Stochastic control applied to the ISWEC Wave Energy System

ISWEC (Inertial Sea Wave Energy Converter) is a fl oating marine device able to harvest sea waves energy by the interaction between the pitching motion of a fl oater and a spinning fl ywheel which can drive an electric PTO. In the ISWEC the hull dynamics is governed and controlled by the gyroscopic torque. The optimal control logic results in tuning the fl oater dynamics to the incoming waves in order to maximize the power transfer from the waves to the fl oater. In this paper the control problems of the ISWEC are stated and a control scheme based on the sub-optimal stochastic control logic is presented. The control scheme here presented has been tested using real wave records acquired at the deployment location in Pantelleria Island, which is one of the most energetic sites of the Mediterranean Sea

Hardware-In-the-Loop test rig for the ISWEC wave energy system

The Hardware-In-the-Loop (HIL) simulation is a powerful mean to reduce costs in the design and manufacturing process of an engineering system. HIL techniques allow to use real components inside a simulation of a mathematical model. In this work such techniques are used on the ISWEC wave energy system. ISWEC (Inertial Sea Wave Energy Converter) converts sea waves energy to electric energy by means of the gyroscopic effects produced by a spinning flywheel. The peculiarity of the system lays in the fact that all the moving parts needed to produce energy are sealed inside a hull and therefore protected from the aggressive ocean climate. During the research process on the ISWEC, the gyroscope and the electric generator have been manufactured and mounted on a test rig able to simulate the wave actions on the hull of ISWEC. Those real parts of the system have been replaced inside the full mathematical model of ISWEC. Such HIL system is validated against real wave tank tests carried out at the INSEAN in Rome. The HIL simulations proved to reproduce the real behavior in water waves of ISWEC with errors as small as the 10%

Hardware-In-the-Loop test rig for the ISWEC wave energy system

The Hardware-In-the-Loop (HIL) simulation is a powerful mean to reduce costs in the design and manufacturing process of an engineering system. HIL techniques allow to use real components inside a simulation of a mathematical model. In this work such techniques are used on the ISWEC wave energy system. ISWEC (Inertial Sea Wave Energy Converter) converts sea waves energy to electric energy by means of the gyroscopic effects produced by a spinning flywheel. The peculiarity of the system lays in the fact that all the moving parts needed to produce energy are sealed inside a hull and therefore protected from the aggressive ocean climate. During the research process on the ISWEC, the gyroscope and the electric generator have been manufactured and mounted on a test rig able to simulate the wave actions on the hull of ISWEC. Those real parts of the system have been replaced inside the full mathematical model of ISWEC. Such HIL system is validated against real wave tank tests carried out at the INSEAN in Rome. The HIL simulations proved to reproduce the real behavior in water waves of ISWEC with errors as small as the 10%

Performance Assessment Of The Full Scale Iswec System

— ISWEC (Inertial Sea Wave Energy Converter) is a system using the gyroscopic reactions provided from a spinning flywheel to extract power from sea waves. The flywheel and the energy conversion systems works inside the sealed floating body thus being protected from the marine environment to obtain reliable and durable operation. The goal of this work is to identify a strategy to optimize the performance of the ISWEC and to introduce a mathematical tool suitable for this purpose. The control of the device aims to exploit all the available control parameters in order to maximize power generation. At first the tuning of PTO control law is analyzed and then the additional control degree provided by the gyro speed is considered too. The control strategies are identified with a constrained multivariable optimization algorithm taking into account the device physical limits. The system analyzed in the present work is a 100 kW ISWEC device deployed at the Island of Pantelleria, Italy

ISWEC (Inertial Sea Wave Energy Converter): Modellazione, Controllo ed Analisi di Produttività

A partire dagli anni Settanta sono stati proposti e studiati centinaia di dispositivi di conversione di energia dal moto ondoso (noti in letteratura scientifica come sistemi cimoelettrici o WEC, Wave Energy Converter), sebbene attualmente non sia ancora stata identificata un’architettura definitiva per sfruttare tale fonte di energia. ISWEC (Inertial Sea Wave Energy Converter) è un sistema che sfrutta l’effetto giroscopico di un volano per convertire l’energia delle onde in energia elettrica. Il volano è contenuto all’interno di uno scafo stagno e risulta quindi protetto dall’ambiente esterno, garantendo affidabilità e funzionamento durevole del dispositivo. Questo lavoro si propone di identificare una strategia di ottimizzazione per il funzionamento di un sistema ISWEC con potenza nominale di 60 kW e installato presso Pantelleria

