Chapter 11: Conventional Sources Of Energy
Long before there was anyone to burn it, the coal India uses today was a living forest floor. Plant matter piled up in swamps, in broad deltas, on coastal plains and in basin lowlands, faster than it could rot away. Sediment settled over it, and more sediment settled over that. The weight of the overlying layers, helped by movements of the earth itself, pressed and heated the buried mass until it changed chemically. What went in as wood came out as rock — a combustible rock made largely of carbon, between 60 and 90 per cent of it by weight.
In India this happened in two great episodes, far apart in time. One set of rock sequences, called Gondwana, is a little over 200 million years old. The other, the Tertiary deposits, was laid down much later, about 55 million years ago. That gap in age still shows up as a difference in quality at the mine face today.
India now holds a coal reserve of 344.02 billion tonnes and is the second largest producer of coal in the world after China. About 72 per cent of the electricity in the country is generated from it. Every switch flipped in an Indian home reaches back to that swamp.
Diagram
Fig. 11.A1 Caption: Buried plant matter turns into coal when the weight of overlying sediments presses and heats it for millions of years. Brief: Four-stage cross-section from left to right — swamp with living vegetation, buried vegetative layer under water, thickening sediment layers above with downward pressure arrows, compressed coal seam at depth; label each stage, mark ‘increasing depth and pressure’ with a downward arrow at the right.
11.1 Coal
Conventional sources of energy are those which people have used for a long time and are still tapping and using abundantly. Four of them are studied in this chapter — coal, petroleum, natural gas and hydel power. Except for hydel power, all of them are non-renewable, they cause pollution, and in the longer run they cost more than renewable sources of energy.
Coal is a combustible solid stratified rock made of organic and mineral matter. It is composed of carbon (60 to 90 per cent), hydrogen (1 to 12 per cent), oxygen (2 to 20 per cent) and nitrogen (1 to 3 per cent), along with small amounts of phosphorus and sulphur. It occurs as a sedimentary rock, in association with carbonaceous shale, sandstone and even fine clay.
How Coal Is Formed
Coal is formed by the accumulation of plant matter in swampy areas, broad deltas, coastal plains and basin lowlands. This vegetative matter was then subjected to geological processes that changed it both physically and chemically.
The mass of vegetative matter was probably changed into coal by heat and pressure. That heat and pressure came from the increasing weight of the sediments piling up above it, and also from the movements of the earth.
The Four Varieties Of Coal
Coal is classified by how much carbon, moisture and volatile matter it holds. Volatile matter is the part of the coal that escapes as gas when it is heated, so a coal rich in it burns fast and smokily. Depending on these amounts, four varieties are recognised. (a) Anthracite coal is the hardest and ranks highest among the varieties. It is shiny and lustrous, almost jet-black, and so completely compressed that it shows no banded structure. (b) Anthracite has a carbon content of 90 per cent, burns slowly and without smoke, burns for a long time and leaves very little ash behind. Its calorific value — the heat given out when a fixed quantity of the fuel is burnt — is high, which is why it is preferred for domestic purposes across the world. (c) Bituminous coal is hard, black and compact, and makes up almost 80 per cent of the world’s total coal output. It varies greatly in composition, with a carbon content ranging from 50 to 80 per cent. (d) Lignite, also known as ‘brown coal’, is a lower grade coal. It comprises 40 per cent of carbon along with a good deal of moisture and less of combustible matter. (e) Peat represents the first stage in the transformation of wood into coal, and has the least carbon content of all, which makes it inferior to the other three varieties. It is an accumulation of vegetable matter that has undergone varying degrees of decomposition and carbonisation.
Bituminous coal is not one thing but a family, and the chapter separates three members of it. Steam coal, with a carbon content of 80 per cent, is the best of the bituminous coals. Household coal, black and lustrous with a fine carbon content varying from 50 to 80 per cent, has the widest use for domestic purposes in India simply because it is easily available.
The third member matters most to industry. Coking coal is high-grade bituminous coal, and its special value lies in what happens when it is heated in coke ovens — it fuses into coke, a hard, almost pure carbon fuel that is an important ingredient in the smelting of iron and steel in blast furnaces.
Diagram
Fig. 11.1 Caption: Bituminous coal is hard, black and compact. Brief: Close photograph of broken lumps of bituminous coal; show the hard, blocky fracture and the dull-to-lustrous black surface clearly.
