Module 1 energy 2023

MINISTRY OF EDUCATION AND TRAINING NONG LAM UNIVERSITY FACULTY OF FOOD SCIENCE AND TECHNOLOGY Course: Physics Module 1: Energy Instructor: Dr Nguyen Thanh Son Academic year: 2022-2023 Contents Module 1: Energy 1.1 Energy resources using traditional materials 1.1.1 Energy resources using traditional materials 1.1.2 Problems with these resources 1.1.3 Alternative energy sources 1.2 Thermionic engine/converter 1.2.1 Principle of thermionic emission 1.2.2 Thermionic engine 1.3 Electric energy 1.3.1 Electricity is a secondary energy source 1.3.2 Electricity generation 1.4 Nuclear energy 1.4.1 Einstein’s mass – energy relation 1.4.2 Nuclear reaction 1.4.3 Nuclear fission and nuclear fusion 1.5 Solar energy 1.5.1 Energy from the sun 1.5.2 Applications of solar technology 1.6 Other energy sources 1.6.1 Wind energy 1.6.2 Hydroelectric energy 1.6.3 Biomass energy 1.6.4 Fuel cells Physics Module 1: Energy 1.1 Energy resources using traditional materials Energy is one of the most fundamental parts of our universe It is a scalar physical quantity In physics textbooks, energy is often defined as the ability to work or to generate heat While one form of energy may be transformed to another, the total energy remains the same This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system In other words, energy is subject to the law of conservation of energy According to this law, energy can neither be created (produced) nor destroyed by itself and it can only be transformed We use energy to work Energy lights our cities Energy powers our vehicles, trains, planes and rockets Energy warms our homes, cooks our food, plays our music, and gives us pictures on television Energy powers machinery in factories and tractors on farms Energy from the sun gives us light during the day It dries our clothes when they're hanging outside on a clothe line It helps plants grow Energy stored in plants is consumed by animals, giving them energy; and predator animals eat their prey, which gives the predator animal energy Everything we is connected to energy in one form or another There are many sources of energy Energy is present in the universe in various forms, including mechanical, electromagnetic, chemical, and nuclear, etc Furthermore, one form of energy can be converted into another For example, when an electric motor is connected to a battery, the chemical energy in the battery is converted into electrical energy in the motor, which in turn is converted into mechanical energy as the motor turns some device The transformation of energy from one form to another is an essential part of the study of physics, engineering, chemistry, biology, geology, and astronomy When energy is changed from one form to another, the total amount present does not change Conservation of energy means that although the form of energy may change, if an object (or system) loses energy, that same amount of energy appears in another object or in the object’s surroundings 1.1.1 Energy resources using traditional materials These traditional materials (or resources) include: coal, oil and natural gas (collectively called fossil fuels) All three were formed many hundreds of millions of years ago before the time of the dinosaurs hence the name fossil fuels • Coal Coal is a hard, black colored, rock-like substance It is made up of carbon, hydrogen, oxygen, nitrogen, and varying amounts of sulphur There are three main types of coal - anthracite, bituminous and lignite Anthracite coal is the hardest and has more carbon, which gives it a higher energy content Lignite is the softest and is low in carbon but high in hydrogen and oxygen content Bituminous is in between Today, the precursor to coal - peat - is still found in many countries and is also used as an energy source Coal is mined out of the ground using various methods Some coal mines are dug by sinking vertical or horizontal shafts deep under ground, and coal miners travel by elevators or trains deep under Physics Module 1: Energy ground to dig the coal Other coal is mined in strip mines where huge steam shovels strip away the top layers above the coal The layers are then restored after the coal is taken away The coal is then shipped by trains and boats and even in pipelines In pipelines, the coal is ground up and mixed with water to make what is called a slurry This is then pumped many miles through pipelines At the other end, the coal is used to fuel power plants and other factories Coal is used to generate electricity Power plants burn coal to make steam The steam turns turbines which generate electricity ` A variety of industries use coal's heat and by-products Separated ingredients of coal (such as methanol and ethylene) are used in making plastics, tar, synthetic fibers, fertilizers, and medicines The concrete and paper industries also burn large amounts of coal Coal is baked in hot furnaces to make coke, which is used to smelt iron ore into iron needed for making steel It is the very high temperatures created from the use of coke that gives