Power Optimization of TENGs via Load Capacitance Sizing

A power optimization strategy is described for triboelectric energy harvesting systems by optimizing the load capacitor size in a full-wave rectifier (FWR). In ac harvesters such as triboelectric nanogenerators (TENGs) with an FWR, the average power delivered to the rectifier increases in each cycle, ultimately reaching a steady state determined by system parameters. Through cycle-level analysis of input voltage, current, and rectifier turn-on time during mechanical motion, an optimal load capacitance is identified that maximizes power delivery while minimizing transient time to reach this maximum power. This approach achieves peak power delivery via capacitor sizing alone, eliminating the need for additional circuitry. Experimental results using a vertical contact-separation TENG with internal capacitance varying from 24 pF to 96 pF demonstrate that the optimal rectifier capacitance of 390 pF achieves maximum power delivery (900 nW at 1.7 Hz and 2.7 μ W at 5 Hz) in the second cycle, while suboptimal capacitances either fail to reach peak power or delay it to the seventh cycle or later. Sensitivity analysis reveals that the method exhibits high robustness, with capacitances within ±30% of the optimal value can still maintain ≥ 90% of peak power, providing flexibility when implementing or selecting the capacitor size.