Power supply for wireless sensor systems

The power supply of wireless sensor systems is an issue of growing importance since replacement of batteries is expensive over the sensor lifetime. We will present an energy harvesting system which generates electrical energy from flowing media without any rotating parts. Available energy densities in flowing media are in the range of 256 W/m² in air at a flow velocity of 10 m/s and 1600 kW/m² in water at 2 m/s, respectively. The generator consists of piezoelectric bimorph cantilevers with very low maintenance requirements. The cantilevers are oscillating in a von Karmanpsilas vortex street induced by a flow disturbance. Modeling and analytical calculations give parameters for a design optimization which have been verified by a finite element simulation. The working principle has been proved using a functional model of the generator. Maximum voltages of 0.83 V have been achieved at air flow velocities of 35 m/s. The cantilevers delivered up to 108 muW at a velocity of 45 m/s.