RIASSUNTO
ABSTRACT
A new method for the integrated modeling of electrified marine propulsion systems has been introduced to predict and identify the best propulsion solution with higher energy efficiency, lower emissions and lifecycle cost. The benefits of advanced hybrid electric propulsion systems with diesel, NG, or hydrogen fuel cell engines and large battery ESS verse traditional diesel-mechanical powertrain systems are modeled and compared. Case studies on vehicle and passenger ferries, tugboats, fishing and small commercial boats are used to demonstrate the new methods and the benefits of the new approach.
INTRODUCTION
Marine transport has been essential for international trade. However, the increasing concerns of air pollution and environmental impact led to actions among regulators, classification societies, ship operators, ship owners, and other stakeholders. Over the past years, the International Maritime Organization (IMO) introduced and revised the emission limits of the main air pollutants contained in ships exhaust gas, including sulphur oxides (SOx) and nitrous oxides (NOx), and prohibits deliberate emissions of ozone depleting substances (ODS) in light of technological improvements and implementation experience through MARPOL Annex VI (IMO, 1997∽). In recent years, all-electric and hybrid electric propulsion systems for marine vessels have seen increased levels of adoption. This trend has been driven by regulatory caps on emissions in harbours and offshore waters, with these regulations coming from regional and national governments and the IMO (Eyring, 2005; European Commission, 2011), as well as fluctuating oil prices. Additional benefits that have encouraged adoption by industry include improved energy conversion efficiency, reduced Greenhouse Gas (GHG) emissions and ship induced noise, and in many cases, superior performance over traditional diesel propulsion systems.
Some research focuses on the Life-cycle assessment (LCA) to evaluate the environmental impacts of a material through the entire "life-cycle" of a new-built ship from its initial production through to its eventual reuse, recycling, or disposal. Poskilly studied a hybrid electric power system with the combination of diesel gensets, lithium ion batteries, photovoltaic systems and cold-ironing operation for Roll-on/Roll-off cargo ships to identify the optimized operation profile of the ship with reduced impacts (Ling-Chin and Roskilly, 2016). Others carried out optimal design and performance analysis on integrate a renewable energy system with traditional marine power system to combine solar PV, PEM fuel cell and diesel generator, such as the study carried by Hamid et. al. on a cruise ship in Sweden (Ghenai, et al., 2019) to make marine transport greener and sustainable.