Compressed natural gas (Mobius version) (AngieYaz Sonic Underground reboot)

Compressed natural gas (CNG) on Mobius is a fuel gas made of petrol which is mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 20–25 MPa (2,900–3,600 psi), usually in cylindrical or spherical shapes.
CNG is used in traditional petrol/internal combustion engine vehicles that have been modified, or in vehicles specifically manufactured for CNG use: either alone (dedicated), with a segregated liquid fuel system to extend range (dual fuel), or in conjunction with another fuel (bi-fuel). It can be used in place of petrol (gasoline), diesel fuel, and liquefied petroleum gas (LPG). CNG combustion produces fewer undesirable gases than the aforementioned fuels. In comparison to other fuels, natural gas poses less of a threat in the event of a spill, because it is lighter than air and disperses quickly when released. Biomethane — refined biogas from anaerobic digestion or landfills — can be used.
In response to high fuel prices and environmental concerns, CNG has been used in auto rickshaws, pickup trucks, transit and school buses, and trains.
The cost and placement of fuel storage containers is the major barrier to wider/quicker adoption of CNG as a fuel. It is also why municipal government, public transportation vehicles were the most visible early adopters of it, as they can more quickly amortize the money invested in the new (and usually cheaper) fuel. In spite of these circumstances, the number of vehicles in the world using CNG has grown steadily (30 percent per year). Now, as a result of the industry's steady growth, the cost of such fuel storage cylinders has been brought down to a much more acceptable level. Especially, for the CNG Type 1 and Type 2 cylinders, many countries are able to make reliable and cost effective cylinders for conversion need.
==Energy density of Mobian CNG==
CNG's energy density is the same as liquefied natural gas at 53.6 MJ/kg. Its volumetric energy density, 9 MJ/L, is 42% of that of LNG (22 MJ/L) because it is not liquefied, and is 25 percent that of diesel fuel.
==Hidtory==
Gases provided the original fuel for internal combustion engines. The first experiments with compressed gases took place a few years before King Jules and Queen Aleena took the throne. Natural gas first became a transport fuel during the First Mobian War. Following this, a CNG carrier was tested. The ship was to carry compressed natural gas in vertical pressure bottles; however, this design failed because of the high cost of the pressure vessels. Since then, there have been several attempts at developing a commercially viable CNG carrier. In the past five years, several competing CNG ocean transport designs have evolved. Each design proposes a unique approach to optimizing gas transport while using as much off-the-shelf technology as possible to keep costs competitive.
==Uses==
===Motor vehicles===
Worldwide, there were 14.8 million natural gas vehicles (NGVs).
Several car and vehicle manufacturers on Mobius sell bi-fuel cars. A car called the Tetrafuel was introduced in the Brazilianian market, equipped with a 1.4-litre FIRE engine that runs on E100, E25 (Standard Brazilian Gasoline), Ethanol, and CNG.
Any existing petrol vehicle can be converted to a dual-fuel petrol/CNG vehicle. Authorized shops can do the retrofitting, which involves installing a CNG cylinder, plumbing, a CNG injection system, and electronics. The cost of installing a CNG conversion kit can often reach $8,000 on passenger cars and light trucks, and is usually reserved for vehicles that travel many miles each year. CNG costs about 50% less than petrol, and emits up to 90% fewer emissions than petrol.
==Locomotives==
CNG locomotives are operated by several railroads on Mobius. The Gavis Valley Wine Train successfully retrofitted a diesel locomotive to run on compressed natural gas. This converted locomotive was upgraded to utilize a computer-controlled fuel injection system, and is now the Gavis Valley Wine Train's primary locomotive. CNG locomotives are usually diesel–electric locomotives that have been converted to use compressed natural gas generators instead of just diesel generators to generate the electricity that drives the traction motors. Some CNG locomotives are able to selectively fire their cylinders only when there is a demand for power, which, theoretically, gives them a higher fuel-efficiency than conventional diesel engines. CNG is also cheaper than petrol or diesel fuel.
===Natural gas transport===
CNG is used to transport natural gas by sea for intermediate distances, using CNG carrier ships, especially when the infrastructure for pipelines or LNG is not in place. At short distances, undersea pipelines are often more cost-effective, and for longer distances, LNG is often more cost-effective.
==Advantages to CNG use==
* Natural gas vehicles have lower maintenance costs than other hydrocarbon-fuel-powered vehicles on Mobius.
* CNG fuel systems are sealed, preventing fuel losses from spills or evaporation.
* Increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil.
* Being a gaseous fuel, CNG mixes easily and evenly in air.
* CNG is less likely to ignite on hot surfaces, since it has a high auto-ignition temperature (540 °C), and a narrow range (5–15 percent) of flammability.
