Energy Resources and it’s Sources (With Diagram)

Read this article to learn about Energy Resources and it’s Sources !

The energy crisis is a global problem today. The survival of the man will be difficult if the energy problem is not solved on the priority basis. Many scientific organisations as Department of Science and Technology, Department of forestry and environment.

Department of Non-conventional energy. Department of Oceanography, Fuel Research Institute and several other regional, National and International Institutes are engaged in researches on this current problem.

There are several energy sources in the world such as coal, oil (petroleum and its products), natural gas, electricity, nuclear energy, solar energy, thermal and wind energy. Nuclear energy is supposed to be the latest source of energy. Now efforts are being made to harness energy from solar radiations, nuclear fission, wind, thermal power, tides of the ocean and biogas etc. Fossil fuel reserves are limited and it is estimated that the stock of the mineral oil will lost in 21st century if it continues to be used at present rate. Thus, there is a need to exploit various sources of energy.

The energy consumption is maximum in developed countries as compared to developing nations. The per capita daily consumption is highest in America and then come Canada, U.K., Germany, Soviet Russia, Japan, Mexico, Brazil and India in decreasing order. United States of America alone consumes about 35 per cent of the world total energy Soviet Russia consumes about 16 per cent and India consumes only two per cent of the total available energy of the world.

The following Table 15.6 presents a comparative idea of energy consumption by some countries:

In the world coal reserves are much bigger and will lost longer than the petroleum reserves. The main coal producing countries are China, Russia, USA, UK, India, Germany, Japan, Poland, Czechoslovakia and France. The oil producing countries are Saudi Arabia, Iran, Iraq, Nigeria, Libya, Arab Republic, Indonesia, USA and Russia. In India new resources of oil have been explored recently in the sea bed of Mumbai high and Gujarat.

According to latest information India has coal reserve of about 1,31,000 million tons which is sufficient for coming 1000 years if the current rate of production and consumption continues. The annual crude oil production in India is 8 million tons as against its requirement of 20 million tons which is much less than its total requirement. The annual oil consumption which was 33 million tons by 1980-1981 is increasing at fast rate and has now become more than double. The oil and Natural Gas Commission in India is exploring new oil and gas fields.

Agriculture, industry and automobiles are the main sectors where the consumption of oil is maximum. The tremendous increase in population would need more food and that need can be fulfilled by increased oil production. The cost of petroleum is continuously increasing in the world due to which India is greatly affected.

Therefore, some suitable alternative sources of energy will have to be developed to replace petroleum. Now efforts are being made to find out new sources of fertilizers which are not petroleum based. Among them, bio-fertilizers, genetic engineering techniques, sewage and some nitrogen fixing blue-green algae have been found successful.

Nitrogen fixing blue-green algae are used as bio-fertilizers in the paddy fields without any harmful effects on our biosphere. Serious efforts are being made now to produce natural gas for fuel purpose. The object of the process is to produce synthetic methane from coal. Burning of coal releases CO₂ gas into the atmosphere and causes environmental pollution.

Different Sources of Energy:

Energy from Plants:

Green plants by virtue of possessing special pigments are able to absorb and use a portion of solar energy for the synthesis of food. The process is called photosynthesis. By this, organic substances are synthesized from carbon dioxide and water using the light energy absorbed by the special pigment chlorophyll. In this process solar energy is converted into chemical energy or food energy and molecular oxygen is produced as a by-product. All other organisms including man directly or indirectly depend upon the energy accumulated in green plants in the form of organic food.

The total solar energy reaching the earth is 3 x 10²⁴ J per year. Out of this, green plants utilize about 0.1 per cent resulting to net annual production of 2 x 10¹¹ tonnes of organic matter utilizing 3 x 10¹² J energy. The total solar energy received in India is 6 x 10¹³ MWH, with 300 days, of average Sunshine per year. Thus, there is a vast scope for harvesting solar energy through improved photosynthetic efficiency.

The increase in photosynthetic efficiency will lead to an increase in food, biomass and energy. The fossil fuels (coal, oil and natural gases) that we use today resulted when ancient wide spread dense forests were fossilized and converted into major coal beds during the carboniferous period about 300-350 million years ago.

Thus photosynthesis is a vital process in the living world of this planet. A detailed study of the biophysical, and biochemical aspects of this process is urgently needed for improving the photosynthetic efficiency and productivity to meet the future food and energy requirements. Photosynthetic efficiency is much greater in algae and bacteria. It is 16% in algae and bacteria as compared to 1-2% in land plants.

Energy Plantations:

Fuel wood has been the primary energy source for mankind from the beginning of civilization and still continues to be the main source of energy in the developing countries. Plant based energy is obtained by energy plantations which can produce biomass from selected trees in the shortest possible time at a low cost.

