Lecture 03

Environmental Science

Matter and Energy


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MATTER  Atomic Structure

Matter is anything that has mass and that occupies space. There are four states or conditions in which matter may exist: solids, liquids, gases, and plasma. A physical change is one that changes a specific state of matter, such as ice, into a different state of matter such as water.  Physical change does not change the substance chemically. Ice becoming steam or meat cut into smaller pieces is organized differently. Chemical change alters the elements or compounds. Coal burning completely becomes carbon dioxide and energy.

 

Energy Flow and the Environment

 The Law of Conservation of Matter states:  Matter can not be created or destroyed.  The earth is a closed system containing all the matter it will ever have.  Chemicals cycle between living organisms and their environment. There is no away and thus waste or pollution becomes a problem. The chemical forms are elements and compounds. Compounds can be made up of elements, and/or mixtures. Mixtures are made up of compounds and/or elements.  Organic compounds contain Carbon and Hydrogen.

Advanced industrialized societies try to keep economic growth by increasing through-put of matter and energy resources in their systems. At some point the waste becomes unmanageable. A short-term solution is to recycle matter; however it takes high-quality energy to recycle and waste heat is added to the environment. This approach only works if there is a cheap source of high-quality energy available. 

 

Matter and Energy           

      Matter quality is a measure of usefulness based on availability and concentration. High-quality matter is organized, concentrated and found in the earth's surface. Low-quality matter is disorganized, dilute and deep in the earth or dispersed in the atmosphere or the ocean. 

          

                             

 

A measure of disorder is called entropy. Low-quality energy has high entropy.  Energy is the capacity to do work and transfer heat. Energy comes in many forms; heat, light, electricity, chemical bonds, mechanical and nuclear energy.

The measure of energy, in matter, to do useful work is called energy quality. High-quality energy is concentrated, organized and does much useful work. Low-quality energy is dilute, unorganized, and does little useful work  Energy tasks should be related to the usefulness or energy quality in order to save energy. Very high-quality energy is needed for industrial processes such as providing electricity. High-quality energy should be used for moving vehicles, industrial processes and producing electricity. Moderate-quality energy can be used for cooking, producing steam, electricity and hot water. Low-quality energy should be used for space heating.

 

 Energy Systems and Flow

ENERGY  Work and Energy     T. Bone Pickens Solution to Achive Energy Independence

Energy can be defined as the ability to do work, and work results when a force is applied through a distance. You do work when you push a rock over a cliff; an engine does work when it moves an automobile; a living cell does work when it divides. Work occurs only if a force causes some object to move. When you push a rock over a cliff, your body uses energy to overcome the forces of friction, inertia, and gravity holding the rock in place. The bigger the rock, the more work is required and there­fore the more energy is needed to move the rock. Power is the amount of work done in a given time interval. Power is measured in either horsepower, where one horsepower results in the movement of 550 pounds one foot in one second, or watts, in which 746 watts (W) equal one horsepower. Electric output is often mea­sured in kilowatts (thousands) or megawatts (millions).

Low waste Societies manage Energy Flow and Matter Recycling to reduce throughput. This model works with nature to reduce throughput.  Solar energy provides 99% of the energy used to heat the surface of the earth and our buildings. The 1% left is commercial energy generated from mineral resources, which are mostly non-renewable fossil fuels. Countries use energy sources differently. Developing countries  use potentially renewable biomass as their main source of heating and cooking fuel. U.S.A. is the world's largest user of energy. As a developed country, U.S. uses 25% of the world's commercial energy, which comes from non-renewable resources primarily. Only 7% come from renewable energy sources. The internet uses about the same energy as the airline industry - about two per cent of a developed country's energy consumption.

 

 

Sources of U.S. Energy

   Oil                    

39.0%

   Hydroelectric

3.4%

   Non-renewable natural gas

24.0%

   Geothermal

3.0%

   Coal               

22.0%

   Solar  

5.0%

   Wind  

0.6%

   Nuclear          

8.0%

 

                                                                        US Dept. of Energy

 

Our quality of life and effect on the environment is determined by what type of energy we use. Dependence on nonrenewable fossil fuels is the primary cause of air and water pollution, land disruption and projected global warming according to some environmental sources.  

