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It is unassailable that Earth is undergoing some changes due to climate change, and fossil fuels are still the main power source all over the world. Rain regularity over the last years has become uncertain, what has significantly affected dams' water reservoirs. Hence their capacity for producing hydroelectric power has decreased and may continue to decrease. Indeed, this fact has forced governments to mainly use conventional power sources to supply energy. Consequently, electricity price has notoriously risen. In order to propose a solution to this issue, REDEEM Project (Recycling Dams for Eolic Energy Making), led by several professors and researchers of Universitat Politècnica de Catalunya (Barcelona, Spain), is studying the feasibility of installing small scale wind tur- bines in dam areas to reuse the existing infrastructure and take advantage of thermal winds. This Bachelor's Thesis has assessed the wind resource in several dam and valley areas located in Catalonia (Spain) by evaluating wind speed measurements taken in situ by weather stations belonging to MeteoCat (Catalan meteorology agency). Once the wind speed distribution at each location was known, it was possible to calculate the annual en- ergy output by a selected set of small scale wind turbines. Additionally, other interesting parameters have been calculated, such as the power coefficient (Cp), which determines how efficient the turbine is. All calculations are based on technical specifications provided by manufacturers. Moreover, the project has evaluated the possibility of employing floating structures and foundations, typically deployed in offshore environments. Eventually, an economic study has been carried out to determine the economic viability of the project at the best location. For this purpose, initial and variable costs, cost of energy, payback time and profit have been calculated for each turbine. This project has resulted in some of the studied locations being interesting candidates for wind energy generation, that is, being able to produce a very reasonable amount of energy per year. Besides, the economic evaluation has demonstrated that the installation is viable from a financial point of view as turbines have obtained rather low cost of energy values and relatively short payback times.

Lifting line vortex models have been widely used to predict flow fields around wind turbine rotors. Such models are known to be deficient in modelling flow fields close to the blades due to the assumption that blade vorticity is concentrated on a line and consequently the influences of blade geometry are not well captured. The present study thoroughly assessed the errors arising from this approximation by prescribing the bound circulation as a boundary condition on the flow using a lifting line free-wake vortex approach. The bound circulation prescribed to free- wake vortex model was calculated from two independent sources using (1) experi- mental results from SPIV and (2) data generated from a 3D panel free-wake vortex approach, where the blade geometry is fully modelled. The axial and tangential flow fields around the blades from the lifting line vortex model were then compared with those directly produced by SPIV and the 3D panel model. The comparison was carried out for different radial locations across the blade span. The study revealed the cumulative probability error distributions in lifting line model estima- tions for the local aerofoil flow field under both 3D rotating and 2D non-rotating conditions. It was found that the errors in a 3D rotating environment are consider- ably larger than those for a wing of infinite span in 2D flow. Finally, a method based on the Cassini ovals theory is presented for defining regions around rotating blades for which the lifting line model is unreliable for estimating the flow fields., peer-reviewed

The flow around the blade of a horizontal axis wind turbine wind tunnel model, operating at its optimal tip speed ratio in axial flow, has been investigated by means of stereoscopic particle image velocimetry (SPIV). The aim was to assess the possibility of measuring the loads impinged on the blade, using the acquired velocity field and its spatial derivatives. Thus, the three-dimensional (3D) velocity field and the pressure distribution surrounding the blade, as well as the aerodynamic loads, responsible for thrust and torque, were obtained with a non-intrusive method. The SPIV equipment was mounted on a traverse system and provided with phase-locked velocity planes perpendicular to the blade axis, scanning the blade from the root to the tip, at a fixed azimuthal position. The obtained velocity fields were used to estimate the pressure distribution and the aerodynamic loads on each plane, using a 3D formulation. Finally, these results were compared and discussed with similar results obtained computationally with a panel method model, showing good consistency. In the future, the proposed methodology could be used to study relevant topics such as active load control techniques, rotational augmentation, dynamic stall phenomena and the aerodynamics of small wind turbines operating at low Re numbers, among others. The processed and averaged flow fields from the experimental SPIV data are made available online to the reader. See appendix for description of the files.

This paper presents a simplified model for the dynamic analysis of a floating off-shore wind turbine (FOWT), which can be suitable for early feasibility and pre-engineering studies, where the complete system has to modeled in order to predict its behavior and to assess the performance. The model solves the equation of motion in time domain and considers Morison equation for computing the hydrodynamic loads. The aerodynamic loads are included by considering the wind thrust at hub height and the loads from the mooring system have been computed as a non-linear model. A methodology is also presented for calculating the structural properties of the system. The model is tested for two load cases and compared to results obtained with the more complex model FAST. The comparison between the response of the models is satisfactory. The simplified model allows to capture the main motions of the FOWT with an acceptable accuracy. A further feature of the model is to calculate the power generation of the floating wind turbine. The results show that the losses in comparison with a bottom-fixed off-shore wind turbine are below 1% or 1.1% according to the load case, which confirms the good performance of the studied FOWT.