These plants yield solid, liquid or gaseous fuel through burning, gasification, digestion etc. Such plantations can be raised in both hills and plains particularly on marginal land. It has been calculated that about 4 tonnes of dry matter can be obtained in 0.25 hectare land which is sufficient for an average family. According to Khoshoo, 1983 around 1.86 million square km of marginal or stripland is available in India for such plantation which would yield around 1,400 million trees. Water hyacinth (Jalkumbhi) when grown in water enriched with sewage, may produce 8-10 tons of plant material/acre which may yield 3500-7000 cubic metre of methane.

Plants suitable for Energy plantation:

Tree species:

Ailanthus excelsa

Anogeisus latifolia

Millingtonia hortemis

Trema orientalis

Givotia rottleriformis

Duabanga sonnertides

Erythrina indica

Cedrela toona

Casuahna equisetifolia

Dipterocarpus indicus

Eucalyptus globulifera

Ficus bengalensis, F. religiosa, F. elastica.

Ficus glomerata

Aleurites moluccana

Butea monosperma

Moringa tinctoria

Stereospermum angustifolium

Aguilaria agallacha

Odine odier

Abies pindrow

Grevelia robusta

Dendrocalamus strictus

Shrubs:

Jatropha glandulifera

Clerodendron enerme

Altantia monophylla

Memecylon edule

Kydia calyxeina

Ipomoea carnea

Tecoma gracillis

Dodonaea viscosa

Macaranga peltola

Grewia latifolia

Herbs:

Phaseolus trilobatus

Psophocarpus tetragonoloba

Sesbania aegyptiaca

Cymopsis tetragonoloba

Crotalaria juncea

Glyricidia maculata

Ipomoea batatas

Butea vulgaris

Bambusa arundinacea

Cucumis melo

Alternanthera sessilis

Cymbopogon martini

Amaranthus paniculatus

Aquatic plants:

Eichhornia crassipes

Juncus indicus

Typha latifolia

Polygonum glabrum

Lemna, Wolffea, Pistia

Salvinia, Hydrilla.

Now-a-days extensive cultivation of alga Spirulina platensis is being undertaken in India. This alga contains proteins, carbohydrates and lipids in varying amounts and is a rich source of hydrocarbons. It has been calculated that a 200 square miles of algal farm could provide enough petroleum substitute (30,000 barrels/day) (Khoshoo, 1983). Spirulina platensis contains 60% crude protein rich in Tryptophan, Lysine and Vitamin B12.

Recently, the NBRI, Lucknow has started its culture on mass scale in sewage. Dabur Research Foundation and some other pharmaceutical companies in India prepared SPIRULINA health capsule which is said to be richest source of iron, beta-carotin, vit. B12, glutamic acid and a variety of other essential amino acids. It cures heart ailments, stress and builds fitness. The use of blue-green alga as a self-generating source of nitrogen in rice field is well known.

Now-a-days much emphasis is being laid on the cultivation of sea weeds. Many varieties of sea weeds are used for various purposes such as food, pharmaceuticals, textiles, fodder, fertilizers and biogas. It is estimated that the total annual yield of sea-weed is about 50,000 tonnes and if all resources are explored it can produce tremendous energy.

Some of the important plants for energy plantation which are extensively grown in India are Leucaena leucocephala, Casuarina, Poplar tree and Eucalyptus. Recently an exotic plant Palonia has been introduced from China for agroforestry purpose. This tree species has good adaptability in Indian soils and is fast growing one. Leucaena leucocephala possesses all the qualities as wide adaptability, high genetic variability, hardyness, resistance to diseases and pests, adaptability to different edaphic conditions, requiring only marginal inputs of fertilizers, high regeneration potential and easy propagation, wood with high caloric value and ability of wood to bum without sparks and smoke, nitrogen fixing ability by virtue of root nodules, fast growth and high yield of biomass per unit area. It is used as a source of fuel, fodder and fibre.

Rice bran oil is a rich source of edible oil. In Japan bran oil is used in cooking. Paddy contains about 25 kg of oil/tonnes. In India the annual production of rice bran oil is about 80,000 tonnes. The plantation of energy plants would result in an inexhaustible source of renewable energy. The agro-industrial products, their by-products and their residues can play a very important role in the production of energy. Biomass from com, sorghum, sugar cane, cassava also provide base material for production of alcohol and gases. The biomass available from oil seeds, fruits and vegetable wastes, cow dung, waste from the sea weeds, rice husk and a variety of other waste organic matter can serve as a suitable medium for the production of gases.

Biomass obtained from biotic sources is an important source of energy. Biomass collected in the form of wood, roots, foliage, algae etc. from agricultural land or forest can be converted into energy source either in gaseous, liquid or solid forms through diverse ways. Biomass from natural forests and energy plantations will serve as dependable and renewable energy sources in future. For increasing forest biomass fast growing tree species are planted, harvested and regenerated on short-term rotation of 2-4 years.

