Differences Between Renewable and Non-renewable Energy Resources
Discuss about the Power Generation Using Coal.
Renewable energy refers to energy that is obtained as a result of various natural processes that are continuously replenished. Examples of such sources include wind, geothermal, hydro-power, solar and energy from biomass. However, there exists some controversy on the categorization of some energy resources such as fuelwood. According to manual 44E of the UN F series manuals, the term renewable is only applicable to fuelwood that is grown at the same rate at which it is cut (Khoie, 2005). From this example, non-renewable energy can be defined as a natural resource that cannot be replenished at the same rate as its consumption. Non-renewable energy may also be defined as forms of energy which can be regenerated after a considerable amount of time (Hodgson, 2010). Such sources exist in the form of coal, fossil fuels, and natural gas. Non-renewable sources of energy are thus considered to be finite as opposed to renewable energy sources which cannot be depleted. The reason behind this is the fact that although non-renewable forms of energy eventually regenerate, the time frame required for their replenishment is not workable and as such, these resources will eventually run out. In addition, non-renewable energy sources, unlike renewable sources, present some health and environmental issues. Gases released from combustion of fossil fuels are toxic when inhaled and are the main cause of global warming (Hodgson, 2010). Renewable sources only produce low levels of carbon emissions and are therefore considered environmentally friendly. Despite this, non-renewable sources are still the most widely used energy resources owing to the relatively low cost involved in their production.
Mining of coal and its use poses several environmental issues. The main problem surrounding the use of coal for power production is the emission of greenhouse gases which are produced when coal is combusted. Coal is among the biggest contributors to greenhouse gas emissions. Greenhouse gases are the number one cause of global warming. The various processes involved in mining coal also present other environmental issues such as pollution of water and soil through leached chemicals which have either been used in the mining process or exposed during mining (Balat, 2007). Aside from this, mining also presents geological issues. Boring tunnels underground creates weaknesses which if not carefully monitored, could result in extensive property damage and fatalities.
The main advantage of coal as an energy source is its abundance around the world. Coal can be found on every continent on the globe. It is also relatively cheap and simple to mine and utilize for power production as compared to other fossil fuels. Relatively easy strip mining techniques such as sub-surface mining and pit mining are used to access coal. These techniques, however, also impact negatively on the environment since they are highly destructive (Farley, 2007). They entail the use of explosives and heavy machinery to remove material from the ground. Various chemicals and elements encountered and used during mining also pose several environmental hazards.
Environmental and Geological Issues Surrounding Extraction and Their Effect on Mining
The working fluid in coal-powered thermal plants is water. A coal generator consists of four essential components. These are the turbine, boiler, condenser, and pump. The general working principle involves boiling of water at extremely high temperatures to convert it into saturated steam. This steam is then directed towards a turbine at high pressure to drive the turbine blades with some efficiency. The turbine blades, in turn, rotate a shaft connected to a synchronous generator which produces electricity. The steam driving the turbine blades loses heat and pressure upon exiting the turbine and cannot be reused in the same state. It first passes through a condenser where it is converted to its initial state before being redirected to the boiler where the cycle begins once again (Breeze, 2005).
One of the main issues to consider before the construction of a power plant can begin is the location where the plant is to be situated. However, this is not a major problem in the case of coal power plants. Proximity to a water body is advantageous, but a coal power plant can be established almost anywhere provided that the ground is stable and safe for construction and that the site is located as far away as is feasibly possible from the nearest residential area (Li, Liang, Ma, & Zhang, 2013). Any form of construction requires rigorous assessment of the major components involved to ensure safety and maximum lifespan of the structure. Such tests, therefore, go without saying in the case of a coal power plant whose failure could potentially cause irreparable damage and loss of life
Coal power plants serve to convert the energy stored in coal into useable electricity through a series of processes that form a cycle. Coal generators are so called because they rely on coal as the primary source of energy. Steam, however, is the required component. In this way, coal power plants are fairly similar to nuclear power plants based on their basic working principle. Pulverized coal is combusted in a heat exchanger or boiler where liquid water is converted to a gaseous state by the heat produced. The steam produced has to be under significantly high pressure at a high temperature. The reason for using pulverized coal is to increase the exposed surface area to combustion which maximizes the energy content liberated. This steam is then piped to a turbine, specifically, the turbine blades. Issues of aerodynamics apply here. The turbine blades should be designed such that the maximum surface area is impacted by the oncoming high-pressure steam. This also increases the rate of power conversion. The turbine is coupled to a generator such that the rotational power in the turbine is transferred directly to the generator which produces the actual electric power. The steam, now depleted of most its heat and pressure, is then directed to a condenser where it is converted back to its original state (Breeze, 2005).