The lower-grade varieties look different to the eye, and the difference is visible in the second photograph.
Diagram
Fig. 11.2 Caption: Lignite is browner and duller than bituminous coal because it holds far less carbon and much more moisture. Brief: Close photograph of a lump of lignite coal; show the brownish-black colour, the earthy texture and the visible woody grain.
The four varieties therefore form a single ladder, and the rung a coal sits on is decided by how far the change from plant matter has been carried.
Flowchart
Fig. 11.A2 Caption: The four varieties are stages of one change, arranged by rising carbon content. Nodes: plant matter → peat (least carbon, first stage) → increasing heat and pressure, moisture and volatile matter driven off → lignite (40 per cent carbon) → increasing heat and pressure → bituminous (50 to 80 per cent carbon) → branches into steam coal (80 per cent carbon), household coal (50 to 80 per cent carbon) and coking coal (heated in coke ovens → coke → blast furnace) → increasing heat and pressure → anthracite (90 per cent carbon, no banded structure)
Where Each Variety Is Found And What It Is Used For
Each of the four varieties sits in a different part of India and does a different job there. (a) Anthracite is found in Jammu and Kashmir only, in the far north, and India’s reserves of it are not sufficient. Being a smokeless fuel with a high calorific value it is ideal for domestic use, and it is also used for metallurgical processes and in the iron and steel industry. (b) Bituminous coal is found mainly in the Gondwana coalfields. It is used to produce coke, coal gas and steam coal, and is therefore called coking coal; because it feeds factories it is also called industrial coal. (c) Lignite is found in Tamil Nadu, Rajasthan, West Bengal, Kerala and Puducherry, and is used for the generation of electricity. (d) Peat occurs in patches on the Nilgiri mountains in the south, in the Kashmir valley and in the swampy areas of the coastal plains. Besides generating energy it is used as a filter and absorbent material for toxic substances, and is widely used as a plant substrate as well as bedding material for cattle.
11.1.1 Distribution
India has a total coal reserve of 344.02 billion tonnes and is the second largest producer of coal in the world after China. About 72 per cent of the electricity in India is generated from coal, a figure released by the Ministry of Coal on 21 December 2023. The oldest coalfield in India is at Raniganj in West Bengal, and the largest is at Jharia in Jharkhand.
In India, coal occurs in rock sequences of mainly two geological ages. The Gondwana sequences are a little over 200 million years in age, while the Tertiary deposits were formed in a much later geological epoch, about 55 million years ago.
That difference in age decides what India actually has. India does not have extensive deposits of the highest grade anthracite coal, which carries 90 per cent carbon. What is mostly available is the coal of the Gondwana fields, which is mainly of bituminous quality, with 50 per cent to 80 per cent of carbon.
11.1.1.1 Gondwana Coalfields
The Gondwana fields account for 98 per cent of the total reserves of coal in India. Gondwana coal is almost free from moisture and contains sulphur and phosphorus only in small variable quantities, which is what makes it fit for steel plants.
It is mined from deep collieries — a colliery is a coal mine together with the buildings and machinery at its mouth — and the coal drawn from them goes to the steel industry.
The Gondwana coalfields are largely confined to river valleys, such as those of the Damodar, the Mahanadi and the Godavari. The major resources of Gondwana coal lie in coalfields occupying the Indian heartland, in the States of West Bengal, Jharkhand, Odisha, Chhattisgarh, Madhya Pradesh, Maharashtra, Uttar Pradesh, Andhra Pradesh and Telangana. These coalfields account for four-fifths of India’s coal reserves.
Table 11.1 sets out those States against the valley that carries their fields, and the individual coalfields in each.
11.1.1.2 Tertiary Coalfields
The Tertiary coal of India, being much younger, never underwent the same degree of change. Compared with Gondwana coal it has a higher moisture content and more sulphur, and its calorific value is less.
Tertiary coalfields are found in Assam, Arunachal Pradesh, Meghalaya, Nagaland and Kashmir. Besides these, brown coal or lignite occurs in the coastal areas of Tamil Nadu and Gujarat and in the inland basin of Rajasthan. The Neyveli lignite field in Tamil Nadu is the largest lignite deposit field in South India.
