Development of wind torch for bicycles

Abstract

A proof of concept has been developed to extract electrical power from the wind that flows on the bicycle when it is in motion. The wind power is converted into electrical power using a DC generator, which develops voltage as a function of the wind speed. A regulating circuit is used to supply constant voltage to energize rechargeable batteries, which can power up LED torchlight. In the present work, a 6" two-bladed propeller with a 24V DC generator and a three-bladed 6" wind turbine with a 12V DC-generator were tested in a low speed wind tunnel at the National Aerospace Laboratories, Bangalore, in the range 0-20m/s. During tests, the wind turbine developed a power of about 1.5W at about 15m/s, whereas the propeller developed comparable power at a higher wind speed. The wind turbine started at lower wind speeds compared to the propeller. The wind turbine was found to be superior at lower speeds, generating sufficient to charge multiple 1.2V re-chargeable batteries in the range 5-10m/s, making it more suitable for bicycles. During daytime when light is not required, the wind turbine can charge the batteries. During night times when light is required, the wind torch can charge the batteries as well as support the load of the LED lights. Even though the device may marginally increase the aerodynamic drag, a net gain occurs since the tyre friction of the conventional dynamo is totally avoided. Even though the primary target is to provide light to cyclists, the device can also be used to charge cell phone batteries and such applications.