Positives and Negatives of Using Coal Energy
The use of coal as an energy source presents several problems from an environmental standpoint. However, coal remains one of the most widely used energy sources in the world mainly due its relative abundance and low cost. Coal is found in over 70 countries around the world and supplies about 30% of the world’s primary energy needs (Farley, 2007). The widespread availability of coal and the relative ease involved in harvesting its energy makes it one of the most preferred energy resources today. One environmental problem resulting from the continued use of coal is the destruction of natural scenery around the mining site. Large pits and mounds of dirt are characteristic of surface mining techniques. Moreover, various toxic gases such as Sulphur dioxide are released from thermal plants when coal is combusted (Farley, 2007). Such gases pose significant health risks to humans and plant life alike. Acid rain, a by-product of Sulphur Dioxide, leads to land and water pollution. Another problem associated with coal use and mining is the unsafe environment coal mines create. In some parts of the world, the extensive hollowing of the earth forces the displacement of locals since the land beneath them may collapse without warning (Hodgson, 2010
. Despite these drawbacks, coal continues to be a major source of energy as a result of some of its numerous advantages. Firstly, coal is found in great abundance around the world meaning that its supply is always stable. This, along with the relatively simple process of coal mining, makes it one of the cheapest alternatives for power production. Coal is also very reliable. For many years, coal has been used for the large-scale production of electricity as well as other energy demands. The use of coal in thermal plants to produce electricity and other forms of energy is a well-known practice and the technology behind it is well understood (Breeze, 2005). In addition, coal is also much easier to mine and transport than other resources such as oil and natural gas which require long pipelines that are expensive to maintain.
Coal, natural gas, and fossil fuels are found deep below the surface. Surface mining techniques are required to reach such fuel deposits. Surface mining involves the removal of surface vegetation, dirt, and bedrock to reach deposits found deep underground (Hatherly, 2013). This highly destructive process causes significant damage to the environment and more specifically, the scenery around the mining site. Sub-surface mining involves digging of shafts and tunnels deep below the surface (Hatherly, 2013). Continued exploration of a site over extended periods of time creates a potentially harmful network of cavities below the surface. These cavities induce geotechnical and structural hazards which may cause a mine to suddenly collapse leading to the destruction of property, injuries and in most cases, loss of life. Several incidents of collapsed mines have been recorded putting pressure on mine owners and mine companies to maximize the safety of miners by employing the necessary safety facilities. Several chemicals used in various stages of coal mining if not carefully handled and disposed of may cause pollution on a substantially large scale. Chemicals such as cyanide, sulphuric acid, and methyl mercury often escape into the environment thereby poisoning the entire food chain. Metal sulphides buried underground are often exposed during mining. When they come into contact with atmospheric oxygen, strong sulphuric acid, and heavy metal oxides are formed. These by-products often leach into underground water and surface waterways thus contaminating the water. This phenomenon is known as Acid Rock Drainage (ADR) (Goodarzi, 2006). Such water is rendered inhabitable for fish and other aquatic life. These toxins also leach into the surrounding floodplain soils leaving it useless for agricultural purposes. Coal mining also poses significant health hazards to the miners. Exposure to harmful gases and chemicals over long periods of time may lead to serious health issues such as lung cancer and blood poisoning. The inherent risks involved in mining have led to significant advancements in ensuring the safety of mine workers and the surrounding inhabitants. As a result, casualties of mine related incidents have reduced drastically in recent years.
Main Principles of a Coal Generator
Several factors influence the construction of coal power plants. Issues of location and proximity to load centers constitute the first step of constructing a coal power plant, which is, planning. The intended construction site should be surveyed extensively before construction can begin. All potential risks at the construction site must be assessed. Factors such as the availability of water should also be examined since coal power plants require large amounts of water. There should be a continued supply of water throughout the year if the plant is to operate at the intended capacity. The proximity to load centers is also an important factor to consider since it offers an opportunity to reduce the set-up cost (Li, Liang, Ma, & Zhang, 2013). The farther the load center is located from the plant, the more equipment required to implement the necessary infrastructure for supply of power. The geological structure of the proposed site should be able to support the plant to avoid the risk of a collapsed power plant. In a case where the site is ideal for a power plant in terms of proximity to load centers and a good water supply, if the geological nature of the site is lacking, ground improvement concepts can be applied to provide a structurally sound base for the foundations of the plant. The coal power plant should also be designed such that there is no conflict of operational aspects. For example, it would not be practical to have the heat exchanger or boiler next to the condenser. Other components such as the steel to be used in the construction of the plant and pressurized equipment must be up to the required standards. Materials and equipment should be assessed as to their susceptibility to stress and degradation due to heat and vibration (Shibli, n.d.). Today, emission of greenhouse gases is a major concern especially in large coal factories. For this reason, facilities must be put in place to reduce emissions as well as monitor them.
