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ENERGY HARVESTING storage Comparison of Energy Harvesting Systems for Wireless Sensor Networks A Quantitative Investigation of Inertial Power Harvesting for Human-powered Devices Hyeon Joo OUTLINE Power requirement Suitable scavenging energy source Energy conversion device Vibration Power requirement Power requirement Power requirement Actuator and Communication consumes a large proportion of total power Suitable scavenging energy source Mechanical energy source Steady state mechanical source Steady state: wind, flow, current.. Intermittent mechanical source Human activity(walking, typing.. 5.88J/2steps ) Vehicles passing Vibration Energy depends on the amplitude and its freq. Mass of harvesting device relative to the vibrating mass Mechanical energy source Typically vibration is made up of a number of fundamental freq. and their harmonic Energy conversion devices Vibration m: seismic mass k: spring of stiffness u(t): Position of case x(t): Position of the seismic b: Damping coefficient Vibration m: seismic mass k: spring of stiffness u(t): Position of case x(t): Position of the seismic b: Damping coefficient Mx’’(t) + Bx’(t) + Kx(t) = - Mu’’(t) Vibration m: seismic mass k: spring of stiffness u(t): Position of case x(t): Position of the seismic b: Damping coefficient Vibration mx’’(t) + bx’(t) + kx(t) = - mu’’(t) Vibration ωn : natural freq : damping factor ω =ωn = peak power (resonant) ω : vibration freq Vibration Increase the damping factor Reducing the peak power, but increase bw Vibration Thus, fixed freq = low d.f. Various freq = high d.f. Vibration Harvested energy is proportional to the m Vibration Piezoelectric conversion (pressure) Commonly used material: PZT, BaTiO3, PVDF Electrostatic conversion The formation of a parallel plate capacitor Electromagnetic conversion Magnetic and coil Intermittent mechanical conv. Piezoelectric conversion Electro-active pol