The fast growing trees as for example. Eucalyptus, Zizyphus, Prosopis, Popler, Albizzia, Acacia etc. are not only important from silviculture point of view but are known to reclaim the waste land and check soil erosion as well. The reclamation of waste land or usar land can be coupled with biomass production. Acacia, Terminalia, Prosopis, Ficus etc. can be raised on saline and alkaline soils.

Among the various non-conventional sources of energy, forest biomass plays a significant role in solving the fuel wood crisis. Recent data reveal that one seventh of world’s fuel need is met by forest biomass. This figure is equivalent to 20 million barrels of oil per day.

Many countries, for example Bangladesh, China, France, Germany, India, Indonesia, Japan, Pakistan, Sweden, UK, and USA are actively engaged in research in the field of bioenergy. Several International agencies as Food and Agricultural Organization (FAO), International Development Research Centre (IDRC), United Nations Educational, Scientific and Cultural Organizations (UNESCO), United Nations Environmental Programmes (UNEP), United Nations Industrial Development Organization (UNIDO) and World Health Organization (WHO) are also engaged in Bioenergy research and development programmes.

Importance of Fuel Wood Plantations:

Plants absorb and convert solar energy into chemical or food energy through photosynthesis which is stored in their body. When the parts of the plants are burnt that stored energy is released in the form of heat. When plants are grown for producing fuels for cooking and various other purposes, the process is called fuel wood plantation. For fuel wood plantation such tree species are selected as are fast growing.

The advantages of fuel wood plantations are as follows:

1. The fuel wood would save enormous quantity of cow dung which is applied as natural manure or farmyard manure (FYM) or compost.

2. Fuel wood plantation would provide an inexhaustible and renewable source of energy.

3. Use of fuel wood produces non-hazardous mineral-rich ash which can be used as fertilizer.

4. It causes little or no pollution.

5. Plants create pleasant and beautiful surrounding and provide safe habitat for wildlife.

6. There is little or no energy input in fuel wood plantation.

7. Fuel plants also provide us fruits seeds, edible leaves, forage, tannins, gums, dyes and several other useful substances.

8. Soil erosion is checked through plantation.

9. There is no problem of waste disposal.

Petro plants (Hydrocarbon Plants):

Several plants are known to yield liquid hydrocarbons, the substitute for liquid fuels .Such plants are called Petro plants. The hydrocarbons present in such plants can be converted into petroleum hydrocarbons of high molecular weight (10,000). More than 385 plant species belonging to Euphorbiaceae, Asclepiadaceae, Apocynaceae, Convolvulaceae, Sapotaceae and some other families have been screened for hydrocarbon contents. Now, the efforts are being made to increase the biomass of such plants and convert their hydrocarbons into petroleum products Indian Institute of Petroleum, Dehradun and National Botanical Research Institute Lucknow have undertaken research programme in this area.

A large number of species belonging to Euphorbiaceae secrete latex containing 30% hydrocarbon Hevea brasiliemis (rubber tree) is important source of hyrdocarbon. These plants may be utilized either to get diesel fuel or high quality liquid fuel. Euphorbia abyssinica, E. resinifera E lathyris produce good amount of biomass. Khirta, E splendens. E pulcherima also have enough fuel potential.

There are few trees such as. Eucalyptus, Agathis dammara. Canarium ovatum which produce cheaper fuel. Jatropha curas tree yields 2 kg of seed oil per plant/year. The oil obtained from this plant is expected to replace the conventional diesel fuel (Khoshoo, 1983). Some other common plants producing hydrocarbons are listed below.

Some Plants producing Hydrocarbons or Petro plants:

Thevetia nerifolia

Calotropis procera

Vitis quadranguris

Sansevieria

Aloe vera

Euphorbia nerifolia

Jatropha curas

Wrightia tomentosa

Plumeria alba

Allamonda cathartica

Calotropis gigantia

Cryptostegia grandiflora

Artocarpus integrifolia

Bassia latifolia

Argemone mexicana

Givorta rotalariformis

Ceropegia tuberosa

Pedalium marex

Agave americana

Euphorbia hirta

E. royleana

Tabernaemontana cornaria

Plumeria acutifolia

Nerium odorum

Asclepias curassavica

Stapelia grandiflora

Mimusops elengi

Besides higher plants, some algae also yield hydrocarbons. Botryococcus braunii, an unicellular green alga contains about 70% hydrocarbons. The algal hydrocarbons is very similar to crude oil. This alga can thus be exploited for production of hydrocarbons. For large scale production of hydrocarbons it is therefore necessary to increase the algal biomass. Hydrocarbons are recovered from the algal cells by centrifugation. Chlorella pyrenoidosa is another fresh water alga which can yield hydrocarbons. When this alga is subjected to hydrogenation for about an hour at high temperature 50 per cent of algal biomass is converted into oil with a little amount of ammonium carbonate.

