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In the discussion of energy, the fundamental concept is that of work which is defined as motion against an opposing force. Energy is the capacity to do work. An object traveling at high speed and impacting on another object can do more work—can drive the object farther against an opposing force—than the same object moving slowly. This contribution to energy, the energy ascribed to motion, is called kinetic energy. The kinetic energy of an object of mass m traveling at a speed ? is ½ m?2. An object may also have energy by virtue of its position. An object high above the surface of Earth has more energy (can do more work) than one at its surface. This contribution to the total energy, the energy due to position, is called potential energy. The relation between the object’s position and potential energy depends on the nature of the force field it experiences. The potential energy of a body of mass m at a height h above the surface of Earth is mgh, where g is the acceleration of free fall at the location.

More important for chemistry is the potential energy of one charge near another charge. The Coulomb potential energy of a charge q 1 at a distance r from a charge q2 is given by q1 q2 /4??0 r, where ?0 is a fundamental constant called the vacuum permittivity. Energy is also stored in the electromagnetic field in the form of photons. The energy of a photon of radiation of frequency ? is hv, where h is Planck’s constant. Energy is conserved; that is, the sum of the kinetic and potential energies of a single body remains constant provided it is free of external influences (forces). Thus, a falling weight accelerates: The fall implies a reduction of potential energy and the acceleration implies an increase in kinetic energy; the sum, though, is constant.

A generalization (which can be interpreted as an implication) of the conservation of energy is the first law of thermodynamics, which focuses on a property of a many-body system called the internal energy. The internal energy can be interpreted as the sum of all the kinetic and potential energies of all the particles comprising the system. The first law of thermodynamics states that the internal energy of an isolated system is constant. The first law is closely related to the conservation of energy, but it acknowledges the possibility of the transfer of energy as heat, which is outside the reach of mechanics itself. The special theory of relativity states that the mass of a body is a measure of its energy: E = mc2, where c is the speed of light. That is, energy and mass are equivalent and interconvertible. Changes in mass are measurable only when changes in energy are considerable, which in practice commonly means for nuclear processes.

In chemistry we are often concerned with the transfer of energy from one location (e.g., a reaction vessel) to another (the surroundings of that vessel). One mode of transfer is by doing work. For example, work is performed when gases evolved in a reaction push back a movable wall (e.g., a piston) against an opposing force, such as that due to the external atmosphere or a weight to which the piston is attached. Another mode of transfer is as heat. Heat is the transfer of energy that occurs as a result of a temperature difference between a system and its surroundings when the two are separated by a diathermic wall (a wall that allows the passage of energy as heat). A metal wall is diathermic; a thermally insulated wall is not diathermic. Finally, energy may leave a system as electromagnetic radiation, for example as in chemiluminescence—the emission of radiation from matter in energetically excited molecular states produced in the course of a chemical reaction, and as a result of spectroscopic transitions. We may concentrate on the first two modes of transfer, work and heat.

At a molecular level, work is the transfer of energy that makes use of or drives the orderly motion of molecules in the surroundings. The uniform motion of the atoms in a piston driven back by expanding gas is an example of orderly molecular motion. In contrast, heat is the transfer of energy that makes use of or causes disorderly motion in the surroundings. When we say that a chemical reaction gives out heat, we mean that energy is leaving the reaction vessel and stimulating thermal motion (random molecular motion) in the surroundings.

The energy of a chemical system is stored in the potential and kinetic energies of the electrons and atomic nuclei. This stored energy is sometimes referred to as chemical energy; however, this is only a shorthand way of referring to the kinetic and potential energies of all the particles in an element or compound. The internal energy of a system changes when a chemical reaction occurs because the electrons and nuclei settle into different arrangements, as in the change of partnerships of H and O atoms in the reaction 2H2(g) + O2(g) ? 2H2O(g). The energy released in a chemical reaction can be transferred to the surroundings (and put to use) in a variety of ways regardless of the manner in which the energy accumulated in the first place. Thus, energy may escape as heat and be used to raise the temperature of the surroundings, including raising the temperature of water that is then employed in a turbine to do work. The energy may also escape as work. The work may be accomplished electrically, as when electrons are driven through an external circuit and used to drive an electric motor.

