Dynamical analysis and experimental campaign for an inertial Wave Energy Converter with two degrees of freedom

An increased awareness of the negative effects of non-renewable energy sources on our planet and a progressive reduction in the use of fossil hydrocarbons have contributed to the rapid development of renewable energies in recent decades. This has favored the research and dissemination of modern technologies capable of harvesting energy from the environment and transforming it into electricity. Alongside the best-known sources of renewable energy, such as solar and wind power, there is another lesser known resource with immense potential: wave energy. Sea waves, in fact, represent a continuous and more predictable source of energy than the wind and the Sun. There are already numerous devices, some operational and others still in the experimental phase, which harness the energy of the sea. However, most of these systems only use part of the possibilities offered by wave motion. The Politecnico di Torino, through its MOREnergy Lab research center, has developed several solutions capable of exploiting this resource more effectively. However, so far, all of these devices are of the active type, i.e. equipped with a control system to optimize their efficiency. The new 2DoPe concept, on the other hand, introduces an innovative approach based on completely passive technology, eliminating the need for an active controller to manage energy production. However, experimental testing often involves significant logistical and financial challenges, especially when several dry and wet tests are required. For this reason, it is essential to develop reliable numerical models that enable virtual simulation and performance evaluation under controlled conditions. In this thesis, a large-scale prototype of the 2DoPe device, designed and constructed by researchers of the MOREnergy Lab, was tested under free decay analyzes to enable precise identification of its inertial properties and characterization of the friction function, which arises from the mechanical energy transmission between the pendulum unit and the PTO systems. Key parameters such as mass, center of gravity, and inertia moments were compared with numerical values to assess the accuracy of the identification process. In addition, an optimization process was performed to determine the best values for the friction and inertia parameters, improving the accuracy of the numerical model. This allowed for a preliminary validation of the 2DoPe concept within a numerical environment, yielding promising results in terms of model accuracy and dynamic response. At the same time, the study clearly highlighted the critical influence of the friction model on the behavior of the system, demonstrating its significant impact on both the accuracy of simulations and the optimization of the practical performance of the device. The conclusions drawn from this study provide a solid foundation for future model-based experimental correlations and make progress in considering 2DOPE a viable alternative to existing devices.