A novel miniature wind generator for wireless sensing applications

This paper describes a novel miniature wind generator for wireless sensing applications. The generator consists of an aerofoil that is attached to a cantilever spring. The airflow over the aerofoil causes the cantilever to bend, the degree of bending being a function of the lift force from the aerofoil and the spring constant. As the cantilever deflects, the flow of air is reduced by a bluff body and the lift force therefore decreases causing the cantilever to spring back. The aerofoil is hence exposed to the full airflow again and the cycle is repeated. When the frequency of the movement matches the resonant frequency of the structure, the aerofoil has the maximum displacement. A permanent magnet is fixed on the aerofoil and a coil is attached to the base of the generator. The movement of the aerofoil causes the magnetic flux cutting the coil to change, which generates electrical power. The device has dimensions of 12 cm × 8 cm × 6.5 cm. Experiments have shown that the generator can operate at wind speeds as low as 2.5 m-s^-1 with a corresponding electrical output power of 470 μW. This is sufficient for periodic sensing and wireless transmission. When the wind speed is 5 m-s^-1, the output power is 1.6 mW.