Material Selection for Vortex-Induced Vibration Energy Harvesting in Water Systems: Environmental and Performance Insights from the Verona Case Study in Italy

Wastewater treatment plants are essential environmental infrastructures that operate continuously and require considerable electrical energy, while simultaneously conveying persistent flows that dissipate low-grade hydraulic energy. Recovering even a fraction of this overlooked resource could support decarbonisation targets and provide autonomous power for environmental monitoring and digital water services, without additional land take or large hydropower installations. Within the Horizon Europe project H-HOPE – Hidden Hydro Oscillating Power for Europe – this study investigates how the selection of structural materials affects the performance of vortex-induced vibration energy harvesters (VIV-EH) deployed in controlled water environments. Rather than optimising device geometry or control strategies, the analysis focuses on how broad material classes influence feasibility, energy potential, and environmental suitability when integrating harvesters into existing wastewater infrastructure. Operational records from a municipal wastewater treatment plant in northern Italy were analysed. A validated one-dimensional modelling framework was used as a comparative tool to estimate annual energy production for harvesters manufactured from widely available metallic and composite materials under realistic operating conditions.Results show a consistent trend: lighter materials with favourable stiffness-to-mass ratios generate larger oscillation amplitudes and substantially higher harvested energy. Fibre-reinforced composites achieve the highest performance, with an estimated annual production of approximately 800–875 kWh/year for the specific case study. Aluminium alloys produce slightly lower yields (≈800 kWh/year) while retaining advantages in recyclability and manufacturability. In contrast, high-density metals such as structural and stainless steel, typically yield 450–480 kWh/year, highlighting how increased mass suppresses the vortex-induced response. These differences arise solely from material choice, without modifying hydraulic conditions, device geometry, or plant operation.From a renewable-energy perspective, these results indicate that material-driven design is a practical lever for scaling small, autonomous generators across water networks, providing reliable power for sensors, process control and digital water management. Because devices exploit existing hydraulic infrastructure, they can be replicated modularly and integrated alongside other renewables as part of distributed energy portfolios, supporting resilience and local self-sufficiency. However, performance advantages must be considered alongside environmental trade-offs. Composites show limited recyclability and higher embodied energy compared with metals such as aluminium and stainless steel, which favour circularity but offer lower energy conversion. The study relies on a simplified modelling framework and a single representative site, broader validation under different hydraulic regimes and long-term material ageing will require pilot-scale deployment. Despite this, the comparative trends provide robust guidance for design and prioritisation.Overall, the study demonstrates that targeted material selection can unlock “hidden hydropower” within wastewater systems, delivering incremental yet scalable renewable generation aligned with European decarbonisation goals while enhancing the sustainability and reliability of essential water services.