11.1.2 Advantages
The main advantages of coal are the following. (a) Coal is used as a source of power for running machines, trains, ships and dynamos. (b) Coal is used for manufacturing iron and steel. (c) Coal is used as a source of direct heat and energy for domestic purposes, in the potteries and for building materials such as cement, the burning of bricks and tiles, and in iron and brass foundries. (d) Coal is used as raw material in thermal power plants, which is how the greater part of India’s electricity is produced.
11.1.3 Disadvantages
Set against those uses are five real limits, and most of them are limits of quality and cost rather than of quantity. (a) The calorific value of the coal found in India is low, so a tonne of it yields less heat than a tonne of a higher grade coal would. (b) Coal reserves are scattered in small amounts in India. (c) The cost of production and of transportation of coal is quite high. (d) There are limited reserves of coal in India. (e) Large scale pollution is caused at the site of mining and at the place of use.
11.2 Petroleum
The word ‘petroleum’ comes from two words, ‘petra’ which means rock and ‘oleum’ which means oil. Petroleum therefore means ‘rock oil’, and the name is exact — it is a liquid that is drawn out of rock.
Petroleum is a complex mixture of hydrocarbon compounds. There is not even the tiniest part of crude petroleum which goes waste or remains unused, and that is why petroleum is called ‘liquid gold’.
The same substance is met in three different states, and each state carries a different name. The liquid petroleum is called crude oil, the petroleum gas is called natural gas, and the semi-solid to solid forms of petroleum are known as asphalt, tar, pitch and bitumen.
Where It Sits Underground
Petroleum is found in underground reservoirs, held in sedimentary rock formations such as sandstone, shale and limestone. These rocks are porous, so the oil is not lying in a pool but soaked into the rock, the way water sits in a sponge.
In some wells, crude oil is found along with natural gas and water. The three separate by weight, which is why a single well can yield gas as well as oil.
Petroleum is not burnt in the form in which it comes out of the ground. Petrol, diesel, kerosene, tar, Liquefied Petroleum Gas (LPG), lubricants and paraffin wax are some of the products obtained during the refining process.
11.2.1 Advantages
When drilled from the earth, crude petroleum is a viscous dark liquid made up of many hydrocarbons. It is used both as a fuel and as a raw material, and in liquid form it can be transported through pipes or by vehicles.
Petroleum has high density; one kilogram of oil can generate 10,000 kcal of energy. A kilocalorie is the heat needed to raise the temperature of one kilogram of water by one degree Celsius, so this is a very large amount of heat from a very small mass. It has a broad area of applications as a source of energy, and some of these are the following. (a) It is used as fuel, and its fuel derivatives include ethane, diesel, gasoline, jet fuel, kerosene and LPG. By providing a lubricant and a compact, convenient fuel, petroleum plays a major role in transportation on land, on sea and in the air. (b) Petroleum after refining is used as raw material for the production of various petrochemical products, such as synthetic rubber, synthetic fibre, polystyrene, PVC, phenol, gasoline, carbon black, printing ink, film photography, cosmetics, paints, varnishes, lubricating oil and paraffin wax. (c) Petroleum is used for power generation. In India this use is confined to a few thermal stations which are located close to oil wells and refineries, and to diesel and gas turbine stations.
The map below carries the coal, oil and refining story of India together, so that the mines, the oilfields and the refineries can be read against one another.
Map
Map 11.1 Caption: Coal, oilfields and refineries in India. Brief: Political outline of India showing the full extent of India as officially defined, drawn at a scale of 1:20,000,000; shade the coalfields, mark oilfields and refineries with the separate symbols shown in the key headed ‘Mineral Fuels’; number the coalfields against the coalfield reference list; label the Arabian Sea, the Bay of Bengal, the Indian Ocean, the Andaman Sea, Mumbai High and the Tropic of Cancer.
11.2.2 Disadvantages
Petroleum’s usefulness is matched by five drawbacks, and the first of them is the one that governs the rest. (a) Petroleum is a natural fossil fuel and is non-renewable, so its availability is limited. With ever-increasing demand, petroleum resources are fast depleting. (b) Extracting and burning petroleum generate greenhouse gases, which contribute to environmental pollution and global warming. (c) Its costs are quite high, because of its limited supply and high demand. (d) It is highly inflammable and can cause fires. (e) During extraction from the sea or during transportation, if oil spills into water it can pollute the water and cause the death of a number of marine animals.
