Design and simulation of a system to generate electricity from mechanical vibrations

Abstract

Electricity generation from human footsteps is often affected by low power output. Vibration energy transducers such as piezoelectric materials often generate very little power and are prone to deformation by external forces. The main aim of the project was to design and simulate a system that generates electricity from human footsteps. Specific objectives were to determine how much power is generated from human footsteps, to select a configuration for the system, design and simulate the system. To obtain the power generated from human footsteps, an experiment was carried out to determine the force exerted by human footsteps and the power output. The experiment involved using a sample of individuals to walk along piezoelectric sensor plates to determine how much force was exerted, contact time and power output. A rack and pinion configuration was chosen as a suitable mechanism for the system. The components of the system such as the spring, rack and pinion, top and bottom plates were modelled and designed by stress and force analysis in order to obtain parameters for the simulation of the system. The system was then simulated in scilab taking parameters of a 24V DC generator. The results obtained from the simulation indicated that there was power produced from the system. However, alternating voltages and currents were produced creating need for a bridge rectifier to convert AC to DC in order to charge and store the energy in a battery. Adjusting the gains of the system such as the load resistance affected the voltage output. For example, increasing the load resistance lowered the voltage output and vice versa. The system can thus be improved through adjusting the gains, using springs with the right stiffness and right selection of the DC generator.