A survey of flow-based energy harvesters for powering sustainable wireless sensor nodes

Self-powered wireless monitoring systems, wireless electronic devices, and embedded microsystems have gained enormous interest in recent years due to the vast sensing and monitoring applications in various fields, including civil infrastructure, oil and gas industry, healthcare, environment, military, agriculture, and consumer electronics. The main component of these systems is a wireless sensor node (WSN). The continuous operation of WSN depends on an uninterrupted power source, which is now delivered from electrochemical batteries with short life cycles and related major environmental problems. One potential solution to avoid replacing batteries in WSNs is to explore energy harvesting as a sustainable method for either directly replacing batteries or enabling regular battery recharge. Various energies surround the wireless sensor nodes, including thermal, solar, vibrational, acoustic, and fluid flow. This paper discusses the recent advancements in the field of flow energy harvesters based on fluid flow in open environments as well as in pipelines and channels. Flow energy harvesters (FEHs) transform the energy from fluid flow into electrical energy. This electrical energy is then utilized to power WSN. Mainly, two types of FEHs, flow-induced rotation-based energy harvesters (mini turbines) and flow-induced vibration-based energy harvesters (electromagnetic, piezoelectric, and hybrid mechanisms-based harvesters), have been reviewed and discussed in detail concerning device architecture, fluid type, bluff body shapes, fluid pressure and velocity, conversion mechanism, performance parameters, and implementation. Most of the reported piezoelectric energy harvesters have overall sizes ranging from millimeters to centimeters. The power output of the flow-induced rotation-based energy harvester ranges from 0.1 to 170 mW, whereas the power output of piezoelectric flow-induced vibration-based energy harvesters ranges from 0.38 nW to 20 mW, and the power output of the reported electromagnetic flow-induced vibration-based energy harvester ranges from 2 nW to 234 mW. However, the reported output of hybrid flow energy harvesters (HFEHs) ranges from 16.55 μW to 648 mW. HFEHs can produce the highest power densities because of their combined piezoelectric and electromagnetic energy conversions.