11.2.3 Oil Refineries
Crude oil is refined and processed in refineries, where the mixture is separated into groups of products of different weights. The lightest come off first and the heaviest last.
The light distillates are gasoline, LPG and naphtha. The middle distillates are diesel and kerosene. The heavy ends are fuel and lubricating oils, bitumen and petroleum coke.
Flowchart
Fig. 11.A3 Caption: Refining separates one crude oil into three groups of products, from the lightest to the heaviest. Nodes: crude oil → refinery → branches into light distillates (gasoline, LPG, naphtha), middle distillates (diesel, kerosene) and heavy ends (fuel oil, lubricating oils, bitumen, petroleum coke)
Who Owns The Refineries
In India most of the refineries are in the public sector, with five in the private and/or joint sector. The Reliance Petroleum Limited refinery at Jamnagar in Gujarat was the first refinery in the private sector.
Why They Stand Where They Stand
Most of the refineries are located near the oilfield or near the coast. Two reasons decide this. The first is cost — moving crude a long way inland is expensive. The second is safety, because crude oil is inflammable and carrying it deep inside the country raises the risk.
Some of the important refineries of India are given in Table 11.2, with the State each lies in, the year it was commissioned and the work it does. A few entries state capacity in MMTPA, which stands for million metric tonnes per annum — the mass of crude the refinery can process in a year.
Read the commission-year column down the table and a century of change appears in it, from a single refinery beside an Assam oilfield in 1901 to coastal refineries built to handle crude arriving by sea. The function column tells you where each one gets its crude, and that is the clearest guide to why it was built in that State.
11.2.4 Distribution
The entire oil production of India so far comes from three areas — the Assam-Arakan belt, the Gujarat-Cambay belt and the Mumbai High offshore zone.
The first belt runs from the extreme north-east of Assam to the eastern border of the Brahmaputra and Surma valley. The second belt extends from Mehasana in Gujarat in the north to the continental shelf off the coast of Ratnagiri in Maharashtra in the south. A continental shelf is the shallow, gently sloping floor of the sea just off a coast, before the deep ocean begins.
In order of importance, the main areas of mineral oil deposits are the following.
Mumbai High
Mumbai High lies in Maharashtra, about 176 km off Mumbai in the Arabian Sea. This huge oil deposit was struck in 1974, and it is the most productive oilfield in India, with a reserve of 5 crore tonnes of oil. A crore is ten million, so this is a reserve of fifty million tonnes.
The name, then, records a piece of geology rather than a piece of geography — it describes the shape of the rock, not a position on the map. It also explains the cost. Oil that lies 1,400 m below the sea floor, 176 km from land, cannot be reached by an ordinary rig, and a self-propelled jack-up platform must be built, moved and held in place before a single tonne is lifted. That expense is one reason petroleum is a costly fuel even where a country has its own field.
Oilfields Of The Eastern Region
India’s oldest and most important oil bearing area, in the eastern part of the Himalayas, is Assam. The Digboi oilfield, situated in the Tinsukhia district of Assam, is the oldest oilfield and also the site of the oldest oil refinery in India.
Assam’s oil is not confined to Digboi. Moran, Bappapung, Hausanpung and Hugirijang also have oilfields.
Oilfields Of The Western Region
In Gujarat, the Cambay basin is the site of the main oil bearing sand. The other oilfields of importance in Gujarat are Kalol, Koyali, Kosamba, Sanand, Kathana, Ankleshwar and Navgaon.
Besides these oilfields, a number of potential oil bearing fields have been discovered in the States of Tripura, Punjab, Nagaland, Gujarat, West Bengal and Jammu and Kashmir, and also in the Kaveri, the Krishna and the Godavari basins in the south.
11.3 Natural Gas
Natural gas occurs in association with mineral oil, and therefore an oilfield yields natural gas almost invariably. It is mainly composed of methane, which makes up 95 per cent of it, with small amounts of propane and ethane. Methane is the simplest of the hydrocarbons, and it is what burns when a gas flame is lit.
Natural gas is a fossil fuel. Its deposits mostly accompany oil deposits because it has been formed in the same way — by the decomposing remains of dead animals and plants buried under the earth.