 

Potential and Kinetic Energy

Energy can be divided into two basic forms: potential and kinetic. Potential energy, repre­sented by a rock poised at the edge of a cliff or water in a cloud, is energy available to do work. Living organisms store potential energy in the form of high-energy phosphate bonds which, when broken, release energy for use by the living system. Kinetic energy, on the other hand, is associated with movement. A moving car, the wind, falling water, and the earth’s movement all have the kinetic energy of motion. You use kinetic energy to place a book on top of a table. The book on the table has poten­tial energy that would be converted to kinetic energy if it were to fall to the floor.

 

Thermodynamic Laws

   Energy, or the accountability of energy, is described by the first and second laws of ther­modynamics. These laws describe what happens to energy used to perform work and why energy cannot be recycled like minerals in cans and bottles. The first law of thermodynamics is known as the law of conservation of energy, states that energy is never created or destroyed but can be transformed from one form to another. The total amount of energy available in a system always remains the same, although it can be distributed in different forms at different times. As gasoline burns, it releases light, thermal radiation, and heat energy which are in part converted to energy to move a car. Although there is a specific amount of energy in gasoline that changes to other forms when burned, energy is neither created nor destroyed. One can not get more energy out of a system than one puts in. There is no free lunch or something for nothing. If one looks at the following table we find the efficiency of producing various forms of energy. Electricity is produced by burning some fuel to produce steam which turns a turbine which is connected to a generator that produces the electricity. This entire process "looses" 72% of its original energy to convert coal or oil energy into electricity. We are willing to do this for the convenience that electricity has to offer. (by the way the lost energy is usually in the form of heat which goes into the environment)

 

 

Energy Production Efficiency

                Form

Efficiency

Electricity

28%

Natural Gas

95%

Gasoline

90%

Food

25%

 

 

      The second law of thermodynamics states that no reaction involving the transformation of energy from one form to another occurs without some energy changing to a less usable form (heat). No energy transformation is 100 percent efficient. For example, coal is burned to produce steam to turn electric generators, but not all the potential energy of coal is con­verted to usable heat energy. Heat losses occur in the furnace, some of the steam cools before it can do productive work, and friction in the generator reduces the amount of usable heat further. The more energy we use the more low-grade energy (heat) or entropy  (disorder) is added to the environment. You can't break even.   In living systems, each time energy is changed from one form to another;  low-quality heat is put into the environment.

 

      The sun supplies the earth with energy that can be converted into potential energy by green plants, making energy available to us in food. A high proportion of the energy at each level in the food chain is lost as heat. This is another example of the second law of thermodynamics and it is an important consideration in the balance of energy on earth.

 

SOURCES OF ENERGY

      A major problem facing the world today is the inequality of acquiring, distributing, and using energy resources. Institutional and polit­ical factors complicate the problem. As indus­trial nations continue to grow and less devel­oped countries’ needs for energy increase, the present supply of energy will be strained and eventually prove insufficient.

 

Electricity    Electricity a Form of Energy       Living in an Electrical World

      One of the greatest demands for energy is in the form of electricity. Thus, much of our dis­cussion of energy sources will relate to the use of raw materials in the production of electricity. Electricity is the current resulting from the flow of electrons in a conductor. An electron is a very small, negatively charged subatomic particle, and a conductor is made of copper wire or similar material through which free electrons can move easily. Electric current is relatively easy to produce. A coiled conductor, such as copper wire, is pulled back and forth through a magnetic field. The conductor is loaded with negatively charged free electrons which react to the magnetic field. By forming a loop with the conductor and placing it between the north and south poles of a magnet, an elec­tric current is made to flow through the loop.

