Abstract
The multi-rotor (MR) wind turbine concept can be used to upscale wind turbines without increasing the rotor diameter, which can be beneficial for transport, manufacture and design of wind turbines blades. The rotor interaction of a MR wind turbine leads to a faster wake recovery compared to an equivalent single-rotor (SR) wind turbine wake. In this article, the benefit of the faster wake recovery of MR wind turbines is quantified using Reynolds-averaged Navier-Stokes simulations of a 4}4 rectangular MR wind farm, for three different inter wind turbine spacings. The simulations predict an increase of 0.3-1.7% in annual energy production for the MR wind farm with respect to an equivalent SR wind farm, where the highest gain is obtained for the tightest inter wind turbine spacing. The gain in AEP is mainly caused by the aligned wind directions for the first downstream wind turbine in a wind turbine row of the MR wind farm, which is verified by an additional large-eddy simulation.
Highlights
The upscaling of wind turbine blades has led to multi-megawatt turbines equipped with blades approaching 100 m, which are challenging to design, transport and manufacture
The gain in annual energy production (AEP) is mainly caused by the aligned wind directions for the first downstream wind turbine in a wind turbine row of the MR wind farm, which experiences 7-16% more power compared to the same wind turbine in SR wind farm due to the faster wake recovery of the MR wind turbine wake
The Reynolds-averaged Navier-Stokes (RANS) results are in contradiction with results from large-eddy simulations (LES) performed by Ghaisas et al [3], who showed that all downstream MR wind turbines in a row of five wind turbines produce 1545% more power compared to a row of SR wind turbines
Summary
The upscaling of wind turbine blades has led to multi-megawatt turbines equipped with blades approaching 100 m, which are challenging to design, transport and manufacture. These challenges can be circumvented by the multi-rotor (MR) wind turbine concept, as discussed by Jamieson et al [1]. [3] employed large-eddy simulations (LES) to show that a row of five MR wind turbines with an inter spacing of 4Deq has a reduced power deficit compared to a row of equivalent SR wind turbines when the wind direction is aligned with the row orientation. The main RANS results are verified by an additional LES test case, as described in Appendix A
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