New models for smart energy harvesting devices EU-funded scientists developed analytical and computational tools to investigate a new class of piezoelectric energy harvesting devices for renewable energy resources. Energy Fundamental Research © Maksim Kabakou, Shutterstock The aim of energy harvesting is to scavenge energy from the environment to power electrical devices without use of external power supply. The key idea of the smart devices explored in the EU-funded project FSI-HARVEST (Numerical modelling of smart energy harvesting devices driven by flow-induced vibrations) was to invert the traditional ambition to avoid the potentially dangerous interaction of structure and the surrounding fluid, and instead harness the available flow energy. In this way, potentially harmful fluctuations are harnessed to provide independent power supply to small electrical devices. Possible applications include microelectromechanical systems, monitoring sensors at remote locations, or even in vivo medical devices that depend less on local energy storage and also require less effort to maintain. This energy converter technology simultaneously involves the interaction of the structure and the surrounding fluid, the electric charge accumulated in the material and a controlling electrical circuit. To understand the observable properties of such future devices and to increase their robustness and performance, FSI-HARVEST developed mathematical models for the complex physical system and investigated specific numerical techniques allowing robust systematic computational analyses. Scientists used the method of weighted residuals for solving differential equations. The approximate solutions were obtained by a variant of the finite element method in space and a discontinuous Galerkin scheme for evolving the solution in time. The highly nonlinear mathematical model is solved by means of the Newton-Raphson applied to all the involved physical fields. Computational analysis complemented the approach and was used to validate the mathematical models. Scientists developed a unique frequency-domain model that offers a holistic analysis of the electromechanical circuit, allowing with just one computation to predict the optimal operation states for a given harvester set-up with respect to the generated power output. In general, the team explored different configurations to test structural excitation mechanisms and its interaction with the surrounding fluid. These numerical investigations into the overall system enabled FSI-HARVEST to determine ways into optimal design of these smart energy harvesters by taking into account electric power supply under varying exterior conditions Keywords Energy harvesting, computational tools, piezoelectric, renewable energy, FSI-HARVEST