The Gas That Reaches A Kitchen
The gas supplied for household use is called LPG, or Liquefied Petroleum Gas, and it is a by-product obtained after refining crude oil. Its main component is butane, the others being propane and ethane.
LPG is odourless, and yet the LPG in our domestic gas cylinders gives a foul smell. That smell is put there on purpose. It is due to ethyl mercaptan, a foul smelling gas added to LPG so that any leakage from the cylinder can be detected instantaneously.
Diagram
Fig. 11.3 Caption: Liquefied Petroleum Gas is stored under pressure in sealed steel tanks and cylinders. Brief: Photograph of a large horizontal LPG storage tank at a bulk plant, with the pipework and safety valves at one end visible and the LPG marking legible on the side.
In many places, LPG is being replaced by Piped Natural Gas, or PNG, which is not stored in a cylinder like LPG but is continuously supplied through a pipeline from the source. The difference is one of delivery rather than of chemistry — a cylinder has to be carried and changed when it runs empty, while a pipeline keeps supplying as long as the source does.
The Gas That Runs A Vehicle
The gas used for running vehicles is known as CNG, or Compressed Natural Gas, and as the name suggests it is obtained from natural gas. It is being used as an alternative to petrol and diesel for vehicles.
Delhi has totally switched over to CNG for its public transport vehicles, and the taxis, buses and autorickshaws of the city run on this fuel.
Flowchart
Fig. 11.A4 Caption: One gas reaches the user in three different forms, each named for how it is delivered or used. Nodes: natural gas (methane 95 per cent, with propane and ethane) → branches into LPG (by-product of refining crude oil, mainly butane, filled into cylinders, ethyl mercaptan added as a warning smell), PNG (same gas piped continuously from the source, no cylinder) and CNG (compressed for vehicles, used in place of petrol and diesel)
11.3.1 Distribution
Over three-fourths of India’s natural gas comes from Mumbai High. The rest is produced in Assam, Tamil Nadu, Rajasthan and Tripura.
11.3.2 Advantages
Natural gas is the cleanest of the three fossil fuels in this chapter, and most of its advantages follow from what it is made of. (a) Compared to petroleum or coal, natural gas is an eco-friendly fuel as it causes less damage to the environment. It is made up of methane and results in less carbon emissions. (b) It is easier to preserve than other fuels, and can be stored and transported through pipelines, small storage units, cylinders or tankers on land and sea. (c) It can be piped into houses for heating and cooking purposes and for running a variety of appliances. (d) It is a cleaner and cheaper fuel than diesel or gasoline. (e) It is lighter than air and tends to disperse when there is a leakage, unlike propane, which being heavier than air collects into explosive pockets. (f) It is used for producing hydrogen and ammonia for fertilizers, and some paints and plastics.
11.3.3 Disadvantages
Against these come five drawbacks, and the first of them is a matter of safety rather than of supply. (a) Leaks of natural gas are difficult to detect and are very dangerous. Such leaks may cause explosions or fire, and when inhaled the gas is highly toxic; leakage can have serious consequences, as methane is more toxic than carbon dioxide. (b) For use as fuel, every constituent except methane has to be extracted. This processing results in many by-products — hydrocarbons such as propane and ethane, sulphur, water, helium, nitrogen and carbon dioxide. (c) Like all fossil fuels, natural gas, though found in abundance, is non-renewable and hence likely to be exhausted at some point of time. (d) The infrastructure for natural gas production and distribution is fairly expensive, and includes separate plumbing systems and specialised tanks. (e) Natural gas, when used as fuel in vehicles, provides less mileage than gasoline.
11.4 Hydel Power
Electricity generated from water is called hydel power or hydroelectricity. It is produced from the energy that is released when water falls from a high level with great force.
How Falling Water Becomes Current
The water flowing in a river is collected by constructing a big dam, where the water is stored. It is then allowed to fall from a height.
The blades of the turbine located at the bottom of the dam move with the force of that falling water. The turning blades in turn rotate the generator, and the generator produces electricity.
Flowchart
Fig. 11.A5 Caption: A dam turns the fall of water into electric current in four steps. Nodes: river water flows → dam stores it at a high level → water is allowed to fall from that height → falling water strikes the turbine blades and turns them → turbine rotates the generator → electricity is produced → water continues downstream and back to the river
Hydro power does not cause any pollution, it is renewable, and normally the hydro power projects are multi-purpose projects, which are used to control floods and for irrigation, navigation and other purposes. A multi-purpose project is one built to do several jobs at once instead of only generating power.
