In addition to the use of lng as motor fuel, it is also projected to be a potential fuel for shipping industry[28] and [29].

Recently, China and Norway has developed LNG marine engine [30] and it is expected that this step will be promising in extending the LNG technology. According to this news, even though a LNG fueled engine is more expensive than a conventional engine but it will be viable investment as LNG is less expensive than diesel. Hence, LNG is providing an economic alternative to diesel in the heavy duty trucking industry, in port facility vehicles, and increasingly in marine and rail applications.

Although the use of LNG as vehicle fuel is capturing wider attention worldwide, yet LNG faces some significant challenges to achieving its full potential share of the global NGV market. The challenges are listed as follows:

There are very few global regulations for L-NGV applications and there are many remaining gaps in the existing international standards. The lack of harmonized standards and regulations impede opportunities to reduce the cost of manufacturing and purchasing different LNG equipment.

II.A number of countries have their own national interest and policies regarding the utilization of energy for transportation which prohibits the development of various types of L-NGVs in the areas where there could be a strong LNG market.

III.Many manufacturers of heavy-duty engines and vehicles – even those producing NGVs – have not yet adapted their products for LNG. There are too few products, in particular, for the very heavy truck-haulage industry or for larger off-road vehicle applications where LNG could provide economic and environmental benefits.

IV.Retrofit systems being installed on various heavy duty trucks operate at slightly different working pressures, requiring the LNG to be delivered at different pressures. This complicates the opportunity to develop a network of harmonized LNG fuelling stations.

V.Consistency of fuel quality, particularly in the cryogenic processing of biogas and in LNG fuelling stations faces special challenges that need to be addressed.

Hence, in order to accept LNG as a vehicle fuel it is recommended to add more global regulations for L-NGV and to develop infrastructures (LNG fuelling stations and LNG kits for heavy to light duty vehicles) along with more advanced technologies.

3.2. Electricity production

The use of LNG is not only limited up to transport sector but it is also useful in the production of electricity. The utilization of the cryogenic exergy of LNG for the production of electricity has been reported by many research groups [31], [32], [33], [34] and [35]. In [35] the authors propose the introduction of a combined Rankine–Brayton cycle with CO₂ as a working fluid. An additional source of heat is necessary, which is obtained by means of combustion of some amount of CH₄ in oxygen, producing combustion gases with a large content of CO₂ (95%). The transmission of heat to the evaporating LNG would be very irreversible.

Deng et al. [36] proposed a combined plant producing electricity and refrigeration. The process would utilize the cryogenic exergy of LNG, but also the chemical exergy of some amount of CH₄ burnt in oxygen. This solution would not comply with the principle of combined cogeneration processes, because the cold cycle can be combined with the refrigeration cycle without any additional heat source. The working fluid would be CO₂ having very inconvenient thermal properties. Hence, in the proposed installation large exergy losses would appear.

Use of natural gas for power generation has been reported by Oliveira et al. [37] and Oshima et al. [38]. According to Okamura et al. [39] LNG is a major source of energy for transport and power generation sector, in Japan. They analyzed that the use of LNG contribute greatly to improving the atmospheric environment and reducing CO₂ emissions.

The possibilities of the utilization of cryogenic exergy of LNG for electricity production without any additional combustion of any its portion, have been analyzed by Szargut et al. [40] and Dispenza et al. [41]. According to their study LNG delivered by sea-ships contains considerable cryogenic exergy which can be utilized for electricity production before its evaporation and introduction into the system of pipelines. The liquefaction of natural gas consumes a considerable amount of exergy [42] and some part of that consumption may be recovered by means of a cold power plant utilizing the cryogenic exergy of LNG. The simplest method of that utilization might be based on the principle of a cold Rankine cycle absorbing the evaporation heat from the environment and rejecting the heat of condensation to preheat and evaporate LNG. Querol et al. [43] have reported the method of power generation from LNG. They carried out the thermoeconomics of different power generation methods and found that the use of LNG for power generation is effective.

In addition to transportation and generation of power, LNG is also used in fertilizer industry [15] and it is also gaining foothold for cooking, heating homes instead of LPG.

4. Storage and transport of LNG

Types of storage facilities for LNG depend on whether the liquid is to be used to meet winter shortages of gas (Peak shaving facilities to meet the seasonal fluctuating gas demand) or to supply base load gas by long distance shipment. In the later case, complete ships cargos should be loaded into and unloaded from LNG tankers. Apart from the necessary insulation for minimizing evaporation losses, it is essential to keep the LNG cargo away from contact with the ship structure as mild steel becomes brittle below 223 K, and could lead a disastrous situation. Evaporation losses may be as low as 0.1% per day for the tank contents, provided insulation is sufficient. For ocean going vessel reliquefaction facilities, facilities usually cater for about a 0.3% boil-off.

LNG on shore can be contained in double walled metal tanks not dissimilar to those used in ships, i.e. aluminum or nickel steel inner vessels or membranes, surrounded by insulation and external weather-proofing. In addition, pre stressed concrete tanks can also be erected above ground, or can be cast below the surface. Finally, existing underground spaces specially prepared for LNG storage can be used. The main advantage of in-ground tanks, both concrete and natural, is that they do not require containment dykes to collect products from leaking or burst containers. The attraction of above-ground tanks, on the other hand, is improved control of heat leakage and also the possibility of repairs.