◄UNIT 4:PROPAGATION OF MECHANICAL WAVESUNIT 6:MOTION IN ORBITS►

UNIT 5:FOSSIL, NON FOSSIL FUEL AND POWER PRODUCTION

  • UNIT 5:FOSSIL, NON FOSSIL FUEL AND POWER PRODUCTION


    Most of the energy that we consume comes from fossil fuels. Coal, petroleum and 
    natural gas are called fossil fuels. Millions of years ago, during the carboniferous 
    age, due to the change in atmospheric conditions and other changes, the forests 
    were destroyed and they were fossilized. 
    With the action of bacteria and other microorganisms on the surface of the 
    earth, these trees and other vegetations were decayed and disintegrated. Years 
    after these trees were available in solid, liquid and gaseous state. The solid 

    form is coal. It is the most widely used form of fossil fuel for domestic purposes.


    5.1.1. Fossil fuel
    History of usage of Fossil Fuel
    Before steam engines were invented, heavy industry depended on mechanical 
    water power to grind flour, saw wood, and so forth. Industrialization led to a 
    higher rate of energy usage. Fossil fuel led to development and it played a crucial 
    rule as energy sources, inputs for agriculture, and feed stocks for chemical 
    manufacture. The Industrial Revolution marked a big change for people of the 
    world. 
    Many of the agriculture based societies that used human and animal labor forces 
    switched to use machines to do work. Coal was commonly used in the early era 
    of industrialization until internal combustion engine and the automobile were 

    invented. Oil and gas became the most common fossil fuel people used. 

    Fossil fuels are hydrocarbons, primarily coal, fuel oil or natural gas, formed 
    from the remains of dead plants and animals. In common dialogue, the term 
    ‘fossil fuel’ also includes hydrocarbon-containing natural resources that are not 
    derived from animal or plant sources.
    Coal, oil and natural gas are called ‘fossil fuels’ because they have been formed 
    from the fossilized remains of prehistoric plants and animals. Fossil fuels are 
    non-renewable energy source since they take millions of years to form. They 
    ultimately get their energy from the sun.
    Types of Fossil Fuels 
    • Coal 
    Coal is a hard, black colored rock-like substance formed when dead plants were 
    subjected to extreme heat and pressure for millions of years. Coal is formed 
    through coalification. Coal is made of decomposed plant matter in conditions 
    of high temperature and pressure. Its formation is similar to oil’s but it takes 
    less time to form.
    It is made up of carbon, hydrogen, oxygen, nitrogen and varying amounts of 
    sulphur. There are two ways to mine coal: surface mining and underground 
    mining. 
    • Natural Gas 
    Natural gas is formed from the remains of tiny sea animals and plants that 
    died millions of years ago. The gas then became trapped in layers of rock-like 
    water in a wet sponge. Raw natural gas is a mixture of different gases. Its main 
    ingredient is methane. The strange smell of natural gas (like rotten eggs) comes 
    from a chemical added by the companies. 
    • Oil (Petroleum) 
    Oil is formed from the remains of animals and plants that died millions of years 
    ago. The organic material was then broken down into hydrogen and carbon 
    atoms and a sponge-like rock was formed, full of oil. 
    Oil cannot be used as it is when it is drawn from the ground. Oil refineries clean 
    and separate the oil into various fuels and by products. The most important of 

    these is gasoline.

    Uses of Fossil Fuels 
    The main systems of fossil fuels are the steam cycle and the gas turbine 
    cycle. Fossil fuels are used to generate electrical energy in a series of energy 

    transformations. The following is an example:


    Advantages of Fossil Fuels
    1. Can be easily transported via pipelines, railroads, trucks and ships.
    2. They are easily available. More and more extractions are occurring all over 
    the world and therefore resulting in a large amount of readily available 
    energy sources.
    3. Oil refineries close to the sea have easy access to shipping.
    4. Fossil fuels are easily combustible. In other words, they produce larger 
    amounts of energy.
    5. Creates infrastructure jobs for the surrounding communities.
    6. Much of our infrastructure is designed to run using fossil fuels.
    7. Although fossil fuels are considered as a relatively new energy source, in 
    reality they have been around for hundreds of years.
    8. Every machine that is not run by electricity uses fossil fuels. Vehicles, 
    machines, devices, etc. are powered by coal, petroleum or natural gas.
    9. They are considered to be very stable.
    10. They are easy to set up. Since fossil fuels are easily available, their power 
    plants can be constructed anywhere in the world. They are also easier 
    to extract and process, as well as capable of producing large amounts of 
    energy at a single location.
    11. Fossil fuels are easy to store and transport because they are so stable. They 
    are easily distributed.
    12. Easy transportation allows countries around the world to enjoy affordable 
    power.

