The use of LNG in passenger cars is far less viable because on average passenger cars stand idle more often, which would give rise to high evaporative losses. The use of LNG requires storage facilities for the cold (-162 0C) liquid natural gas at the roadside refueling stations and special fuelling equipment which can handle cryogenic temperatures. In addition, the trucks must be equipped with special dual fuel engines to be able to use LNG. Moreover, the fuel tank on board of the truck needs to be adapted for LNG usage. These requirements make the use of LNG relatively expensive. Nevertheless, the use of LNG in the transport sector can still have substantial environmental benefits. It is reported that a truck powered by a dual fuel LNG-diesel engine can emit up to 75% lower NOx emissions and about 13% lower Well-To-Wheel CO2 emissions compared to diesel powered trucks. Overall, the technology to use LNG as a transport fuel is well developed, but is expected to remain a niche market.
Although natural gas is a fossil fuel, it is the cleanest burning fuel available today. The increasing world wide demand for cleaner energy leads to an increasing trade in liquefied natural gas. The natural gas is liquefied by cooling it to approximately −162 °C. Liquefied natural gas occupies a much smaller volume than compressed natural gas which makes it much more cost-efficient to transport over long distances to places without a local source for natural gas, and where pipelines do not lead to. Where moving natural gas by pipelines is not possible or economical, LNG can be transported by ships or by trucks equipped with special cryogenic containers. At its destination the LNG is re-gasified and distributed as pipeline natural gas, but using LNG in heavy duty trucks can be a viable option as well.
Special LNG trailers can deliver the liquid fuel from the storage tanks to liquefied natural gas fueling stations. At the site of the fueling station the LNG has to be stored in very well insulated tanks. The insulation only, however, will not keep the temperature of LNG low enough. LNG is stored as a so-called "boiling cryogen", a very cold liquid at its boiling point which stays at the low temperature by evaporative cooling. (McMullen et al, 2002) As long as the LNG vapor is allowed to leave the storage tank, the temperature will remain constant. At the refueling site this boil off natural gas vapor can be compressed to CNG (Compressed Natural Gas) and be sold to passenger cars. This fuel type is called “LCNG”, Liquefied Compressed Natural Gas and is preferable for passenger cars.
Electric tractors emerge as viable alternatives for some operations
The use of liquefied natural gas in vehicles is a tradeoff between the duty cycle (i.e. the time in operation) of the vehicle and the evaporation rate (boil off rate). In general the annual mileage of passenger cars is too low to compensate for the boil off losses. However, the direct use of LNG can be an attractive alternative for heavy duty vehicles, which travel high miles in one go.
It has been shown that the Well to Wheel (WTW) CO2 emission of LNG can be about 13% lower than the WTW CO2 emission of a diesel powered truck (Kroon, 2009). However, this percentage may differ depending on the origin of the LNG and hence the energy it takes to transport the liquefied natural gas to its destination. The LNG transport ship can lose up to 6% of the natural gas due to evaporation. Furthermore it is assumed that the efficiency of a LNG truck engine is equivalent to the efficiency of a diesel truck engine. This is only the case for so called natural gas diesel dual fuel engines (Frailey, 1998). The natural gas diesel dual-fuel engine combines the advantages of natural gas with the diesel engine’s high efficiency rating, which is about 20 percent superior to that of the compressed natural gas engine. However, few truck manufacturers are building these natural gas diesel dual-fuel engine. It is estimated that the he overall greenhouse gas emission saving of LNG powered trucks compared to conventional diesel trucks is about 10%. (Kroon, 2009
Dual fuel engine: 80% LNG and 20% diesel:
Dual fuel engines are based on diesel engines. The engines have been converted so they can also be powered by LNG fuel. The fuel is a mix of 80% LNG and 20% diesel. This type of engine was applied on the first LNG fueled inland vessel, but will most probable not be applied anymore in newly equipped vessels.
Dual fuel/ pilot diesel engine: 98% LNG and 2% diesel:
In this case the engine is fully optimized for natural gas combustion. This LNG dual fuel system has already been in use for more than ten years in coastal and ocean shipping. The engines are now also supplied for inland shipping. The LNG dual fuel engines are specifically designed as dual fuel systems, so only a limited quantity of pilot fuel is required but needed for combustion. This involves proportions of 2% diesel and 98% LNG. The dual fuel engine can n also run fully on diesel.
New Holland is the alternative fuels leader in agriculture - having developed the first commercialized Compressed Natural Gas (CNG) tractor - the T6 Methane Power. The new T7 prototype furthers the Brand’s position, driving greater value for our customers. It more than doubles the autonomy compared to a CNG design. In comparison to the T6 Methane Power CNG, this is a fourfold increase in fuel capacity. It delivers the same power and torque as the equivalent diesel tractor while delivering autonomy without the need for any extra tanks. It’s also quieter – a significant reduction in drive-by noise levels makes it perfect for tasks near livestock or in urban areas.
To spearhead this latest development, CNH Industrial partnered with Bennamann, a UK-based expert whose multi-patented approach converts fugitive methane to clean biofuel – offering an energy independent and sustainable farm system. When the T7 prototype is integrated within this process, an operation’s overall carbon footprint can be ‘better than zero.’ Bennamann’s system also provides new opportunities and revenue streams for farmers. These include fuel production at a stable cost; sale of excess biomethane on the open market; generation of 100% natural fertilizer; and conversion of excess methane into electricity for export or local use.
The new technology present in the T7 Methane Power LNG has been put through its paces on a variety of farms across myriad applications. This premiere is the first step towards the serial production and commercialization of the world’s first LNG tractor. A tractor that will make our customers more sustainable, energy independent and productive – true to our purpose of Breaking New Ground.