      When the loop is rotated, the current will flow first in one direction and then in the other, cre­ating what we call alternating current (ac). Large generating facilities use an energy source such as water, steam, or wind to turn the blades of a turbine. The conductor loops are attached to the spinning turbine so they move back and forth through a magnetic field. The electricity generated is then transmitted via conductors to areas where it is used for lighting, heating, cooling, or other purposes.

      The cost of transmitting electricity continues to rise sharply as problems are recognized and treated. Environmental damage from transmis­sion line cuts has resulted in expensive re­search to achieve the best placement. Through­out their length, some high-voltage electric lines are un-insulated except for the surround­ing air. Extremely high voltage (1000 kilovolts) causes lines to spark in the air, creating high levels of ozone in the nearby area which is a health hazard. Scientists are developing special forms of liquid and gas for insulating material as well as investigating the possibility of underground transmission. With an anticipated three to six-fold increase in the use of electric power, solutions to these problems are imperative.

 

 

Primary Sources Of Energy

         Energy that requires no conversion process is referred to as a primary source of energy. Sources from which energy can be de­rived directly include solar radiation, tidal en­ergy from the earth-moon-sun system, and nuclear and thermal energy from the earth. Secondary sources include those forms requir­ing other energy input to convert them to their fuel state. Examples are fossil fuels, wind, wa­ter, and hydrogen.

 

Solar Energy  Sun to Earth

      Solar radiation is our greatest energy source, exceeding the sum of other sources we use by a factor of 5000. The direct conversion of solar energy by photosynthesis utilizes less than 0.03 percent of the incoming solar radiation. That energy is used as the foun­dation of all life on earth and as a future source of energy when stored as fossil fuels. Close to 80 percent of the solar radiation the earth receives is reflected back to the atmo­sphere or is lost as heat. Some of this sunlight can be collected and converted to electricity by several methods, including heat conversion and direct conversion. Solar energy stored in the ocean could be used by taking advantage of the temperature difference between the sun-heated ocean surface and the colder water un­der the surface.

Passive solar systems make use of the spon­taneous movement of heat by conduction, convection, radiation, or evaporation. They rely heavily on location and architectural design to admit solar radiation in the winter and to block it in the summer. Usually, optically transparent surfaces of glass or plastics on the exterior of buildings allow solar radiation to enter. The ra­diation is absorbed by a surface, usually dark in color, thereby raising the surface’s tempera­ture. The heated surface emits long-wavelength (infrared) radiation which is trapped inside the building because glass and plastic prevent the loss of this form of radiation. This is referred to as the greenhouse effect. Some form of thermal mass (storage system) is used to retain the heat without pumps or fans.

      An active solar system is similar to a passive one except that it contains a distinct collector, heat storage medium, and pumps or fans to circulate the heat. The thermal energy can also be used to operate a compres­sor-type air conditioner for cooling.

      Hybrid solar wall panels are being tested in Pennsylvania as a means of incorporating solar thermal collection, storage, and distribution into existing buildings. The panel, which uses phase-change material to collect, store, and distribute solar energy, is expected to reduce electrical space heating demands and save en­ergy. Phase materials change from a solid to a liquid (change of phase) as they absorb energy, returning to a solid as they release energy. This material can absorb 70 times more energy per pound than water thereby reduc­ing the physical size of the thermal energy stor­age system.

      Photovoltaic cells, first developed by E. Becquerel in 1839, convert solar energy di­rectly to electricity. In 1954 Bell Telephone Laboratories developed a silicon photovoltaic solar cell. This device is used in camera light meters to determine the amount of incoming solar energy and as the power source for long-lived sat­ellites. Engineers now suggest mounting photovoltaic cells on earth satellites to capture solar energy and then transmitting the energy to the earth via microwave beams. Cells can also be placed on buildings to convert solar energy directly into electricity. The high cost of manufacturing these cells is the primary deterrent to their widespread use. If costs decrease and their efficiency of 13 to 14 percent increases, they could become an unlimited source of energy.