Atomic nuclei are also centers of energy storage as a result of their internal structures. This energy is released when the nucleons (protons and electrons) undergo rearrangement and thereby change the strength of their interactions. The changes in energy are so great that they give rise to measurable changes of mass. For all chemical processes, the changes in mass accompanying acquisition or loss of energy are totally negligible. 

Modern societies rely on a variety of energy sources to heat homes, propel transportation vehicles, and produce goods for shelter, food, health care, and entertainment. Some of these sources are renewable, whereas others are nonrenewable. A renewable energy source, for example, solar energy, is one that is virtually inexhaustible on the human time scale. A nonrenewable energy source, for example, natural gas, is one that can be either completely consumed (during a lifetime or during several lifetimes) or depleted to such an extent that it is no longer economical for humankind to obtain it. About 80 percent of commercial energy is obtained from three kinds of fuel: oil, coal, and natural gas. When these fuels burn in air they release energy. They are called fossil fuels because they are believed to have formed from the remains of plants and animals subject to heat and pressure for millions of years.

Natural gas is a mixture of methane (CH4), 60 to 90 percent, and smaller amounts of other gaseous hydrocarbons, including ethane (C2H6), propane (C3H8), and butane (C4H10). It is valued because it burns hotter and produces less air pollution than other fossil fuels. Complete combustion of a hydrocarbon substance produces carbon dioxide and water. It has been estimated that in 2001, 2.39 trillion cubic meters of natural gas were consumed worldwide, with estimated remaining reserves of 150 trillion cubic meters.

Oil (also referred to as petroleum) is a complex liquid mixture of organic substances, principally of hydrocarbons containing five to sixteen carbon atoms. Most crude oil, once removed from a well, is sent by pipeline to a refinery, where it is distilled to separate it into gasoline, heating oil, diesel oil, and asphalt. The use of catalysts during the refining process increases the yield of gasoline.  

Coal is the most plentiful fossil fuel, comprising 80 percent of the fuel reserves of the United States and 90 percent of those of the world. It is a complex mixture of organic compounds and is anywhere from 30 to 95 percent carbon by mass. It also contains sulfur compounds. When coal is burned, the sulfur is converted to sulfur dioxide, a troublesome air pollutant. The description of coal as being of high quality is based on its having a low sulfur content and high carbon content. Lignite coal (brown coal) has low carbon content and produces the least energy upon combustion (about 15 kJ/g). Bituminous coal (soft coal) has higher carbon content and produces more energy. It is the most extensively used coal. Anthracite coal (hard coal) has the highest carbon and heat content (about 30 kJ/g), but supplies of it are limited in most places. In 2001, 4.41 billion metric tons of coal was consumed worldwide, with estimated reserves of 985 billion metric tons. (A metric ton is 1,000 kilograms [2,679 pounds].)

The combustion of fossil fuels produces carbon dioxide gas, a heat-trapping gas. For the past 250 years (since the beginning of the Industrial Revolution), the increased use of fossil fuels has caused the atmospheric concentration of carbon dioxide to increase by a factor of about 25 percent. It is now generally believed that this increase has produced higher global temperatures—a phenomenon called the greenhouse effect.

Commercial nuclear power is generated by nuclear fission reactions. When slow-moving neutrons strike nuclei of uranium-235 or plutonium-239, these nuclei are split, releasing energy. The energy is used to heat water and drive a turbine, in turn producing electrical energy. Currently nuclear power supplies more than 16 percent of the world’s total electricity.

A typical nuclear reactor utilizes uranium oxide, whose uranium content is approximately 3 percent uranium-235, and 97 percent uranium-238, by mass. During the fission reaction, the uranium-235 is consumed and fission products form. As the amount of uranium-235 decreases and the amounts of fission products increase, the fission process becomes less efficient. At some point, the spent nuclear fuel is removed and stored. Some of the radioactive fission products, because of their radioactivity and long half-lives, must be stored securely for thousands of years. Thus, nuclear waste management poses a tremendous challenge.

