Design of a new Kaplan pico-turbine runner bades

Within the frame of the design of a pico-hydro power plant for developing countries, the University of Applied Sciences of Fribourg (Switzerland) aims to develop a low-cost Kaplan turbine with a power output of at least 1 kW. The current paper presents the study and the results of the development of this new turbine as well as the seeming paradox to use advanced simulation technics in order to design a low-cost turbine. At first, a turbine with NACA profiled blades was designed to obtain the best performance. Numerical simulations (CFD) and experimental tests were performed to characterize the turbine performance. The first prototype is manufactured by a 5-axis CNC machine. Nevertheless, in developing countries this technology is not accessible and therefore, a new approach for the design has to be considered and applied. The manufacturing processes within these countries is studied and presented. The best known manufacturing techniques for those countries are those based on metal sheets and welding. Hence, a pico-turbine which can be completely realized using these techniques is designed and investigated. The challenge was to determine the optimal thickness, the guide blade angle and the best bending of the runner blades, which are then welded on a hub. The turbine performance is characterized by CFD simulations. By varying the parameters mentioned above, the best compromise between feasibility and performance is found. The results show that the low-cost turbine has a reduced mechanical power of 50 % compared to the standard turbine. Nevertheless, the achieved overall power output is by far sufficient for the intended application and the simplicity of design guarantees an uncomplicated maintenance. Currently, the concept is being validated and tested in Madagascar. Besides the use in developing countries, the turbine has the potential to be installed in mountain regions or any other isolated regions within developed countries.