The basic concept of the present work is the development of new technology and technical Regulatory framework for conversion of existing shuttle ferries and containerships in order for their diesel propulsion plants to operate on either using liquefied natural gas (LNG) or Diesel fuel. Two types of ships will be examined in this work, namely open type ferries and large containerships. Two different national groups of project partners will be involved, namely Greek and Chinese. The former will focus on the shuttle ferries operating on (Greek) domestic routes and the latter on the containerships operating on national and international routes.
The main feedstock of Greece is coming from the import of petroleum products that consists the highest percentage on the annual national energy balance. Consequently, the associated high cost and negative environmental impact dictates for immediate corrective measures to be taken. By taking into account the large number of Greek passenger ships operating on domestic coastal routes and their essential role in the national economical and social development, the utilization of a reduced emission and energy efficient propulsion system is of great interest and importance.
Based on the latest global industry reports, China is among the largest shipbuilding countries in the world. Most of the Chinese shipbuilding enterprises focus on dry bulk carriers and container vessels, while only a few large corporations have the orders for tankers. Due to the global economic recession Chinese shipyards seek ways to increase their turnaround and enter new markets (i.e. high-valued vessels). To this direction, they are keen to embrace any available or new state-of-the-art idea such as the conversion of the diesel propulsion engines of existing and new containerships into dual fueled diesel-liquefied natural gas.
The dual-fuel diesel engine, when acting as main propulsion system in any type of merchant marine vessel, can burn gas or fuel-oil, depending on the energy source available on board. Depending on environmental considerations as well as relative price and availability, the dual-fuel diesel engine has the advantage of using either gas or diesel/heavy fuel oil. This project sees significant opportunities arising for existing and new gas-fuelled vessels as fuel prices rise and modern exhaust-emission limits tighten. Indeed, previous research indicates that the dual-fuel diesel engine, can deliver significant reductions in CO2, NOx and SOx emissions fulfilling Tier-II and Tier-III regulations.
The expected results of the project will be as follows:
− Full set of plans and procedures required for an open type ferry to be issued a conversion permit towards the conversion of her propulsion plant into a dual fueled Diesel-LNG engine. Development of new technical Rules and Regulations governing the conversion of open type ferries and operate their main propulsion engines on either natural gas or diesel fuel.
− Theoretical and experimental investigations of the parameters affecting the Diesel-LNG fueled engine performance (power output, emissions etc.)
− Theoretical investigation of the critical parts/assemblies of the LNG fueling system (i.e. storage tanks, piping, cryogenic system, gasification system etc.) for open type ferries and containerships − Technical requirements and specifications of ship safety arrangements (i.e. fire fighting, gas detection, ship evacuation etc.)
− The system of LNG storage tanks and double wall piping shall be specifically designed to suit the special operational and safety requirement of the vessels under investigation
− The optimum propulsion plant configuration will be also proposed in order sustainability and cost effectiveness to be ensured
− Proposal to the Governing Regulating Bodies to implement the findings of this research in form of new related regulations or/and improved existing legislation for open type ferries and containerships
− Investigation of LNG bunkering alternatives at national (Greece-China) and international level − Estimate the cost effectiveness of the proposed schemes for the Greek and Chinese sides
− Environmental evaluation of the proposed schemes (gaseous emissions, EEDI, EEOI)
The use of liquefied natural gas (LNG) as ship fuel is not a new idea. LNG has been used for many years on gas carriers with boilers (in the case of steam turbine propulsion), four-stroke diesel mechanical propulsion or diesel electric propulsion. All these solutions are based on consumption of the readily available (on board) LNG as fuel, and/or boil-off gas from the LNG tanks. In recent years, the LNG infrastructure, particularly in Norway, has been developed to the extent that several ship types, namely Ro-Ro and smaller ferryboats, use LNG as fuel. Based on the obtained experience, LNG fuel is now established as a clean and reliable fuel for propulsion and auxiliary power generation.
Using LNG fuel is a very efficient way to reduce emissions. All SOx emissions are eliminated, the NOx emissions are reduced up to 85%, whereas the CO2 emissions decrease by 25%-30% due to the high air fuel ratio (lean burn concept) and the low carbon to hydrogen ratio of LNG fuel. In addition, Gas Engines exhibit very low particulate emissions, no visible smoke and no sludge deposits.
The commercial available gas engine portfolio includes three main technologies: a) Dual fuel engines run on different mixtures of gas and diesel or alternatively on diesel alone. The gas, diesel and air mixture is combusted in a Diesel (compression-ignition) cycle and gas used is injected at high pressure (range of 300 bar). Those engines could be either medium speed four-stroke or slow speed two-stroke. b) Spark Ignition Gas engines run only on gas, and combustion of the gas and air mixture takes place in an Otto cycle triggered by spark plug ignition. The gas is injected at low pressure (4–6 bar). Those engines are medium speed four-stroke. c) Dual fuel engines can run in gas mode or diesel mode. In gas mode, 99% of the fuel is gas and 1% (the pilot fuel) is diesel, and combustion of the gas and air mixture takes place in an Otto cycle with ignition being triggered by the injection of the pilot fuel. In diesel mode, the fuel is 100% diesel fuel and combustion of the diesel and air mixture takes place in a Diesel cycle. In gas mode, the gas is injected at low pressure (4– 6bar). Those engines are of the medium speed four-stroke type.
LNG usage will come into force in the forthcoming future, imposed by the implementation of stringent emission limits and the increased environmental awareness for clean transportation. For the Greek territory it would be of great importance the conversion of the propulsion plants of the existing open ferries, which are used for short distance route close to urban areas interconnecting the mainland with the Greek archipelago islands, from the Diesel fuel mode to the LNG-Diesel fuel mode. That is owing to the following reasons: the fuel economy that is obtained using LNG fuel and the lower gaseous emissions compared to the Diesel engines. The former is crucial for the Greek state since both Diesel and LNG fuels are imported, whereas the latter will have a positive consequence for improving the air quality of the urban area. On the other hand, the Chinese side, due to their activities in the shipbuilding sector, is greatly interested either in converting the propulsion plant of existing containerships for the Diesel mode to the LNG mode or in studying containerships propulsion plants operating with LNG fuel.
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