Design of a shrouded wind turbine for low wind speeds

Abstract

The use of renewable energy is promoted worldwide to be less dependent on fossil fuels and nuclear energy. Therefore research in the field is driven to increase efficiency of renewable energy systems. This study aimed to develop a wind turbine for low wind speeds in South Africa. Although there is a greater tendency to use solar panels because of the local weather conditions, there are some practical implications that have put the use of solar panels in certain areas to an end. The biggest problem is panel theft. Also, in some parts of the country the weather is more suitable to apply wind turbines. Thus, this study focused on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in South Africa. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the implementation of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of a open wind turbine developed for South Africa. The most important matter at hand when dealing with a shrouded wind turbine is to determine if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. Theory was revised to determine the available energy in the shroud after initial calculations showed that the power coefficients should have been higher than the open wind turbine with the same total diameter. A new equation was derived to predict the available energy in a shroud. The benefits of shrouded wind turbines are fully discussed in the dissertation content.