Other Resources of Energy:

Energy consumption and its qualitative trends characterize the life style of a country. The highly industrialized countries depend upon different sources of energy such as coal, oil, natural gas, hydroelectric power and fission fuels for their developmental activities. In developing countries, on the other hand, there is more dependence on non-conventional sources of energy like fire wood, animal wastes and agricultural wastes rather than the fossil and fission fuels. Energy is consumed in different sectors as industry, transport and agriculture.

The following table 15.7 gives the details of total energy consumption in different sectors in India:

Various sources of energy, i.e., coal, hydroelectric, thermal power, nuclear energy, wind energy, biogases etc., are discussed here as under:

Coal:

India has vast coal reserves which may be sufficient for coming 1000 years. Coal is used as a fuel in railways, thermal power plants, domestic cooking and many industries. Nevertheless, the use of coal often causes environmental pollution. The emission of smoke, ash and other particulate matter (fly ash) from coal burning poses a serious threat to human health.

Nuclear energy:

The generation of electricity from radioactive uranium and plutonium fuels by nuclear power plants has solved energy problem to some extent but at the same time it is creating several problems. Many harmful gases are released by atomic power plants and radioactive wastes are posing a serious threat to the environment. In spite of development of nuclear waste management technology the atomic power plants are not as safe as claimed by atomic scientists.

Even slight leakage of radioactivity in the coolant water will tend to accumulate and amplify in plants, animals and human beings and cause mutations, body deformity, many physiological disorders and even death. It will be fatal to human beings if misused. Proper use of x-rays, y-rays may be beneficial to human and agriculture, but their misuse proved to be deleterious. Recent Pokhran nuclear explosion in 1998 is well known.

A small quantity of radioactive material can produce an enormous amount” of energy. For example, one tons of Uranium²³⁵ (U²³⁵) produces energy equal to that produced by three million tons of coal or 12 million barrels of oil. Presently there are 300 atomic power plants in the world. The principal atomic power producing countries are USA, Soviet Russia, UK, France, Japan, Germany, China and India. India ranks 7th among the atomic power producing countries of the world.

Wind Energy:

Air in motion is called wind. Wind is created when air that has been warmed over sun- heated land rises, leaving a vacuum in the space it once occupied. Cooler surrounding air then rushes in to fill the vacuum. This movement of rushing air is then known as wind.

Wind Energy is the kinetic energy associated with the movement of large masses of air in the shape of winds blowing across the earth’s surface. Ancient civilizations first used wind energy when they sailed boats in the rivers and oceans. The ancient Persians were the first to use wind energy on land by developing the first windmill, sometime in the 7th century. By the 12^th and 13^th centuries, windmills were used on a large scale in many European countries. Windmills were mostly used to mill grain, pump water, saw timber and provide other forms of mechanical energy. Since the late century, wind energy is being used to generate electric power.

India has an estimated wind power potential of 20,000 MW. About 100 sites having a potential of more than 4500 MW have been taken up for wind power generation. These are located mostly in Tamil Nadu, Karnataka, Andhra Pradesh, Gujarat, Kerala, Madhya Pradesh and Lakshadweep. The country’s largest wind farm is located near Kanyakumari.

Harnessing of Wind Energy:

Modem wind energy systems consist of the following three basic components:

i. Tower on which the wind turbine is mounted.

ii. Rotor that is turned by the wind.

iii. Nacelle, which houses the equipment, including the generator that converts the mechanical energy in the spinning rotor into electricity.

By connecting a spinning rotor (an assembly of blades attached to a hub) to an electric generator, modem wind turbines convert wind energy turning the rotor into electrical energy. Small wind turbines are capable of generating between 50 watts and 60 kilowatts of power, and use rotors ranging in diameter from less than 1 m to 15 m.

Large wind turbines are huge structures with rotors having diameters between 60 m and 100 m and are capable of generating 2 MW to 3 MW of power. The height of poles raises between 10 m to more than 100 m. Wind turbines can be installed in single units, in clusters of two to ten turbines and in large groups, called wind power plants or wind farms.

Biogas:

Biogas production technology offers a low cost alternative source of energy. Lacs of gobar gas plants installed in rural areas are the important and cheapest source of energy without any kind of pollution. The enormous quantity of animal dung (gobar) available in India may produce about 22,425 million m³ gobar gas. Animal dung is collected in a concrete tank or steel chamber. The chamber is covered by a metallic lid to make it air tight. In the absence of air anaerobic bacteria, decompose the dung and produce biogas or gobar gas (Fig. 15.8).