The formation of coal is a process spanning millions of years. Coal is created through a process called coalification. This process involves the physical and chemical alteration of peat over extended periods of time. Peat, which is mainly composed of decayed plant material, goes through a series of changes as a result of decomposition, heat and pressure applied on it over large periods of time. Deposits of peat are formed in waterlogged environments where plant matter collects. The rate of decomposition in such an environment slows down over time as the plant material builds up while all the available oxygen in the organic rich water is used up by the bacterial decay process. For coal to form, the peat must be buried by layers of earth. The pressure induced by the burial expels water from the mixture while applying pressure on the peat. Pressure, along with increasing heat resulting partly from decomposition, causes the breakdown of complex hydrocarbons within the peat. As the peat is altered in this way, various components such as methane gas are also expelled from the mixture. This process continues as the deposits become increasingly carbon-rich due to the dispersal of other elements. This is why there are several types of coal classified according to their carbon content. These are: lignite (65%-70%), sub-bituminous coal (70%-76%), bituminous coal (70%-86%) and anthracite (86%-98%). Anthracite is the form of coal used for fuel around the world. Other forms of coal such as peat and bituminous coal are still used in some parts of the world such as India for fuel. Peat, however, is technically not a form of coal since its carbon content is lower than 60% (Balat, 2007).
Coal Power Plant Construction.
I believe that this course will help me develop various capabilities that I can employ in future.
The use of coal as an energy source and the subsequent study of the topic reveals a series of intertwined properties and merits which make coal one of the most widely used energy resources today. Given the significance of coal as a source of energy, its demerits, although extensive, can and should be mitigated to facilitate the continued use of coal. It is apparent that a cease in the use of coal as an energy source would not be feasible especially with the ever-growing energy needs we face today.
Coal has been used for power production for power production since the first plant was built in New York in 1882. Despite the cons of coal as a major pollutant and health hazard, it has been in use for hundreds of years. Although the general process has not changed much, practitioners have made several advancements to improve safety, efficiency, and alleviate the major problems associated with the use of coal. These advancements are evidence that the importance of coal as an energy source significantly outweigh its demerits as a pollutant. One might argue that some of the drawbacks resulting from the use of coal were not known to specialists until recent years, the continued use of coal is only rational when one considers the intrinsic worth of coal.
The most apparent problem associated with the use of coal as a source of energy, as mentioned earlier, is the high amount of greenhouse gases burning coal produces. Aside from that, fatal accidents during mining continue to occur until today. Although several countermeasures are in place today to reduce such incidents and improve the safety of workers, more has to be done to minimize casualties occurring as a result of mining accidents. It is, however, difficult to ascertain the structural integrity of a mine and any data that can suggest how close a mine, or a section of a mine, is to failure is even harder to access.
References
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Breeze, P. (2005). Power generation technologies. Oxford: Newnes.
Faé Gomes, G., Faria Vilela, A., Zen, L., & Osório, E. (2013). Aspects for a cleaner production approach for coal and biomass use as a decentralized energy source in southern Brazil. Journal Of Cleaner Production, 47, 85-95. https://dx.doi.org/10.1016/j.jclepro.2012.09.037
Farley, J. (2007). Clean coal technologies for power generation. Energy Materials, 2(3), 134-138. https://dx.doi.org/10.1179/174892408×373464
Goodarzi, F. (2006). Assessment of elemental content of milled coal, combustion residues, and stack emitted materials: Possible environmental effects for a Canadian pulverized coal-fired power plant.International Journal Of Coal Geology, 65(1-2), 17-25. https://dx.doi.org/10.1016/j.coal.2005.04.006
Hatherly, P. (2013). Overview on the application of geophysics in coal mining. International Journal Of Coal Geology, 114, 74-84. https://dx.doi.org/10.1016/j.coal.2013.02.006
HEPBASLI, A. (2004). Coal as an Energy Source in Turkey. Energy Sources, 26(1), 55-63. https://dx.doi.org/10.1080/00908310490251864
Hodgson, P. (2010). Energy, the environment and climate change. London: Imperial College Press.
Khoie, R. (2005). A method for evaluating and selecting renewable and non-renewable energy technologies. International Journal Of Environmental Technology And Management, 5(2/3), 203. https://dx.doi.org/10.1504/ijetm.2005.006850
Koornneef, J., van Keulen, T., Faaij, A., & Turkenburg, W. (2008). Life cycle assessment of a pulverized coal power plant with post-combustion capture, transport and storage of CO2.International Journal Of Greenhouse Gas Control, 2(4), 448-467. https://dx.doi.org/10.1016/j.ijggc.2008.06.008
Li, Z., Liang, Y., Ma, J., & Zhang, P. (2013). The Construction and Practice of Energy Consumption Management System for Coal-Fired Power Plant. AMM, 448-453, 2781-2785. https://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2781
Shibli, A. Coal power plant materials and life assessment.
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