INTRODUCTION TO ENERGY & SOCIETYImportance of energy in our daily life:

Consider the beginning of a typical day. As we get out of bed, we’re probably concerned with whether we feel warm enough, with turning on lights so we can see, and with cooking something for breakfast.

All of these activities depend on energy. Many of us live in homes with electric heating; if not, natural gas or heating oil arc other popular choices. We rely on electricity for lighting. Most of us would use electric stoves or electric microwave ovens for cooking; the rest of us probably rely on gas stoves. Energy is the central topic of this course. Although we are introducing the word now1 we arc going to defer its formal definition until Chapter 2. For now, we’ll rely on an intuitive definition or understanding of energy.

Of course, cooking breakfast means that we have to have something to cook. Not many of us these days subsist entirely on what we can raise or catch ourselves. Having food available first requires planting, cultivating, and harvesting on farms. Most farmers use a variety of agricultural machinery that operates with gasoline or diesel fuel. The harvested food has to be transported to plants where it is processed or prepared and then packaged. Then the packaged food is transported to warehouses and stores for sale to us, the consumers. Transportation from farm to processing plant, and from processing plant to stores will use gasoline or diesel fuel. Various kinds of energy might be used in the processing of foods, including electricity, natural gas, and heating oil.

As we get dressed and begin to go about our daily routine, we depend on a huge variety of manufactured articles. Very, very few of us weave our own doth, turn logs into boards to make wooden articles, or make any of the other items we use throughout the day. Manufacturing begins with the production of raw materials, such as making metals from their ores. Many kinds of energy might be used in such operations, including electricity, heating oil, or coal. Then the raw materials have to be fabricated into useful articles. Fabrication might include molding casting, machining, or weaving (as but a few examples). Many of these operations use electrically powered machinery, and coal, heating oil or natural gas as heat sources. The manufactured articles then have to be transported to stores. Then on most days we must get ourselves out and around. If we walk or bicycle, we use energy from our own muscles for transportation. Cars or light trucks have gasoline engines or possibly small engines that use diesel fuel. Electric cars, or

hybrid electric/gasoline cars are coming onto the market too. If we take the bus, we are probably relying on diesel fuel or natural gas. Trains may have diesel locomotives or operate using electricity. Small airplanes may use gasoline as fuel; others use jet fuel.

Our manufacturing and transportation, in addition to the many uses of energy in the home for warmth, cooking and lighting, together consume prodigious quantities of energy (Figure 1.1). The key idea that should come from thinking about how we get through the day is this:

“ENERGY IS UBIQUITOUS IN OUR LIVES AND, IN FACT, IS SO COMMON THAT WE SELDOM EVEN THINK ABOUT IT”

For most of us it’s likely that we rely most often on two kinds of energy electricity and gasoline. We surround ourselves with electrical appliances and gadgets. Most of us own a majority of the items on this list: television set, microwave oven, stereo system, personal computer, electric razor, hair dryer, refrigerator, lamps for reading or study, coffee maker, electric clock, electric pencil sharpener, electric tooth brush, power tools, and radio. In the kitchen, for example, most people now expect to find a stove, a refrigerator, and, often, a dishwasher and a microwave oven. What else can we find in the ‘modern kitchen’? A coffee maker, an espresso machine, an electric can opener, a pasta maker, a bread maker, a crock pot, an electric carving knife, a toaster or toaster oven (or both), and a blender or food processor. If there’s a problem, it’s how to find counter space to use all this stuff or some place to store it, not whether or not there will be enough electricity to operate these gadgets.

The idea of even asking whether there would be ‘enough’ electricity to operate a gadget we’re buying when we got it home might sound silly. Almost invariably we simply assume that we can purchase and plug in a limitless number of electrically operated items. (Admittedly, there are occasional exceptions, particularly with large electrical appliances such as clothes dryers or electric stoves, or possibly with some hobby items such as electrically operated machinery for a home workshop.) Usually, if we think of any limit at all, it’s that we are limited by the number of electric outlets we have available for plugging items into. We can even solve that problem if we remember to buy some ‘cube taps’ (that let us plug three items into a single outlet) or outlet strips (that provide five or more electrical outlets from an original single outlet). Though it’s very unwise and perhaps even illegal in some localities, some of us probably even plug cube taps into outlet strips, or connect two or more outlet strips together.