Application of Linear Model Predictive Control to the ISWEC

Wave energy is one of the promising offshore renewable energies. Nowadays many different kind of prototypes are being studied, designed and developed. ISWEC is a gyroscopic effect based device, with a sealed hull and slack mooring. The analysis of the system dynamic and its optimized control are cur-rently under research. In this paper, an online control technique is proposed, using linear MPC algorithm and implementing an observer over an augmented model, which can model and predict the incoming wave in a novel manner. Some comparisons with an optimized spring-damper existent control technique are shown. At the end, an evaluation of controller’s hardware feasibility is also presented

Modeling and optimization of a Wave Energy Converter using ANSYS AQWA

In the framework of renewable energy, Wave Power represents a highly promising resource for the production of green energy as it is characterized by very high power density values. Moreover, Marine Energy is currently still an open field, even though the amount of research investments and patents in this field has been rising in the past 40 years. Real waves are not monochromatic and are in fact a classical example of stochastic phenomena. As such, real waves are highly complex and can be studied by means of statistical frequency domain analysis. Devices able to transform this kind of energy in a more usable form, i.e. electricity, are called WECs (Wave Energy Converters). In 2009 Politecnico di Torino started studying and designing ISWEC (Inertial Sea Wave Energy Converter) to be deployed in Pantelleria Island, one of the most powerful sites in Italy. The core of the system is a one degree of freedom gyroscope enclosed in a sealed floating hull: the spinning motion of the flywheel, combined with the motion of the floating hull, produces a gyroscopic torque that can be exploited by means of a generator called PTO (Power Take Off). The gyroscope motion unloads an inertial reaction on the hull that combined with the waves, allows power absorption. The geometry of the hull and the hydrodynamic description of the system are key factors in designing such a device. The team in Politecnico di Torino chose ANSYS AQWA to tackle the hydrodynamic subproblem. The software capability that allows for the calculation of the hydrodynamic of the floating system, was fundamental in determining the most suitable geometry of ISWEC hull. The article presents and explains the results obtained using the software for the following tasks. As a first step, a parametric analysis comparing numerous geometries was carried out with AQWA-LINE. Furthermore, it was possible to use ANSYS AQWA as the core software for dynamic simulation of the whole system, implementing the gyroscope model and the dynamic interaction between the spinning gyroscope and the floating hull by means of a DLL developed in Fortran environment

Modeling and optimization of a Wave Energy Converter using ANSYS AQWA

In the framework of renewable energy, Wave Power represents a highly promising resource for the production of green energy as it is characterized by very high power density values. Moreover, Marine Energy is currently still an open field, even though the amount of research investments and patents in this field has been rising in the past 40 years. Real waves are not monochromatic and are in fact a classical example of stochastic phenomena. As such, real waves are highly complex and can be studied by means of statistical frequency domain analysis. Devices able to transform this kind of energy in a more usable form, i.e. electricity, are called WECs (Wave Energy Converters). In 2009 Politecnico di Torino started studying and designing ISWEC (Inertial Sea Wave Energy Converter) to be deployed in Pantelleria Island, one of the most powerful sites in Italy. The core of the system is a one degree of freedom gyroscope enclosed in a sealed floating hull: the spinning motion of the flywheel, combined with the motion of the floating hull, produces a gyroscopic torque that can be exploited by means of a generator called PTO (Power Take Off). The gyroscope motion unloads an inertial reaction on the hull that combined with the waves, allows power absorption. The geometry of the hull and the hydrodynamic description of the system are key factors in designing such a device. The team in Politecnico di Torino chose ANSYS AQWA to tackle the hydrodynamic subproblem. The software capability that allows for the calculation of the hydrodynamic of the floating system, was fundamental in determining the most suitable geometry of ISWEC hull. The article presents and explains the results obtained using the software for the following tasks. As a first step, a parametric analysis comparing numerous geometries was carried out with AQWA-LINE. Furthermore, it was possible to use ANSYS AQWA as the core software for dynamic simulation of the whole system, implementing the gyroscope model and the dynamic interaction between the spinning gyroscope and the floating hull by means of a DLL developed in Fortran environment