Gobar gas is used mainly in cooking and lighting. Besides gas, waste (slurry) of gobar gas plants can yield about 206 million tonnes of organic fertilizer every year. Biogas is a mixture of several gases such as methane, CO₂, N₂, O₂, as given in Table 15.8.

Solar Energy:

120 trillion tonnes of coals every year which is twenty times more than the world’s total reserves. The energy released from the Sun is due to the process of thermo-nuclear fusion continuously taking place in the sun. As the Sun will continue to shine for billions of years, it will continue to provide us with this abundant form of energy. If we can harness even some percentage of solar energy, it will go a long way in solving most of our energy requirements.

Solar Cooker:

Solar cooker is a kind of insulated box with a black polished base. There is a big mirror fitted at some angle to reflect the sunrays at a particular point to give more heat for cooking (Fig. 15.9). The solar cooker is kept in bright sunlight having food items in the containers. The food prepared by the solar cooler is very tasty and nutritious, although it takes more time. One drawback is that foodstuffs requiring high heat such as fried items and chapattis cannot be prepared in the solar cooker. Another drawback is that the solar cooker has to be directed towards the Sun after regular intervals of time.

It is the cheapest source of cooking food and is a boon for the rural areas. These cookers can save 30-50% of conventional fuels like wood, coal, LPG, kerosene, etc. India was the first country in the world to start commercial manufacture of solar cookers in the year 1982. However more efforts are still required to make it popular among the masses.

Solar Water Heater:

It consists of a solar heat collector and a storage tank. The heat collector comprises of a blackened sheet with tubes to carry the flowing water, front glass cover and insulated outer base. The blackened sheet of the heat collector gets heated when sunlight falls over it through the glass cover. It can raise the temperature of water up to 90°. The collector is connected to a storage tank from which water is drawn for use. Such water heaters are used in domestic buildings, hotels and industries Fig. 15.10.

Solar Desalinization Unit:

It is similar to solar water heater but here the water is kept stagnant. Water is kept in a blackened metal box with a sloping transparent roof, which is exposed to solar radiation as the water gets heated, some of it gets evaporated and the vapours condense into pure water drops

Solar Air Heater:

It is similar to solar water heater but instead of water, air is heated. It is used for drying food grams, vegetables, etc. and also for industrial purposes.

Solar furnace:

A solar furnace consists of thousands of small mirrors, arranged in such a manner so as to concentrate the solar energy. The largest of these is located at Odeillo in France, which uses 9600 reflectors with a total area of approximately 1860 sq m (about 20,000 sq. fit) to produce temperatures as high as 4000°C. Such furnaces are ideal for research that require high temperatures and contaminant-free environments for example, materials research.

Solar power plant:

The principle employed is similar to that of a solar furnace. Here, the high temperature generated, is used for boiling water to produce steam. The steam is then used to drive a turbine for the generation of electricity. Such a power plant has been established at Gurgaon, with a capacity of 50 KW (Fig. 15.11).

Conversion of Solar energy into electricity:

In solar power plants, the radiant energy of the Sun is first converted into heat and thereafter into mechanical energy and electricity. However, in such cases, the efficiency becomes low due to energy losses at each stage. There are certain materials that can convert the solar energy directly into electricity. It is done through solar or photovoltaic cells.

Solar or Photovoltaic cell: Solar cells are mainly made from thin slices of silicon and gallium or other semi-conductor materials, which convert solar radiation directly into electricity. In the photovoltaic principle, light excites electrons to move from one layer to another through semi-conductive silicon materials.

This produces an electric current. A number of solar cells are connected together to form solar modules that can generate sufficient amount of power. Current use of solar cells is limited to remote areas that are not connected by direct power lines and devices such as satellites and spacecraft’s. Many villages in India have been provided street lighting through such solar cells. India has great potential as far as solar energy is concerned, because most of the areas of the country remain hot and sunny for a long period of time.

Hydel Energy:

Mankind has used the power of flowing water since long for a number of purposes, such as to grind grains, saw wood, etc. However, today hydel energy refers to the generation of electricity from the energy of flowing water. The flowing water supplies energy to turn the turbines and generate electricity. Since water is used as an energy source, it is also known as hydroelectricity.

Hydroelectric power plants are commonly operated by constructing artificial reservoirs. The reservoirs are built by constructing dams across the river, thus impounding the water. The impounded water is the potential energy source. However, in some mountainous regions, where the streams have steep gradients, hydroelectricity is generated without the construction of reservoirs (Fig. 15.12).

In India, about 25% of the total energy requirements are met through hydroelectricity. India has tremendous potential for generating hydel power, as the country possesses a vast network of rivers throughout its length and breadth. Moreover, the mountainous regions of the country can provide us with enough hydel power.

The total hydroelectric potential of India is estimated to be around 150,000 MW, of which less than one-sixth has been exploited so far. The important hydroelectric power plants are situated in Punjab, Andhra Pradesh, Karnataka, Kerala and Orissa Major hydroelectric projects in the form of Narmada Dam and Tehri Dam are being developed in the states of Madhya Pradesh and Uttaranchal respectively.