Fig.1 Energy usage in a busy city

Our assumption about the eternal availability of essentially unlimited quantities of electricity is tested when there is a power failure. When the electricity supply suddenly fails, we might have a momentary bit of panic until we assure ourselves that we’re OK, but then many of us react to a power failure with a feeling of annoyance or anger. We were watching that TV show, or cooking that meal, or reading that book feeling that we could do those sorts of things as much as we wanted, any time we wanted, and now, suddenly— no electricity. It’s sometimes helpful to remember that not everyone in the world gets to enjoy a lifestyle based on assumptions we take for granted. There are places in the world where, if electricity is available at all, it is only ‘on’ for a certain period each day. In some places the use of electricity has been strictly rationed. For example, during the last years of the horrible dictatorship of Nicolai Cauciescu in Romania, each apartment or home was allowed one 25-watt light bulb. In other places, electricity does not exist at all, for instance, in rural regions of many of the impoverished nations in Africa and Asia.

We usually have the same cavalier attitudes toward gasoline. We expect that we can drive around without ever once worrying about whether we will be able to buy

gasoline whenever and wherever we need it, and as much as we want. (Probably only a few of those who recall the gasoline shortages during the oil embargoes of the 1 970s, or perhaps the gasoline rationing during the Second World War, may challenge this attitude.) Even at 2 am. on Christmas morning we can find someplace to buy gasoline. Gasoline seems to be as easily and widely available as water.

But, just as with electricity, it is helpful to remember that the assumptions we make about the availability of gasoline are not valid everywhere in the world. They apply only to the so-called developed or industrialized nations. Even within that small subset of the world’s nations, gasoline is cheaper in the United States than in virtually any other nation. In many industrialized nations, even those such as Japan or the western European countries with strong economies and modern industries, gasoline costs $3.30 per gallon. About the only countries in the world where gasoline is cheaper than it is in the United States are Venezuela, which has enormous domestic supplies of petroleum and Iraq, where the national economy has been grossly distorted by the United Nations sanctions following the 1990—91 Persian Gulf War.

Another way of illustrating our dependence on energy is to consider it from the other perspective: how we would live if electricity and fuels (especially petroleum products and natural gas) were not available any more.

• What would we eat? Probably the best we could do would be foods raised by ourselves or foraged in the woods. Many people living in large cities would probably starve. • How would we get around? We could use horses, if we had them. We could ride bicycles, until they broke or wore out. Most of us would be confined to an area that would be accessible by walking. Perhaps if we were lucky enough to live near the coast or near a navigable river, we could travel by boat—one that we paddled or rowed, or that used the energy of the wind to sail, or a steamboat that used wood as fuel.

• How would we stay warm? We could use firewood, if we had access to it and for as long as the wood lasted. A few clever persons might rig up solar energy collectors, or figure out how to use windmills or water wheels to operate electrical generators. • What would we use in our daily lives? When our clothes, tools, and utensils broke or wore out, we would have no replacements, except for things that could be made of wood (assuming we hadn’t burned it to stay warm), or wool or cotton

doth. • How would we regulate our days? Most of us would rise at dawn and go to bed at dark, because there would be little artificial light other than fires.

In essence, the vast majority of people—especially city dwellers—would quickly freeze and starve in the dark. Of the survivors, most would be reduced to a fairly brutish existence not unlike that experienced by the poor during medieval times. A very few, those who were competent at subsistence farming and at manufacturing or repairing of small tools and machinery (the Amish, for example), might 4make it.’

Energy and its forms:In our daily lives, we come across energy in various forms. When we lift a load or run along the road, we use muscular energy. The fan or tube-light in your home consume electrical energy. We directly get the energy from the Sun in the form of light and heat. When crackers are burst during Diwali, we receive tremendous amount of sound energy. We use chemical energy (LPG gas) for cooking, running vehicles (petrol or diesel), etc.

