Optimal Load Capacitance for Triboelectric Energy Harvesters to Maximize Transient Power

This paper describes an analytic method to determine the optimal load capacitance of a full wave rectifier (FWR) in triboelectric energy harvesters. The amount of average power delivered from the harvester to the rectifier grows in each cycle, eventually reaching a peak value. In steady state, the average rectifier power depends on the harvester characteristics and the load capacitance of the rectifier. For a given harvester, if the load capacitance is too small, the rectifier power does not reach the maximum power in steady state. Alternatively, if the load capacitance is too large, the number of cycles to reach maximum power increases, causing additional delay. An analytic method is proposed to estimate the optimum value of this capacitance, which ensures maximum power while minimizing the transient time. The results are validated with the measurement results of a triboelectric harvester.