      There are fewer potential environmental problems for solar energy derived from solar collectors than for most other major power sources. However, some problems do exist. Each collection facility with a 1000-megawatt output requires 39 to 52 square kilometer of land. About 15,540 to 20,720 square kilometers of land area would be required for the present U.S. consumption of 400,000 megawatts. The land, expected to be primarily desert region, would undergo changes in its habitat. Water would be in short supply at most sites, and at sites where water is used, the increase in temperature would add heat to the environment as it is released in cooling ponds or towers

 

Geothermal Energy 

      Geothermal resources, defined as reserves of heat near the earth’s surface, are created when material from the hot interior of the earth protrudes into the cool outer layer creating hydrothermal reservoirs, lavas and magmas, or hot, dry rock. The most common and economical are hydrothermal reservoirs, where steam is obtained from wells reaching 1200 to 1500 meters into the ground. This steam is used to drive turbines on the ground near the wells. A world map would reveal that these heat reserves are found in very specific regions .

      From an environmental point of view, geothermal energy creates several problems. The highly mineralized water used by a geothermal facility must be discarded. Before it could be discarded, the water would need to be treated in some cases in a manner similar to desalination. Pollution would also result from nox­ious gas by-products, especially sulfur dioxide and hydrogen sulfide. In addition, heat released from these plants will have an impact on the surrounding habitat. Once these environmental problems are solved, geothermal energy could provide an alternative power source in the limited areas where the earth’s heat is easily accessible.

 Tidal Energy     Tidal Power Generator

      Utilization of the tides for energy is not a new idea. There is mention in the Doomsday Book of a tidal mill at the Port of Dover on the English Channel in 1066. The source of this en­ergy is the gravitational force of the earth-moon-sun system. In the open ocean, tide changes average only about 0.6 meters. The physical characteristics of shorelines, es­tuaries, and bays together with wind conditions greatly amplify these changes. Where amplifi­cation is some 50 to 100 times, tides can be used to produce electricity. The greatest re­lease of this energy occurs where the water is forced to flow through dams built in narrow areas. The total amount of energy in ocean tides, if it were accessible, is estimated to be sufficient to provide about half the energy needs of the entire world. Unfortunately, there are so few sites where harnessing this energy is practical.

      The effects of tidal energy extraction on marine life could present a major environmental problem, particularly in estuaries. Because the velocity of the flowing tide increases near the dam, oyster beds and the habitats of small plants or animals near the tidal dam would be disrupted.

 

Nuclear Energy

      Nuclear energy originates within the nucleus of an atom. Some elements have the ability to give off particles, from the nucleus, thus changing the atom. When the nucleus of an atom changes it results in a nuclear change which can be natural radioactive decay, nuclear fission or nuclear fusion. The law of matter conservation does not apply to nuclear change because a small amount of nuclear mass is converted into energy. The law of conservation of energy and mass is upheld because the total amount of energy and matter remain unchanged.  Natural radioactive decay yields radioactive isotopes. Radioactive isotopes are useful for:

    · Carbon dating fossils

    · Tracers for detecting pollution outlets

    · Killing screw worms in cattle

    · Diagnosis and treatment of diseases of heart blockage, thyroid uptake, and cancer

      Nuclear fission splits the nucleus causing a chain reaction that yields several elements and lots of heat that can produce high-pressure steam. Nuclear fusion combines two elements at high temperatures, which forms a heavier element and energy. When controlled fusion becomes available, it will be a good source of energy. 

      Atoms of different elements vary from one another in weight and numbers of particles. At­oms are made of three kinds of particles: elec­trons, protons, and neutrons. Electrons have a negative charge, protons a positive charge, and neutrons no charge. Protons and neutrons are found in the center of the atom while electrons, which are equal in number to protons, orbit the nucleus like satellites orbiting the earth.

