Investigation of hybrid systems for diesel powered ships

Abstract

The combination of a prime mover and an energy storage device for reduction of fuel consumption has been successfully used in the automotive industry. The potential of a load levelling strategy and the energy management optimisation through the use of a Hybrid Diesel propulsion system for ocean going ships is investigated. The goal of Diesel Hybrid systems is to reduce exhaust gas emissions by reducing fuel oil consumption though an introduction of an energy storage medium. Part of the research is based on operational data for a shipping fleet containing all types of bulk carriers. The engine loading and energy requirements are estimated and the sizing of suitable propulsion and the battery storage system is proposed. The changes in overall emissions are estimated and the potential for fuel savings is identified. The emission estimation is made by applying a bottom up approach, and the use of fuel based factors. The thesis includes an assessment of the calculation error imposed by the usage of fuel-based factors, and a determination of the uncertainty in the approximation of global shipping emissions is made. Constructional and volume constraints are identified and a concept feasibility is performed.

The thesis demonstrates the use of developed ship voyage simulator, which is a time domain quasi-steady simulation tool. The system components of the Hybrid and the conventional machinery system are modelled, the weather characteristics and the hull-fluid interaction are implemented in a modular, scalable and expandable manner. Using the simulation tool, an assessment of simulated bottom up approach with the results of the IMO formula is presented for a number of examined voyages. Moreover, simulator outputs of the propulsive demand are fed to the optimisation algorithm, which is based on the equivalent cost minimisation strategy. In addition, a pseudo multi-objective optimisation algorithm for CO2 and PM reduction is also presented. The results indicate that the ship simulator estimates shipping emissions with a significantly smaller error than the adopted formulae of the IMO.

The hybrid solution for diesel powered ships is under specific scenarios financially viable, and the fuel savings based on the statistical analysis are notable when ageing of the engines and performance deterioration models are included. Nevertheless, when the optimised performance of the Hybrid power layouts is compared to optimally tuned engines at ISO conditions, instead of the actual prime mover performance, the fuel saving potential for auxiliary loads is reduced and also leads to non-feasible results for propulsive loads. Nonetheless, the Hybrid power systems permit the use of sophisticated prime mover energy management for both propulsive and auxiliary loads. This proved to lead to notable fuel savings for the combined shipboard power trains.

More information

Identifiers

ORCID for S.R. Turnock: orcid.org/0000-0001-6288-0400

Catalogue record

Export record