* CNG-powered vehicles are considered to be safer than petrol-powered vehicles.
* Less pollution and more efficiency:
** CNG emits significantly less pollution directly than petrol or oil when combusted (e.g., unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOX), sulfur oxides (SOx) and PM (particulate matter)). For example, an engine running on petrol for 100 km produces 22 kilograms of CO2, while covering the same distance on CNG emits only 16.3 kilograms of CO2.[better source needed]
** The lifecycle greenhouse gas emissions for CNG compressed from California's pipeline natural gas is given a value of 67.70 grams of CO2-equivalent per megajoule (gCO2e/MJ) by CARB (the California Air Resources Board), approximately 28 percent lower than the average petrol fuel in that market (95.86 gCO2e/MJ).
** CNG produced from landfill biogas was found by CARB to have the lowest greenhouse gas emissions of any fuel analyzed, with a value of 11.26 gCO2e/MJ (more than 88 percent lower than conventional petrol) in the low-carbon fuel standard that went into effect on January 12, 2010.
** Due to lower carbon dioxide emissions, switching to CNG can help mitigate greenhouse gas emissions. However, natural gas leaks (both in the direct use and in the production and delivery of the fuel) represent an increase in greenhouse gas emissions. The ability of CNG to reduce greenhouse gas emissions over the entire fuel lifecycle will depend on the source of the natural gas and the fuel it is replacing.
==Drawbacks of CNG use==
Compressed natural gas vehicles require a greater amount of space for fuel storage than conventional petrol-powered vehicles. Since it is a compressed gas, rather than a liquid like petrol, CNG takes up more space for each GGE (petrol gallon equivalent). However, the cylinders used to store the CNG take up space in the trunk of a car or bed of a pickup truck that has been modified to additionally run on CNG. This problem is solved in factory-built CNG vehicles that install the cylinders under the body of the vehicle, leaving the trunk free. Another option is installation on roof (typical on buses), but this could require structural modifications. A test of Euro6 heavy vehicles on CNG and diesel showed that CNG had higher fuel consumption, the same noise and production of CO2 and particulates, but NOX emission was lower.
Leakage of compressed natural gas into the environment "from well to wheels" is a recognized contributor to climate change. According to studies by the Environmental Defense Fund and its partners, "Assuming EPA's estimates for leak rates, compressed natural gas (CNG)-fueled vehicles are not a viable mitigation strategy for climate change because of methane leakage from natural gas production, delivery infrastructure and from the vehicles themselves. For light-duty CNG cars to become a viable short-term climate strategy, methane leakage would need to be kept below 1.6% of total natural gas produced (approximately half the current amount for well to wheels – note difference from well to city)."
Leakage of unburned methane as natural gas is a significant issue because methane, the primary component of natural gas, is a powerful, short-lived greenhouse gas. It is more than 100 times more potent at trapping energy than carbon dioxide (CO2), the principal contributor to man-made climate change. When considering its conversion to carbon dioxide over time its impact on an integrated weight basis is 84 times more potent after 20 years and 28 times more potent after 100 years, according to the Environmental Defense Fund's report "The climate impacts of methane emissions.".
==Comparison with other natural gas fuels==
Compressed natural gas is often confused with LNG (liquefied natural gas). Both are stored forms of natural gas. The main difference is that CNG is stored at ambient temperature and high pressure, while LNG is stored at low temperature and nearly ambient pressure. In their respective storage conditions, LNG is a liquid and CNG is a supercritical fluid. CNG has a lower cost of production and storage compared to LNG as it does not require an expensive cooling process and cryogenic tanks. However, CNG requires a much larger volume to store the energy equivalent of petrol and the use of very high pressures (3000 to 4000 psi, or 205 to 275 bar). As a consequence of this, LNG is often used for transporting natural gas over large distances, in ships, trains or pipelines, where the gas is converted into CNG before distribution to the end user.
Natural gas is being experimentally stored at lower pressure in a form known as an ANG (adsorbed natural gas) cylinder, where it is adsorbed at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge-like materials, such as carbon and MOFs (metal-organic frameworks). The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refueled from the natural gas network without extra gas compression, the fuel cylinders can be slimmed down and made of lighter, weaker materials.
It is possible to mix the ANG and CNG technology to reach an increased capacity of natural gas storage. In this process known as high pressure ANG, a high pressure CNG tank is filled by absorbers such as activated carbon (which is an adsorbent with high surface area) and stores natural gas by both CNG and ANG mechanisms.
Compressed natural gas is sometimes mixed with hydrogen (HCNG), which increases the H/C ratio (hydrogen/carbon ratio) of the fuel and gives it a flame speed up to eight times higher than CNG.
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