Design, Development and Testing of a Combined Savonius and Darrieus Vertical Axis Wind Turbine

With a growing focus on renewable energy, interest in design of wind turbines has also been expanding. In today’s market, the horizontal axis (windmill) turbine is the most common type in use; but, vertical axis (Darrieus) turbines have certain advantages. Darrieus turbines, which are lift-driven, have a higher power potential than the horizontal, or drag-driven turbines. The main flaw with their design is their inability to self-start. Darrieus turbines require an external energy source to bring the device to a minimum rotational speed. This paper presents design, construction and testing of a vertical axias (Darrieus) wind turbine with 3 blades, starting solely from the low energy of the wind. A separate drag device (Savonius type turbine) on the top of an existing Darrieus turbine was mounted to make the turbine self start at low wind speed. The cut-in speed of the turbine was 3 m/s, cut-off speed was 20 m/s and power obtained was 50 Watts at wind velocity of 6 m/s. The testing with primiarly available permanent magnetic generator sponsored by industry resulted in 35 Watts at 9m/s.