Wind tunnel experimental analysis of a complex terrain micrositing

The technical and economic feasibility of wind energy projects are defined by identifying the correct wind potential in the site and by the technological choice of equipment. The optimal micrositing of wind turbines determines the success of the project. Most current tools are insufficient to evaluate air flow in a complex terrain where wind effects such as acceleration, deceleration are difficult to be predicted The uncertainties related to the energy outcome present an increasing problem as the precision regarding the amount of the energy that may be commercialized is even higher. The combined use of wind tunnel and mesoscale numerical modeling represents the solution for wind power site assessment in a complex terrain. This paper presents a review of the contribution that wind tunnels have recently made for physical modeling of both the velocity field and the turbulence intensity as a methodology for the atmospheric boundary layer study in a complex terrain. Hence, it describes an experimental simulation of the atmospheric boundary layer (ABL) in a wind tunnel over a complex area to characterize the mean flow (detachment and reattachment) and the turbulence intensity with emphasis in the wind energy production. The experiment was conducted in a wind tunnel and employed two terrain categories: Category I – plain terrain and Category III-IV – moderately rough, corresponding, respectively, to the power law exponent p=0.11 and p=0.23. The complex terrain wind profiles were correlated with that in the plain terrain to show the changes of the velocity and show the extension of turbulence wake caused the by variable topography of the area. The measurements of the wind velocity and turbulence intensity were performed with a hot wire anemometry system. Results demonstrate that velocity profile and turbulence intensity profile vary significantly over the complex area, which makes an accurate experimental evaluation necessary to certify the micrositing layout. Power losses due to wake effects can easily reach 20% of the total power, which may make a plant infeasible.