::NATURAL GAS VEHICLES::SEMINAR II - MEC3892

SECTION 1GROUP 13

DR MIRGHANI ISHAG AHMADMOHD REDZUAN MOHD ZAIN 0439509MUHAMMAD AFFANDI ABD TALIB 0436397MUHAMMAD HAFIZ AB HALIM 0432711

WHAT IS NATURAL GAS

• a highly combustible odorless and colorless hydrocarbon gas largely composed of methane.

• produced in pressurized deposits located deep in the earth's crust, commonly located just above oil deposits.

• created in roughly the same manner as oil, by geologic processes that act upon organic matter over millions of years.

• High combustibility coupled with low emissions makes natural gas a highly valued resource.

• More economical than electricity, natural gas is primarily used for heating homes, cooking and running appliances such as water heaters and clothes dryers.

HOW NATURAL GAS PRODUCED

• Aside from natural gas deposits, tiny microorganisms called methanogens produce natural gas by breaking down organic matter.

• Methanogens reside in the intestines of humans and many animals, including cattle, and can also be found near the surface of the earth in anaerobic conditions.

• These microorganisms are responsible for landfill gas, more properly termed biogenic methane, as distinguished from thermogenic methane, or deposited natural gas.

• Though a great deal of natural gas escapes into the air from various biogenic sources, efforts are underway to develop technology that can harvest unconventional natural gas.

• This would compliment natural gas deposits, which by some estimates are quite extensive.

What is a natural gas vehicle

• natural gas vehicles (NGVs) are designed to run only on natural gas

• bi-fuel NGVs have two separate fueling systems that enable the vehicle to use either natural gas or a conventional fuel (gasoline or diesel).

• dedicated NGVs demonstrate better performance and have lower emissions than bi-fuel vehicles because their engines are optimized to run on natural gas.

• the vehicle does not have to carry two types of fuel, thereby increasing cargo capacity and reducing weight.

• fueled with compressed natural gas (CNG) or liquefied natural gas (LNG).

• Compared with vehicles fueled with conventional diesel and gasoline, NGVs can produce significantly lower amounts of harmful emissions.

• some natural gas vehicle owners report service lives two to three years longer than gasoline or diesel vehicles and extended time between required maintenance.

• driving range of NGVs generally is less than that of comparable gasoline and diesel fueled vehicles because of the lower energy content of natural gas.

• Extra storage tanks can increase range, but the additional weight may displace payload capacity.

• NGV horsepower, acceleration, and cruise speed are comparable with those of an equivalent conventionally fueled vehicle.

How Natural Gas Vehicles Work

Light-duty natural gas vehicles work much like gasoline-powered

vehicles with spark-ignited engines. This schematic shows

basic CNG fuel system components.

CNG enters the vehicle through the natural gas fill valve (A) and flows into high-pressure cylinders (B). When the engine requires natural gas, the gas leaves the cylinders and passes through the master manual shut-off valve (C). The gas travels through the high-pressure fuel line (D) and enters the engine compartment. Gas enters the regulator (E), which reduces the gas pressure used for storage (up to 3,600 psi) to the required vehicle fuel injection system pressure. The natural gas solenoid valve (F) allows natural gas to pass from the regulator into the gas mixer or fuel injectors. The solenoid valve shuts off the natural gas when the engine is not running. Natural gas mixed with air flows down through the carburetor or fuel-injection system (G) and enters the engine combustion chambers where it is burned to produce power, just like gasoline.

Some heavy-duty vehicles use spark-ignited natural gas systems, but other systems exist as

well. High-pressure direct injection engines burn natural gas in a compression-ignition

(diesel) cycle.

Advantages and Disadvantages

Advantages

• NGVs are safer. The fuel storage tanks on an NGV are thicker and stronger than gasoline or diesel tanks. There has not been an NGV fuel-tank rupture in more than two years in the United States.

• Natural gas costs are lower than gasoline. On average, natural gas costs one-third less than gasoline at the pump.

• Natural gas is convenient and abundant. A well-established pipeline infrastructure exists in the United States to deliver natural gas to almost every urban area and most suburban areas. There are more than 1,300 NGV fueling stations in the United States, and more are being added every day.

• Natural gas prices have exhibited significant stability compared to oil prices. Historically, natural gas prices have exhibited significant price stability compared to the prices of petroleum-based fuels. This stability makes it easier to plan accurately for long-term costs.

• NGVs have lower maintenance costs. Because natural gas burns so cleanly, it results in less wear and tear on the engine and extends the time between tune-ups and oil changes.

Disadvantages

• they aren't as roomy as gasoline cars. This is because NGVs have to give up precious cargo and trunk space to accommodate the fuel storage cylinders.

• these cylinders can be expensive to design and build -- a contributing factor to the higher overall costs of a natural-gas vehicle compared to a gasoline-powered car.

• limited driving range of NGVs, which is typically about half that of a gasoline-powered vehicle.

• For example, Honda's natural gas Civic, the Civic GX, can go up to 220 miles without refueling. A typical gasoline-powered Civic can go approximately 350 miles without refueling.

• If a dedicated NGV ran out of fuel on the road, it would have to be towed to the owner's home or to a local natural gas refueling station, which might be harder to find than a "regular" gas station.

• natural gas, like gasoline, is a fossil fuel and cannot be considered a renewable resource.

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