Unit 6
Energy Resources
Learning Outcomes
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Prerequisites
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All of us speak about energy. We have learned in our primary classes about energy. Energy is the capacity to perform work. The total quantity of usable energy available to people is called as Energy supply. Energy comes from either Renewable sources or Non-renewable sources. The world is trying to find new sources of energy. We know that we are running short of petroleum and coal. We are now tapping different sources of energy and now speak of CNG, Fossil fuel, wind energy, biogas, electric energy and Geothermal Energy. |
Key words
Energy, Resources, Biofuels, Future fuels, Clean energy, Hydrogen energy
Discussion
1.6.1 Energy Resources
We all know that planet earth has enormous amounts of energy resources. The use of energy by human beings dates back to several centuries. Energy is the capacity to perform work. We use various forms of energy to do work. The total quantity of usable energy available to people is called as Energy Supply.
Energy is of many kinds electrical energy, kinetic energy, mechanical energy and chemical energy. Electrical energy operates on several appliances like pump sets, fans, grinders, vacuum cleaners, washing machines and other industrial equipment. Heat energy is used to cook food on stoves, shape metals, make bricks and for several industrial processes requiring heat as a major factor or as a catalytic factor. Similarly, mechanical energy is used for many activities like moving vehicles, lifting and breaking materials, handling and aligning objects. Energy may be obtained directly from an energy source or it may be obtained indirectly. Energy is derived from one or more than one source.
The chief sources of energy are:
- Fossil fuels
- Flowing water
- Biomass and
- Atomic minerals
In addition, solar energy, wind power, tidal energy, chemical and geothermal power also provide some amounts of energy. The sources and use of energy by the population differ from a developed country to a developing country. It depends on the energy resources available with them.
Sources of energy are classified into two major groups as renewable and non-renewable energy sources.
- Renewable sources are those which will be available for our human consumption again and again. The energy derived from water as hydro-electric power, Sun as solar energy and wind energy are renewable energy resources.
- Non-renewable energy sources are those which are permanently consumed for generating the energy and needs further supply. Fossil fuels like coal, oil and gas, fissionable materials for nuclear power generation and geothermal sources come under this category.
1.6.2 Types and classification
1.6.2.1 Energy from Fossil Fuels
About 85 per cent of the world’s commercial energy comes from coal, oil, and natural gas. These are called fossil fuels since they have formed from the fossilized remains of prehistoric plants and animals.
The use of these sources depends on their availability in a country .
Coal is made up of organic material which has escaped from oxidation in the carbon cycle. It is an altered residue of plants and trees of older forests, which have been buried under sediments, and they were subjected to a set of geological processes and transformations.
Coal is burned to create heat to turn water into steam. The steam is then used to rotate tur-bines which will rotate the dynamos to generate electricity. It is also converted into another useable form called coke. It is a charcoal– like solid which is an essential raw material used in the production of iron and steel.
Coal occurs in sedimentary basins as coal seams or layers. There are four types of coal occurring in the order of decreasing carbon content, volatiles and moisture, as
- Anthracite
- Bituminous coal
- Sub-bituminous coal and
- Lignite.
Peat is partially decayed plant matter found in recent swamp deposits. Peat and wood are the basic materials before the formation of lignite. Anthracite is a rare form but is the hardest variety of coal. It also contains more carbon and produces more heat than the other varieties. Bituminous coal is the most commonly used coal by industries. It contains more carbon and produces more heat than either lignite or sub-bituminous coal. It is also suitable for making coke.
Coal contains some sulphur compounds. The sulphur content may be very low (< 1%) or medium (1-3%) and high (> 3 %).
Coal is mainly used in thermal power plants. While using it, the one having low sulphur will cause less air pollution. The production of thermal power depends on the ash-content of the coal used. The higher the ash content, the lower the efficiency of the boiler and furnaces.
Use of coal also generates solid wastes and ashes. For every megawatt of energy produced by a thermal plant, about one acre of land is needed to dump the wastes (ash).
Coal-based thermal planst pollute the atmosphere by gaseous emissions of sulphurdioxide and nitrogen oxide, and produce tremendous amount of solid wastes, fly ash and bottom ash.
Coal mining, transport, washing, processing, shipping, combustion and final disposal of ash may lead to potentially adverse environmental effects like aesthetic degradation, noise pollution, dust pollution and the release of trace elements into water, soil and air. Coal is a non-renewable form of energy, the use of which is to be done very economically.
Oil
The next major source of energy comes from oil. The oil that is derived from rocks is called Petroleum. (Petro means rock, oleum means oil). Petroleum furnishes about 40 per cent of the commercial energy used in the world. It provides most of the energy used for transportation and other activities of the population.
In general, Petroleum and natural gas (methane) are hydrocarbons. They are fossil fuels formed from organic material, free from complete decomposition after burial. Petroleum is a complex mixture of hydrocarbons containing N, S and O.