steel the strength and flexibility for products such as bridges, buildings, and automobiles • Oil or petroleum Oil is another fossil fuel It was also formed more than 300 million years ago Some scientists say that tiny diatoms are the source of oil Diatoms (a kind of algae) are sea creatures having the size of a pin head They one thing just like plants: converting sunlight directly into stored energy In the Figure 1, as the diatoms died they fell to the sea floor (1) Here they were buried under sediments and other Figure Process of oil formation rocks (2) The rocks squeezed the diatoms, and the energy in their bodies could not escape Under great pressure and heat, oil and natural gas were eventually generated As the earth changed and moved and folded, pockets where oil and natural gas can be found were formed (3) Oil has been used for more than 5,000-6,000 years The ancient Egyptians used liquid oil as a medicine for wounds, and oil has been used in lamps to provide light In North America, Native Americans used oil as medicine and to make canoes water-proof The demand for oil continued to increase as a fuel for lamps Petroleum oil began to replace whale oil in lamps because the price for whale oil was very high As mentioned above, oil and natural gas are found under ground between folds of rock and in areas of rock that are porous and contain the oils within the rock itself To find oil and natural gas, companies drill through the earth to the deposits deep below the surface The oil and natural gas are then pumped from below the ground by oil rigs They then usually travel through pipelines or by ship The petroleum or crude oil must be changed or refined into other products before it can be used Physics Module 1: Energy Oil is stored in large tanks until it is sent to various places to be used At oil refineries, crude oil is split into various types of products by heating the thick black oil Oil is made into many different products - fertilizers for farms, the clothes you wear, the toothbrush you use, the plastic bottle that holds your milk, the plastic pen that you write with There are thousands of other products that come from oil Almost all plastic comes originally from oil The oil products include gasoline, diesel fuel, aviation or jet fuel, home heating oil, oil for ships and oil to burn in power plants to make electricity • Natural gas Natural gas is lighter than air Natural gas is mostly made up of a gas called methane Methane is a simple chemical compound that is made up of carbon and hydrogen atoms Its chemical formula is CH4 - one atom of carbon along with four atoms of hydrogen This gas is highly flammable Natural gas is usually found near petroleum underground It is pumped from below ground and travels in pipelines to storage areas Natural gas usually has no odor, and we cannot see it Before it is sent to the pipelines and storage tanks, it is mixed with a chemical that gives a strong odor The odor smells almost like rotten eggs The odor makes it easy to smell if there is a leak Natural gas is a major source of electricity generation through the use of gas turbines and steam turbines Natural gas is also used for heating and cooking Natural gas is an essential raw material for many common products, such as paints, fertilizers, plastics, antifreezes, dyes, photographic films, medicines, and explosives as well Another use is powering natural gas vehicles in many countries such as Argentina, Brazil, Pakistan, Italy, Iran, and the United States 1.1.2 Problems with these resources • Someday they will run out Fossil fuels are generally such fuels as coal, natural petroleum (oil) and coal These materials were derived from the fossilized remains of plants and animals Much of the world has relied upon these fuels for decades and more As the years go on, the sources of these fuels have become less and less The problem with fossil fuels is that they will someday run out It takes time for these energy sources to develop within the crust of the earth At the current rate of consumption, there is no way that these fuels can develop naturally and not be used up Currently there are ways being developed to sustain these fuels More efficient uses of these energies are being produced Cars with better gas mileage are being manufactured Hybrid cars which use electricity as well as gas are just one of many products which have been developed to sustain the use of fossil fuels Still these fuels are being depleted Fossils fuels cannot last forever at the current rate of consumption Alternatives are being developed to sustain the lifestyles that we have become accustomed to • They have adverse impacts on the environment Another problem with the use of fossil fuels is no matter how safely and efficiently these fuels are being used, they still have adverse impacts on the environment The combustion of these fuels contributes pollutants to the atmosphere and contributes to the greenhouse effect This effect increases global warming and the melting of the polar ice caps Physics Module 