WHAT IS FUEL?

A fuel is any material that can be used to generate energy as heat energy and to be utilized for work.

The fuel source can be of different forms to generate heat energy. The heat energy discharged by the burning of fuels is changed over into mechanical energy by means of a heat engine.

The generated heat will be further used for different occasions such as for warmth, cooking, and for generating mechanical energy simultaneously.

Hydrocarbon oxygen-containing molecules are by far the most common source of fuel used by humans for daily uses. Other substances, including radioactive metals, are also utilized as a fuel; however, these fuels are dangerous and need high measures of safety and precautions.

Fuels may stay in relation to other devices for storing its potential energy so that they can directly release electrical energy whenever required by the user.

Devices such as batteries and capacitors are used as an energy storing devices. Similarly, mechanical energy generated from fuels is stored in flywheels, springs, compressed air and etc.

DIFFERENT TYPES OF FUEL

SOLID FUEL

Solid fuel refers to various types of solid material that are used as fuel to produce heat energy that is usually released through combustion. Solid fuels include wood, charcoal, peat, coal, hex-amine fuel tablets, and pellets made from wood (see wood pellets), corn, wheat, rae, and other grains.

Solid fuels have been used by humans for many years to create fire. Coal was the fuel source that brought the industrial revolution. Coal generates a very high amount of concentrated heat in firing furnaces and used for running steam engines.

Wood was also extensively used to run steam locomotives. Both peat and coal are still used in electricity generation. Nowadays, the use of coal has been restricted or prohibited in some urban areas, due to unsafe levels of carbon and toxic emissions.

The use of wood as a solid fuel is decreasing day by day for heating purposes. In some areas, smokeless coal is often being used for heat generation and for cooking purposes.

Peat briquettes are used as smokeless fuel and also used as coal fire burning medium.

LIQUID FUEL

Liquid fuels are highly combustible and energy-generating fuel to generate heat and thus to produce mechanical energy.  Liquid fuel takes the shape of its container in which it is stored. It is the fumes of liquid fuels that are flammable instead of the fluid.

Most liquid fuels that have been widely used are derived from the fossils of dead plants and animals by exposure to heat and pressure inside the Earth’s crust.

There are several types of liquid fuel such as hydrogen fuel (for automotive uses), ethanol, jet fuel, and bio-diesel. Emulsified fuels of oil-in-water such as Orimulsion fuel have been developed by scientists in order to make heavy oil fractions which can be used as liquid fuels for other devices.

Many liquid fuels play a primary role in transportation and in economic growth.

Some common properties of liquid fuels are that they are easy to transport and can be handled easily. They are relatively easy to use in all engineering applications and in-home.

Fuels like kerosene are widely used for cooking and lighting purposes. In some countries, Kerosene fuel is distributed by the government for cooking purposes under government subsidy policy.

Diesel fuel is similar to gasoline or says petrol. It is a mixture of aliphatic hydrocarbons (presence of long hydrocarbon chain with Aldehydes) extracted from petroleum. Diesel fuel is widely used in heavy vehicle engines. Kerosene is used in lamps and for cooking, heating, and for running small engines.

Natural gases are composed basically of methane & can only exist in liquid form at very low temperatures range regardless of pressure; which limits its direct use in most applications. LP gas is a mixture of propane and butane, both of which are compressible gas under standard atmospheric conditions.

Compressed natural gas (CNG) is denser than air & does burn clean, and is much more easily compressed. CNG is commonly used for cooking and space heating. On the other hand, LPG gases and compressed propane are seeking increased use in motorized vehicles. Propane is the third most commonly used motor fuel globally.

FUEL GAS

Fuel gas remains in a gaseous state under ordinary conditions. Many fuel gases are composed of hydrocarbons such as methane or propane, hydrogen, carbon monoxide.

Such gases are sources of potential heat energy and light energy which can be readily transmitted and distributed through pipes for general consumption. Fuel gas is contrasted with liquid fuels and from solid fuels, though some fuel gases are liquefied for storage or transport.

The gaseous nature of fuel gases can be advantageous for avoiding the difficulty of transporting solid fuel and also the dangers of spillage likewise liquid fuels. Fuel gases can also be dangerous as it is very active to fire sparks.

It is possible for a fuel gas to be undetected and collect in certain areas, leading to the risk of a gas explosion. For this reason, odorizers are added to most fuel gases so that they may be detected by a distinct smell. The most common type of fuel gas in current use is natural methane and acetylene gas.

BIOFUEL

Biofuel can be broadly defined as solid, liquid, or gas fuel derived from biomass. Biomass can also be used directly for heating or for power generation later known as biomass fuel.

Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants, wood, dry sugarcane skin, and cow dung. Many small scale industries use biomass for heat generation.

The earliest fuel found by humans is wood. Evidence shows the controlled fire was used up to 1.5 million years ago at Swartkrans, South Africa.

It is unknown which hominid species had first used fire, as both Australopithecus and an early species of Homo were present at the sites. As a fuel, wood has continued to be in use even in the present days for many purposes. Wood has an energy density of 10– 20 MJ/kg. It is assumed that 1 kilogram of coal will produce 2.4 kilowatt-hours of electricity.

 Recently biofuels have been developed in the form of Bioethanol and Biodiesel for use in automotive transport. But there is a widespread public debate about how carbon-efficient these fuels are.