    13. The price of fossil fuels is inexpensive compared to other sources of energy.

    Disadvantages of Fossil Fuels
    Fossil fuels, for all their pros, have many cons that have major concerns for 
    human being, animals and the environment.
    The biggest disadvantage of fossil fuels is the air pollution that many are 
    claiming is causing global warming.It is claimed that with global warming, the 
    Earth’s climates are changing. Below is a list of the disadvantages of fossil fuels.
    1. Air Pollution and its effects on the Earth and environment. This includes the 
    concepts of global warming and climate change.
    2. They are non-renewable sources of energy. As fossil fuels are extracted to an 
    unlimited level, they would surely deplete one day. They are non-renewable, 
    so it is likely that when fuel reserves have been completely used up, there is 
    nothing more left. It wouldtake millions of years to replace them. They are 
    on a limited amount, and we are not actually sure where that limit is.
    3. Pipelines transporting fossil fuels spoil the natural beauty.
    4. They affect marine life through oil spills. Fossil fuels, being needed to be 
    transported to their processing plants via land, air and water poses a threat 
    to the environment. The process can involve leaks in oil tankers or ships 
    getting drowned deep under the sea. The crude oil contains some toxic 
    substances that, when mixed up with water, pose serious hazards to marine 
    life. 
    5. Risk of political issues and terrorism
    6. Most facilities that are powered by coal require large quantities of coal to 
    have on hand for use. Storage facilities for the coal are required, this can be 
    pricey.
    7. Coal mining is a very dangerous and many workers have been killed in the 
    mines as well as becoming ill with lung diseases after working the coal 
    mines.
    8. While fossil fuels are relatively inexpensive, the prices are rising due to 
    Middle Eastern countries holding large reserves of oil such as petroleum.
    9. Coal mining has created destroyed lands and the mines are creating hazards 
    in the event of natural disasters.
    10. They need huge amounts of reserves. Coal power plants for example need 
    regular and huge supply of resources to produce large amounts of electricity 
    on a constant basis, which means they need reserves to carry out their 
    operations.
    11. The extraction of natural gas is leaving large craters within the Earth’s 

    surface.

    5.1.2. Non fossil fuel
    Non fossil fuels are alternative sources of energy or renewable source of energy 
    that do not rely on burning up limited supply of coal, oil or natural gas. They 
    should generate power that can be utilized indefinitely. They include sun light, 
    wind, hydro, tidal and waves from water, geothermal all of them generate 

    energy.


    Non-fossil fuels are considered to be extremely important for power creation. 
    This is because they are usually renewable energy sources that could be tapped 
    for hundreds of years and not run out. In addition, energy production using 
    non fossil-based fuels usually generates much less pollution than fossil-based 

    energy sources.



    It is easy to think that the advantages of fossil fuels outweigh their disadvantages. 
    All over the World, Fossil fuels are gaining popularity as energy sources because 
    they are relatively inexpensive and look like clean. Remember that fossil fuels 
    are comprised of three substances: coal, oil and gas. In the following lines we 
    are going to discuss some of the common advantages and disadvantages of 
    fossil fuels transportation and storage.
    5.2.1. Advantages associated with transportation and storage of 
    fossil fuels
    - The majority of oil transported by maritime means reaches their 
    destination. Normally there are no serious oil spillages. In fact, as soon as 
    the pipeline is damaged by accident or sabotage, pumping is stopped and 
    pollution remains limited. 
    - Oil depots are usually situated close to oil refineries or in locations where 
    marine tankers containing products can discharge their cargo.
    - The long life of the permanent assets, relatively trouble-free operation 
    with minimum maintenance, the large-volume shipments that are 
    possible, the high mechanical efficiencies that are obtained with low 
    rolling resistances. 
    - The total costs of moving slurry during the life of the line do not increase
    in proportion to inflation. The advantage over rail and truck transport is 
    clear, as the costs of these latter modes escalate with inflation.
    - Taller and wider stockpiles reduce the land area required to store a set 
    tonnage of coal. Larger coal stockpiles have a reduced rate of heat lost, 
    leading to a higher risk of spontaneous combustion.
    - Waterways are usually circuitous, resulting in slow delivery times. 
    However, transport of coal on barges is highly cost-efficient.
    - Transportation by gas pipelines are less costly and are thus more common.
    5.2.2. Disadvantages associated with transportation of fossil fuels
    - At sea, the relative disadvantages derive from the possibilities of oil spills 
    and discharging of polluting products such as the residue from tank and 
    bilge cleaning.
    - Oil is always corrosive to a greater or lesser extent, because it contains 
    acidic gases. The pipes deteriorate from the inside and if they are not 
    changed in time, they finish by leaking. 
    - The construction of major pipelines crossing several countries requires 
    intense negotiation.
    - On the other hand, slurry pipelines involve potential environmental 
    problems. Water requirements are substantial: almost one ton of water is 
    needed to move one ton of coal.
    - Even though pipelines are useful, in certain cases the construction of gas 