      The sum of the neutrons and protons in a nucleus constitutes the mass number. For ex­ample, uranium-235 has 92 protons and 143 neutrons, so its mass number is 235. The mass of a proton is about the same as that of a neu­tron, and each has a mass of about the same as a hydrogen atom. The mass of the electron, however, is only 1/1836 that of a proton or neu­tron The number of protons in an atom is called the atomic number. Groups of atoms of the same element with the same atomic numbers but different mass numbers are called isotopes. Isotopes of an element have the same number of protons but different numbers of neutrons in their nuclei. Those of the isotopes of uranium are U235, and U238. Uranium is a naturally occur­ring radioactive element consisting of 99.3 percent U , 0.7 percent U235, and a minute frac­tion of U234. Because U235 is readily fissioned, or split into nuclei of lighter elements, it con­stitutes a major energy source today.

      Conventional generating facilities burn fossil fuels such as coal or oil to convert water into steam, which turns a turbine generator to produce electricity. In plants that generate electric­ity by nuclear power, a fuel such as enriched uranium is contained in fuel rods assembled in the re­actor core. When a U235 atom is bombarded by neutrons, the nucleus of the uranium atom captures a neutron and becomes unstable. These unstable atoms can change in several ways. One possibility is for unstable atoms to fission, or split into two or more smaller atoms. The resulting fission products weigh slightly less than the original material. This weight loss represents weight or mass converted into energy. Furthermore, when an atom fissions, several free neutrons are released. These are available to strike other atoms, causing them to fission and thus creating a chain reaction.

      If the chain reaction is to continue, there must be enough atoms packed together into a critical mass. (Critical mass is the smallest mass of fissionable material needed to maintain a self-sustaining chain reaction.) When several bundles of fuel rods are placed close together in the reactor core, a critical mass is reached. The heat generated within the fuel element is trans­ferred through the fuel element when a coolant flows over the rods. Examples of coolants are water, pressurized water, gas, or liquid metal. The heat now transported in the coolant is used either to turn the turbines directly or to release heat to a secondary coolant which turns the turbines. The rods containing the fuel can be moved in or out of the fuel bundle to increase or decrease the number of neutrons available and thereby control the reaction rate.

 

Fission Reactors

       Light-water reactors are the primary sources of nuclear energy today. Water is used as a coolant to remove heat. Either boiling water or water under pressure serves as the driving force for the turbines. Light-water reactors consume fissionable U235 and have a low efficiency—about 32 percent. In boiling water reactors, the water passes over the fuel rods and is converted to steam, which drives the turbines. In pressurized water reactors, hot water from the core heats water to drive a turbine generator. Gas-cooled reactors are essentially the same as light-water reactors but use helium gas instead of water. They operate at an efficiency of about 39 percent, which means that they use less than 1 percent of the energy in naturally occurring ura­nium. They are a drain on our very low sup­ply of U235.

      Breeder reactors, on the other hand, could provide a more economical source of energy because they produce more nuclear fuel than they use. Breeder reactors convert a greater amount of U238  to Pu239 producing more Pu239  than was actually initially present.

 

Problems

      A nuclear accident that according to one author was “The Day We Almost Lost Detroit” occurred near Monroe, Michigan. In1966 the sodium coolant was blocked in an experimental breeder reactor and some fuel assemblies were destroyed. An accident occurring at the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, on March 28, 1979, caused the public to become acutely concerned about the use of nuclear power. Prior to that time, only a few relatively unpublicized accidents had occurred at nuclear reactors. In 1952 the Chalk River reactor in Canada, an experimental heavy-water reactor, had a block in its liquid coolant system which caused the core to be destroyed.

      Many safety questions remain unanswered in the aftermath of the Three Mile Island and the Chernobyl events. The future of nuclear power, according to some people, is now pre­carious. Releases of radioactivity could occur at points other than the power plant in the nuclear fuel cycle such as in transit, at the reprocessing plant, or at waste disposal sites. These nuclear accidents do not in themselves indicate that nuclear power is not a feasible form of energy. Rather, accidents reinforce the fact that we must continue to study and test all possible methods of energy production. Government agencies must establish high standards of safety and performance and provide protection from sabotage of nuclear facilities. If some nuclear developments prove costly in terms of environmental damage or safety hazards, we must see that alternative approaches are sought.