The common forms of energy we come across are as fallows:

Energy: A body which is capable of doing work possesses energy. Thus energy is the ability or the capacity to do work.

Unit of energy: The unit of energy is the same as that of work. Thus S.I. unit of energy

is joule (J) and its C.G.S. unit is erg

Energy appears in various forms namely, heat, light, sound, electricity etc.

Heat energy: It is the energy which causes a sensation of hotness or coldness.

Example: Energy obtained by burning wood. Heat energy is measured in calories or kilo calories.

Electrical energy: Energy possessed by an electron in motion is referred to as electrical energy.

Units of electrical energy: Watt hour (W h) It is the electric energy, and is usually expressed as watt-hour (W h) I W h = 1 watt x 1 hour

= 1J1S x3600s

Thus, I W h=3600J Kilowatt hour is a multiple of W h and is a bigger unit of energy.

1 kilo watt hour = 103 watt hour = 3600 x 103J = 3.6MJ

Light energy: It is the energy possessed by a luminous source which causes sensation of sight. Example: Light energy emitted by sun.

Sound energy: It is the energy possessed by vibrating bodies which produces sensation of hearing. Example: The ringing of a bell.

Magnetic energy: Energy possessed by a magnet is called magnetic energy.

Chemical energy: Energy released or absorbed by atoms or molecules during chemical reaction is called chemical energy. Example: Energy released during combustion of a fuel like LPG.

Nuclear energy: Energy released during fission or fusion of nucleus is called nuclear energy. Example: Atom bomb and hydrogen bomb release energy in the form of heat and radiation Nuclear energy is used in nuclear reactor to generate electric power.

Mechanical energy: Energy possessed by a body due to its position or motion is known as mechanical energy. Mechanical energy is classified into potential energy and kinetic energy.

Potential energy: It is the energy possessed by a body in a stored form.‘ Example: Wound spring of a clock possesses potential energy. When the spring unwinds, it uses this energy for the movement or rotation of the hands of the clock. This potential energy possessed by the spring is called elastic potential energy. Stretched bow, stretched elastic band and compressed gas molecules possess elastic potential energy.

Kinetic energy: Energy possessed by a traveling particle is called kinetic energy. Example: Wind possesses kinetic energy and this energy is used to rotate the blades of a wind mill. For a body of mass m and velocity v, kinetic energy is defined as KE = 1/2mv2.

Kinetic energy of a body increases, with velocity or speed of the body increases. To increase the kinetic energy of a body, net force has to be applied. Thus the work done by this force is equal to the change in the kinetic energy of the body. This is known as work-energy theorem.

Inter-conversion of Energy in Different Forms:Though energy is available in different forms, energy in one form can be converted into energy in another form.

We use diesel or petrol to run our vehicles or trains. Diesel is used to run water pumps and many other appliances. These are examples of conversion of chemical energy to mechanical energy. Electrical energy is converted into heat energy in heaters; into light energy in glowing of electric bulb; into mechanical energy in electric trains, electric motor, electric fan, etc. A vibrating body produces sound. Here mechanical energy is converted into sound energy. Coal when burnt produces heat an example of conversion of chemical energy into heat energy. When you rub your palms with each other, heat is generated, so mechanical energy is converted into heat energy. We can cite many such examples of inter-conversion of energy from one form into another form of energy.

Sun – The ultimate source of energy:

Our Earth receives all its energy needs from the Sun—directly or indirectly. It primarily comes in the form of heat and light. A part of the energy emitted by the Sun—the solar energy is reflected back or absorbed by the intervening medium between the Sun and the Earth. But a large part of the solar energy reaches the Earth and is absorbed by the land and the sea during the day-time.