Scientists hope to someday use controlled nuclear fusion to produce energy. Nuclear fusion, which involves the coming together of light nuclei to form heavier ones, is the process by which stars generate energy. In order for nuclear fusion to occur, the nuclei must have extremely high temperatures. Research has focused on the fusion of deuterium (hydrogen-2) nuclei and tritium (hydrogen-3) nuclei, a process that requires about 50 million degrees Celsius. The principal renewable energy sources are biomass from crops such as trees and corn, hydropower from flowing rivers, geothermal power from heat stored in Earth, wind energy from the movement of winds, and solar energy from the Sun.

Wood is part of an array of plant matter referred to as biomass that can be burned to produce energy. The combustible substances in biomass are primarily carbohydrates (and of these, primarily cellulose). Cellulose, whose simplest or empirical formula is CH2O, undergoes combustion to form carbon dioxide and water. Wood fuels continue to be used in the rural areas of developing countries. Hydroelectric power is a well-developed energy source. Today, hydropower provides about 19 percent of the world’s electricity supply. Because it is a clean, renewable source of energy, hydropower should continue to serve as a vital energy source.

There has been a rapid growth in the use of wind turbines to generate electricity. In 2001 the amount of electricity generated in this way worldwide corresponded to the amount that would have been obtained from burning 15 million barrels of oil. Although this represents only about 0.05 percent of worldwide energy production in 2001, this fraction will increase. Solar energy is the most significant and promising renewable energy source. Solar energy is converted to electricity by solar cells (also known as photovoltaic cells). A great deal of solar energy is used currently in what is known as passive heating (which can be directly experienced as the heat gain in a greenhouse caused by sunlight). 

THE loadshedding-driven sleepless nights and disrupted daily routines of last summer are still haunting the people as the weather turns hot. The situation has not improved since last year; indeed all the signs are that it is getting worse.Credit goes to brave Pakistanis for surviving through the winter despite 10-hour power and gas loadshedding. But in the upcoming summer when the mercury is going to consistently hover round 40°C, occasionally rising to 50°C in some places, a power crisis of a similar order is going to prove unbearable. Last summer the national media reported tragic deaths due to heatstroke and dehydration. The energy crisis in winter forced thousands of industries to shut down operations, affecting industrial production and the livelihoods of thousands of families.

Considering the indispensability of energy — since 1947, per capita electricity dependence in Pakistan has grown 82-fold — the current state of affairs can be regarded as a ‘national crisis’. The quickest and pragmatic solution — multi-gigawatt capacity addition based on local coal and hydropower — will require at least 2-3 years (5-7 years for hydropower) provided that bold and concerted steps are taken on a war footing.

Assuming optimistically that this will happen, we still have to devise ways in the interim to meet the electricity deficit in the country which has soared to over 40 per cent. The challenge now is how to survive this summer and how to stop the crisis from getting worse. The solution lies in a collective national effort.

Two key elements of a possible solution are: categorical change in the pattern of energy consumption and change in lifestyles.

The current energy consumption trends in Pakistan are extremely inefficient, whether it be in the domestic, industrial, trade or commercial sectors. With minimal effort, well over ten per cent of national electricity can be saved by applying only the first level of energy conservation, that is a change in attitude. It is simple, instant and effective and all it requires is a stop to using energy unnecessarily.

Leaving lights and home appliances on even when they are not being used is a common practice in our society. Similarly, many businesses such as shops dealing in cloth and garments, jewellery, cosmetics, home appliances and electronics are usually extravagantly lit. It is commonly observed that shops that could do with two or three 40-watt tube lights to meet the desired level of luminance use as many as 15 to 20 tubes. Not only does this increase power consumption, it also generates heat and makes the environment uncomfortable.

A further economy of 10-15 per cent can be achieved by introducing the second level of energy-conservation practices, especially in industry. Collectively, just through conservation, more than half of the electricity deficit can be met. However to do that, public education is essential. With the help of effective electronic and print media campaigns the government can quickly educate the masses.

The second part of the solution is a change in lifestyles. It would begin with the acknowledgement that the country is facing a national disaster and every citizen has to pitch in to overcome it. The nation has to draw a clear line between necessities (lighting, fans, TVs, computers, etc) and luxuries (air conditioners, microwaves, etc). There is not enough electricity to meet both requirements.

