Here is my favourite essay on the ‘Sources of Energy’. Find paragraphs, long and short essays on the ‘Sources of Energy’ especially written for school and college students.
Essay # 1. Non-Conventional Energy Sources:
A plenty of energy is needed to sustain industrial growth and agricultural production. The existing sources of energy such as coal, oil, uranium etc. may not be adequate to meet the ever increasing energy demands.
These conventional sources of energy are also depleting and may be exhausted at the end of the century or beginning of the next century. Consequently sincere and untiring efforts shall have to be made by the scientists and engineers in exploring the possibilities of harnessing energy from several non-conventional energy sources.
The various non-conventional energy sources are as follows:
(i) Solar energy
(ii) Wind energy
(iii) Energy from biomass and biogas
(iv) Ocean thermal energy conversion
(v) Tidal energy
(vi) Geothermal energy
(vii) Hydrogen energy
(viii) Fuel cells
(ix) Magneto-hydro-dynamic generator
(x) Thermionic converter
(xi) Thermo-electric power.
Brief Description of important Non-Conventional Energy Sources:
(a) Solar Energy:
On this planet, human life and all other forms of life are completely dependent on the daily flow of solar energy. The production of food and all other life-support systems of the natural environment are dependent on the sun.
i. Solar energy travels in small particles called photons. Converting even a part of the solar energy at even a very low efficiency can result in a far more energy that could conceivably be harnessed or utilised for power generation.
ii. The amount of solar energy is expressed in “solar constant”. The solar constant is the total energy that falls on a unit area exposed normally to the rays of the sun, at the average sun-earth distance.
The most accepted value of solar constant is 2.353 kW/m2. A number of scattering and absorption processes in the atmosphere reduce the maximum heat flux reaching the earth’s surface to around 1 kW/m2.
The Heat Flux Reaches Earth’s Surface by Two Modes:
(i) Direct
(ii) Diffuse.
It is the only direct heat energy which can be collected through a “collector”. The ratio of direct to totally heat energy varies from place to place and depends on atmospheric conditions like dust, smoke, water vapour and other suspended matter. The ratio varies between 0.64 and 0.88 according to different investigators.
Since the altitude of the sun and length of day vary with the season, the solar energy received on a summer day is many times the energy received on a winter day. As a result the total energy for most of the areas in plains in India is around 6000 MJ/m2 per year.
Advantages of Solar Energy:
1. It is a renewable source of energy.
2. Free of cost.
3. Non-polluting source of energy.
Disadvantages of Solar Energy:
1. Low efficiency.
2. It is of intermittent type in nature, so for night hours this energy is not available, and as such, storage is required.
Impact on Environment:
1. Solar thermal system may pose a health hazard because of the careless disposal of the heat transfer fluids (e.g. glycol nitrates and sulphates; CFCs and aromatic alcohols) used.
2. Solar photovoltaic modules pose disposal problems owing to the presence of arsenic and cadmium.
3. The total system comprising solar power generator with accessories contains several pollutants.
4. Solar reflectors cause hazard to eyesight.
(b) Wind Energy:
Man has been served by the power from winds for many centuries but the total amount of energy generated in this manner is small. The expense of installation and variability of operation have tended to limit the use of the windmill to intermittent services where its variable output has no serious disadvantage. The principal services of this nature are the pumping of water into storage tanks and the charging of storage batteries.
i. Windmill power equipment may be classified as follows:
a. The multi-bladed turbine wheel. This is the foremost type in use and its efficiency is about 10 per cent of the kinetic energy of the wind passing through it.
b. The high-speed propeller type.
c. The rotor.
ii. The propeller and rotor types are suitable for the generation of electrical energy, as both of them possess the ability to start in very low winds. The Propeller type is more likely to be used in small units such as the driving of small battery charging generators, whereas the rotor, which is rarely, seen, is more practical for large installations, even of several hundred kilowatts capacity.
iii. In India, the wind velocity along coastline has a range 10-16 kmph and a survey of wind power has revealed that wind power is capable of exploitation for pumping water from deep wells or for generating small amounts of electric energy.
Modern windmills are capable of working on velocities as low as 3-7 kmph while maximum efficiency is attained at 10-12 kmph.
iv. A normal working life of 20 to 25 years is estimated for windmills.
v. The great advantage of this source of energy is that no operator is needed and no maintenance and repairs are necessary for long intervals.