      High-level radioactivity gives off large amounts of ionizing radiation for a short time and small amounts for a long time (about thousands of years). According to some environmental proponents there is no safe method of storing radioactive wastes.  The advantages of nuclear power plants is they do not emit air pollutants like coal plants do and water pollution and land disruption is low to moderate if the plant is operated correctly. Risk of exposure to radioactivity is very small in U.S. and developed countries. However, explosions and meltdowns are possible.  In the U.S., there is widespread lack of confidence in the Department of Energy (DOE) to enforce safety in the commercial and military facilities. The government is storing nuclear weapons and  wastes but no one has a long-term scientifically and politically safe solution.

 

Nuclear Fusion

      So far, our discussion of nuclear reactors has centered on fission reactions in which a heavy element like uranium is broken down to release energy. Another type of nuclear reaction is fusion. In fusion or thermonuclear reactions, lighter elements are combined into fertile materials, as in the hydrogen bomb. Very high temper­atures hotter than the sun’s interior are required to have a controlled fusion reaction.

      Two concepts are currently being considered for fusion reactors: magnetic confinement and laser implosion. In the first, hydrogen isotopes are present in a gas or plasma contained in a magnetic field. The magnetic field accelerates the isotopes to high velocities, causing collisions and fusion. In the second concept, concentrated light from lasers compresses a pellet of deuterium and tritium, causing fusion. Overall, there are some thirty possible fusion reactions.

 

Secondary Energy Sources

   Secondary energy sources involve the release of trapped solar energy. Fossil fuels, organic materials, and wastes generally can release energy trapped by living systems. Wind, rivers, and ocean gradients can be harnessed to release energy.

 

Fossil Fuels

   Coal, oil, and natural gas were formed from plant and a small amount of animal material deposited more than 300 million years ago. Coal developed from deposits in swamps rich in plants that partially decomposed in an oxygen-deficient environment. These plants accumulated in thick layers of peat which were then covered by sand, clay, and silt as the sea level changed. As more sediment was deposited, water and organic gases were squeezed out, increasing the amount of carbon in the deposits. These processes continued until peat became converted into coal. Coal occurs in layers 0.6 to 9 meters thick throughout the world, with the largest concentrations being found in the United States. It is often divided into three classifications: lignite; bituminous; and anthracite. Sulfur content is also a means of classification: low (0 to 1 percent); medium (1.1 to 3 percent); and high (more than 3 per­cent). Much of the United States’ supply is low-sulfur bituminous coal.

      There are many problems associated with using coal as an energy source. Coal is a dirty fuel both in terms of recovery and usage. It is difficult to mine because it is found in thin lay­ers or veins between rock formations. Coal is the most abundant and dirty fossil fuel. Most of the deposits are located in the U.S., the former Soviet Union and China. Coal is used to generate electricity and make steel. Subsurface mining of coal is very dangerous and labor intensive. Surface mining is used for coal close to the earth's surface. Both of these have harmful environmental effects such as polluting nearby streams and groundwater. Burning coal releases radioactive particles, carbon monoxide CO, carbon dioxide CO2, sulfur and nitrogen compounds SO2, NO, NO2.  Research done by the Department of Energy gives the environmental costs of producing electricity were per kilowatt-hour:

· Coal 5.7 cents

· Nuclear 5.0 cents

· Oil 2.7 cents

· Natural gas 1.0 cents

· Biomass under .7 cents

· Solar cells under .4 cents

· Wind and Geothermal under .1 cents

   Working conditions in mines are often poor, resulting in health problems such as black lung disease. Surface mining, or removing whole layers of hillsides, results in tremendous environmental destruction because, until the land is successfully reclaimed, it is unsuitable for any other purpose. Water leaching from tailings or deposits sends acid runoff into surrounding water. When coal is burned, it produces undesirable gases such as sulfur dioxide and releases them into the environment. A process called solvent refining can remove undesirable sulfur and ash from coal, but it is expensive, making low-sulfur coals more desirable.

