The Emerald Ace was built as world’s first newly built hybrid car carrier, and is equipped with a hybrid electric power supply system that combines a 160kW solar generation system with lithium-ion batteries that can store some 2.2MWh of electricity. On the Emerald Ace, electricity is generated by the solar power generation system while the vessel is under way and stored in the lithium-ion batteries. The lithium-ion batteries can supply the electric power which the vessel required and the diesel-powered generator can be completely shut down during rest in port, resulting in zero emissions.
The tribological characteristics of cold drawn stainless steel bars were presented in a previous paper. The existence of three different wear modes was reported. This paper describes the cause and the transition of these modes using martensitic stainless steel. The results of experiments show that Mode 1, initial mild wear, is caused by the lubricating layer applied during specimen manufacture. Mode 2, severe adhesive wear, is caused by severe adhesion of the wear particles and the sliding surface due to the crushing of wear debris and material agglomeration. Mode 3, relatively mild wear, is caused by the accumulation of the fine oxidized wear debris on the sliding surface.
The possible cruising distance of the electric boats is still short compared with that of similar-sized internal combustion engine boats. Currently, electric boat operators have to estimate the possible cruising distance from weather (wind direction or power), wave (height and tide), and battery (voltage, current, state of charge) conditions. Battery failure has to be avoided from the viewpoint of operational safety. In order to solve this problem, a Navigation Support System (NSS) that provides the possible cruising distance and the recommended speed, and restricts the output power to achieve the desired operation, was developed. In this paper, in order to realize this system, an estimation algorithm and an output power restriction algorithm based on the analysis of characteristics of the boat, the motor and the battery discharge is derived. Verification tests in actual seas confirm the system’s usability.
The authors have investigated the effects of liquefied Dimethyl Ether (DME) mixed with conventional fuels of diesel engines. From those studies, it was clarified that DME mixing can drastically reduce unburned exhaust emissions, such as CO, HC and Particulate Matter (PM). However, the effect of sulfur content in fuels was not clearly examined. In this study, combustion analysis was carried out by varying sulfur ratio in fuels using a small size direct injection four stroke diesel engine. The test fuels were low sulfur Marine Diesel Oil (MDO, JIS A heavy oil) and MDO/DME mixed fuel. Di-t-butyl Disulfide (DBDS) was added to change the sulfur component ratio of those fuels. Experimental results obtained show that the injection duration and the specific fuel consumption increase with increasing the sulfur ratio in fuels, while the ignition delay decreases with an increase in sulfur ratio. Results also show that even though the sulfur content was increased, NOx emission and PM emission were reduced with DME mixing. It is assumed that the transfer rate of sulfur in fuel to sulfate in PM is in the range of 1.0 to 2.4% for MDO base fuel, and 0.4 to 0.9% for DME mixed fuel.
Growing interest in the numerical simulation of total ship propulsion plant demands an easy to handle diesel engine simulation tool in a field which is as extensive as there are applications — every design process or research project has its own fit-for-purpose model. Moreover, engine simulation is a trade-off between model simplicity, execution time, and accuracy. In this paper attention is focused on the development of a diesel engine dynamics simulation model which combines fast-simulation time, sufficient accuracy, and limited engine data requirement. The cycle mean value modeling methodology is adopted in this paper and the derived results were validated against experimental data of prototype engine.
Diesel engines are used as the main power source of marine transport and the continuous improvement of their performance offers better specific fuel oil consumption (SFOC). From the standpoint of Carbon Dioxide (CO2) emission, marine engines are environment friendly compared to those used in land transportation and other industries. Attention should be focused only on CO2 emissions but also on other greenhouse gases (GHG), such as Nitrous Oxide (N2O), which is the result of a reaction between nitrogen and sulfur components of low-grade fuels. N2O is known as the third major GHG following CO2 and methane (CH4). The global warming potential (GWP) of N2O is 310 times as large as that of CO2 because N2O in the atmosphere is very stable, and it becomes a source of secondary contamination after photo-degradation in the stratosphere. N2O concentration 1800 years before was less than 280 ppb, but in the last 200 years it has increased rapidly. Since N2O emission from natural sources is very difficult to control, discussions on N2O emission reductions should be centered on artificial N2O which represents 35% of the total N2O emissions. To argue this point, it should be noted that there are some reports on the N2O exhaust characteristics from stationary power plants and land transportations, but those of marine transportations are very limited. In this experimental study, the authors investigated N2O emission characteristics of an actual ship at the sea, and examined relationships between N2O and other gaseous emissions. The experimental results showed that N2O emission exhibited different characteristics compared with NO which makes up over 80 percent in NOX, and had exhaust characteristic very similar to SO2 emission. But when based on the excess air ratio, the difference between these two species increased with decreasing excess air ratio.