    pipelines is technically impossible or too expensive.



    Fossil fuels have been formed from the organic matter: these are remains of 
    long-dead plants and animals. They contain a high percentage of carbon and 
    hydrocarbons. Primary sources of energy we are using in our country and 
    around the world in particular include petroleum, coal, and natural gas, all 
    fossil fuels. With the needs increase of energy, the production and use of these 
    fossil fuels create serious environmental concerns. Until a global movement for 
    renewable energy is successful, the negative effects of fossil fuel will continue.
    5.3.1. Climate Change and Global Warming
    Global warming occurs when carbon dioxide is accumulated in the atmosphere. 
    Carbon monoxide is produced by the combustion of fossil fuels and converted 
    into carbon dioxide. These gases trap more sunlight; therefore, less light is 
    reflected back into space. They are called Greenhouse Gases, because the 
    effect is like being in a plant glasshouse, or in a car with the windows wound 
    up. As a result, the surface temperature of the earth is increasing drastically.
     If the increase is enough it will distress the ecological systems. The 
    consequences are: severe weather, droughts, floods, drastic temperature 
    changes, heat waves, and more severe wildfires. Food and water supplies 
    are also threatened. Tropical regions will expand; allowing disease-carrying 
    insects to expand their ranges.
    5.3.2. Hole in the Ozone Layer
    Ozone is a gas in the Earth’s upper atmosphere whose chemical formula is O3
    Ozone acts to block out much of the sun’s ultraviolet radiation which causes 
    skin cancer and contributes to the fluctuations of global climatic conditions 
    that affect the environment. 
    However, the World is facing a serious confrontation as the emissions of 
    chlorofluorocarbons and other destructive gases are causing ozone holes to 
    appear in the stratospheric ozone layer. As a consequence, the concentration of 
    detrimental ultraviolet radiation is increasing at ground level and jeopardizing 
    humans, crops and ecosystems.
    5.3.3. Acid rain
    Acidic rain, which is made up of several acidic compounds, forms when sulfur 
    dioxide and nitrogen dioxide react in the air with water, oxygen and other 
    chemicals. The wind carries the acidic compounds into the air, and they later 
    fall to the ground in either dry or wet form.
    They form an acidic ‘rain’ which can destroy vegetation. Some of these gases 
    are from natural sources, such as lightning, decomposing plants and volcanoes. 
    However, much of these gases are the result of emissions from cars, power 
    stations, smelters and factories.
    The effects of acid rain are as follows :
    - Acidification of lakes, streams, and soils .
    - Direct and indirect effects (release of metals, for example: Aluminum 
    which washes away plant nutrients).
    - Killing of wildlife (trees, crops, aquatic plants, and animals).
    - Decay of building materials and paints, statues, and sculptures .

    - Health problems (respiratory, burning- skin and eyes)

    5.3.4. Air Pollution
    Air pollution is the release of excessive amounts of harmful gases (e.g. methane, 
    carbon dioxide, sulphur dioxide, nitrogen oxides) as well as particles (e.g. dust 
    of tyre, rubber, and lead from car exhausts) into the atmosphere. Areas of 
    high air pollution indexes have populations with higher rates of asthma than 
    cleaner environments do. 
    5.3.5. Changes in Food Supply
    Changing weather affects the agricultural industry and the human food supply. 
    Carbon emissions contribute to increasing temperatures and decreasing 
    precipitation, changing the growing conditions for food crops in many areas. 
    Major changes in crop yield will cause food prices to rise around the world.
     In addition, climate change influenced by carbon emissions forces animals, 
    many of which are hunted as food, to migrate to higher altitudes or northern 
    habitats as the climate warms.
    5.3.6. Water Pollution
    1. Sewage is the household waste water. Many detergents contain phosphates 
    which act as plant fertilizers. When these phosphates and the sewerage reach 
    rivers, they help water plants to grow in abundance, reducing the dissolved 
    oxygen in the river water. 
    2. Biodegradable detergents are more environment-friendly because they are 
    readily broken down to harmless substances by decomposing bacteria.
    3. Suspended solids in water, such as silt reduce the amount of light that reaches 
    the depths of the water in lakes and rivers. This reduces the ability of aquatic 
    plants to photosynthesise and reduce the plant and animal life. Turbidity is 
    the measure of ‘cloudiness’ or the depth to which light can reach in water.
    5.3.7. Population Explosion
    It is the rapid increase in population in developing countries causing famine, 
    and also in developed countries causing more demand for energy and with 