 

Oil and Gas

   The formation of oil and natural gas is not as clearly understood as that of coal. Oil, normally found in pockets in ma­rine sedimentary rock, is thought by geologists to be a product of the decomposition of organic matter that accumulated on the bottom of basins with oxygen-deficient water. Bacteria then decomposed this mixture by removing oxygen and nitrogen, leaving carbon and hydrogen. Pressure and heat converted the material into droplets of liquid oil and minute bubbles of gas when sediments increased. The oil and gas were forced into layers between rocks where the space was large.

    Oil's low price has encouraged developed and developing countries to become addicted in their dependence on it. Oil's extraction does cause environmental degradation and pollution. The oil extracted from the ground can be converted to other products through the process of cracking. Oil shale needs the energy from half a barrel of conventional oil to produce a barrel of oil from shale. Oil Sands (link) can be mined profitable now but large amounts of water and air pollution are released.  Natural Gas has remained cheaper than oil.  It can easily be transported by pipeline and is used in highly efficient fuel cells.

Natural gas must be converted to liquid form (LNG) to be transported by tankers. New ways to convert natural gas  (link) to liquid make it cheap and convenient to use in vehicle.

 

Wind Power

      Solar radiation is the major cause of winds on the earth’s sur­face. As varying amounts of solar energy fall on the earth, the atmospheric pressure changes, causing winds. Windmills are used in parts of the world today to generate small amounts of electricity. The blades of the windmill, placed so that they rotate when wind strikes their feathered surfaces, are attached directly to an electric generator. Wind power is a potential source of energy in the Great Plains and along coastal areas. The Aleutian Islands have a constant high-velocity wind, mak­ing them a reasonable source of power.

      The potential amount of wind energy is great. Engineers estimate that a wind of 32 kilometers per hour blowing through a rectangle 16 kilometers long and 46 meters high produces about 380,000 kilowatts. Windmills cannot effectively produce commercial electrical power from wind velocities of less than 20 mph. On the other hand, at velocities above 48 kilometers per hour, the windmill structure can be damaged. Wind power extraction causes no air or water pollution.

 

Ocean Thermal Gradient

      In many tropical and subtropical areas of the world, the sun heats the ocean surface to a range of 24 to 300C. This warm water circulates to the polar regions, where it cools and flows back to the equatorial region along the ocean bottom and on the eastern side of the ocean basin. In these cooler layers 600 meters below the surface, temperatures range from 2 to 80C .

      In one proposed system to produce electricity using warm ocean water would have the warmed water enter the upper section of the plant at 250C. It would pass over an ammonia boiler, heating ammonia or another fluid with a low temperature of evaporation to 200C. The vapor would leave the boiler, expand through a turbine, and then enter a condenser. Ocean water at 50C  would condense the vapor and generate electricity. Water at 250C  is taken in at the surface and vaporizes another fluid, which turns a turbine. Water at about 50C is taken in at the bottom and acts as a coolant.

      There are practical rather than environmental problems in the use of ocean thermal gradients as an energy source. First, it is difficult to build equipment that can be used in highly corrosive ocean waters. Second, adequate means of transporting electricity to shore must be developed for floating facilities.

 

Water Power       Hydroelectric Power

      Hydroelectric energy is an important source of power for the world today, yet only a small part of the estimated worldwide hydroelectric power capabilities is now being used. Since the sun’s radiation drives the rain cycles that feed the surface runoff, hydroelectric power uses solar energy indirectly. In fact, it is the only solar energy power used on a widespread basis today. A storage hydroelectric plant accumulates water behind a dam in a reservoir and releases it through the turbine.

      Hydroelectric power is relatively inexpensive when compared to other sources. As the demand for more energy increases, there must be greater efforts to remove silt from behind dams. Although hydroelectric energy does not cause air pollution and little water pollution, it does block fish migration, disrupt river flow, and flood usable land, particularly when a number of dams are placed along a single river system.

