In 2014, Scania launched the first Euro 6 trucks powered by liquefied natural gas. Interest has been strong around the world, and Scania is now starting to sell the vehicles in the Netherlands.
Interest in liquefied natural gas (LNG) is growing fast. As well as providing the environmental benefits of gas power, LNG brings cost benefits. It is considerably cheaper to create the infrastructure needed for LNG than it is for compressed natural gas (CNG).
Another advantage is that transport companies can drive up to 1,000 kilometres on a tank of LNG, compared with just 250 to 300 kilometres on a tank of CNG. This bigger operating radius makes the fuel a competitive alternative for use in regional distribution, while CNG is currently mostly used for limited city distribution and garbage collection.
Countries such as Australia, Brazil, India and China have big gas reserves and are expected to have a strong focus on gas. In Europe, meanwhile, the trend for gas is being driven by price, with the cost in most countries 40 to 50 percent lower than diesel.
What’s more, gas vehicles are significantly quieter and better for the environment. Carbon dioxide emissions are reduced by close to 10 percent, particle emissions are almost completely eliminated, and nitrogen oxide emissions are cut by more than a third.
Sara Johansson works in Scania’s Customised Truck Development division. “The question isn’t whether LNG is going to be big, but rather when this is going to happen,” she says. “LNG vehicles have a higher purchase price, but the many environmental advantages and lower fuel costs outweigh the higher purchase price for many customers.”
“This way, we can quickly and simply reach a lot of people in a range of locations around the world.”
Anatomy of an LNG tank
LNG is kept at minus 132 degrees Celsius and under 10 bar of pressure. Such a low temperature cannot be achieved using the vehicle’s active cooling system alone, and the LNG is stored in something akin to a thermos, surrounded by a vacuum inside an insulating layer.
- Heat exchanger. The heat exchanger vaporises the LNG into a gas. It does not change the fuel pressure. The heat for this process is obtained from the engine cooling system, which is connected to the side of the LNG tank.
- The economiser pressure regulator reduces the tank pressure by venting gas to the fuel line when the engine is running. It then determines whether fuel should be used from the top of the tank (in a gaseous state) or from the bottom of the tank (in a liquid state), depending on the pressure in the tank. The Scania LNG tank has an economiser function set at 10 bar. This means that when the pressure reaches 10 bar fuel is taken from the top of the tank to reduce the pressure.
- Filling nozzle fittings. These are where the nozzles are fitted during a visit to a filling station. The lower, larger connection is where the LNG nozzle is connected. The upper connection is a vent connector to vent back gas to the filling station in case of excess pressure in the tank during filling.
- Fuel level sensor. The fuel level is measured by a capacitive sensor located inside the tank, which can distinguish between fuel in its liquid and gaseous states. As a result, it is able to supply accurate information on the fuel volume to the fuel level gauge in the cab.
- Safety valves. The primary safety valve is set at 16 bar and vents out of a pipe behind the cab. The secondary safety valve is set at 24 bar and has a red seal to show when gas has been vented and something is therefore amiss with the LNG fuel system.
- Check valve. This protects the tank from fuel spillage in the event of an accident or a fill coupler failure.
- Manual shut-off valves. These allow for the isolation of the tank for servicing. The red handle is the fuel cock, which leads to the fuel line. The grey handle is the ventilating valve and is usually closed during normal operation.
- Solenoid valve. This is closed when the system is not being powered. It opens when the engine is running and provides fuel to the engine. The solenoid valve is located downstream from the heat exchanger.