Advantages And Disadvantages Of Cng & Lng

Comparison of the advantages and disadvantages of the two natural gas fuels

As the price of fuels continues to rise, high prices have caused headaches for many transportation practitioners. Every increase in fuel prices is depriving truck drivers of their poor profits. The search for alternative fuels has become one of the tasks of the domestic transportation industry. Speaking of the two most basic forms of gas fuel for trucks today, what is the difference between fuels of CNG and LNG?

● Advantages of natural gas and diesel:
In terms of fuel consumption, although the retail price of domestic diesel in China has fallen to 5.19 yuan/liter, the current natural gas’ price is about 3.43 yuan depending on the locality. Due to the similar energy efficiency of diesel and natural gas, each liter of natural gas can save nearly 2 yuan compared to the same consumption of diesel in vehicles.

● The difference between the fuel of CNG and LNG
Since it is to introduce the difference between the two fuel for trucks, we must first talk about the characteristics of them. Before the presentation, let's make a brief introduction to the English descriptions of the two fuels. CNG is the abbreviation of Compressed Natural Gas, and LNG is the abbreviation of Liquefied Natural Gas. The main content of both fuels is the methane.

● Advantages and disadvantages of CNG:
Advantage:
1: Easy to use
Disadvantages:
1: Long inflation time
The filling time of CNG is longer. To be compared with that of LNG, it will take double or even more time to fill the gas cylinders with the same capacity.

2: Low loading efficiency of gas cylinder
Because CNG can be stored in the gas tank just by high-pressure compression,the loading efficiency of the gas cylinder is much lower than that of LNG.

3: Short recharge mileage, only suitable for short-distance transportation.
Generally speaking, the vehicles which adopt CNG fuel are used in cities and nearby areas. Due to the limitation of capacity of gas cylinders, more gas filling stations need to be established to meet the gas filling requirements. First, it causes a waste of limited resources, secondly , it affects the user's effective running time. 

● Advantages and disadvantages of LNG:
Advantage:
1: Long recharge mileage
LNG is liquefied natural gas. While improving gas quality, it overcomes the above insurmountable shortcomings of CNG fueled vehicles. Using LNG as fuel, the vehicle can travel more than 500 kilometers with a steel cylinder of 335L, completely solving the problem of vehicle mileage.

2: High gas cylinder loading efficiency
The weight of a LNG steel cylinder of 335L is 225kg, and the weight with full filled LNG is 353kg, which is equivalent to the weight of the same fuel tank of the diesel vehicle. And it is installed on the frame, which greatly lowers the center of gravity of the vehicle. While saving the cost, it also improves the driving safety of the vehicle.
3: Low storage pressure
The storage pressure of LNG is 1.6MPa, which is lower than 20MPa of fuel CNG.

Disadvantages:
1: Few LNG filling stations
Because the construction speed of LNG filling stations in China is not as fast as that of CNG filling stations, the direct result is that the number of LNG filling stations is insufficient, which is also the main reason for the limitations of LNG trucks sales.

2: Expensive
LNG is expensive. First, the cost of LNG production is very high. When natural gas is liquefied into liquid by cooling under 162 ℃  below zero, the energy consumption of this cryogenic process is about twice as high as that of producing CNG of the same volume. The second is that the domestic LNG liquefaction plant is remote and generally adopts long-distance transportation on land, while CNG uses natural gas transported by pipeline. The cost of transportation of LNG is much higher than that of CNG.
LNG must be stored at a low temperature of 162 ℃  below zero, so it is required that the steel cylinder has good thermal insulation performance, so the steel cylinder needs a double-layer vacuum structure. In order to ensure a vacuum state for a long time,and has better thermal insulation performance, it is required to wrap Insulation material round the inner liner of steel cylinder, and an adsorption device is added to adsorb the air remaining in the vacuum layer.