making the balance of power supply and demand a challenge during this period (McLoughlin et al 2013)
The value of the surface heat flux Q H changes sign at the same time (Fig. 3b), while the latent heat flux decreases over time (Fig. 3b)
Summary
1.1 The Evening Boundary Layer and Turbine Wakes. Electricity demand typically increases in the early evening, making the balance of power supply and demand a challenge during this period (McLoughlin et al 2013). The wind-power capacity of the world continues to grow, and providing stable electricity supply via wind power remains an ongoing challenge to power-grid operators due to the variability of wind-energy production. It is important to understand utilityscale wind-turbine-wake behaviour during the evening transition because wakes undermine downwind wind-power production. An enhanced understanding of wake evolution during the evening transition can be helpful in other situations. Offshore wind farms often experience land and sea breezes such that coastal flow undergoes a similar transition to that of a continental evening transition (Angevine 2007) and can affect wind-power production
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
