CNG - Compressed Natural Gas
CNG refers to the Compressed Natural Gas
This is a fuel gas is made from natural gas, which contains mostly methane (CH4), which has been compressed to less than 1% of its volume at standard atmospheric pressure.
At a pressure of 20-25 MPa (2,900-3,600 psi), it is stored or kept and dispersed in hard containers, generally in the cylinder or spherical shapes.
CNG is utilised in conventional petrol/internal combustion engines that have been altered or in vehicles designed exclusively for CNG use: either solo (dedicated), with a segregated liquid fuel system to broaden range (dual fuel), or in combination with some other fuel (bi-fuel).
CNG is an ideal choice for auto-rickshaw, truck, school buses since there has been an increase in the prices of fuel. CNG is cheap as well as environment friendly, hence is the optimum choice of fuel.
CNG can be utilised as a substitute for Petroleum (gasoline), diesel and liquefied petroleum gas )LPG. These can all be substituted for this fuel.
CNG combustion emits fewer harmful gases than the other fuels mentioned.
Natural gas is less dangerous than other fuels in the case of a leak because it is more light than the air and distributes quickly.
You can use biomethane, which is refined biogas from anaerobic digestion and landfills. It's the cost and location of the fuel storage containers that are holding back CNG's widespread and rapid adoption as a fuel.
Municipal governments and public motor vehicles were among the first to adopt it, as they can more rapidly recoup their costs by switching to the fresh (and usually less expensive fuel source).
Even with all of this, the number of motor vehicles using CNG in the world has risen steadily (30 percent per year).
It is now possible to purchase such fuel storage cylinders at a much lower price due to the continuous growth of the industry.
There are many countries that are able to produce CNG Type 1 and Type 2 cylinders that are trustworthy and cost efficacious.
As it is not liquefied, CNG has a volumetric energy density of 42 percent that of liquefied natural gas and 25 percent that of diesel fuel.
Advantages of CNG or Compressed Natural Gas
1. Green Fuel or Environment Friendly
CNG or the compressed natural gas is a green fuel and is considered as environment friendly. As a result of its lead and sulphur-free composition, CNG minimises hazardous emissions. The spark plug's life is extended because it is non-corrosive.
Lead fouling of spark plugs and lead or benzene pollution are removed because CNG does not contain any lead or benzene.
2. Safe Fuel
As a result of CNG's attributes, it is a safe fuel. It's saved in high-gauge, accredited seamless cylinders, so there's very little possibility of a spill. In the event of a spill, it simply rises and scatters into the atmosphere, where it blends easily and evenly with the surrounding air.
3. Low Operational Costs
When compared to other fuels, CNG vehicles have a relatively low operating cost. They are economically cheap and cost-effective in comparison to other fuels.
4. Increased Life Span of other oils
There is also a real benefit to using CNG, as it does not pollute and dissolve the crankcase oil. Thereby helping in enhancing the lifespan of lubricating oils.
5. Less Damage To The Car
When compared to conventional gasoline and diesel, CNG combustion leaves virtually no impurities.
In other words, engine harms to the pipes, and tubes are whittled down.
6. Economic Benefits
CNG is a more affordable fuel than gasoline and diesel combined. A vehicle's average fuel consumption is 8 litres per 100 kilometres. We can however convert it to CNG and it will consume 5,5kg/100km of methane. Shifting to CNG will save you a lot of money.
7. Enhanced Performance
Due to the fact that natural gas has an octane rating of an estimated 130, while super and unleaded have octane levels of 95 and 98, respectively. Committed natural gas engines are higher in value and performance than gasoline engines.
The benefits of using CNG are unquestionable. More and more people are likely to transfer to CNG in the coming years or purchase CNG vehicles in the long term.
8. Dual Performer
CNG vehicle is considered as a dual performer. It has the advantage or major benefit of running on both CNG as well as Petrol.
9. Limited Flammability
Due to its high auto-ignition temperature (540 degrees centigrade) and limited range of flammability (5 percent to 15 percent), CNG is a little less likely to self-ignite on hot surfaces.
As a result, it won't burn if the CNG concentrations in the atmosphere are less than 5 percent or greater than 15 percent.
Inadvertent combustion is highly unlikely due to the high ignition temperature and restricted flammability spectrum.
These are just a few of the benefits of CNG and it is sure that in coming years, more and more people will be inclined towards it, due to its significant advantages for the people.
Disadvantages or Drawbacks of Compressed Natural Gas
Apart from the advantages, CNG is packed with some disadvantages as well. These are as follow;
1. More Space is required
Compared to traditional petrol-powered automobiles, compressed natural gas automobiles need more area for fuel storage.
CNG requires more space or area because it is a compressed gas and not a liquid like petrol (petrol gallon equivalent).
To compensate for this, CNG cylinders must be stored in the boot of the car or a motor vehicle that has been converted to function on CNG or compressed natural gas. Motor automobiles that have been manufactured as CNG vehicles solve this issue by installing the cylinders under the vehicle's body, leaving the trunk clear and free. This serves as an advantage, hence pre-fitted moto vehicles with CNG kits help in avoiding this issue. Installing it on the roof of the vehicle is another alternative, but it would involve structural changes.
2. High Fuel Consumption
According to the research, CNG has relatively high fuel consumption and tends to produce some noise, CO2, and particulates, but its NOX emissions are lower than that of diesel.