FOSSIL FUEL

Fossil fuels are hydrocarbons compound primarily coal and petroleum (liquid petroleum or natural gas). This fossil fuel was formed from the fossilized remains of ancient plants and animals when exposed to high heat and pressure in the absence of oxygen in the Earth’s crust over hundreds of millions of years.

This biogenic theory was first introduced by German scholar Georg Agricola in 1556 and later by Mikhail Lomonosov in the 18th century. Commonly, the term fossil fuel also includes hydrocarbon-containing natural resources that are not derived entirely from biological sources, such as tar sands (also said as Alkatra in Nepali/Hindi languages). These latter sources are properly known as mineral fuels.

Fossil fuel contains high percentages of carbon and hydrogen and include coal, petroleum, and natural gases. They range from volatile materials with low – (carbon: hydrogen ratios like methane) and liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal.

Methane can be found in hydrocarbon fields alone, associated with oil, or in the form of methane catharses.

It was estimated by the Energy Information Administration that in 2007 primary sources of energy consisted of petroleum 36.0%, coal 27.4%, natural gas 23.0%, amounting to an 86.4% share for fossil fuels in primary energy consumption in the world. Non-fossil sources in 2006 included hydroelectric 6.3%, nuclear 8.5%, and others (geothermal, solar, tidal, wind, wood, waste) amounting to 0.9%.  World energy consumption has grown by about 2.3% per year.

Fossil fuels are non-renewable resources of energy because they take millions of years to form, and reserves are being depleted much faster than new ones are being made.

So, we must conserve these fossil fuels and use them in a proper manner. The production and use of fossil fuels raise necessary environmental concerns. A global movement toward the generation of renewable energy is therefore underway to help meet increased energy needs.

The burning of fossil fuels produces around 21.3 billion tonnes which is equal to (21.3 Gigatonnes) of carbon dioxide (CO2) per year.

Carbon dioxide is one of the major causes of the greenhouse effect because it enhances radioactive force and contributes to global warming, causing the rise in the average surface temperature of the Earth.

NUCLEAR FUEL

Nuclear fuel is any material that is consumed to generate nuclear energy or simply heat energy. Technically speaking, all matter can be a nuclear fuel because any element under the right conditions will release nuclear energy.

The materials commonly referred to as nuclear fuels are those which produce energy without being placed under extreme pressure.

Nuclear fuel is a material that can be ‘burned’ by nuclear fission or fusion in order to generate nuclear energy or simply heat energy.

Most nuclear fuels contain heavy fissile elements that are capable of nuclear fission. When these fuels are struck by neutrons, they are capable of emitting neutrons in a continuous energy chain.

This makes nuclear fuels to produce a self-sustaining chain reaction that releases a huge amount of heat energy. Nuclear fuels are used in a very controlled way inside a nuclear reactor.

Any rapid uncontrolled rate of reaction during use may result in a nuclear weapon.

The most common fissile nuclear fuels are uranium-235 (235U) and plutonium-239 (239Pu). The actions of mining, refining, purifying, using, and ultimately disposing of nuclear fuel together make up the nuclear fuel cycle. Not all types of nuclear fuels create power from nuclear fission.

Plutonium-238 and some other elements are used to produce small amounts of nuclear power by radioactive decay in radioisotope thermoelectric generators and other types of atomic batteries.

Also, light nucleoside such as tritium (3H) can be used as fuel for the nuclear fusion reaction. Nuclear fuel has the highest energy density of all practical fuel sources.

NUCLEAR FISSION

The most common type of nuclear fuel used by humans is heavy fissile elements that can be made to undergo nuclear fission chain reactions in a nuclear fission reactor.

Nuclear fuel can refer to the material or to physical objects (for example fuel bundles composed of fuel rods), perhaps mixed with structural, neutron moderating, or neutron reflecting materials.

The most common fissile nuclear fuels are 235U and 239Pu. The action of mining, refining, purifying, using, and ultimately disposing of these elements together make up the nuclear fuel cycle which is important for its relevance to nuclear power generation and nuclear weapons.

NUCLEAR FUSION

The stars that undergo nuclear fusion consists of atomic nuclei that can release energy by the absorption of a proton or neutron. In most stars, the fuel is provided by hydrogen, which can combine to form helium through the proton-proton chain reaction or by the CNO cycle.

When the hydrogen fuel is consumed, nuclear fusion continues with progressively heavier elements although the total net energy released is lower.

It is because of the smaller difference in nuclear binding energy. Once iron-56 or nickel-56 nuclei are produced, no further energy can be obtained by nuclear fusion as these have the highest nuclear binding energies.

The elements then use energy instead of giving off energy when fused. Therefore, fusion stops and the stars die.

In attempts by humans, fusion is only carried out with hydrogen (an isotope of 2 and 3) to form helium-4 as this reaction gives out the most net energy which is not easy to generate and control.

Fuels that produce energy by the process of nuclear fusion are currently not utilized by humans but are the main source of fuel for stars.

Fusion fuels tend to be light elements such as hydrogen which will combine easily.

Energy is required to start fusion by raising the temperature so high all materials would turn into plasma, and allow nuclei to collide and stick together with each other before repelling due to electric charge. This process is called fusion and it can give out energy.

ENERGY CONSUMPTION, PRODUCTION COST AND USES