1: Energy ♦ Environmental problems with coal, oil, and gas • We consider the wide variety of environmental problems in burning fossil fuels - coal, oil, and gas They probably exceed those of any other human activities The ones that have received the most publicity in recent years have been the "greenhouse effect," which is changing the earth's climate; acid rain, which is destroying forests and killing fish; and air pollution, which is killing tens of thousands of people every year, while making tens of millions ill and degrading our quality of life in other ways • Coal, oil, and gas consist largely of carbon and hydrogen The process that we call "burning" actually is chemical reactions with oxygen in the air For the most part, the carbon combines with oxygen to form carbon dioxide (CO2), and the hydrogen combines with oxygen to form water vapor (H2O) In these chemical reactions, a substantial amount of energy is released as heat Since heat is what is needed to instigate these chemical reactions, we have a chain reaction: reactions cause heat, which causes reactions, which cause heat, and so on • The carbon dioxide that is released is the cause of the greenhouse effect A large coal-burning plant typically burns million tons of coal and produces 11 million tons of carbon dioxide every year The water vapor release presents no problems, since the amount of water vapor in the atmosphere is determined by evaporation from the oceans - if more is produced by burning, that much less will be evaporated from the seas The greenhouse effect and global warming • Electromagnetic radiation is an exceedingly important physical phenomenon that takes various forms depending on its wavelength Every object in the universe constantly emits electromagnetic radiation, and absorbs (or reflects) that which impinges on it According to the laws of physics, the wavelength of the emitted radiation decreases inversely as the temperature increases Conversely, the rate at which an object emits radiation energy increases very rapidly with increasing temperature (doubling the absolute temperature increases the radiation 16-fold) Now let us consider a bare object out in space, such as our moon It receives and absorbs radiation from the sun, which increases its temperature, and this increased temperature causes it to emit more radiation Through this process it comes to an equilibrium temperature, where the amount of radiation it emits is just equal to the amount it receives from the sun That determines the average temperature of the moon If this were the whole story, our earth would be 54 degrees cooler than it actually is, and nearly all land would be covered by ice • The reason for the difference is that the earth's atmosphere contains molecules that absorb infrared radiation They not absorb the visible radiation coming in from the sun, so the earth gets its full share of the visible radiation But a fraction of the infrared radiation emitted by the earth is absorbed by those molecules which then reemit it, frequently back to the earth That is what provides the extra heating This is also the process that warms the plants in a greenhouse - the glass roof does not absorb the visible light coming in from the sun, but the infrared radiation emitted from the plants is absorbed by the glass and much of it is radiated back to the plants That is how the process got its name - greenhouse effect It is also the cause of automobiles getting hot when parked in the sun light; the incoming visible radiation passes through the glass windows, while the infrared emitted from the car's interior is absorbed by the glass and much of it is emitted back into the interior • Molecules in the atmosphere that absorb infrared radiation and thereby increase the earth's temperature are called greenhouse gases Carbon dioxide is an efficient greenhouse gas Our problem is that burning coal, oil, and gas produces carbon dioxide, which adds to the supply already in the atmosphere, increasing the greenhouse effect and thereby increasing the temperature of the earth The average temperature of the earth has been about degree warmer in the 20th century than in the 19th Physics Module 1: Energy century, which is close to what is expected from this carbon dioxide increase As the rate of burning coal, oil, and gas escalates, so too does the rate of increase of carbon dioxide in the atmosphere • Two side effects will accentuate this temperature rise One is that the increased temperature causes more water to evaporate from the oceans, which adds to the number of water molecules in the atmosphere; water vapor is also a greenhouse gas The other side effect is that there would be less ice and snow Acid rain • In addition to combining carbon and hydrogen from the fuel with oxygen from the air to produce carbon dioxide and water vapor, burning fossil fuels involves other processes Coal and oil contain small amounts of sulfur, typically 0.5% to 3% by weight In the combustion process, sulfur combines with oxygen in the air to produce sulfur