The major source for oil and gas is the fine grained, organic rich sediments that are buried to a depth of 500 m or below stagnant oceanic waters. These might have experienced a thrust due to an increase in pressure and heat. The water is deficient in oxygen. Various geological and biological (bacteria) processes have promoted the chemical transformation of these organic materials into hydrocarbons. They tend to migrate through the porous sediments called reservoir rocks.
Like coal, oil also contains some impurities that can cause air pollution. But refineries can remove many of these pollutants when they process the petroleum.
Natural gas is the most convenient fossil fuel. It causes little or no air pollution. Natural gas is a clean source of energy because it is refined naturally during its formation within the earth and does not require further refining. In addition, it can be compressed into a liquid and transported long distances through pipelines.
Natural gas accounts for about 21 per cent of the commercial energy used in the world. Millions of people use natural gas to heat their homes, cook their meals, and dry their laundry.
Typical gas consists of hydrocarbons, having a very low boiling point. Methane, the first member of the paraffin series makes up 85 % of the typical gas.
Clean Energy Sources
Clean energy is energy derived from renew-able, zero-emissions sources (“renewables”), as well as energy saved through energy efficiency (“EE”) measures. Renewable power is booming, as innovations bring down costs and starts to deliver on the promise of a clean energy future. This means that renewables are increasingly displacing “dirty” fossil fuels in the power sector, offering the benefit of lower emissions of carbon and other types of pollutants. But not all sources of energy marketed as “renewable” are beneficial to the environment. Biomass and large hydroelectric dams create difficult tradeoffs when considering the impact on wildlife, climate change, and other issues.
1.6.2.2 Solar and Wind Energy
The energy received from the sun’s electro-magnetic radiation is called solar energy. It is also used to produce electric power. This is a non-conventional and renewable energy source.
Do you know the two methods through which sunlight can be converted into electric power?
They are:
- photovoltaic conversion, and
- solar thermal conversion
It is reported that the solar energy falling on the earth every 29 seconds is equivalent to the human energy requirement of a day.
It comes from the Sun and is plentiful. The distribution is sparse. It must be collected and concentrated to produce usable power. This requires some special devices. Hence, harnessing of solar energy is an expensive affair.
A typical solar water heater consists of a coil of copper pipe brazed to a blackened metal base. This assembly is covered by a transparent glass plate or a plastic sheet. The water which is passed through coil gets heated up by the radiation. Very high amount of heat is trapped in this process during summer months.
Solar energy is also caught to provide power using solar cells. Solar cells are the devices made from crystals of silicon to produce electricity from sunlight. They are the Photovoltaic cells. Research continues on the applications of solar energy for pumping up water, refrigeration, solar ponds and temperature control in buildings.
Advantages of consumption by Solar energy
- Unlimited supply,
- Does not produce air, water, thermal, and noise pollution,
- No danger of large-scale disasters,
- Conserves earth’s resources and
- Technology is available for immediate use.
Disadvantages
Solar cells are more expensive. They cannot completely replace the conventional fuels.
Wind Energy
The rapid depletion of fossil fuels and the in-crease in environmental pollution call for an efficient use of other energy sources and to identify alternate sources also.
Wind is a powerful agent for providing power. It is the best renewable energy source available on earth.
Wind energy can be harnessed very easily. The blow of wind is allowed to rotate the blades of a windmill, coupled to a turbine. This drives a power generator.
Merits and demerits of Wind Energy
- The generation period is low (5 months). This is because of the seasonal availability of a reasonably useful wind.
- Power generation starts immediately after commissioning the plant.
- Power is cost free; generation is cheaper and recurring cost is less.
- Installation cost is heavy, and the maintenance of machinery is also expensive.
- This is a pollution free and environment friendly generation of power.
A wind power plant is also a source of income. A wind power generator of 200 kw/250 kw, generates at an average of six to seven lakh units every year.
1.6.2.3 Energy from Biogas
Biogas is the methane gas produced or re-leased from the organic wastes like sewage, garbage, manure or crop residues. These are decomposed substances in the absence of air. This is similar to the natural gas in origin.
Biogas can be collected using a container filled with the wastes and closed at the top with a tap for trapping the gas. The wastes are mostly animal excreta or dungs which are allowed to decay and decompose naturally inside the container. After producing the gas, the used-up materials can be used as a high-quality organic manure in crop lands.
Community biogas plants, industrial biogas plants, night soil biogas plants, family size biogas plants and improved chulhas are some of the bio-energy sources employed and are under operational conditions in several parts of the world.
Tidal Power
Tides and Waves can generate enormous energy for consumption. The tides, which are dashing against the shores continuously, can generate the tidal power. This can be obtained by using a tidal dam built with a turbine. This is more expensive when compared to the hydroelectric power installations.
In high tide zones such provisions help in harnessing this power. There is also a limitation that it can produce electricity only at certain times of a year.
1.6.2.4 Energy from Nuclear and other Sources
Many of the environmentally conscious countries in the world depend on nuclear power for their electricity generation. At present about 17 % of the world’s electricity is generated through nuclear sources.
Nuclear source is clean, compact and concentrated. Nuclear power plants are similar to coal plants in that heat is used to produce steam to drive a turbine. But the basic difference between them is the atomic fission instead of chemical combustion.
