Factors Influencing Machinery System Selection for Complex Operational Profiles
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- Institutt for marin teknikk 
BackgroundThe environmental consequences, caused by global emission of green house gases (GHG), have received increasingly concern in recent years. CO2 emissions from the maritime sector represent 3,3% of the world s total CO2 emissions and are forecast to increase the next decades. To meet the new and stricter regulations on emissions, the International Maritime Organization (IMO) has announced that by 2015 the regulations known as Tier III will take effect in the emission controlled areas (ECA), and globally by the year 2020. They are currently debating technical, operational and market-based measures for reducing GHG emissions from the shipping industry. Hybrid power systems, which is a power system combining power production and energy storage, have been used in several industries and have received particular interest in the power production and car industries. Introducing it to power production onboard ships, the performance of the vessel can be improved and the emission of GHG can be reduced. Overall Aim and FocusThe overall objective of this thesis is to identify the cutting point between selecting hybrid power systems which combine energy production with energy storage capacity and diesel electric systems based on operational profiles and external influences such as cost, route, distance, weather conditions, maneuvering and type of operations. MethodThis thesis is a research of the influencing factors on selection of the most efficient machinery solutions for vessels with complex operational profiles. The first part of the report is a review of diesel electric power and propulsion systems, and state of the art configurations of it, which have been proven able to handle variations in load in an efficient manner. The influencing factors, such as operations to perform, weather conditions, emissions and rules and regulations, have been evaluated and described in order to create a platform for supporting the decisions made when selecting a machinery system based on the planned operational profile of the vessel. A stepwise method has been made to evaluate the influencing factors up against the operational profile. The first step is a simple overview of the operational profile to evaluate the degree of variation in operations and loads. Further on, the power demands in the planned operations are evaluated with focus on the possible dynamic loads. Finally, a screening process is presented to evaluate whether a hybrid of diesel electric and energy storage configuration is beneficial for a type of ship, compared to a pure diesel electric system. To estimate the potential economical benefits of hybridization compared to a diesel electric configuration, a simple calculation on savings in lifetime costs is conducted as the fourth step.ResultsThe ability of the vessels machinery to handle the dynamic loading picture during specialized operations in an efficient matter is of the utmost importance. Especially regarding operating costs, not only for the fuel consumption, but also the maintenance cost and emissions of green house gases. To illustrate the selection process, a case, where selecting the best-suited machinery system for a PSV is the goal, was made and run through the method. Two scenarios were simulated, one where the fuel and battery prices were held constant over a period of 25 years. The other scenario, which is believed to be the most likely due to the last year s trend in fuel prices, has a 2% annual increase in fuel price and a 20% decrease in battery prices every 10 years. The calculations show, in both scenarios, that a hybrid of diesel electric and batteries as energy storage will give reductions in costs compared to pure diesel electric. The payback time of hybridization is less than five years in both cases which indicates that, in addition to reduce emissions, this might be a good investment for the ship-owner. However, the savings and potential benefits turned out to be larger for the case with varying prices. This had a potentially 10% reduction in cost after 25 years of operation. For vessels operating with a large amount of variations in loads and which experience several transients and low loads, a hybrid system with an energy storage unit will assist the engines in handling the load peaks and troughs, which lead to a more efficient operation compared to diesel electric. Diesel electric system has been a preferred choice of machinery for ships with complex operational profiles in recent years. However, despite the higher installation cost, the hybrid system turns out to be a more profitable choice in the future.