dioxide (SO2), which is the most important contributor to acid rain Air consists of a mixture of oxygen (20%) and nitrogen (79%), and at very high temperatures, molecules of these can combine to produce nitrogen oxides (NO), another important cause of acid rain Sulfur dioxide and nitrogen oxides undergo chemical reactions in the atmosphere to become sulfuric acid and nitric acid, respectively, dissolved in water droplets that may eventually fall to the ground as rain This rain is therefore acidic • After the rain falls, water percolates through the ground, dissolving materials out of the soil This alters the soil’s pH and introduces other materials into the water If the soil is alkaline, the water's acidity will be neutralized, but if it is acid, the acidity of the water may increase This water is used by plants and trees for their sustenance, and eventually flows into rivers and lakes There have been various reports indicating that streams and lakes have been getting more acidic in recent years Air pollution and health effects • The greenhouse effect and acid rain have received more media attention and hence more public concern than general air pollution This is difficult to understand, because the greenhouse effect causes only economic disruption, and acid rain kills only fish and trees, whereas air pollution kills people and causes human suffering through illness • We have already described the processes that produce sulfur dioxide and nitrogen oxides, which are important components of air pollution as well as the cause of acid rain But many other processes are also involved in burning fossil fuels When carbon combines with oxygen, sometimes carbon monoxide (CO), a dangerous gas, is produced instead of carbon dioxide Thousands of other compounds of carbon, hydrogen, and oxygen, classified as hydrocarbons or volatile organic compounds, are also produced in the burning of fossil fuels During combustion, some of the carbon remains unburned, and some other materials in coal and oil are not combustible; these come off as very small solid particles, called particulates, which are typically less than one ten thousandth of an inch in diameter, and float around in the air for many days Smoke is a common term used for particulates large enough to be visible Some of the organic compounds formed in the combustion process attach to these particulates, including some that are known to cause cancer Coal contains trace amounts of nearly every element, including toxic metals such as beryllium, arsenic, cadmium, selenium, and lead, and these are released in various forms as the coal burns • All of the above pollutants are formed and released directly in the combustion process Some time after their release, nitrogen oxides may combine with hydrocarbons in the presence of sunlight to form ozone, one of the most harmful pollutants • Let us summarize some of the known health effects of these pollutants: Physics Module 1: Energy Sulfur dioxide is associated with many types of respiratory diseases, including coughs and colds, asthma, bronchitis, and emphysema Studies have found increased death rates from high sulfur dioxide levels among people with heart and lung diseases Nitrogen oxides can irritate the lungs, cause bronchitis and pneumonia, and lower resistance to respiratory infections such as influenza; at higher levels it can cause pulmonary edema Carbon monoxide bonds chemically to hemoglobin, the substance in the blood that carries oxygen to the cells, and thus reduces the amount of oxygen available to the body tissues Carbon monoxide also weakens heart contractions, which further reduces oxygen supplies and can be fatal to people with heart disease Even at low concentrations, it can affect mental functioning, visual acuity, and alertness Particulates, when inhaled, can scratch or otherwise damage the respiratory system, causing acute and/or chronic respiratory illnesses Depending on their chemical composition, they can contribute to other adverse health effects For example, benzo-a-pyrene, well recognized as a cancer-causing agent from its effects in cigarette smoking, sticks to surfaces of particulates and enters the body when they are inhaled Hydrocarbons cause smog and are important in the formation of ozone Ozone irritates the eyes and the mucous membranes of the respiratory tract It affects lung function, reduces ability to exercise, causes chest pains, coughing, and pulmonary congestion, and damages the immune system Volatile organic compounds include many substances that are known or suspected to cause cancer Prominent among these is a group called polycyclic aromatic, which includes benzo-a-pyrene mentioned above Toxic metals have a variety of harmful effects Cadmium, arsenic, nickel, chromium, and beryllium can cause cancer, and each of these has additional harmful effects of its own Lead causes neurological disorders such as seizures, mental retardation, and behavioral disorders, and it also contributes to high blood pressure and heart disease Selenium and tellurium