Experimental study on a modified Savonius wind rotor for street lighting systems. Analysis of external appendages and elements

This paper is aimed at investigating the performance of a Savonius generator in the presence of external aerodynamic appendages. The Savonius generator is a slender (high aspect ratio) vertical axis wind turbine and is part of a public lighting system (a street lamp) powered by renewable energy sources, particularly wind and solar energy. The external elements are self aligning systems, a conveyor and a deflector, used to increase the rotor's aerodynamic performance. The high aspect ratio, required for architectural integration, and the use of self aligning aerodynamic appendages distance this Savonius assembly from all the other ones tested in previous research works. For this reason, new tests have been carried out in static and dynamic conditions on a 1:1 scale model in the Environmental Wind Tunnel (EWT) of Marche Polytechnic University (UNIVPM); three different rotors at different wind velocities were analyzed for each possible combination of aerodynamic appendages. The results showed that the rotor's performance could be increased with the simultaneous application of a conveyor and deflector, reaching a maximum power coefficient of about 0.3. Also static measurements were performed on a locked rotor at different angles of attack. The torque angular distribution showed a periodic behavior with no negative torque values.