 

Hydrogen

      Hydrogen gas is a potential source of energy of the future. Currently, hydrogen is produced mainly from methane gas or by steam break­down processes driven by fossil fuels. Hydrogen can be produced by electrolysis, using electric power from another energy source. As petroleum and natural gas become less avail­able, hydrogen might be used directly as a fuel. Scientists indicate that hydrogen can be transmitted as a gas in pipelines, stored in holding tanks, and used as fuel in automobiles and other forms of transportation.

      Present technology is not developed to allow large-scale use of hydrogen. Research shows that fewer air pollutants result from using hydrogen in internal and external combustion engines than from burning fos­sil fuels. A major drawback to the use of hydrogen as a fuel is its explosiveness as a pure gas.

 

Energy Conservation      World Percent Energy Usage     U.S. Percent Energy Usage

      Improving our use of energy can have a sub­stantial impact on total energy consumption. By conserving energy through more efficient use and preventing waste, we can greatly reduce the demand for new energy. The total annual energy growth rate required to maintain our nation’s standard of liv­ing could be reduced from about 3 percent to less than 2 percent, making total consumption 25 percent less than that projected for the year

      If an engine could operate without friction, it would be 100 percent efficient. Through ther­modynamic studies we can compare the amount of energy released with the amount of fuel used. The heat loss in any thermodynamic reaction might be used to heat buildings. For example, heat dissipated into the air or water by power plants could be put to such use in industrial sites.

      Energy conservation practices require an energy-conscious public. When you go to a drug store three blocks away, you can take your bike or walk. Upon leaving home, you can turn off the lights and lower the thermostat. Approximately 30 percent of the energy con­sumed in the United States is used in the home or in the operation of commercial buildings, and another 40 percent is used in industrial processes. Home uses include energy for heating, cooling, lighting, food processing, and recreation. Heating and cooling of buildings ac­counts for 18 of the 30 percent. Modern build­ings (with very few exceptions) are not designed to conserve energy, and some consume extraordinary amounts. By using insulation, orienting the building to make the most of natural heating and cooling, and using energy-economic building materials, savings in money and energy can occur. Attic and wall insulation greatly reduces the energy exchange. In the average home, proper attic insulation pays for itself in two to five years, depending on climate. If glass area is reduced and double-pane glass or storm win­dows are used, energy is conserved. Weather stripping around windows and doors is also effective. Individuals building their own homes can save fuel by orienting them so that the sun is directed in during the heat of the day in the winter and onto the rooftop during the sum­mer. Overhang, shade trees, and earth banks keep a home cooler in the summer. We need to increase the energy efficiency of energy conversion devices we use. Your total energy costs depends on your usage habits.   Three of the poorest energy efficient using devices, in widespread use today, are incandescent light bulbs (5% efficiency), vehicles with internal combustion engines (wastes 86-90% fuel energy) and nuclear power plants providing electricity for space heating or water heating (wastes 86-92%) with nuclear fuel, radioactive waste treatment and retiring nuclear plants included)       

      One potential force in energy conservation is the federal government. Cheaper energy prices in the United States are partly the result of national policy to keep prices down through sub­sidies such as oil depletion allowances, price controls, price regulations, and permissiveness with health and environmental risks. Such policies distort the energy market. When the true cost of energy is borne by the consumer, conservation practices will be encouraged.

      Energy conservation requires a combined effort of individuals, industry, and governmental agencies. The best short-term, intermediate and long-term alternatives are a combination of improved energy efficiency and greatly increased use of locally available renewable energy resources. If we are to make a transition from our pres­ent use of fossil fuel to new energy sources, it must be done more rapidly than the transition from wood to coal, which took about 80 years There does not appear to be one best form of energy available for future use. All sources need to be developed to determine the best form for each region. We need not one source of energy, not one solution, but a sys­tems approach to the problem.