affect the respiratory system, causing death at higher concentrations • It is well recognized that toxic substances acting in combination can have much more serious effects than each acting separately, but little is known in detail about this matter Information on the quantities of air pollutants required to cause various effects is also very limited There can however be little doubt that air pollution is a killer 1.1.3 Alternative energy sources • Alternative energy is an umbrella term that refers to any source of usable energy intended to supplement or replace fuel sources without the undesired consequences of the replaced fuels • The sources of alternative energy are nuclear, solar, wind, geothermal and other energies; each of them having Figure Left: Normal earth Right: What the earth would be if we its own advantages and are not using alternative energy sources disadvantages Alternative energy sources hold the key towards the future; without them, our planet will eventually head into a blackout, or back to the Middle Ages, as shown in Figure Physics Module 1: Energy • Oil fuels the modern world No other substance can have the enormous impact which the use of oil has had on so many people, so rapidly, in so many ways, and in so many places around the world • Alternative energy sources must be compared with oil in all these various attributes when their substitution for oil is considered None appears to completely equal oil • But oil, like other fossil fuels, is a finite resource There will always be oil in the earth, but eventually the cost to recover what remains will be beyond the value of the oil Also, a time will be reached when the amount of energy needed to recover the oil equals or exceeds the energy in the recovered oil At that point oil production becomes a net energy loss • Oil being the most important of our fuels today, the term "alternative energy" is commonly taken to mean all other energy sources and is used here in that context Realizing that oil is finite in practical terms, there is increasing attention given to what alternative energy sources are available to replace oil The table below mentions many alternative energy sources that have been developed so far Alternative energy sources Hydro-power electricity Solar energy Wind energy Wood/other biomass Tidal power Wave energy Nuclear fission Nuclear fusion Geothermal energy Ocean thermal energy Ethanol Biofuel 1.2 Thermionic engine Also known as thermionic generator or thermionic converter, thermionic engine is a device in which heat energy is directly converted into electrical energy; it has two electrodes, one of which is raised to a sufficiently high temperature to become a thermionic electron emitter, while the other, serving as an electron collector, is operated at a significantly lower temperature It utilizes the same principles as the thermionic vacuum tube, an electronic device in which electrons are driven from a cathode to an anode by the application of a high potential bias 1.2.1 Principle of thermionic emission ♦ Principles of thermionic emission • A thermionic converter can be viewed as an electronic diode that converts heat into electrical energy via thermionic emission It can also be regarded in terms of thermodynamics as a heat engine that utilizes an electron-rich gas as its working fluid Physics Module 1: Energy Figure Schematic of a basic thermionic converter • A thermionic converter is a diode of which one electrode is heated to a sufficient high temperature (~1700 K) so that electrons are thermionically emitted The electrons are collected on a cooled counter electrode (~900 K), converting heat into electricity • A major problem in developing practical thermionic power converters has been the limit imposed on the maximum current density because of the space-charge effect As electrons are emitted between the electrodes, their negative charges repel one another and disrupt the current Two solutions to this problem have been pursued One involves reducing the spacing between the electrodes to the order of micrometers, while the other entails the introduction of positive ions into the cloud of negatively charged electrons in front of the emitter The latter method has proved to be the most feasible from many standpoints, especially manufacturing It has resulted in the development of both cesium and auxiliary discharge thermionic power converters • Emission of electrons is fundamental to thermionic power conversion The energy required to remove an electron from the surface of an emitter is known as the electronic work function (ϕ) Its value is characteristic of the emitter material and is typically one to five electron volts (eV) Some electrons within the emitter have an energy greater than the work function and can escape The proportion depends on the temperature The current density J0, in amperes per square meter, or the rate at which electron is emitted from the surface of the emitter, is given by the Richardson–Dushman equation J0 = RT exp( −eϕ / kT) (1) where T is