We will have to compromise on luxurious lifestyles in order to meet the necessities. Markets and commercial places can substantially reduce their power consumption by changing their working hours. An early start and early end to capitalise on daylight as much as possible should be recommended rather than having opening hours from afternoon until late at night.Air-conditioning, usually a sign of a luxurious lifestyle, needs to be dropped. Bearing in mind that a typical domestic AC consumes far more electricity in one hour than a fan does over 24 hours, air conditioning should not be allowed except for sensitive applications such as hospitals and research centres. The choice is between using ACs for a few hours and then doing without electricity in peak summer months or avoiding ACs and other luxury gadgets but having round-the-clock electricity available to meet fundamental needs.

Any such policy should be made at the highest level and its implementation should also begin there because charity starts at home. The common man would only be convinced of the looming crisis when he sees the ruling elite practise what it preaches.

The ruling class should lead by example in matters of power conservation. If it does so the common man will follow suit. It is time for the elite to take energy-saving initiatives like abandoning the use of central air conditioning, travelling by special flights and irrelevant use of official transport.

These recommendations are neither impractical nor a step backward, as some sections may perceive them to be. If implemented they can not only avoid the collapse of a bankrupt energy infrastructure but also ensure progress. Even those who have access to easy money and can afford different gadgets such as generators to offset reduced power supply will still feel the heat one way or the other. The bottom line is, in order to safely get through the current energy crisis the nation has to differentiate between its necessities and its luxuries.

If loadshedding is still unavoidable despite all these measures, Wapda/KESC should organise the cuts in a sensible way to cause minimum discomfort. Loadshedding schedules should be properly planned and announced

In two short years, energy-smart Cuba has bolted past every country on the planet. the World Wildlife Fund (WWF) has declared Cuba to be the only country on the planet that is pproaching sustainable development. Key to this designation is the island’s Revolución Energética, an energy conservation effort launched only two years ago. For two decades, Cuba has been developingrenewable energy and energy-conservation strategies to cope with the fuel shortage. Educating citizens about energy conservation has been one of Cuba’s programs to move toward a more sustainable energy future.

The solutions to Cuba’s energy problems were not easy. Without money, it couldn’t invest in nuclear power and new conventional fossil fuel plants or even large-scale wind and solar energy systems. Instead, the country focused on reducing energy consumption and implementing small-scale renewable energy projects.

Ecosol Solar and Cuba Solar are two renewable energy organizations leading the way. They help develop markets for renewable energy, sell and install systems, perform research, publish newsletters, and do energy efficiency studies for large users.Ecosol Solar has installed 1.2 megawatts of solar photovoltaic in both small household systems (200 watt capacity) and large systems (15-50 kilowatt capacity). In the United States 1.2 megawatts would provide electricity to about 1000 homes, but can supply power to significantly more houses in Cuba where appliances are few, conservation is the custom, and the homes are much smaller.

About 60 percent of Ecosol Solar’s installations go to social programs to power homes, schools, medicals facilities, and community centers in rural Cuba. It recently installed solar photovoltaic panels to electrify 2,364 primary schools throughout rural Cuba where it was not cost effective to take the grid. In addition, it is developing compact model solar water heaters that can be assembled in the field, water pumps powered by PV panels, and solar dryers.

A visit to “Los Tumbos,” a solar-powered community in the rural hills southwest of Havana demonstrates the positive impact that these strategies can have. Once without electricity, each household now has a small solar panel that powers a radio and a lamp. Larger systems provide electricity to the school, hospital, and community room, where residents gather to watch the evening news program called the “Round Table.” Besides keeping the residents informed, the television room has the added benefit of bringing the community together.

“The sun was enough to maintain life on earth for millions of years,” said Bruno Beres, a director of Cuba Solar. “Only when we [humans] arrived and changed the way we use energy was the sun not enough. So the problem is with our society, not with the world of energy.”

To find out how to solarize your home go to:

http://mysmartphoneapps.blogspot.com/2009/08/cuba-leapfrogs-world-with-sustainable.html