    that, it increases pollution and destruction of the environment.



    Study the figure 5.3 and try to respond to the following questions: 
    i) Predict and write down what is observed in the picture above
    ii) Do you think that the picture above produces food? Explain your 
    reasoning.
    iii) The power Plant ejects big amount of smoke in the atmosphere. 
    What kind of combustibles do you think are used there?
    iv) Apart from the gaseous smoke ejected, discuss other problems 

    met during the production of energy using fossil fuel.

    5.4.1. Nuclear fuel and nuclear fission
    Nuclear fuel is any material that can be consumed to derive nuclear energy. 
    The nuclear fuel can be made to undergo nuclear fission chain reactions in a 
    nuclear reactor. The most common nuclear fuels are 235U (uranium 235) and 
    239Pu (plutonium 239). Not all nuclear fuels are used in fission chain reactions.
    Nuclear fission is a process, by which a heavy nucleus splits into two or more 

    simpler pieces. This process releases a lot of energy.


    When a neutron strikes an atom of uranium, the uranium nucleus splits into 
    two lighter atoms and releases heat simultaneously. Fission of heavy elements 
    is an exothermic reaction which can release large amounts of energy both as 
    electromagnetic radiation and as kinetic energy of the fragments.
    A chain reaction refers to a process in which neutrons released in fission 
    produce an additional fission in at least one further nucleus. This nucleus in 
    turn produces neutrons, and the process continues. If the process is controlled 

    it is used for nuclear power or if uncontrolled it is used for nuclear weapons. 


    5.4.2. Controlled fission (power production) and uncontrolled fission 
    (nuclear weapons)
    Nuclear fission is based upon the release of neutrons during the reaction. If 
    more than one neutron is released for every fission reaction it will accelerate, 
    less than one it will decelerate. 
    Of the three neutrons, liberated during a fission reaction, only one triggers a 
    new reaction and the others are simply captured. The system is in equilibrium. 
    One fission reaction leads to one new fission reaction, which leads to one 

    more, and so on. This is known as controlled fission.

    In an uncontrolled fission reaction (weaponry) the appropriate amount of 235U 
    is simply mixed with a moderator, making the reaction go out of control. As the 
    reaction is out of control, the exponential acceleration of the reactions creates 
    massive amounts of energy.
     This can be kept from going off by keeping the moderator and the 235U separate, 
    both below critical mass, until the desired time of explosion. In a controlled 
    reaction there is a higher proportion of 238U to ease the reaction. 
    However, this is difficult to control as the reaction becomes faster or slower. To 
    counteract this, control rods, made of neutron absorbing materials (i.e. Boron) 
    are added or removed between each fuel rod.
    5.4.3. Problems associated with the production of nuclear power
    - The problem of radioactive waste is still unsolved. The waste from nuclear 
    energy is extremely dangerous and it has to be carefully looked after for 
    several thousand years. 
    - High risks: Despite a generally high security standard, accidents can still 
    happen. It is technically impossible to build a plant with 100% security. 
    A small probability of failure will always last. The consequences of an 
    accident would be absolutely devastating both for human beings and the 
    nature. 
    - The more nuclear power plants (and nuclear waste storage shelters) are 
    built, the higher is the probability of a disastrous failure somewhere in 
    the world. 
    - During the operation of nuclear power plants, radioactive waste is 
    produced, which, in turn, can be used for the production of nuclear 
    weapons.
    - Nuclear power plants could be preferred targets for terrorist attacks. 
    Such a terrorist act would have catastrophic effects for the whole world. 
    - The energy source for nuclear energy is Uranium. Uranium is a scarce 
    resource; its supply is estimated to last only for the next 30 to 60 years 
    depending on the actual demand.
    - The timeframe needed for formalities, planning and building of a new 
    nuclear power generation plant, is in the range of 20 to 30 years in the 
    western democracies. In other words, it is an illusion to build new 

    nuclear power plants in a short time.