The total power generation capacity of a hydroelectric plant depends on two things — the head of water and the volume of water flowing towards the turbine. The head is simply the height through which the water falls, so a taller fall and a fuller flow both mean more power.
Hydroelectricity is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste, and it has a considerably lower output of the greenhouse gas carbon dioxide (CO₂) than fossil fuel powered energy plants.
India was one of the pioneering countries in establishing hydro-electric power plants. The power plant at Darjeeling, in the hills of northern West Bengal, was established in 1898, and the one at Shimsha, also called Shivanasamudra, in Karnataka, in 1902.
11.4.1 Advantages
The advantages of hydel power are the following. (a) Hydel power is a clean, non-polluting source of energy. The water used does not contaminate air or water by producing harmful wastes or poisonous by-products. (b) It does not produce any greenhouse gases, and so protects us from the harmful effects of global warming. (c) It is a renewable source of energy, which can be used again and again. (d) The dams built to produce hydroelectricity help to conserve and store water. (e) It is economical and sustainable, as it saves on fossil fuels and is cheaper than electricity produced from fossil fuels and from nuclear power.
11.4.2 Disadvantages
The costs of hydel power are not paid at the power house but at the site of the dam, and there are four of them. (a) The cost of building dams for producing hydroelectricity is quite high. (b) Building a large dam alters the natural water-table level, which is the level below the ground at which the rock and soil are saturated with water. (c) Building a large dam can cause serious geological damage, such as triggering earthquakes in the area. (d) Building dams to produce electricity displaces many people from the area, and disturbs their life physically, mentally and psychologically.
11.4.3 Bhakra Nangal Dam
The Bhakra Nangal Project is a joint venture of the Punjab, Haryana and Rajasthan Governments. The two dams, one at Bhakra and another at Nangal, are together referred to as the Bhakra-Nangal Project.
The Bhakra-Nangal project comprises four parts. (a) Two dams, at Bhakra and at Nangal. (b) The Nangal hydel plant. (c) The power houses. (d) The Bhakra canal system.
The Four Parts In Detail
Each part does a distinct job, and together they make the project a multi-purpose one. (a) The Bhakra Dam is built across the Sutlej river near the border between Punjab and Himachal Pradesh. Its reservoir, 90 km long, is known as Gobind Sagar, and it has a storage capacity of 9.3 billion cubic metres. (b) The Nangal Dam has been constructed at Nangal on the river Sutlej in Punjab, and it supplies water to the Bhakra irrigation canals. (c) Four power houses, at Ganguwal, at Kotla, on the left bank and on the right bank, have a combined installed capacity of 1204 MW. A megawatt is a million watts, so this is a large station by any measure. (d) The Bhakra Canal System provides irrigation facility to 10 million acres of land in Punjab, Haryana and Rajasthan.
The aims of these projects are three — to provide water for irrigation, to generate hydro-electricity, and to prevent flooding from the Sutlej-Beas rivers.
Diagram
Fig. 11.4 Caption: The Bhakra Nangal Dam holds back the Sutlej and releases it in a controlled flow through the year. Brief: Photograph of the Bhakra dam wall across the Sutlej with the reservoir behind it and water discharging at the foot; show the full height of the concrete wall and the forested valley sides.
How The Project Works Through The Year
The dam holds excess waters during the monsoon and provides a regulated release during the year. That single act of storing and releasing is what makes the project serve three aims at once.
It provides irrigation to fields in Punjab, Haryana and Rajasthan. The Bhakra main line is a canal that mostly supplies irrigation water to Haryana.
The Bhakra Dam has ten power generators, with five on each side. The power generated at the dam is distributed among the partner states of Punjab, Haryana, Rajasthan, Himachal Pradesh, Chandigarh and Delhi.
Three additional power plants stand on the two canals, the Nangal Hydel Channel and the Anandpur Sahib Hydel Channel, which originate from the Nangal dam. Water leaving the reservoir therefore generates power more than once on its way to the fields.
