Energy harvesting from water flow by using piezoelectric materials

As a promising energy-harvesting technique, an increasing number of researchers seek to exploit the piezoelectric effect to power electronic devices by harvesting the energy associated with water flow. In this emerging field, a variety of research themes attract interest for investigation; these include selection of the excitation mechanism, oscillation structure, piezoelectric material, power management interface circuit, and application. Since there has been no comprehensive review to date with respect to the harvesting of water flow using piezoelectric materials, herein relevant work in the last 25 years is reviewed. To ensure that key aspects of the water-flow energy harvester are overviewed, they are discussed in the context of energy-flow theory, which includes the three stages of energy extraction, energy conversion, and energy transfer. The development of each energy-flow process is reviewed in detail and combined with meta-analysis of the published literature. Correlations between the harvesting processes and their contribution to the overall energy-harvesting performance are illustrated, and directions for future research are also proposed. In this review, a comprehensive understanding of water-flow piezoelectric energy harvesting is provided and it is aimed to guide future research and the development of piezoelectric harvesters for water-flow-powered devices is promoted.