Development of a Thermoelectric and Electromagnetic Hybrid Energy Harvester from Water Flow in an Irrigation System

A hybrid energy harvester is presented in this paper to harvest energy from water flow motion and temperature difference in an irrigating pipe at the same time. The harvester is based on the integration of thermoelectric and electromagnetic mechanisms. To harvest the water flow motion, a turbine fan with magnets that are attached on the blades is placed inside of the water pipe. Multiple coils turn the water flow energy into electricity with the rotation of the turbine. The thermoelectric generators (TEGs) are attached around the pipe, so as to harvest energy due to temperature difference. For a maximum temperature difference of 55 degrees C (hot side 80 degrees C and room temperature 25 degrees C), twelve serial-connected TEGs can generate voltage up to 0.346 V. Under a load resistance of 20 ?, the power output of 1.264 mW can be achieved. For a maximum water flow rate of 49.9 L/min, the electromagnetic generator (EMG) can produce an open circuit voltage of 0.911 V. The EMG can be potentially used as a water flow meter due to the linear relationship between water flow rate and output voltage. Under the joint action of TEG and EMG, the maximum terminal voltage for TEG is 66 mV and for EMG is 241 mV at load resistances of 10 and 100 ?, respectively, resulting in a corresponding power output of 0.435 and 0.584 mW.