Harnessing of Hydel Energy:

Hydroelectric dams harness the energy of water released from the reservoir to turn hydraulic turbines. The turbines convert the energy of the falling water into mechanical energy which is used to generate electricity. Dams designed to generate electricity deliver water to a building called a powerhouse, which contains highly specialized power-generating equipment’s.

Large pipes carry water from the reservoir down into the powerhouse. Water exits through small openings which concentrate the flow and direct it onto the blades of a large hydraulic turbine. The force exerted by the falling water rotates the blades and drives the shaft of an electric generator. The shaft spins giant magnets in the generator, which create an electric current. Power lines then transmit the current to the consumers.

Ocean Energy:

Another alternative source of energy is from the rise and fall of tides in the ocean and hence it is also called tidal energy. Tides are caused due to the gravitational pull of the moon and due to the Earth’s rotation. The tidal movement of water has a lot of energy, which is now being looked into for producing electricity. Such plants have been installed at the Bay of Fundy Canada and La Ranee in France. In India, three potential sites have been identified, viz. the Gulf of Kutch, the Gulf of Cambay, both in Gujarat; and Sundarbans in West Bengal.

Harnessing of Ocean Energy:

The principle employed for harnessing tidal energy is the same as that in a hydroelectric plant. A minimum range of 8 m in the height of tides is necessary for harnessing tidal power. To harness tidal power, dams are built across the entrance to a bay or estuary, thus creating a reservoir.

As the tide rises, water is initially prevented from entering the landward side. During high tide the water is allowed to flow through the dam into the reservoirs. This water is allowed to run out through a turbine that generates electricity. During low tide, the water, stored in the reservoir, is allowed to flow back into the sea, which is now at a lower level; thus again moving the turbines.

Ocean Thermal Energy Conversion (OTEC):

The surface temperature of ocean water in the tropical region is around 28°C. However, at a depth of around 600 m, the temperature of water falls to 1°C. This difference in tem­perature between the surface and deeper parts of the ocean can be used to generate electricity Equipment’s have been designed that bring the surface warm water and the cold water through pipes. The warm water is used to evaporate liquid ammonia into vapour.

The vapours come out at high pressure, which moves the turbines to produce electricity. The ammoma vapour is again condensed back into its liquid form by passing it through cold water, thus completing the cycle. Although, theoretically, there exists a great potential in OTEC, it remains to be seen whether it is commercially feasible or not.

Geothermal Energy:

Geothermal implies the ‘heat of the Earth’. Geothermal energy is manifested on the Earth surface in the form of volcanoes, geysers and hot water springs. The temperature in the interior of the Earth is very high and all the rocks are in the molten state, called magma. If the magma reaches the surface, it forms volcanoes, but most of the molten rock stays underground, creating huge subsurface regions of hot rocks.

In certain areas, water seeping down through cracks and fissures in the crust, comes in contact with this hot rock and is heated to high temperatures. Some of this heated water circulates back to the surface and appears as hot springs and geysers. However, the rising hot water may also remain underground, forming geothermal reservoirs. Geothermal reservoirs, which may reach temperatures of more than 350° C, can provide a powerful source of energy.

The natural steam and hot water obtained from geothermal reservoirs are exploited for various purposes including power generation. Italy, New Zealand, Russia, Japan, Iceland and USA are the main countries exploiting this resource. In India, geothermal energy in the form of hot springs occur widely especially in the Himalayan region, such as Manikaran, Badrinath, Kullu, Puga Valley (Ladakh), etc. Thus, geothermal energy forms a good resource for future use. Presently, a geothermal power plant is being established at Tatapani village, Ambikapur district, Chhattisgarh.

Harnessing of Geothermal Energy:

Geothermal reservoirs, which are shallow (about 5 km deep), can be reached by drilling a well. The hot water or steam from these wells can be used to turn turbine generators to produce electricity. A power plant that uses this natural source of hot water or steam is called a geothermal power plant. In addition to generating electricity, geothermal water is used directly in spas to heat greenhouses, for industrial processes and for space heating in homes and other buildings. People in over 35 countries have developed geothermal water for such purposes (Fig. 15.13).

Nuclear Energy:

Nuclear energy is the energy stored in the atomic nucleus. Two nuclear processes can be used to release this energy that binds the nucleus. Nuclear fission and nuclear fusion. Nuclear fission is the splitting of the atom’s nucleus into smaller fragments and nuclear fusion is the combining of atomic nuclei. In both the processes, a tremendous amount of energy are released.