What the sequence shows is that the three aims are not three separate schemes but one store of water used three times over. The flood that had to be held back in July becomes the head of water that drives the turbines in March and the canal supply that reaches a field in Haryana afterwards. It also shows why the same design is argued about: a store that large needs a valley to sit in, and the reservoir covers whatever was in that valley before.
11.4.4 Hirakud Dam
The Hirakud Dam is built across the Mahanadi River, about 15 km from Sambalpur in Odisha. It is one of the first major multi-purpose river valley projects started after India’s independence.
The dam regulates the flow of the Mahanadi river and produces hydroelectricity through several hydroelectric plants. It also helps control floods in the Mahanadi delta, and it irrigates 75,000 sq km of land.
Diagram
Fig. 11.5 Caption: The Hirakud Dam regulates the Mahanadi and protects the delta downstream from flooding. Brief: Photograph of the Hirakud dam structure across the Mahanadi, showing the sluice gates and the lifting gear along the crest, with the stored water on one side.
The project provides kharif and rabi irrigation in the districts of Sambalpur, Bargarh, Bolangir and Subarnpur. Kharif is the crop sown with the arrival of the monsoon, and rabi the crop sown after it, so a supply that serves both means water in the canals in two different seasons.
The water released by the power plant is not allowed to run to waste. It is used to irrigate areas in the Mahanadi delta, so the same water generates electricity first and waters a field afterwards.
11.5 Summary
- Conventional sources of energy are those which people have used for a long time and are still tapping abundantly — coal, petroleum, natural gas and hydel power.
- Except for hydel power, all of them are non-renewable, cause pollution and cost more in the longer run than renewable sources.
- Coal is a combustible solid stratified rock of organic and mineral matter, carrying 60 to 90 per cent carbon along with hydrogen, oxygen, nitrogen and small amounts of phosphorus and sulphur.
- Coal formed from plant matter that accumulated in swampy areas, broad deltas, coastal plains and basin lowlands, and was changed by heat and pressure from the weight of overlying sediments and the movements of the earth.
- Coal is classified by its carbon, moisture and volatile matter into four varieties.
- Anthracite has 90 per cent carbon, burns slowly without smoke, leaves little ash and has a high calorific value; it is found in Jammu and Kashmir only.
- Bituminous coal has 50 to 80 per cent carbon and makes up almost 80 per cent of world output; its coking variety fuses into coke for iron and steel smelting.
- Lignite, or brown coal, has 40 per cent carbon with much moisture, and is used to generate electricity.
- Peat is the first stage of the change from wood to coal and has the least carbon of all.
- India has a coal reserve of 344.02 billion tonnes and is the second largest producer after China, with about 72 per cent of its electricity generated from coal.
- Raniganj in West Bengal is the oldest coalfield and Jharia in Jharkhand the largest.
- India’s coal lies in rock sequences of two ages, and the difference in age is a difference in quality.
- Gondwana sequences are a little over 200 million years old, hold 98 per cent of the reserves, are almost free from moisture and are mined from deep collieries for steel plants.
- Tertiary deposits are about 55 million years old and have more moisture and sulphur with a lower calorific value.
- Coal is used for power, for iron and steel, for direct heat in homes, potteries, cement, bricks and foundries, and as raw material in thermal power plants; against this, Indian coal is low in calorific value, scattered, limited, costly to produce and transport, and polluting at the mine and at the place of use.
- Petroleum means ‘rock oil’ and is a complex mixture of hydrocarbons found in underground reservoirs in sandstone, shale and limestone; nothing in it is wasted, which is why it is called ‘liquid gold’.
- Refining yields petrol, diesel, kerosene, tar, LPG, lubricants and paraffin wax.
- One kilogram of oil can generate 10,000 kcal of energy, and refined petroleum also feeds the petrochemical industries.
- It is non-renewable and fast depleting, generates greenhouse gases, is costly, is highly inflammable, and can kill marine life when spilt.
- Most refineries stand near an oilfield or near the coast, to cut the cost of transport and the risk of moving an inflammable liquid inland.
- India’s oil comes from the Assam-Arakan belt, the Gujarat-Cambay belt and the Mumbai High offshore zone.
- Mumbai High, about 176 km off Mumbai, was struck in 1974 and is the most productive field, worked from over 1,400 m by the platform ‘Sagar Samrat’.
