Exploitation Of Marine Current Energy

Abstract

ABSTRACT This paper describes the results of a feasibility study regarding the exploitation of marine currents in the Strait of Messina (Italy). The high kinetic energy contents of these currents suggest the development of some exploitation system. The technical solution, proposed in the study, consists of seabed installed vertical axis turbines, which are able to optimize energy extraction. The work performed at this stage included a basic design of the system and a preliminary evaluation of the Environmental Impact. A costs/benefits evaluation showed that electricity produced by the proposed system is competitive with that based on other energy sources, conventional ones but mostly renewable ones. Moreover fresh water, considered in alternative to electricity production, could be produced at costs comparable with present supplies by shuttle tankers. INTRODUCTION Marine currents represent a large renewable energy resource and can give a significant contribution to fulfilling energy demand, with emphasis put on local supplies. Among the ocean and renewable energy resources marine currents have certainly not been given enough consideration by researchers and energy authorities. The reason can probably be found in the fully marine characteristic of the systems suitable for exploiting marine currents, if compared with either OTEC, wave or tidal energy systems which are essentially land based. As in all the other renewable and non-conventional energy resources, so the energy extracted from marine currents can hardly exceed a few percent of the global energy consumption, even if in several cases it can play an important role in counteracting energy shortage while coping with environmental constraints in coastal areas or isles, by integrating or substituting energy systems based on conventional resources, like oil, gas or coal. The technical interest of the study stems from the high kinetic energy content of marine currents in the Messina Strait (South of Italy) and from a socio economic context that suggests following the logic of local development, The study, even if targeted at a particular application, is aimed at proposing general guidelines and technological solutions for dealing with analogous situations of exploiting marine currents. The size of the proposed hydro-generator (1 MW electric) and the modular system approach make this solution suitable in various contexts, THE SITE Geography The Messina Strait (fig. 1) is a small sea channel about 30 km long with a minimal width of 3200 m, that separates the Italian mainland from the island of Sicily, connecting the Ionian and Tyrrhenian Seas. It presents a variable bottom profile with a depth of up to 1500 m. The profile is characterized by the presence of a transversal sill, in the northern part of the strait which is also the narrowest. In correspondence of this sill the depth rapidly reaches the minimum of about 80 m over a length of about 7 km. This point constitutes a net separation between the two seas and a "bottle neck" for the water flow.