3. Climate Change
Compressed natural gas leaks into the surroundingsthereby contributing to climate changes.
In research findings by the Environmental Defense Fund compressed natural gas (CNG)-fueled automobiles are not a feasible climate change mitigation strategic approach because of methane leaking from gas production, delivery areas, and the automobiles themselves.
Methane leakage must be kept at less than 1.6 percent of total natural gas production for light-duty CNG vehicles to be a feasible short-term climate approach, approximately half of the current.
Leakage of unburned methane gas is also a major issue as it is the main component of natural gas and has a short life span as a greenhouse gas and is strong. Methane is 100 times more efficient at storing energy than carbon dioxide (CO2), the primary cause of climate change caused by humans.
4. Limited Availability
The concern in India is that we wouldn't have a lot of natural gas reserves, so we have to import most of the natural gas we use. Such frequent purchases add to the expenses, making it an expensive choice over time.
5. Highly Combustible
This is one of the major drawbacks of natural gas is that it is highly flammable, despite being lighter than air. Given the fact that natural gas is odourless, it is also hard to detect a leak.
6. Non-Renewable Resource
On the other hand, it is important to keep in mind that natural gas is a non-renewable resource. Natural gas reserves will be depleted in the coming years, according to experts, and we will have to purchase them from other countries.
7. Emits Co2 or Carbon Dioxide
A major drawback of natural gas is that it emits harmful carbon into the air.
Constant carbon dioxide emissions to the environment will give rise to climate change and global warming. Hence this is a major disadvantage for the environment in the long run.
8. Excessive time to process it
The processing of natural gas is time-consuming and labor-intensive due to the fact that it contains other component parts that must be separated before it can be used for residential or commercial uses.
9. Storage is Expensive
CNG has one major drawback despite its ease of storage and transportation.
Its volume is four times greater than that of petrol, which drives up the price to store because more money must be spent on extra storage space to keep it safe and secure.
These are some of the disadvantages of CNG or compressed natural gas.
Usage or Applications of CNG
Using CNG carrier ships, natural gas is transported by sea for optimal distances when pipes or LNG facilities are not available.
Undersea pipes are more cost-effective for small distances, while LNG is more budget-friendly for greater distances.
Plentiful railroads run CNG-powered locomotives.
To operate on compressed natural gas, the Napa Valley Wine Train effectively modified a diesel locomotive in the early 2000s.
CNG locomotives are generally diesel-electric locomotives that have been transformed for using compressed natural gas generators rather than diesel generators to produce electricity that continues to drive the traction motors rather than the diesel generators.
Theoretically, CNG locomotives can preferentially fire their cylinders only when power is needed. This provides them to have better fuel efficiency than diesel engines.
As a bonus, CNG is less expensive than petrol or diesel.
In 2011, there were 14.8 million natural gas vehicles (NGVs) in the world, led by Iran with 4.07 million, then Pakistan, Argentina, Brazil, India with 1.1 million, and so on.
Quite a few car and vehicle manufacturing companies, such as Fiat, Opel/General Motors, Volkswagen, Toyota, Honda, and others, deliver bi-fuel vehicles.
It is able to switch any current petrol vehicle into a dual-fuel petrol/CNG automobile.
Setting up a CNG cylinder, a CNG injection system, and other electrics can be done by authorised shops.
In the case of passenger cars, the cost of installing a CNG conversion kit can range from 40k to 50k in INR.
CNG usually are less expensive than petrol in the long run and emits up to 90% fewer emissions in comparison to petrol.
LNG vs CNG
Liquefied natural gas (LNG) is most often puzzled by compressed gas (compressed natural gas).
Both types of natural gas are of the stored form.
CNG is kept at atmospheric temperatures and high pressures, while LNG is kept at low temperatures and near atmospheric pressures.
LNG is a liquid, while compressed natural gas is a supercritical fluid.
When compared to LNG, CNG has a less production costs and space because it does not need a costly cooling method and cryogenic tank.
At the same time for CNG, a bigger or greater volume is needed to save the energy equal of petrol, and very high pressure must be used (3000 to 4000 psi, or 205 to 275 bar).
CNG has become increasingly popular and LNG is utilised for long-distance transportation of natural gas, using modes like ships, trains, or pipelines, where the respective gas is modified into CNG before giving to the customer or user.
CNG is being kept quantitatively at low pressures in a form is called 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 numerous sponge-like components, such as activated carbon and MOFs (metal-organic frameworks).
The fuel has a similar or high energy densityin comparison to compressed natural gas (CNG).
It also allows fuel cylinders to be slimmer and made of lighter, weaker materials because they can be filled from the natural gas system without additional gas compression.
CNG can be combined with hydrogen (HCNG), which tends to increase the fuel's H/C ratio (hydrogen/carbon ratio) and provides it up to 8 times the flame speed of CNG.
Codes and Standards
Further impediments to NGV market penetration include a deficiency of harmonised codes and standards along international jurisdiction. The international organisation for standardisation or
IOS has a technical group working on a benchmark for natural gas fueling stations for automobiles. The committee is very active.
Although there are no international safety standards, natural gas vehicles have a stellar safety record.
CNG vehicle nozzles and receptacles are covered by ISO 14469-2:2007, while ISO 15500-9:2012 clarifies the assessments and prerequisites for the pressure gauge.
USA's natural gas automobile safety regulations are covered by the National Fire Protection Association's NFPA 52 code.