Thermoelectric On-Spot Energy Harvesting for Diagnostics of Water Service Pipelines

Abstract

Performance of an on-spot thermoelectric (TE) energy harvester is investigated experimentally and analytically. This research aimed for energy harvesting for powering an acoustic sensor on water service pipe-lines and transmitting the monitoring signals in wireless. For simultaneous cooling and heating purposes in buildings, there are several different temperatures of water/fluid pipes built in confined plumbing space. Hence a human access to examining the pipe condition is significantly limited, even for replacing a battery. Remote monitoring is desired to maintain the pipes healthy in long term operation and hence the local on-spot power supply is important. A set of hot and cold pipes next each other could be an energy source. This work focuses on analytical optimization and the experimental validation of the energy harvesting from such small temperature difference. The advanced sensors and wireless transmitters consumes only in a range of 1-10 × 10−3 W for minimum intermittent operation. From a temperature difference of 1 – 10s degrees C, we investigated two different heat transport approaches, (1) heat pipes and (2) mini-channel cold-plate both fit to a confined 0.1 m gap space. In experimentation, a purified water runs through the hot and cold pipes and the temperatures are controlled by two independent scientific chillers. The pipe diameter is significantly smaller compared to the real but the gap is maintained. The results show a reasonable matched with the analytic model, while the TE modules were not optimally designed. A series of an off-the-shelf TE modules with a size of 40 mm × 40 mm and containing 127 thermo-couples is used. The electrical power harvested from the set of 30 °C and 7 °C water observed 2.4×10−3 W and 81×10−3 W for the heat pipe and mini-channel, respectively. The output voltage at the optimum load was slightly lower than 1.0 V. If it is designed to reach 1.2 V, a DC-DC converter will be applicable for 5 V universal serial bus (USB) interface, which widely matches variety of off-the-shelf monitoring equipment.