the absolute temperature, in kelvins, of the emitter, e is the electronic charge in coulombs, and k is Boltzmann’s gas constant, in joules per kelvin The parameter R in the above equation is also characteristic of the emitter material • Note that the rate of emission increases rapidly with emitter temperature T and decreases exponentially with the work function ϕ It is therefore desirable to choose an emitter material that has a small work function and that operates reliably at high temperatures • Electrons that escape the emitter surface have gained energy equal to the work function, plus some excess kinetic energy Upon striking the collector, a part of the energy is available to force current to flow through the external load, such as a bulb or a resistor, thereby giving the desired conversion from thermal to electrical energy Part of this energy is converted into heat that must be removed to maintain the collector at a suitably low temperature The collector material should have a small work function 1.2.2 Thermionic engine (thermionic converter) • Thermionic converters are designed for use in domestic heating systems They are also used in regulation of current in electric circuits • In a thermionic converter, the electrons received at the anode flow back to the cathode through an external resistance However, because the cathode is hotter than the anode and the work function of the anode is lower than that of the cathode, the rate of electron emission at the cathode is greater than that required at the anode to complete the circuit The surplus electron flow may then be drawn off from the anode as additional electrical energy, effectively converting the heat energy from the cathode into electrical energy at the anode Such devices currently show efficiencies of up to 20% for the energy conversion Physics Module 1: Energy 10 1.4.2 Nuclear reaction • In nuclear physics, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products that are different from the initial particles While the transformation is spontaneous in the case of radioactive decay, it is initiated by a particle in the case of a nuclear reaction For example: Li + H ==> 42 He + ∆E If the particles collide and separate without changing, the process is called a collision rather than a reaction • Energy conservation Energy may be released during the course of a reaction (exothermic reaction) or energy may have to be supplied for the reaction to take place (endothermic reaction) This can be calculated by reference to a table of very accurate particle rest masses According to the reference table, the Li nucleus ( 63 Li ) has a mass of 6.015 atomic mass units (abbreviated u), the deuteron ( 12 H ) has 2.014 u, and the helium-4 nucleus ( 42 He ) has 4.0026 u Thus: Total rest mass on left side = 6.015 + 2.014 = 8.029 u, Total rest mass on right side = × 4.0026 = 8.0052 u, Missing rest mass = 8.029 − 8.0052 = 0.0238 u In any nuclear reaction, the total (relativistic) energy is conserved The "missing" rest mass is ∆m = 0.0238 u and must therefore reappear as energy ∆E released in the reaction; its source is the nuclear binding energy Using ∆E = (∆m)c2, the amount of energy released can be determined Hence, the energy released is 0.0238 x 931.5 MeV = 22.17 MeV • The energy released in a nuclear reaction can appear mainly in one of three ways: kinetic energy of the product particles, emission of very high energy photons, called gamma rays, some energy may remain in the nucleus, as a metastable energy level • When a product nucleus is metastable, it is indicated by placing an asterisk ("*") next to its atomic number The corresponding energy is eventually released through nuclear decay • In physical theories prior to special relativity, mass and energy were viewed as distinct entities Furthermore, the energy of a body at rest could be assigned an arbitrary value In special relativity, however, the energy of a body at rest is determined to be mc2 Thus, any body of rest mass m possesses mc2 of “rest energy,” which is potentially available for conversion into other forms of energy The massenergy relation, moreover, implies that if energy is released from the body as a result of such a conversion, then the rest mass of the body will decrease Such a conversion of rest energy into other forms of energy occurs in ordinary chemical reactions, but much larger conversions occur in nuclear reactions This is particularly true in the case of nuclear-fusion reactions that transform hydrogen into helium, in which 0.7 percent of the original rest energy of the hydrogen is converted into other forms of energy • To calculate the energy released ∆E in a nuclear reaction, we use the formula Physics Module 1: Energy 15 ∆E = [ ∑ mreac tan ts − ∑ m products ]c2 where ∑m reac tan ts is the total rest mass of reactant nuclei (before the reaction) and (3’’) ∑m products the total rest mass of products (after the reaction) If ∆E > the nuclear reaction is exothermic and if ∆E < the nuclear reaction is endothermic Example: Consider two