Merits/Characteristics of Wind Power/Energy:
Some characteristics of wind energy are given below:
1. No fuel provision and transport are required in wind energy systems.
2. It is a renewable source of energy.
3. Wind power systems are non-polluting.
4. Wind power systems, up to a few kW, are less costly, but on a large scale, costs can be competitive with conventional electricity. Lower costs can be achieved by mass production.
Demerits/Problems Associated with Wind Energy:
1. Wind energy systems are noisy in operation.
2. Large areas are needed to install wind farms for electrical power generators.
3. Wind energy available is dilute and fluctuating in nature. Because of dilute form, conversion machines have to be necessarily large.
4. Wind energy needs storage means because of its irregularity.
Impact on Environment:
1. The development of wind farm in a forest area needs cutting of trees leading to environmental degradation.
2. The environment is degraded due to noise pollution caused by wind turbines.
3. Interference of large wind turbines with television signals (through reflection).
4. Visual intrusion of wind turbines gives negative public response on the existing landscape.
(c) Energy from Biomass and Biogas:
Biomass:
Green plants trap solar energy through the process of “photosynthesis” and convert it into organic matter, known as biomass.
Wood, charcoal, agricultural waste produces the bioenergy after burning; cowdung, garbage are aerobically decomposed to obtain the energy.
Dried animal dung or cattle dung cakes are used directly as fuels in rural areas but it produces smoke and has low efficiency of burning.
Biogas:
Biogas is formed due to the decomposition of organic waste matter. During decomposition of organic matter, the gases such as carbon dioxide, hydrogen and hydrogen sulphide are formed.
The organic waste is generally animal dung, plant waste etc. These waste products contain carbohydrates, proteins, which are broken down by bacteria in absence of oxygen caerobic conditions.
Advantages:
1. Continuous supply of energy.
2. Renewable in nature.
3. Cheap in cost.
Disadvantages:
1. Power generating units are huge and bulky.
2. Biogas generation depends on temperature, therefore, in water or cold areas like J & K additional source of energy is required.
Impact on Environment:
1. Domestic use of biomass in rural areas creates air pollution.
2. A large scale energy-crop plantation is water consuming with increased use of pesticides and fertilizers, causing water pollution and flooding.
3. The production of biomass on large scale and its harvesting accelerates soil erosion and loss of nutrients.
(d) Ocean Energy:
India is having large potential of ocean thermal energy which could be of the order of about 50,000 MW.
Ocean Thermal Energy Conversion (OTEC) plants convert the heat in the ocean into electrical energy with the help of temperature difference. The large temperature difference between warm surface sea water (28-30°C) and cold deep sea water (5-12°C) is used to generate electricity with the help of ocean thermal energy conversion system.
Impact on Environment:
1. OTEC plant creates adverse impacts on marine environment since the massive flow of water disturbs thermal balance, changes salinity gradient and turbidity.
2. The leakage of ammonia, used as a working fluid in closed cycle OTEC system, may cause much damage to the ocean ecosystem.
(e) Wave Energy:
The ocean waves are caused by wind, which in turn is caused by uneven heating and subsequent cooling of earth’s crust and rotation of the earth.
The most of the sea surface in the form of wind waves forms a source of energy. Floating propellers are placed in shallow waters, near the shores, and due to motion of the waves the propellers also get the motion and this kinetic energy can be used to drive turbines.
The harnessing of wave energy requires the development of special power conversion devices.
Advantages of Wind Energy:
1. The wave energy is a cheap and inexhaustible source of energy.
2. Wave-power devices, unlike solar or wind devices, do not use up large land masses.
3. It is pollution-free.
4. A staggered array of power devices can produce electricity protect coastlines from the destructive action of waves, minimise erosion and even help create artificial harbours.
Limitations of Wind Energy:
1. Wave lacks dependability.
2. There is a scarcity of accessible sites of large wave activity.
3. Economic factors like capital investment, cost of maintenance, repair and replacement hinder the development.
(f) Tidal Energy/Power:
The rise and fall of tides offers a means for storing water at the rise and discharging the same at fall. Of course the head of water available under such cases is very low but with increased catchment area considerable amounts of power can be generated at a negligible cost.
i. The use of tides for electric power generation is practical in a few favourably situated sites where the geography of an inlet of bay favours the construction of a large scale hydroelectric plant. To harness the tides, a dam would be built across the mouth of the bay in which large gates and low head hydraulic turbines would be installed.
