The energy efficiency evaluation of trawlers becomes more and more relevant as the trend of the government laws follows the path of restrictions to new constructions to encourage improvement to existing vessels, often equipped with outdated technologies. The two conditions a trawler need to meet during its operations, namely the sailing and the trawling phases, require in principle very different performances. Despite the higher speed reached when cruising from ports to fishing grounds, this type of ships experiences increased resistance as well as heavy loaded propellers during the trawling operations at low speed. In the light of the specific tasks of such a kind of vessel, a preliminary assessment of the energy efficiency of the ship-system is of crucial interest to optimize both the operating costs and the impact on the sea environment.
In this context, hydrodynamic performances and the propulsion system have direct consequences on the fuel consumption, hence on the operational costs of the vessel. In the proposed model, the engine fuel consumption is evaluated by suitable statistic regression to account for the prime mover performance into the propulsion chain. Ship resistance in calm water and added resistance due to rough sea conditions are computed by a Boundary Element Method. Both are then integrated into the global efficiency assessment method.
An application of energy efficiency assessment and optimization of a hard-chine 18 meters trawler is presented. The final results are shown as part of a wider decision support system to optimize the overall performance of the vessel operation in different environmental conditions.
One of the major recognized problems of many fisheries is represented by their high fuel consumption resulting in a significant source of greenhouse gas emissions with a consequent considerable impact on the marine ecosystem (Suuronen et al., 2012). This matter together with a generalized over-exploration of the fishery resources often endangers the economic viability of such an activity. These are also part of the motivations that push the dedicated EU Commission to force restrictions to prevent new constructions.