deuterium nuclei fusing to form a helium nucleus: D + D ==> He + ∆E (D consists of a proton and a neutron; He consists of two of each.) Each D has rest mass 2.01410 u and He has rest mass 4.00260 u (1 u = 1.660566 x 10 -27 kg) Calculate ∆E (Ans 3.8 x 10-12 J) 1.4.3 Nuclear fission and nuclear fusion ♦ Nuclear fission • In nuclear physics, nuclear fission is a nuclear reaction in which the nucleus of an atom splits (breaks) into smaller parts, often producing free neutrons and lighter nuclei (fragments) and photons (in the form of gamma rays), as shown in Figure Figure Depicting of a nuclear fission with U-235 • Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where the fission takes place) • Nuclear fission produces energy for nuclear power and for driving the explosion of nuclear weapons Both uses are made possible because certain substances, called nuclear fuels, undergo fission when struck by free neutrons and in turn generate neutrons when they break apart • Nuclear fission can be harnessed and controlled via a self-sustaining chain reaction A chain reaction refers to a process in which neutrons released in a fission produce an additional fission in at least one further nucleus This nucleus in turn produces neutrons, and the process repeats, as shown in Figure The process may be controlled (nuclear power) or uncontrolled (nuclear weapons) If each fission releases two more neutrons, then the number of fissions doubles each generation In this case, in 10 generations there are 1,024 fissions and in 80 generations about x 10 23 fissions • The amount of free energy contained in nuclear fuel is millions of times the amount of free energy contained in a similar mass of chemical fuel such as gasoline, making nuclear fission a very tempting source of energy; however, the products of nuclear fission are radioactive and remain so for significant amounts of time, giving rise to a nuclear waste problem Physics Module 1: Energy 16 Figure Depicting of a chain reaction with U-235 • The most common nuclear fuels are 235U (the isotope of uranium with an atomic mass of 235 and of use in nuclear reactors) and 239Pu (the isotope of plutonium with an atomic mass of 239) These fuels break apart into elements (fragments) with atomic masses centering near 95 and 135 u In a nuclear reactor or nuclear weapon, most fission events are induced by bombardment with another particle such as a neutron • The following two equations are examples of the different products that can be produced when a U235 nucleus breaks apart: 235 U + n ==> 141 Ba + 92 Kr + 3n + 170 MeV, 92 56 36 235 92 U + n ==> 94 40 Zr + 139 52 Te + 3n + 197 MeV In the first equation, the number of nucleons (protons and neutrons) is conserved, e.g 235 + = 141 + 92 + 3, but a small loss in mass can be shown to be equivalent to the energy released Similarity is found for the second equation • If a massive nucleus like uranium-235 breaks apart, then there will be a net yield of energy because the sum of the rest masses of the fragments and generated neutrons is less than the total rest mass of the uranium nucleus and the initial neutron The decrease in mass comes off in the form of energy according to Einstein’s relation The total energy released in fission varies with the precise break up, but averages about 200 MeV or 3.2 x 10 -11 J for U-235 and about 210 MeV for Pu-239 per fission This contrasts with eV or 6.5 x 10-19 J per molecule of carbon dioxide released in the combustion of carbon in fossil fuels Physics Module 1: Energy 17 • Natural uranium is composed of 0.72% U-235 (the fissionable isotope), 99.27% U-238, and a trace quantity 0.0055% U-234 The 0.72% U-235 is not sufficient to produce a self-sustaining critical chain reaction in light-water reactors For light-water reactors, the fuel must be enriched to 2.5-3.5% U-235 ♦ Nuclear fusion • Fusion power is power generated by nuclear fusion reactions In nuclear fusion, two light atomic nuclei fuse together (join) to form a heavier nucleus and in doing so, release energy In a more general sense, the term can also refer to the production of net usable power from a fusion source Most design studies for fusion power plants involve using fusion reactions to create heat, which is then used to operate a steam turbine, similar to most coal-fired Figure Left is a diagram of the He-He reaction power stations as well Right is a diagram of the D-T reaction as fission-driven nuclear power stations • One example of nuclear fusion reactions is 32 He + 32 He ==> 42 He + 11 H + 11 H + ∆E and shown graphically in the left panel of Figure When two of 3He hit each other, the neutrons and protons rearrange themselves into one nucleus ( 42 He ) and two free protons, releasing an amount of energy, ∆E • The easiest and most immediately promising nuclear reaction to be used for fusion power is D + 13 T ==> 42 He + n + 17.6 MeV This is the fusion of deuterium with tritium creating helium-4, freeing a neutron, and releasing 17.6 MeV of energy, as shown in the right panel of Figure The neutron