An Integrated Simultaneous Thermal/RF Energy Harvesting System for Wireless Sensor Networks

This work presents an integrated simultaneous thermal/RF energy harvesting system that is suitable for low-power wireless sensor networks. The system has the ability to combine harvested energy from both DC and AC sources at the same time and provide a regulated output voltage of 1.75V feeding a current load from 150 µA to 770 µA. The system also enables the storage of extra power by charging a supercapacitor in order to use it during power shortage periods. A triple mode maximum power point tracking (MPPT) algorithm is implemented to achieve the best possible efficiency at different source and load conditions. The system is implemented in a 0.18 µm CMOS technology and utilizes a total on-chip flying capacitance of 2.4nF. The overall end - to-end efficiency of the system reaches a maximum of 60.5 % at input thermal voltage of 350m V and RF input power of −8dBm.