Compressed natural gas (CNG) carrier ships are those designed for transportation of

natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...

under high

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

. CNG carrier technology relies on high pressure, typically over 250 bar (2900 psi), to increase the

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of the gas, but it is still 2.4 times less than that of LNG (426 kg/m³). CNG carriers may find their place abreast with the well established technology of

liquefied natural gas Liquefied natural gas (LNG) is natural gas (predominantly methane, CH4, with some mixture of ethane, C2H6) that has been cooled to liquid form for ease and safety of non-pressurized storage or transport. It takes up about 1/600th the volume o ...

LNG carrier An LNG carrier is a tank ship designed for transporting liquefied natural gas (LNG). Overview The first oceangoing liquified natural gas tanker in the world was '' Methane Pioneer'', which entered service in 1959 with a carrying capacity of ...

s as it is economical for medium distance marine transport. Most of the energy consumed for the gas pressurisation can be recovered as electricity using turboexpander while delivering CNG to the inland piping network at unloading

jetty A jetty is a man-made structure that protrudes from land out into water. A jetty may serve as a breakwater (structure), breakwater, as a walkway, or both; or, in pairs, as a means of constricting a channel. The term derives from the French la ...

/harbour. CNG carriers are also alternate solutions to the undersea pipelines as they have less complicated fast loading and unloading features.

Pressure container technology

Several approaches to the problem of cost-effective high-pressure containers are possible. The main variables are the material to be used and the geometry of the containers. Standard method of storing non-condensed gases in metal flasks is not cost-effective for high-volume storage at high pressure. (This does not apply to gases such as

butane Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...

and

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

or their mixtures as in

liquefied petroleum gas Liquefied petroleum gas, also referred to as liquid petroleum gas (LPG or LP gas), is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, Butane, ''n''-butane and isobutane. It can also contain some ...

(LPG). LPG gases liquefy at ambient temperatures under moderate pressure and can be economically stored in steel containers of various sizes.) New approaches to CNG technology include fiber-reinforced plastic containers and containers in the form of metal tubes of moderate diameter (typically 6" or 168 mm internal diameter). In one approach
Coselle
of tubing is wound on a spindle. Such spindles are stackable and may be connected to achieve the desired capacity. In another approach
GASVESSEL
composite material containers are adopted allowing to increase the commercial payload for the CNG ship and significantly reduce the transport cost.

Comparison

The CNG carrier is a single piece equivalent to the combination of floating liquefied natural gas,

and floating regasification plant^RU. Unlike LNG transport, CNG transport has 100% flexibility in changing gas loading / unloading port without any time lag. The capital cost of CNG transport overseas is far less than the overall capital cost needed for LNG transport. The gestation period of LNG transport infrastructure is a few years. Whereas a CNG carrier can be sourced from the available fleet. The CNG carrier is very helpful in bringing a gas field/pipeline to early production. The propulsion fuel cost per unit natural gas transported by a CNG carrier is more than the fuel cost of a LNG carrier as CNG carrier is much heavier. CNG carrier transport is economical up to medium distances (< 2000 nmi) compared to LNG transport. The economical transport range increases with a fall in natural gas price or increasing spread between natural gas and LNG prices. The CNG carrier can act as a storage vessel also to absorb the fluctuations in demand and production from a network of gas pipelines on daily basis and export/import natural gas on a contingency basis. This would enable to discontinue take-or-pay contracts in natural gas

sales Sales are activities related to selling or the number of goods sold in a given targeted time period. The delivery of a service for a cost is also considered a sale. A period during which goods are sold for a reduced price may also be referred ...

and also enable natural gas exchanges between unconnected pipeline networks. The delivery schedule of CNG carriers can be extended/changed without any loss of cargo, unlike LNG carriers where the loss of LNG due to boil-off or evaporation takes place with the increase in journey time. CNG carriers are best suitable for floating storage as there is no loss of cargo with time. The CNG carrier removes the dispatch bottle neck which is preventing monetizing of small isolated offshore gas fields, by enabling them to produce natural gas. Also, it removes the hurdle to monetizing the gas reserves of small isolated offshore associated oil and gas fields, by providing storage and transport of gas which otherwise would have been flared. CNG carrier can also be used to transport

ethane Ethane ( , ) is a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...

either in gas/liquid form and hydrogen gas to widen its applications.

Beneficiary countries

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

and

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

can import CNG from

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

and

Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

can import CNG from

Qatar Qatar, officially the State of Qatar, is a country in West Asia. It occupies the Geography of Qatar, Qatar Peninsula on the northeastern coast of the Arabian Peninsula in the Middle East; it shares Qatar–Saudi Arabia border, its sole land b ...

Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

, Yamen,

Oman Oman, officially the Sultanate of Oman, is a country located on the southeastern coast of the Arabian Peninsula in West Asia and the Middle East. It shares land borders with Saudi Arabia, the United Arab Emirates, and Yemen. Oman’s coastline ...

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

(via

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

) and

Mozambique Mozambique, officially the Republic of Mozambique, is a country located in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Afr ...

can export CNG to all countries having coast line with

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

and

Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...

including

Western Europe Western Europe is the western region of Europe. The region's extent varies depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the Western half of the ancient Mediterranean ...

and India. *

can export CNG to Western Europe via Black Sea and Mediterranean Sea. *

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

can export CNG to Western Europe,

Cuba Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

and

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

. *

Turkmenistan Turkmenistan is a landlocked country in Central Asia bordered by Kazakhstan to the northwest, Uzbekistan to the north, east and northeast, Afghanistan to the southeast, Iran to the south and southwest and the Caspian Sea to the west. Ash ...

and

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...

can export CNG to Western Europe via

Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

Armenia Armenia, officially the Republic of Armenia, is a landlocked country in the Armenian Highlands of West Asia. It is a part of the Caucasus region and is bordered by Turkey to the west, Georgia (country), Georgia to the north and Azerbaijan to ...

Azerbaijan Azerbaijan, officially the Republic of Azerbaijan, is a Boundaries between the continents, transcontinental and landlocked country at the boundary of West Asia and Eastern Europe. It is a part of the South Caucasus region and is bounded by ...

and

Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...

References

{{Reflist, 30em Ship types Natural gas Fuel gas Tankers

Pressure container technology

Comparison

Beneficiary countries

See also

References