Site conditions and turbine performance in a mountain pass

Wind energy is often seen as an energy source to be used in large, flat areas, for example the United States' midwest or the plains of northern Europe. However, as turbine technology develops and electricity transmission becomes constrained, developers are looking to areas that were until recently considered marginal or less interesting. A good example of such areas are the mountain passes of the Alps, where good transportation and transmission links could make the installation of turbines easier and cheaper.

But what of the wind resource in such areas? Standards and experience would lead us to say that terrain complexity in passes would lead to flow complexity, and result in wind climates that are outside of turbine specifications. This presentation will use data from two different sites in Europe and the U.S.A. to show how wind conditions vary between two sites with very different terrain. Turbulence intensity, turbulence length scales and other flow characteristics will be presented, along with data from turbine simulations.

Results show that conditions in the apparently complex pass terrain may be less challenging to the turbine than expected. The turbine simulations show that characteristic turbine loads may be reduced in the pass, compared to the comparison site. We show some mechanisms that may have resulted in these benign conditions and discuss how applicable the results are to other sites.