At the time of high tide the gates are opened and after storing water in the tidal basin the gates are closed. After the tide has receded, there is a working hydraulic head between the basin water and open sea/ocean and the water is allowed to flow back to the sea through water turbines installed in the dam. With this type of arrangement, the generation of electric power is not continuous. However by using reversible water turbine the turbine can be run continuously as shown in Fig. 1.1.
(g) Geothermal Energy:
In many places on the earth natural steam escapes from surface vents. Such natural steam wells suggest the possibility of tapping terrestrial heat (or geothermal energy) in this form and using it for the development of power. Unfortunately, the locations where the steam-producing sub-strata seem to be fairly close to the surface are far removed from centres of civilization where the power could be usefully employed.
Nevertheless, there are probably many places where, although no natural steam vent or hot springs are showing, deep drillings might tap a source of underground steam. The cost of such explorations and the great likelihood of an unsuccessful conclusion are not very conductive to exploitation of this source of energy.
There are two ways of electric power production from geothermal energy:
(i) Heat energy is transferred to a working fluid which operates the power cycle. This may be particularly useful at places of fresh volcanic activity where the molten interior mass of earth vents to the surface through fissures and substantially high temperatures, such as between 450 to 550°C can be found. By embedding coil of pipes and sending water through them steam can be raised.
(ii) The hot geothermal water and/or steam is used to operate the turbines directly. From the well-head the steam is transmitted by pipelines up to 1 m in diameter over distances up to about 3 km to the power station. Water separators are usually employed to separate moisture and solid particles from steam.
Presently, only steam coming out of the ground is used to generate electricity, the hot water is discarded, because it contains as much as 30% dissolved salts and minerals, and these cause serious rust damage to the turbine. The water, however, contains more than l/3rd of the available thermal energy.
Advantages of Geothermal Energy:
1. It is almost free from the pollution.
2. It is a cheap and clean source of energy.
Disadvantages of Geothermal Energy:
1. The drilling operations result in the noise pollution.
2. Air pollution results in case of release of gases like H2S, NH3 present in the steam waste.
Impact on Environment:
1. Gases escape into the atmosphere and drop down as acid rain.
2. The soil and water are polluted by the chemicals like sulphates, chlorides and carbonates of lead, arsenic.
3. Owing to the discharge of waste hot water, rivers are infected and consequently drinking water, farming and fisheries are adversely affected.
4. The exhausts, blow downs and centrifugal separation cause noise pollution.
(h) Hydrogen Energy:
Hydrogen energy is a non-conventional energy source. Hydrogen is considered as an alternative future source of energy. It has a tremendous potential because it can be produced from water which is available in abundance in nature. Hydrogen atoms in the core of sun combine to form helium atoms which is called as fusion reaction. It gives radiant energy which sustains the life on the earth.
Hydrogen can be separated from water by means of electrical energy. It can also be obtained from fossil fuels.
Advantages of Hydrogen Energy:
1. Its burning is non-polluting.
2. Hydrogen energy has a very high energy content.
Applications of Hydrogen Energy:
1. It is used for generating electricity for domestic appliances
2. It is utilised in automobiles.
3. It is employed for industrial uses
(i) Thermo-Electric Power:
According to Seebeck effect, when the two ends of a loop of two dissimilar metals are held at different temperatures, an electromaotive force is developed and the current flows in loop. This method, by selection of suitable materials, can also be used for power generation. This method involves low initial cost and negligible operating cost.
(j) Fuel Cell:
When an electric current is passed through a dilute solution of an acid or an alkali by means of two platinum electrodes, hydrogen is produced at the cathode and oxygen is evolved at aviode. If this process is reversed by removing the power supply and connecting the two electrodes through a suitable resistance, the presence of hydrogen at one electrode and oxygen at the other will produce a small current in the external circuit, water being produced as a by-product. This reverse process of electrolysis is the essence of the “fuel cell technology” as, the chemical energy stored in hydrogen and oxygen have been combined to produce electricity.
i. A fuel cell does not have moving components and as such, it is quieter and requires less maintenance and attention in operation.
ii. Fuel cells convert chemical energy directly to electrical energy at room temperatures.
iii. These cells are very efficient and are not subject to Carnot limitation.