To produce energy, controlled nuclear fission reactions are undertaken in the nuclear reactors. Producing energy through nuclear fusion has not yet been commercially undertaken; as such reactions require a temperatures of approximately 100 million degrees Celsius. The radiant energy of the Sun is because of the continuous fusion reactions taking place in the Sun.

India is also generating nuclear energy through six nuclear power plants, which are:

i. Tarapur, Maharashtra

ii. Kalpakkam, Tamil Nadu

iii. Narora, Uttar Pradesh

iv. Kota, Rajasthan

v. Kakrapara, Gujarat

vi. Kaiga, Karnataka

These nuclear plants generate about 2500 MW electricity per year, which is about 2% of the total energy produced. In comparison, nuclear energy contributes 20% of the energy requirements in USA and 75% in France. In India, nuclear energy is obtained from uranium and thorium. India has great potential for further development of the nuclear energy sector as it has the world’s largest deposits of thorium (about 50% of the world).

Harnessing of Nuclear Energy:

Nuclear energy is harnessed through controlled nuclear fission in nuclear reactors. In the reactor, neutrons are used to cause a controlled fission of certain radioactive elements such as uranium, thorium, etc. Uranium²³⁵ (U²³⁵) is the only naturally occurring fissionable material and is, therefore, essential in the production of nuclear energy. The processing of uranium to increase the concentration of U²³⁵ from 0.7% to about 3% is called enrichment. This enriched U²³⁵ is used as fuel in the fission reaction. When a neutron from another atom strikes the nucleus of U²³⁵ atom, the nucleus of U²³⁵ splits. This releases a huge amount of energy, fission fragments (barium and krypton) and more neutrons.

The neutrons that are released strike the nuclei of other atoms of U²³⁵ and also cause them to undergo fission. This, in turn, releases more energy and more neutrons in a chain reaction. The reactors contain the fuel rod containing uranium and moderators that slow down the speed of neutrons. Fast moving neutrons are less effective at splitting atoms than slow moving neutrons. Water is commonly used as a moderator (Fig. 15.14).

In the production of electricity, the heat produced in a nuclear reactor is used to convert water into steam as in the case of thermal power plants. The steam moves the turbines and generates electricity. After passing through the turbine, the steam is condensed and is returned to the reactor to be heated again (Fig. 15.15).

Need to Promote Non-Conventional Energy Sources:

The power hungry world has been clamoring for more and more energy for industrial and domestic purposes. The energy requirements of the world are bound to increase further, as population continues to explode and the developing countries make further progress in industry and lifestyle. This has led to the depletion of the conventional sources of energy at a much faster rate than before. If the present trend continues, the day is not far when the world will be stripped of all the conventional sources of energy. Thus, there is a pressing need to explore tap new sources of energy so that future generations do not inherit a dark planet.

In this regard, non-conventional energy sources need to be further explored, as there are certain advantages in their promotion such as:

i. They are abundant and renewable.

ii. They are nonpolluting and eco-friendly.

iii. They are the future energy source.

iv. Some of the non-conventional energy sources like wind, mini-hydel projects and geothermal energy can be cheaply exploited.

v. They can be exploited at the local level.

vi. Energy from biogas will be helpful in the rural areas, where conventional electricity has not yet reached.

Conservation of Energy:

All human societies require energy for transportation, heating, cooling, cooking, lighting and for agricultural and industrial use. The world energy supply depends on many different resources. Energy has become a prerequisite for modem day living and it influences all aspects of development of a nation. The developed countries are the major consumers of energy, but the developing countries also require more and more energy for their economic development.

Fossil fuels account for more than 90 per cent of global energy needs, but the problem is that they are non-renewable, i.e. they can be depleted. Though non-renewable sources of energy are being constantly developed, there is a global need to increase energy conservation, so as to minimize the depletion of non-renewable resources.

Conservation of energy refers to the judicious and controlled use of energy.

Conservation of energy can be brought about by the following three main factors:

i. Efficiency in production

ii. Efficiency in transportation

iii. Proper utilization

Efficiency in Production:

This involves designing equipment so as to yield more energy output from a given amount of energy input. Energy conservation is vital as it provides saving in a ratio of 1:3. For example, three units of fuel are required to produce one unit of electricity. Two-thirds of energy is wasted as heat.

There is an urgent need to design equipment’s to capture and use this heat, which otherwise pollute the atmosphere or water as thermal pollution. The term cogeneration refers to the process that utilizes this heat energy. Through cogeneration, the overall efficiency of a typical thermal power plant can be increased from 33% to as much as 75%.

Cogeneration also involves the production of electricity as a by-product from industrial processes that produce and use steam. New power plants, boilers and other energy conversion equipment’s should be built to ensure maximum efficiency.

Efficiency in Transportation:

The transport sector accounts for the major consumption of petroleum, especially in the developed countries.