- Digboi in Assam is the oldest oilfield and the site of the oldest refinery; the Cambay basin holds Gujarat’s main oil bearing sand.
- Natural gas occurs with mineral oil, so an oilfield yields gas almost invariably; it is mainly methane, with small amounts of propane and ethane.
- LPG, a by-product of refining crude, is mainly butane, and ethyl mercaptan is added to it so that a leak is smelt at once.
- PNG is the same gas piped continuously instead of stored in cylinders, and CNG is the compressed form used in vehicles, as in Delhi’s public transport.
- Over three-fourths of India’s natural gas comes from Mumbai High, the rest from Assam, Tamil Nadu, Rajasthan and Tripura.
- It emits less carbon and is easy to store and pipe, but leaks are hard to detect and dangerous, the infrastructure is expensive, and it gives less mileage in vehicles.
- Hydel power is electricity generated by water falling from a height onto turbine blades, which rotate a generator.
- The capacity of a plant depends on the head of water and the volume flowing to the turbine.
- It is clean, renewable and cheap to run, but dams are costly to build, alter the water-table, can trigger earthquakes and displace people.
- The Bhakra Nangal Project, a joint venture of Punjab, Haryana and Rajasthan, holds the monsoon flow of the Sutlej and releases it through the year.
- Gobind Sagar, its 90 km reservoir, stores 9.3 billion cubic metres of water.
- Four power houses carry a combined installed capacity of 1204 MW, and the canal system irrigates 10 million acres.
- The Hirakud Dam across the Mahanadi, about 15 km from Sambalpur in Odisha, was one of the first major multi-purpose projects after independence, controlling floods in the delta and irrigating 75,000 sq km.
Flowchart
Fig. 11.A6 Caption: The four conventional sources, sorted by what they are and what limits each one. Nodes: conventional sources of energy → branches into fossil fuels and hydel power; fossil fuels → coal (peat → lignite → bituminous → anthracite, rising carbon; Gondwana and Tertiary fields; burnt in thermal plants) and petroleum (crude oil → refinery → light distillates, middle distillates, heavy ends) and natural gas (found with oil → LPG, PNG, CNG); all three fossil fuels → non-renewable and polluting → reserves fall as demand rises; hydel power → river stored behind a dam → water falls onto turbine → generator → electricity → renewable and non-polluting, but the dam floods a valley and displaces people
What This Chapter Cannot Tell You
The figures in this chapter are national totals, and a national total hides its own geography. A reserve of 344.02 billion tonnes says nothing about which seam is thick enough to work, and a table of coalfields names them without saying how much any one of them produces or whether it is still being mined.
The data also belongs to particular years — the share of electricity from coal to a release of December 2023, the refinery list to the year each plant was commissioned. Read later, those numbers describe a moment rather than the present.
Nor does the chapter weigh the costs against each other. It states that dams displace people and that mining pollutes, but it gives no measure of either, so the choice between these sources cannot be settled from what is printed here. ## 11.6 Check Your Concepts
- Arrange the four varieties of coal in order of rising carbon content, giving the carbon percentage the chapter states for each, and explain what causes the carbon content to rise along that order.
- Study Table 11.1 and answer the following.
- Name the river valley in which the coalfields of Odisha lie.
- Name the two States whose coalfields lie in the Damodar valley.
- One valley appears against two different States. What does that tell you about where Gondwana coalfields are placed?
- The Bhakra-Nangal Project was built with three aims. Trace the path of the monsoon water that the Bhakra dam holds back, from the reservoir to a field in Haryana, and show at which points along that path each of the three aims is met.
- Table 11.2 gives the year each refinery was commissioned and the crude it works on. Name one thing the table does not tell you about a refinery, and explain why you would need that information before deciding which refinery is the most important in India.
- Give a geographical reason for each of the following.
- Anthracite is used for domestic purposes.
- Oil refineries are located close to oilfields or near ports.
- The location of coalfields is an important factor in industrial development.
- How is a Gondwana coalfield different from a Tertiary coalfield in terms of location and quality?
- Name the two coastal oil refineries, one on the west coast of India and the other on the east coast. Name one inland oil refinery. List the sources of crude oil for these refineries.
- On an outline map of India, mark and name two centres where each of these energy sources is found.
- Coal
- Petroleum
- Natural gas
- Hydel power