(k) Magneto-Hydro-Dynamic (MHD) Generator:
The MHD working principle is based on Faraday’s law of electromagnetic induction which states that change in magnetic field induces an electric field in any conductor located in the magnetic field. This electric field while acting on the free charges in the conductor causes a current to flow in the conductor. In “MHD generator”, an ionised gas is used as a conductor. If such ionised gas is passed at a high velocity through a powerful magnetic field, then current is generated and can be extracted by placing electrodes in a suitable position in the stream. It produces D.C. power directly.
In MHD generation, all kinds of heat sources like coal, gas, oil, solar etc. can be used.
MHD systems are of two types:
(i) Open cycle system; and
(ii) Close cycle system.
Electricity Generation from Non-Conventional Energy Sources:
It has been widely recognised that the fossil fuels and other conventional resources, presently used in generation of electrical energy, may not be either sufficient or suitable to keep pace with the ever increasing world demand for electrical energy. The prospects for meeting this demand and avoiding a crisis in supply would be improved if new and alternative energy sources could be developed.
The important non-conventional electricity sources are:
(i) Magneto hydrodynamic systems
(ii) Solar electric power plants
(iii) Photovoltaic cells
(iv) Fuel cells
(v) Wind energy
(vi) Geothermal energy
(vii) Tidal-energy
(viii) Ocean thermal energy
(ix) Organic wastes, biogas, rice straw etc.
Essay # 2. Renewable and Non-Renewable Energy Sources:
Renewable (Non-Conventional) Energy Sources:
Renewable energy sources include both ‘direct’ solar radiation intercepted by collectors (e.g. solar and flat-plate thermal cells) and ‘indirect’ solar energy such as wind, hydropower, ocean energy and biomass resources that can be managed in a sustainable manner. Geothermal is considered renewable because the resource is unlimited.
Advantages of Renewable Energy Sources:
The advantages of renewable energy sources are:
1. These energy sources recur in nature and are inexhaustible.
2. The power plants using renewable sources of energy do not have any fuel cost and hence their running cost is negligible.
3. As renewables have low energy density, there is more or less no pollution or ecological balance problem.
4. These energy sources can help to save foreign exchange and generate local employment (since most of the devices and plants used with these sources of energy are simple in design and construction, having been made from local materials, local skills and by local people).
5. These are more site specific and are employed for local processing and application, their economic and technological losses of transmission and distribution being nil.
6. Since conversion technology tends to be flexible and modular, renewable energy can usually be rapidly deployed.
Demerits/Limitations of Renewable Energy Sources:
1. Owing to the low energy density of renewable energy sources large size plants are required, and as such the cost of delivered energy is increased.
2. These energy sources are intermittent and also lack dependability.
3. The user of these sources of energy has to make huge additional investment before deriving any benefit from it (whereas in case of conventional energy sources, the processing cost has traditionally been borne by large industries which borrow money from a bank and then charge the customer for each unit of energy used).
4. These energy sources, due to their low energy density, have low operating temperatures leading to “low efficiencies”.
5. Since the renewable energy plants have low operational efficiency, the heat rejections are large which cause thermal pollution.
6. These energy sources are energy-intensive.
If broadly interpreted, the definition of renewable resources also includes the chemical energy stored in food and nonfuel plant products and even the energy in air used to dry materials or to cool, heat and ventilate the interiors of buildings.
From an “operational point of view”, the correct way to treat renewable energy is as a means to reduce the demand for conventional energy forms. Thus, in performing economic and financial analyses, there is no real distinction between renewable energy technologies and those designed to improve the efficiency of conventional energy use.
Another point is that cost-effective approaches to energy efficiency – ranging from no-or- low cost measures (e.g. reducing excess air in boilers, shutting down equipment when not needed) to systems requiring moderate capital investment, such as heat recuperators, boiler replacements or cogeneration units – can improve the financial and economic feasibility of renewable as well as conventional energy systems. Improvements in the efficiency of energy use can be teamed with a variety of energy supply technologies, and this fact must be recognised when assessing the relative economics of renewable and conventional energy systems.
Usefulness of Renewable Energy Resources:
Any analysis of the usefulness of renewable resources in developing countries must consider the following basic facts:
1. The renewable energy resources and conversion systems are technically capable of meeting many of the power and fuel needs of a modern technological civilisation, from small-scale, decentralised uses to large-scale urban and industrial concentration.
2. Although renewable technologies are economically competitive with fossil fuels in their ability to provide electricity, mechanical power, thermal energy and liquid fuels, such technologies have not yet been deployed internationally, and the primary obstacles to their further development are institutional.
