New hybrid diesel electric propulsion system for trawlers

Due to the poor state of the fishery resources, trawlers are not profitable as they use to be. One way of improving their profitability is to reduce operational costs, especially by reducing fuel consumption. A number of fishing vessels is not efficient usually because of their outdated technology. Due to the European Commission restraints to new constructions, the major opportunities for reducing fuel consumption are chiefly related to an improvement of the vessel's propulsion systems. A technical feasibility of a new propulsion system architecture have been studied in 2008 through a research funded by the European Community (EC Regulation 2792/99, Article 17 - Innovative measures. n.27/IM/06 Project). In the propulsion system herein proposed, the overall power required by the vessel is subdivided in multiple power units, each one obtained by coupling a diesel engine with a permanent magnet brushless electric generator, while the propeller is coupled with an electric motor. Trough an electronic management system, it is possible to maintain one or more power units at different operating points to guarantee the minimum overall fuel consumption. In this study two power units have been considered. Many load tests have been done on a marine diesel engine, to evaluate its fuel consumption, torque and power delivered against the revolution speed. An algorithm to control the power units have been obtained from experimental data. The carried tests demonstrated the so conceived propulsion system as really reliable. A fuel saving of up to 15% was achieved with a power units equipped with a 257 kW @ 3800 rpm diesel engine. The proposed propulsion system could be useful both in new vessel and for a re-dumping of existing vessels. Further advantages are related to the possibility to avoid propeller shaft and reduction gear, then reducing weights, noise and pollution.