Compressed Natural Gas Essay, Research Paper
Compressed Natural Gas or CNG is becoming and increasingly attractive fuel for
many transportation uses. One reason for the increase in interest in CNG is that
the emissions of a CNG vehicle are far less than that of a gas powered engine.
Other factors that make the production of CNG vehicle?s is that the gas prices
have risen in the past couple years.
Natural gas is, well, natural gas–the same stuff that heats your stove or your
house. It is largely produced domestically in the United States; it can be imported
through pipelines or as a super-cold liquid on special tanker ships, but because
this is a lot harder than pouring crude or refined oil into a tanker or a pipeline, we
haven’t built up an import dependency for natural gas as we have for petroleum.
Natural gas is distributed nationwide through an extensive network of pipelines,
which feed electrical generation plants and domestic and industrial heating uses.
In order to store a reasonable amount of fuel natural gas has to be compressed to
around 200 times atmospheric pressure–or even more for the tanks aboard large
buses! This is like the pressure a mile and a quarter under the ocean.
It is very easy on the engine, giving longer service life and lower maintenance
costs. CNG is the least expensive alternative fuel when you compare equal
amounts of fuel energy such as gasoline. Because there is a huge and predictable
demand for natural gas from domestic, industrial, and utility users, there is a large
buffering effect against price fluctuations. At the peak of the big gasoline
price run-up in April, 1996, everyone was paying half as much for a gasoline-
gallon-equivalent of 130-octane natural gas as I would have aid for a gallon of 92-
octane unleaded gasoline! You get significantly better fuel economy on the open
road because the high octane rating of the fuel allows timing and mixture to be
adjusted for more efficiency without causing detonation (”knocking”). And
because the fuel tanks have to withstand such enormous internal pressures, they
are incredibly tough, with good results or safety. In addition, because natural gas
is lighter than air and has very narrow flammability limits, if a leak develops it is
very likely that the fuel will dissipate harmlessly into the air without causing a
danger of ignition or explosion. Natural gas has, over the course of the 1990’s,
proven to be the most effective fuel for reducing emissions in an internal
combustion engine. Other key advantages is the emissions that a CNG vechile is far
less than that of a gasoline driven car. The catalytic converter developed for the NGV
had a 1.24 L volume and was composed of palladium/platinum. The exhaust emissions
measured under durability running for petrol and CNG fuels are shown in Table below:
CNG4 k miles0.210.0160.06
50 k miles0.440.0230.11
Petrol4 k miles0.690.0280.05
50 k miles0.790.0550.07
It can be seen that the CO and NMOG levels for the NGV are very favourable while
NOx is more for a CNG vechile.
Some of the disadvantages are that the tanks are quite bulky and heavy.
Locations of the tanks is another concern from putting them in the trunk to putting
them underneath the vehicle. Some other problems that affect use of widespread CNG
is the lack of refueling stations available to refuel and CNG vechile. High capital costs
are involved in setting up a network of refuelling stations. This presents problems that
must be resolved in the early stages of a national development programme. The build-
up of custom at a new public station may be slow, with correspondingly long times for a
return on capital. Another dissadvantage is that cost to convert the vechile. The first
cost of a conversion will be in the range $1,000 to $3,500 and the payback from two
to seven years, depending on annual mileage. Any future reductions in the cost of
lightweight cylinders will have an important effect on the conversion cost.