    5.5.1. Nuclear Meltdown
    A nuclear meltdown is an informal term for a severe nuclear reactor accident 
    that results in core damage from overheating.
    A nuclear meltdown occurs when a nuclear power plant system or component 
    fails so the reactor core becomes overheat and melts. Usually, this occurs due to 
    the lack of coolant that decreases the temperature of the reactor. The commonly 
    used coolant is water but sometimes a liquid metal, which is circulated past the 
    reactor core to absorb the heat, is also used.
    In another case, a sudden power surge that exceeds the coolant’s cooling 
    capabilities causes an extreme increase in temperature which leads to a 
    meltdown. A meltdown releases the core’s highly radioactive and toxic elements 

    into the atmosphere and environment.

    The causes of a meltdown occur due to:
    Loss of pressure control: The loss of pressure control of confined coolant may 
    be caused by the failure of the pump or having resistance or blockage within 
    the pipes. This causes the coolant to cease flow or insufficiency flow rate to the 
    reactor; thus the heat transfer efficiency decreases.
    Loss of coolant: A physical loss of coolant, due to leakage or insufficient 
    provision, causes a deficit of coolant to decrease the heat of the reactor. A 
    physical loss of coolant can be caused by leakages. In some cases, the loss of 
    pressure control and the loss of coolant are similar because of the systematic 
    failure of the coolant system. 
    Uncontrolled power excursion: A sudden power surge in the reactor is a 
    sudden increase in reactor reactivity. It is caused by an uncontrolled power 
    excursion due to the failure of the moderator or the control that slows down 
    the neutron during chain reaction. A sudden power surge will create a high 
    and abrupt increase of the reactor’s temperature, and will continue to increase 
    due to system failure. Hence, the uncontrollable increase of the reactor’s 
    temperature will ultimately lead to a meltdown. 
    5.5.2. Nuclear (Radioactive) Wastes
    Nuclear wastes are radioactive materials that are produced after the nuclear 
    reaction. Nuclear reactors produce high-level radioactive wastes. The wastes 
    must be isolated from human contact for a very long time in order to prevent 
    radiation.
    Short- and long-term storage of spent nuclear fuel has been a challenge for 
    the industry and policymakers. Spent fuel, if not disposed of properly, could 
    contaminate water supplies or be used by terrorists to create a dirty bomb. In 
    the short-term, spent fuel is stored in pools on-site--but they only need to stay 
    there a few months until they are cool enough to move to dry storage (either on 
    site or in a long-term storage facility). Still, at some plants, fuel rods are packed 
    in pools in numbers well above design specifications and stay in the pools long 
    after they are ready to be moved 
    Efforts to reprocess nuclear waste are expensive and come with associated 
    environmental and security risks. Yet a growing number of countries--including 
    Japan and Russia--have begun fuel recycling projects.
    5.5.3. Security Issues
    Most countries either pursuing nuclear power or currently using it have signed 
    on to the Nuclear Nonproliferation Treaty and have agreed to comply with 
    rules that ensure that they will not use nuclear technologies toward making 
    weapons. However, any country with nuclear technology is considered a 
    proliferation risk.

            

             

    3. Which of the following is true about solar energy?
    a) It is becoming cheaper to produce photovoltaic cells
    b) Solar energy can currently replace all of the energy created by 
    fossil fuels
    c) Most solar panels convert more than 25% of the light that strikes 
    them
    4. Identify three technological challenges that limit the use of solar 
    power in Rwanda.
    a) Weight, cost, toxicity
    b) Aesthetics, toxicity, efficiency
    c) Storage, weight, fragility
    d) Cost, storage, efficiency
    5. Which of the following is NOT utilized in the process of harnessing 
    solar energy?
    a) Gas
    b) Mirrors
    c) Steam
    d) Photovoltaic cells
    6. Which issues would better energy storage technologies help solve?
    a) Inconsistent energy demands
    b) Inconsistent power production
    c) The need to keep inefficient power plants on standby
    d) All of the above
    7. a) Design and explain advantages of non fossil fuel.
    b) Suggest disadvantages of non fuel energy if any.
    8. Evaluate different ways used to eradicate environment pollution in 

    Rwanda.

    ◄UNIT 4:PROPAGATION OF MECHANICAL WAVESUNIT 6:MOTION IN ORBITS►