Design and Implementation of Hybrid Energy Harvesting System for Low Power Devices

Objectives: In this paper we report on experimental studies and system design for harnessing energy from three alternate energy sources, which are solar energy, radio frequency energy and piezoelectric energy. Methods/Statistical Analysis: In order to make an integrated unit, we have made a case like structure of the device. For RF energy harvesting, we have designed two antennas on Ansoft HFSS and then got them fabricated. For RF to DC power conversion we have used schottky detectors which are capable of highly efficient impedance matching. Moving on to solar energy, we have used two solar panels and each can produce voltage up to five volts. The panels are placed both inside and outside the system, to ensure that we get power when case is open as well as when it is closed. Finally, for the piezoelectric energy harvesting, we have made a series and parallel combination of piezoelectric sensors and this network is followed by a voltage doubler circuit, which is used to augment the voltage produced by the combination of sensors. Findings: Though the system was designed for harvesting solar as well as piezo energy, our main focus was to harvest energy from RF energy. Power is harvested from both the antennas and it is shown that lotus shaped patch antenna is giving more DC voltage 44 mV and 63 mV at 900 MHz, 1800 MHz respectively at 50 cm than Multi patch fractal antenna is giving maximum voltage 60 mV, 24 mV and 34 mV at 900 MHz, 1800 MHz and 2400 MHz respectively at 50 cm. Application/Improvements: Energy has been successfully harnessed from all three energy sources i.e. RF energy, piezoelectric, solar energy. The system can be used to power low power devices.