Abstract
AbstractIn order to study the effect of vertical staggering in large wind farms, large eddy simulations (LES) of large wind farms with a regular turbine layout aligned with the given wind direction were conducted. In the simulations, we varied the hub heights of consecutive downstream rows to create vertically staggered wind farms. We analysed the effect of streamwise and spanwise turbine spacing, the wind farm layout, the turbine rotor diameter, and hub height difference between consecutive downstream turbine rows on the average power output. We find that vertical staggering significantly increases the power production in the entrance region of large wind farms and is more effective when the streamwise turbine spacing and turbine diameter are smaller. Surprisingly, vertical staggering does not significantly improve the power production in the fully developed regime of the wind farm. The reason is that the downward vertical kinetic energy flux, which brings high velocity fluid from above the wind farm towards the hub height plane, does not increase due to vertical staggering. Thus, the shorter wind turbines are effectively sheltered from the atmospheric flow above the wind farm that supplies the energy, which limits the benefit of vertical staggering. In some cases, a vertically staggered wind farm even produced less power than the corresponding non vertically staggered reference wind farm. In such cases, the production of shorter turbines is significantly negatively impacted while the production of the taller turbine is only increased marginally.
Highlights
Wind power is a very promising clean and sustainable energy form
We studied the effect of vertical staggering on the power production in large wind farms using high-fidelity numerical simulations
We find that vertical staggering can increase the power production in the entrance region of the wind farm by up to 20%, see Figure 4A, compared with the corresponding aligned reference wind farm
Summary
Wind power is a very promising clean and sustainable energy form. The recent decades have shown a rapid development of the wind industry with an ever increasing contribution to the total energy production worldwide.[1]. Jensen model[7] to determine the optimal wind farm layout and find that vertical staggering can increase wind farm power output when the hub height difference between consecutive downstream rows is sufficiently large. Another study by Vasel-Be-Hagh and Archer[12] compared results from wake model calculations with LES results obtained with SOWFA.[23] They find that the Lillgrund wind farm with optimized hub heights generates about 6.3% more power in LES while, as mentioned above, the evaluations using the PARK model predict a 2% increase. We present data from LES in which we study the effect of streamwise and spanwise turbine spacing, turbine rotor diameter, the hub height difference between consecutive turbine rows, and the wind farm layout, on the power output of vertically staggered wind farms.
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