3. Worthwhile and widespread deployment of solar energy systems for the production of electric power, thermal energy and liquid fuels will require advanced materials and concepts to be competitive with conventional options.
In fact, the systems for conversion and storage for many of the renewable sources will only be commercially feasible after sophisticated research and development – surprisingly analogous to that now taking place in the computer and information fields.
Barriers in the Implementation of Renewable Energy Systems:
There are a number of obstacles to the effective deployment and widespread diffusion of renewable energy systems; among these are:
1. Inadequate documentation and evaluation of past experience, a paucity of validated field performance data and a lack of clear priorities for future work.
2. Weak or non-existent institutions and policies to finance and commercialise renewable energy systems. With regard to energy planning, separate and completely uncoordinated organisations are often responsible for petroleum, electricity, coal, foresty, fuelwood, renewable resources and conservation.
3. Technical and economic uncertainties in several renewable energy systems; high economic and financial costs for some systems in comparison with conventional supply options and energy-efficient measures.
4. Skeptical attitudes towards renewable energy systems on the part of energy planners and a lack of qualified personnel to design, manufacture, market, operate and maintain such systems.
5. Inadequate donor coordination in renewable energy assistance activities, with little or no information exchange on successful and unsuccessful projects.
The following points may be mentioned in this connection:
1. The energy demand is increasing by leaps and bounds due to rapid industrialisation and population growth, and hence the conventional source of energy will not be sufficient to meet the growing demand.
2. Conventional sources except hydro are non-renewable and are bound to finish up one day.
3. Conventional sources (fossil fuels, nuclear) also cause pollution, thereby their use degrades the environment.
4. Large hydro resources affect wild life, cause deforestation and pose various social problems.
Owing to these reasons it has become important to explore and develop non-conventional energy sources to reduce too much dependence on conventional resources.
The “renewable energy technologies” are better than most conventional energy technologies in the following ways:
1. Can be produced in large numbers and introduced quickly.
2. Can often be built on, or close to the site where the energy is required, this minimises transmission costs.
3. Can be matched in scale to the need, and can deliver energy of the quality that is required for a specific task thus reducing the need to use premium fuels or electricity to provide low grade forms of energy such as hot water.
4. Although there are physical and environmental risks associated with the construction and operation of renewable energy technologies, as there are with all energy conversion systems, they tend to be relatively modest by comparison with those associated with fossil fuels or nuclear fuels.
5. Increased flexibility and security of supply due to availability of diversity of systems.
Non-Renewable Energy Sources:
The non-renewable energy sources are those which do not get replenished after their consumption e.g. coal once get burnt is consumed without replacement of the same (fossil fuels, nuclear fission fuels).
Essay # 3. Alternative Energy Sources:
There are the sources which are non-traditional. They are alternatives to the conventional energy sources.
The demarcation between conventional and non-conventional is not rigid. Today non- conventional becomes conventional after a few decades.
Concern for the environment due to ever-increasing use of fuels and rapid depletion of natural resources has led to development of alternative sources of energy which are “renewable” and “environmental friendly”.
Essay # 4. Impact of Energy Sources on Environment:
A high quality environment is one:
(i) which offers the most favourable living conditions for people of diverse interests;
(ii) which is conducive to good health and well-being of inhabitants, in which all biological variables are intact and healthy and in which a diverse and stable biotic community is maintained.
i. A normal constituent of environment is energy. A permanent flow of energy controlled by nature takes place from sun to environment. This energy is used by humans, animals, insects etc.
Man, by using this solar energy for food, hydropower, fuel etc., participates harmoniously in the natural flow of energy through the environment. In addition, man is also using sources of energy which are limited, non-renewable and not included in the normal flow of energy through the environment. By doing so, man is polluting the environment:
ii. An important environmental aspect of energy generation is the “air pollution”. Therefore, it is imperative to limit the extent of air pollution to maintain the air quality at a reasonable and acceptable level and protect public health and welfare.
iii. For improving our present level of economy and standard of living, it is necessary to have continued expansion of electric power facilities.
The environmental aspects of power plants are gaining more and more importance. It is possible to build new power plants with little detrimental environmental effects if sufficient thought, planning and study are given to the potential problems before the project is designed and constructed. The engineers and environmentalists, through mutual cooperation, may find a solution which is best from the point of engineering as well as ecology.