Fig.2 Sun-Ultimate energy source

The heat energy of the Sun causes water to evaporate from water bodies, that is, ocean, sea, river, ponds, etc. The evaporated water helps in cloud formation and returns the water to the Earth in the form of rain. The water in the river flows and boats can be plied along it. This results in generation of mechanical energy. Dams are constructed over the river to store water and convert the energy of naturally flowing water results in generation of mechanical energy. Dams are constructed over the river to store water and convert the energy of naturally flowing water (kinetic energy stored in the dams to potential energy and then the potential energy of stored water) is used to generate electricity. Wind energy is generated for generation of electricity in the wind mills. The energy of wind is also derived from the Sun. The solar energy (heat energy) absorbed by the land mass and water-bodies on the surface of the earth raises the temperature of air nearer the earth. Unequal rate of heating and cooling of land- mass and water -bodies results in moving air or wind, especially near the coast. Thus, the energy of wind is indirectly derived from the Sun.

Green plants absorb the light energy of the Sun for photosynthesis and store food in the form of chemical energy. This stored energy in plants is used by humans and other animals in the form of food. Dried plants (wood) are burnt to produce heat energy. The plants and animals buried underground millions of years ago have been converted into coal and petroleum under the action of the Sun. Thus, chemical energy is stored in the form of coal and petroleum. Thus, solar energy is converted into chemical energy which in turn can be converted into various types of energy. When coal is burnt, chemical energy

is converted into heat. Thus, the Sun’s energy reaches us directly or indirectly through a series of conversions to make energy available to us.

Fossil Fuels: Heat is probably the most important and useful form of energy in our life. In ancient times, wood was the most common source of heat energy. The use of coal as a source of energy, made possible the industrial growth. The growing demand of energy in the industrial and transport sector was largely met by coal, petroleum and natural gas. This group of fuels are called fossil fuels. Why do we call them so? These fuels are the remnants or fossils of animals and plants buried under the Earth over millions of years. The high temperature and pressure inside the earth slowly converts the buried plants into coal and buried sea animals into petroleum and natural gas.

Coal is extracted by digging mines. Petroleum and natural gas are found mostly in sedimentary rocks, They are obtained by drilling through the rocks. The petroleum extracted is known as ‘crude oil’ and is carried to the refineries for production of different products like kerosene, petrol, diesel, aviation fuel, LPG (liquefied petroleum gas) etc. by fractional distillation.

We are all familiar with cooking gas supplied to us through LPG cylinder and natural gas that is used for generation of electricity and running of automobiles. Today, fossil fuels are the most important sources of energy. They are concentrated sources of energy used for both domestic and industrial purposes. The thermal power stations use coal, fuel oil or natural gas to generate electricity.

Electricity is the Most Popular Form of Energy:

Electricity has become an integral part of all our activities. We cannot manage without light, fan, geysers grinder, refrigerator, washing machine, TV, water pump, air conditioner and many such devices that run on electricity Industries will come to standstill, trains will stop on the track, and communications will cease if electricity is not available. But electricity is not available in this form. Energy from some other sources are converted into electricity. The major methods of generation of electricity are in 1. Thermal power stations 2. Hydroelectric power stations

Besides, substantial amount of power is generated nuclear power stations. In addition, though in a small scale wind energy, solar energy, tidal energy, and geothermal energy are also used for generation of electricity. The common feature in all these power generators except the solar and biomass—is a rotating turbine in a strong magnetic field. Rotating turbine rotates the armature and electricity is generated. In different types of generators, the energy necessary for rotating the turbine is provided by different means. Let us analyze each case separately.

Sources of Energy — Classification We have discussed earlier that the fossil fuels which took millions of years to form will last for a limited time. There is no new addition. So once these sources of energy are used up, they will not be available again. Such sources whose diminishing stock cannot be replenished is called non-renewable source of energy. Fossil fuels are non-renewable source of energy.

But there are some sources of energy which are not exhausted — they are continually replenished through a number of natural processes. Such sources are called renewable sources of energy. These type of sources include the solar energy, the wind energy, the energy due to flowing river (hydropower), tidal energy, ocean thermal energy, wave energy, biomass energy and geothermal energy. Nuclear energy can be included in this category because we can depend on this source for very long time.