Increase in the prices of petroleum has encouraged the conservation of energy in the transport sector, which can be brought about by the following measures:

i. New engine technologies to get more mileage per litre of petrol

ii. Using more fuel efficient smaller personal automobiles

iii. Encouraging use of engines that run on natural gas

iv. More reliance on electric batteries or highly efficient fuel cells

v. Using other modes of transportation like bicycles and also car-pooling and public transportation

vi. Checking unnecessary travel by fuel consuming automobiles

Proper Utilization:

As the resources for energy are limited and generation of energy is a costly affair, it is the responsibility of every individual to make personal efforts for proper energy utilization. Wastage of energy should be checked at every step, as wasting energy means depleting the natural resources. Energy conservation should become a habit and part of our everyday life.

It can be brought about in the following ways:

i. In the household, turning off the fans, switching off unnecessary lights and other appliances when not in use can conserve energy.

ii. Buildings should be designed in such a way that does not consume more energy for heating or cooling; and may use the natural air and light.

iii. Old technology should be replaced with more energy efficient technologies.

iv. Huge losses of electricity occur during transmission from power plants to the consumers. This should be minimized by using better conductors and transformers.

Future Sources of Energy:

Apart from the conventional and non-conventional sources of energy, research is being done to look for even more energy sources.

Some of the new energy sources that can have future implications are given below:

Hydrogen:

Hydrogen gas is considered as the fuel of the future. It can be used in a similar way as fossil fuels are used. However, it is still largely in the experimental stage.

Advantages:

i. It is a high-energy fuel.

ii. It is a potentially unlimited fuel supply source if produced from water; currently made from natural gas.

iii. If produced from water using solar energy and then used in fuel cells, it would be a zero emission technology.

iv. Produces no carbon dioxide. Disadvantages

v. Highly explosive, though less dangerous than gasoline.

vi. Costly and difficult to produce and store.

Alcohol:

Certain types of biomass can be fermented into alcohols (ethanol / methanol), which can be used as fuels. These can be produced from carbohydrate rich substances like sugarcane, potatoes, sugar beet, etc. and also from woods and grains. Gasohol is a common alcohol based fuel, which is a mixture of ethanol and gasoline.

Advantages:

i. It is a clean, non-polluting fuel.

ii. It can be made from natural gas and other renewable resources.

iii. It can be used in conventional engines with some minor changes.

Disadvantages:

i. Highly corrosive and can damage the engine.

ii. Production is not adequate to replace fossil fuels.

iii. It has low energy content than gasoline.

Fuel cells:

As automobiles consume most of the petroleum and are also a major contributor of air pollutants, research is being done to generate power using environmental friendly technology within the vehicle itself Fuel cells are power-generating systems that produce electricity by combining fuel and oxygen in an electrochemical reaction. Fuel cells can run on methanol, ethanol, natural gas and hydrogen.

Advantages:

i. Highly efficient, as chemical energy is directly converted to electrical energy.

ii. Harmful emissions are absent or negligible.

iii. Well suited for powering automobiles. Disadvantages

iv. Experiments are still in their infancy.

v. Use of hydrogen in fuel cells is difficult to attain under the present technology.

Optimizing Energy Utilization:

The optimal use of available energy resources and its proper utilization will contribute to a large extent in the conservation of energy. This can be done both by man and machines by making concerted individual efforts to stop the wastage of energy, and similarly by enhancing the efficiency of the machines and energy consuming devices.

Some of the important steps that the Indian Government has taken in this regard are briefly given below:

Smokeless Chulhas:

In the rural areas, biomass is the most frequently used source of energy for cooking purposes. Biomass, consisting mainly of wood, barks, sawdust, cow-dung cakes, straws, etc. are burnt in open furnaces called chulhas. These chulhas are inefficient and cause much loss of energy. Moreover, they produce a lot of smoke causing indoor pollution. To overcome this problem, new chulhas with long chimneys have been developed, which are more efficient and smokeless.

Liquefied Petroleum Gas (LPG):

Liquefied Petroleum Gas (LPG) is a mixture of liquefied gases such as propane and butane. It is obtained from natural gas or petroleum. The natural gas is converted into liquid form, under high pressure. LPG is then vaporized for use as a heating or engine fuel. LPG is now commonly used as a cooking fuel in almost all the urban households. There is an urgent need to promote its use in the rural areas, as it is more efficient, and also to save the rural population from the ill effects of wood burning.

Compressed Natural Gas (CNG):

It is presently being used as automobile fuel in most of the developed countries, and is gradually replacing conventional petrol and diesel in vehicles. It is less polluting for the environment. The Delhi Government, in 2004, made it mandatory for city buses to run in CNG.

Industry:

In India, the industrial sector consumes most of the energy. So the machines and tools need to be properly maintained to make them more efficient.

Agriculture:

Wastage of energy in the agricultural sector needs to be minimized by using better implements, pumps and motors.