The yearly increase in electricity demand, driven by the needs that arise in the world, has created challenges of great importance for public policies of different countries. Policies that seek to supply this growing energy consumption with solutions that do not produce a negative environmental or social impact. In response to this difficult situation, governments, industries, and academic community have opted for a progressive change to renewable energy sources. One of the most promising alternatives, with rapid growth and which seems to be adapted to technological, social, and environmental requirements, is the wind energy. Various research has been carried out on this subject around the world, among which those developed in Savonius type Vertical Axis Wind Turbines (SVAWT) stand out. This great interest generated by this category of turbine is partly due to the potential solution that represents its implementation in urban areas or regions with issues in the electric power service. Several characteristics make them ideal for this type of applications, for example, their simple design, their good starting capacity, their operating range for low wind speeds, their independence from the wind direction, etc.The main objectives in wind turbine studies are focused on obtaining the best use of the conversion of wind energy. In this context, one of the topics of greatest interest is the influence of geometric parameters of the rotor on the SVAWT performance. To evaluate this influence, experiments have been developed for different scale models of SVAWT in wind tunnels. However, the experimental evaluation implies high times in its execution and elevated manufacturing costs when these are carried out for multiple designs and conditions. In this sense, Computational Fluid Dynamic (CFD) simulation has provided the freedom to run studies with fewer limitations. Therefore, numerous and varied investigations have been done through this computational tool. Despite the advantages offered by CFD simulations, they are rarely used for large-scale experiments, which are based on a statistical design. This would involve an in-depth analysis of multiple SVAWT models, thus helping to find the optimal settings for the best possible performance.This work investigates the influence of the rotor geometric parameters, including aspect ratio, overlap ratio, twist angle, and number of blades on the performance of the SVAWT. The Response Surface Method (RSM) is applied to examine the influence from a statistical point of view. For this purpose, first a SVAWT is parametrically modeled through the geometric variables of its rotor. Second, the selection and construction of the Design of Experiments (DoE) that defines the magnitudes of the variables in each of the SVAWT configurations are carried out. Third, transient CFD simulations are run on each model defined by the DoE to find the power coefficient (Cp) of the turbine. Cp is a measure of aerodynamic performance. Finally, the solutions obtained numerically are used to generate the Response Surface.The Response Surface is statistically evaluated, finding satisfactory metrics of quality. A global sensitivity analysis is carried out to evaluate the direct and joint influence of each geometric parameter on the Cp. The importance of each parameter in the variability of Cp is classified through quantitative sensitivity indices. Likewise, a graphical representation of the Cp results in the domain of each of the input parameters is made to obtain additional information on the main effects. As a result, the experimental space where it is probable to find maximum values of Cp is delimited, prioritizing, and defining ranges in the geometric parameters. The procedure used in this study and its corresponding results provides tools to examine the performance of different SVAWT models, without having to evaluate experimentally or numerically all the possible options. Moreover, the RMS approach allows studying the effects of all factors with fewer experiments. Further research is needed to establish the configuration of the SVAWT that achieves the maximum value in Cp using direct optimization techniques employed in the Response Surface.

Influence of Geometric Parameters on the Performance of Savonius Wind Turbine Using the Response Surface Methodology

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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