Posters

Abstract

With the continuing trend to increase the AEP production in order to reduce the LCOE, the wind turbine development aimed towards larger rotor diameter sizes. Yet, for some areas of project, aerial constraints, due to aviation or radar for instance, impose a tip height limit. To comply with this limit, the hub height is reduced. This type of turbine with large rotor and small height is later referred as “Stubby Tower” turbine. One aspect of such turbine that as yet to be fully explored is the impact of the reduction of clearance between the lower blade tip height and the ground. It is known that the wind shear has a negative impact on both performance and lifetime of the turbine. Often, this aspect is studied at the Surface Boundary Layer, where the wind gradient is modelled with the power law. But for stubby tower, the low blade tip is lower, almost below the SBL. The wind gradient at this stage is larger than usual and is best fitted with the log-law. The key interest here is, given the large gradient between the low blade tip and the high blade tip, how does the performance of such turbine compare with a regular one? To answer this question, more than 2700 simulations were performed using QBlade Non-Linear Lifting Line module, backed in some cases with STAR-CMM+ simulations. The simulations cover a range of roughness lengths, inflow angles and rotor diameters. The results showed a noticeable reduction of AEP production when the hub high is below 70% of the rotor diameters, and accentuated in the cases where the clearance to the ground is below 15m. This findings are compiled in matrices than can be used in EYA estimation to mitigate the reduction on the P50 before a Site-Specific Power Curve is provided.