Design Of a Spar Buoy for Offshore Wind Turbines

Offshore wind Energy demonstrated to be one of the most promising technologies for growing electric energy demand worldwide. The main objective of this research was to conceive a floating offshore structure for supporting wind turbines. The Mediterranean Sea is characterized by deep water, especially in the western area, from Italy towards Spain, and this makes floating support structures desirable, since in deep water they are cheaper than bottom fixed piles [1]. An aerodynamic, electric and mechanic model was developed and tested against experimental results of laboratory and wind tunnel tests on a small scale wind turbine, demonstrating its reliability, so it was used to determine actions on the floater and a first concept design was performed using commercial software for marine structures analysis. Further steps in this process will include integration of the turbine model with hydrodynamic calculations, as well flume, tank and open sea tests for the designed floate

Stochastic Control of Inertial Sea Wave Energy Converter

The ISWEC (inertial sea wave energy converter) is presented, its control problems are stated, and an optimal control strategy is introduced. As the aim of the device is energy conversion, the mean absorbed power by ISWEC is calculated for a plane 2D irregular sea state. The response of the WEC (wave energy converter) is driven by the sea-surface elevation, which is modeled by a stationary and homogeneous zero mean Gaussian stochastic process. System equations are linearized thus simplifying the numerical model of the device. The resulting response is obtained as the output of the coupled mechanic-hydrodynamic model of the device. A stochastic suboptimal controller, derived from optimal control theory, is defined and applied to ISWEC. Results of this approach have been compared with the ones obtained with a linear spring-damper controller, highlighting the capability to obtain a higher value of mean extracted power despite higher power peaks

Design of a Wave Energy Converter A case of application: ISWEC

Wave energy is one of the most promising renewable energy sources of the last few decades. Wave power has been investigated in Europe since the Seventies. In 1974 Prof. Stephen Salter proposed one of the first Wave Energy Converters (WEC), called Duck, at the University of Edinburgh. In the past four decades, hundreds of Wave Energy Converters have been proposed and studied, but so far a final architecture to harvest wave power has not been identified. Many engineering problems are still to be solved, like survivability, durability and effective power capture in a variable wave climate. ISWEC (Inertial Sea Wave Energy Converter) is a system that exploits the gyroscopic reactions provided from a spinning flywheel for the wave power conversion similarly to what the gyroscopic stabilizer do to reduce the roll motion of a boat. The flywheel works inside a sealed floating body in order to be protected from the outer environment and to grant reliable and durable operation conditions. Such a body is retained by means of two slack mooring lines connected to a deadweight lying on the seabed. The wave action induces the body pitching oscillation that may be damped to obtain the power transfer from the waves to the body. Furthermore an action torque is provided from the PTO on the gyroscope aiming at the energy conversion, while a reaction torque is given from the gyroscope to the hull. In such a way the power transfer from the floater to the PTO is obtained. The aim of the current thesis is to introduce the ISWEC as a possible technology for the wave power conversion. The mathematical model of the device and its validation by means of the experimental tests is here presented and its application for the full scale ISWEC prototype design porocess is shown. Finally an optimal control strategy has been proposed as a possible alternative to the basic linear control technique

Alla Prova del Vento

Sono state realizzate dal Dipartimento di Meccanica del Politecnico di Torino, alcune prove funzionali per un aerogeneratore di piccola taglia (1,5 kW). Nella galleria del vento, del Centro Ricerche Fiat, è stata installata una struttura in grado di resistere alle condizioni più avverse. I risultati sono incoraggianti. Il dispositivo ha dimostrato prestazioni superiori rispetto ad altri di pari tagli

Testing of a gyroscopic Wave Energy System

The extraction of energy from ocean waves has been investigated in Europe since the 1970s. Several devices have been proposed and a few of them have been built full scale and deployed to the ocean. Actually there is not a kind of device that is accepted as the most suitable to exploit wave power. One of the practical problems to be solved in a Wave Energy Converter (WEC) is the durability in the harsh marine environment and the capability to withstand in extreme weather conditions. The durability could be critical if parts of the converter, such as turbine rotors or auxiliary floats, are needed to move or to react while exposed to seawater and spray. One method to solve the problem is to use a WEC composed just by one sealed floating body carrying a gyroscope. The incident waves activate the precession motion of the gyroscope, the output power is produced by damping the precession motion. The whole system operates in the clean environment on the float. In this paper the design and the tests of an ISWEC (Inertial Sea Wave Energy Converter) are presented. The tests are carried out both by a purposely designed test bench in the laboratory and in a wave tank