EU policy with regard to environmental friendly transport focuses on modal shifts towards transport over water and the reduction of greenhouse gases in order to reach the goals set in Kyoto. The tendency is to develop new ways of transportation, focusing on strongly reduced emissions of greenhouse gases per kg of transported cargo. This can be accomplished in three ways: (i) optimising cargo space; (ii) reducing emissions of existing engines by making them run more efficiently, or (iii) creating new engine types with new types of fuels and hence reduce emissions. Most short and medium-sized cargo vessels use diesel or heavy oil as fuel. The technique of these combustion engines has been in use for decades and has not changed much through time. In optimising transportation and ships, the current systems can be improved, but this will not lead to very spectacular improvements in general, particularly with regard to the emission of greenhouse gases as the current techniques have reached their limit. Bijlsma received a request to develop a small carrier of liquid natural gas (LNG) suitable for LNG engines. The environmental advantages of LNG are obvious: use of LNG would lead to a significant reduction in the emissions of CO2 and NOx; the price of LNG is considerably lower than diesel or heavy oil and, the LNG engine is also much more comfortable: There is no unpleasant smell, the engine makes little sound and causes less vibration. The Commission considers LNG as a potential alternative for automotive fuel, along with hydrogen and biofuels (COM(2001)547 final). LNG engines already exist in industry (LNG turbines) and land transport with a minimum range (e.g. city buses). However, LNG-engines are not common on ships due to the specific safety measures on board, and LNG is not widely available. Bijlsma studied the possibility for a ship with LNG propulsion and decided to build the ship and to demonstrate the operability of ship and engine. Organisations in Norway and Sweden showed particular interest in this project.
This project had three main objectives:
- Demonstrate the technical feasibility of a ship engine running solely on Liquid Natural Gas (LNG).
- Demonstrate the possibility of propelling an LNG tanker with its own boil-off, instead of blowing this off.
- Demonstrate an economical and flexible means of distributing LNG for widespread use on land and water.
This project, which ran from 1st December 2002 to 1st January 2005, was successful. The project consortium built and delivered the smallest LNG carrier in the world, i.e. the 1,100 m3 Pioneer Knutsen. The ship is operating to the full satisfaction of its owner, Knutsen, on short sea waterways in Norway; no major problems occurred during the 41 weeks demonstration phase. The ship has a dedicated, fully optimised gas engine resulting in the lowest possible emission of any similar type of vessel running on traditional diesel fuel. Fuelling is provided from the gaseous boil-off of the vessel’s LNG cargo, thus making maximum use of energy (methane) that otherwise would be vented to the atmosphere.
The project achieved all of its objectives:
- The technical feasibility of the ship engine running solely on LNG was demonstrated;
- The possibility of propelling an LNG tanker with its own boil-off was demonstrated;
- It was demonstrated that the LNG-tanker was economical for distributing LNG (Knutzen, the client, is satisfied with the tanker and is considering an order for a new, bigger one; Gaz de France ordered 3 tankers based on a similar principle).
The technology demonstrated works as follows:
- LNG boil off. Natural gas, primarily methane (CH4) becomes liquefied when it is processed to minus 160 degree Celsius. It can then be transported by ship. At the receiving terminal it is made gaseous again and further distributed by pipelines. To maintain the low temperature a small part of the cargo is evaporated, so-called ‘boil-off’ is produced. This is normally blown off into the atmosphere to reduce pressure in the tank. The idea of the project was not only to eliminate this blow off, but also to use this natural gas for the propulsion of the ship.
- Propulsion. The ship is propelled by two propellers powered by electric induction motors. The two alternators driven by the gas engines feed these electric induction motors;
- Safety systems. Stringent safety and emergency shut down systems had to be installed to prevent explosion risks. Also back-up diesel propulsion engines were installed to prevent the ship from being out of control during emergency shut down.
The project resulted in the following direct environmental benefits:
- Avoidance of CH4 emissions. If LNG had blown off, greenhouse gas methane (CH4) would have been released. NH4 has a global warming potential of 20 compared to CO2.
- Saving of diesel. As the ship uses the boil-off for propulsion it doesn’t need diesel. Savings for a small ship like the Pioneer Knutsen: 250 litres diesel per hour.
- Cleaner combustion. Comparing gas as a fuel with diesel, results in the following: 30% reduction of CO2, 60% reduction of hydrocarbons, 80% reduction of NOx and a complete reduction of soot articles.
It was the first time that an engine for medium and small sized cargo vessels was demonstrated running on LNG. The main field of innovation was developing a dedicated LNG engine for ship propulsion including a fuel supply system, which uses boil-off gas to run the engine on, in keeping with regulations of classification offices.
The demonstration value was high: the project demonstrated that the use of LNG, as low emission fuel in medium and small ships is possible. The project overcame some of the barriers for use of LNG in shipping (technical feasibility, development of classification regulations). Dissemination was well done; the project information was disclosed via the dedicated project website, a brochure, presentations and exhibitions at major events in the international LNG and shipbuilding community. The project was granted a nomination for the 2004 EU Clean Marine Award.
The beneficiary considers that the new technology is competitive especially in the case of smaller ships with relatively short trades. A ship with LNG electric propulsion requires a higher investment than a ship with direct diesel propulsion. The beneficiary expects that this is the case now and that this will probably continue to be the case in future. However, when the total cost of ownership during a longer period is taken into account the differences are very small. Gas engines are cheaper in maintenance for example. Several factors determine what solution is most economical, e.g. the capacity of the ship, the speed, the distance, the price of the fuel, the taxes on the fuel, and the frequency of a specific trade. The recent order of Gaz de France for 3 ships based on the same principle and the interest of Knutzen in ordering a 2nd ship are encouraging for business prospects.
The project has added a new and successful experience to the rapid developments in the LNG sector. Demand for LNG is increasing as is the demand for LNG tankers. Developments in propulsion systems are also rapid: gas carriers have used steam propulsion for 40 years but the newest ships are using gas-electric diesel engines or gas-electric engines such as the Pioneer Knutsen.