A nuclear reactor requires a fuel substance whose nuclei can undergo fission. Such substances are called fissionable substances. Uranium-235 and plutonium-239 are the most widely used fuels. In addition to the fuel, reactors require neutrons. These are the stimulators for chain reaction. The safety, design and operation of reactors depend on the way the neutrons are managed.
Nuclear reactors are classified based on the fuel, coolant and moderator used to support the nuclear chain reaction.
The natural concentration of uranium in the earth’s crust is about 2 ppm. Uranium originates in magma. It is concentrated to about 4ppm in granitic rocks, pegmatites, etc. They occur in a large number of minerals. They are called rare-earth minerals (or) radio-active minerals. They contain Uranium or Thorium as an essential part of their chemical composition. Some of them are Oxides and complex oxides.
The disposal of nuclear wastes, some radio-active liquids, and gases will affect the environment severely. Sources are available in the form of fuel bundles, which were once loaded in to the reactor core can provide energy for 1 to 2 years at a stretch before discharge. One kg of Uranium gives an energy equivalent to 25,000 kg of coal.
Geothermal Energy
This refers to the heat energy emanating from the earth’s interior which could be used for heating or for generating electricity. The production of geothermal energy can occur only in areas where hot rocks lie near the earth’s surface.
Iceland, Italy, Japan, the Philippines, New Zealand, and the United States have developed geothermal power plants. The method is simple. Pipes are intalled into the wells drilled over the regions of geothermal sources and connected to a turbine.
Nuclear energy
Nuclear energy is a form of energy which is released from the nucleus of an atom. It is de-livered in huge amounts in processes that in-fluence atomic nuclei made-up of protons and neutrons, the thick centres of atoms. It is particular from the energy of another atomic phenomenon. One technique for delivering nuclear energy is by controlled atomic splitting in gadgets called reactors, which presently work in many areas of the planet for the creation of power. Nuclear energy has been released violently by both nuclear fusions, where nuclei fuse together and nuclear fission, where nuclei split apart.
Hydrogen: Fuel of The Future
Hydrogen is an energy carrier that can trans-form our fossil-fuel dependent economy into a hydrogen economy, which can provide an emissions-free transportation fuel. An alternative fuel must be technically feasible, economically viable, easily convertable to another energy form when combusted, be safe to use, and be harmless to the environment. Hydrogen is the most abundant element on earth. Although hydrogen does not exist freely in nature, it can be produced from a variety of sources such as steam, reformation of natural gas, gasification of coal, and electrolysis of water. Hydrogen gas can used in traditional gasoline-powered internal combustion engines (ICE) with minimal conversions. However, vehicles with polymer electrolyte membrane (PEM) fuel cells provide a greater efficiency. Hydrogen gas combusts with oxygen to produce water vapor. Even the production of hydrogen gas can be emissions-free with the use of renewable energy sources. The current price of hydrogen is about $4 per kg, which is about the equivalent of a gallon of gasoline. However, in fuel cell vehicles, such as the 2009 Honda FCX Clarity, 1 kg provides about 68 miles of travel. Ofcourse, the price range is currently very high. Ongoing research and implementation toward a hydrogen economy is required to make this fuel economically feasible.
The current focus is directed toward hydrogen being a clean alternative fuel that produces insignificant greenhouse gas emissions. If hydrogen is the next transportation fuel, the primary energy source used to produce the vast amounts of hydrogen will not necessarily be a renewable, clean source. The U.S. Department of Energy has recently funded a research project to produce hydrogen from coal at large-scale facilities, with carbon sequestration in mind. Is this the wrong approach? Should there be more focus on other forms of energy that produce no greenhouse gas emissions? If the damage to the environment is interpreted into a monetary cost, the promotion of energy sources such as wind and solar may prove to be a more economical approach. The possibility of a hydrogen economy that incorporates the use of hydrogen into every aspect of transportation requires much further research and development. The most economical and major source of hydrogen in the US is steam reformation of natural gas, a nonrenewable resource and a producer of greenhouse gases. The electrolysis of water is a potentially sustainable method of producing hydrogen, but only if renewable energy sources are used for the electricity.
Today, less than 5% of our electricity comes from renewable sources such as solar, wind, and hydro. Nuclear power may be considered as a renewable resource to some, but the waste generated by this energy source becomes a major problem. A rapid shift toward renewable energy sources is required before this proposed hydrogen economy can prove itself. The transport of hydrogen through under-ground pipes seems to be the most economical when demand grows enough to require a large centralized facility. However, in places of low population density, this method may not be economically feasible. The project mentioned earlier may become an option for individuals to produce their own hydrogen gas at home, with solar panels lining their roof. A drastic change is needed to slow down the effects of our fossil fuel dependent society. Conservation can indeed help, but the lifestyles we are accustomed to require certain energy demands. Transportation is a necessary part of our current world and the switch to a hydrogen economy can provide a sustainable solution.
Recap
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Objective type questions
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Answer to Objective type questions
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Self Assessment Questions
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Assignment
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Suggested Reading
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Reference
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