CHALLENGES OF NATURAL GAS STORAGE

Natural Gas is typically delivered from a gas well to an end-user via a pipeline system. When pipeline infrastructure is not available, NG is either compressed or liquefied for storage and transport. Storing NG presents major technical challenges, as NG storage must be stored at extremely high pressure when compressed, and/or at extremely low temperature when liquefied.

Compressed Natural Gas (CNG)
For Natural Gas to be efficiently stored in gaseous state, it must me compressed. Nearly all NG stored and transported without a pipeline, utilizes standard Compressed Natural Gas (CNG) technology.

Compressed Natural Gas is generally stored at a high pressure of 200-250 bars. High-pressure CNG demands very strong, large, and heavy specially-designed cylindrical tanks. The NG compression process requires expensive, multi-stage, high-pressure compression technology.

Liquefied Natural Gas (LNG)
Natural gas is liquefied at a pressure of 10-20 bars, and at an extreme temperature of minus 161.5° C. The LNG conversion process requires the use of complex and expensive liquefaction equipment, and thermos-like cryogenic tanks. In addition, the process consumes a great deal of energy (25-35% of the original energy gas content) for liquefaction and degasification. LNG storage tanks require a cylindrical or spherical shape.

LNG technology is not as common as CNG. There are only a few thousand LNG fueled heavy vehicles around the world, and serial manufacturing of LNG equipment hardly exists. LNG is subject to economies of scale with advantages in large storage, and is therefore used primarily for large vehicles. An on-board LNG tank for a small vehicle would cost nearly the same amount as a LNG tank for a heavy vehicle, while providing a much lower net volume storage efficiency.