4.2.3.3. Introduction
The increasing penetration of wind energy into the electricity mix has been possible thanks to a constantly growing installed capacity, which has so far been mostly located on land. Land-based installations are, however, increasingly constrained by local ordinances and an often-limiting factor that comprises maximum allowable levels of noise. To further increase the number of land-based installations, it is important to develop accurate modeling tools to estimate the noise generated by wind turbines. This allows for a more accurate assessment of the noise emissions and the possibility to design quieter wind turbines.
Wind turbines emit two main sources of noise:
Aeroacoustics noise from the interaction between rotor blades and the turbulent atmospheric boundary layer
Mechanical noise from the nacelle component, mostly the gearbox, generator, and yaw mechanism.
This work targets the first class of noise generation and aims at providing a set of open-source models to estimate the aeroacoustics noise generated by an arbitrary wind turbine rotor. The models are implemented in Fortran and are fully coupled to the aeroservoelastic wind turbine simulator OpenFAST. The code is available in the GitHub repository of OpenFAST. 1 The code builds on the implementation of NAFNoise and the documentation presented in [aa-MM03] and [aa-Mor05]. OpenFAST is implemented as a modularization framework and the aeroacoustics model is implemented as a submodule of AeroDyn ([aa-MH05]).
The set of models is described in Section 4.2.3.4 and exercised on the noise estimate of the International Energy Agency (IEA) land-based reference wind turbine in Section 4.2.3.5. In Section 4.2.3.5, we also show a comparison to results obtained running the noise models implemented at the Technical University of Munich. This documentation closes with conclusions, an outlook on future work, and appendices, where the input files to OpenFAST are presented.