carries 14.1 MeV and the helium-4 nucleus ( 42 He ) has the remaining 3.5 MeV Conservation of energy gives (2.014102+3.016050)uc2 = (4.002603+1.008665) uc2 + ∆E, where ∆E is the energy released in the reaction As a result, ∆E = 0.01884 uc2 = 0.01884 x 931.5 MeV = 17.6 MeV; 14.1 MeV is given to the neutron and 3.5 MeV to He-4 This means that the D-T fusion reaction is very highly exothermic, making it a powerful energy source • Deuterium is a naturally occurring isotope of hydrogen, and as such is universally available The large mass ratio of the hydrogen isotopes makes the separation rather easy compared to the difficult uranium Physics Module 1: Energy 18 enrichment process Tritium is also an isotope of hydrogen, but it occurs naturally in only negligible amounts due to its radioactive half-life of 12.32 years Consequently, the deuterium-tritium fuel cycle requires the breeding of tritium from lithium using one of the following reactions: n + 63 Li ==> 13 T + 24 He, n + 73 Li ==> 13 T + 42 He + n The reactant neutron is supplied by the D-T fusion reaction mentioned earlier, the one which also produces the useful energy The reaction with 63 Li is exothermic, providing a small energy gain for the reactor The reaction with 73 Li is endothermic but does not consume the neutron At least some 73 Li reactions are required to replace the neutrons lost by reactions with other elements Most reactor designs use the naturally occurring mix of lithium isotopes The supply of lithium is more limited than that of deuterium, but still large enough to supply the world's energy demand for thousands of years • The basic concept behind any fusion reaction is to bring two or more atoms close enough together so that the strong nuclear force in their nuclei will pull them together into one larger atom If two light nuclei fuse, they will generally form a single nucleus with a slightly smaller mass than the sum of their original masses The difference in mass corresponds to an energy released according to the formula ∆E = ∆mc2 • Nuclear fusion occurs naturally in stars Nuclear fusion is the energy source which causes stars to shine and hydrogen bombs to explode The sun is a natural fusion reactor • The energy released in most nuclear reactions is much larger than that in chemical reactions because the binding energy that glues nucleons in a nucleus together is far greater than the energy that holds electrons to a nucleus For example, the ionization energy gained by adding an electron to hydrogen ion (H+) is 13.6 electron volts - less than one-millionth of that it takes to force nuclei to fuse, even those of the least massive element, hydrogen On the other hand, the fusion of lighter nuclei, which creates a heavier nucleus and a free neutron, will generally release even more energy than it took to force them together - an exothermic process that can produce self-sustaining reactions 1.5 Solar energy 1.5.1 Energy from the sun • Solar energy is the energy obtained from the sun • We know today that the sun is simply our nearest star Without it, life would not exist on our planet We use the sun's energy every day in many different ways The sun provides energy in two forms – light and heat The sun’s energy or solar energy can be used to heat water in our homes and businesses It can also be used to produce electricity Energy produced by the sun is called solar power • Sunlight is the earth's primary source of energy This energy can be harnessed via a variety of natural and synthetic processes - photosynthesis by plants captures the energy of sunlight and converts it into chemical form (oxygen and reduced carbon compounds), while direct heating or electrical conversion by solar cells are used by solar power equipment to generate electricity or to other useful work The energy stored in petroleum and other fossil fuels was originally converted from sunlight by photosynthesis in the distant past Physics Module 1: Energy 19 • The earth receives on average about 174 petawatts (1 petawatt = PW = 1015 watts) of incoming solar radiation at the upper atmosphere Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans, and land masses The spectrum of sunlight at the earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet • Solar energy refers primarily to the use of solar radiation for practical ends Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the sun Active solar technologies increase the supply of energy, while passive solar technologies reduce the need for alternate resources ♦ Solar energy storage methods • The storage of solar energy is an important issue in the development of solar energy because modern energy systems usually assume continuous availability of energy Solar energy is not available at night, and the performance of solar power systems is affected by unpredictable weather patterns; therefore, storage media or back-up power systems must be used Thermal mass systems can store solar energy in the form of heat at domestically useful temperatures for daily or seasonal durations Thermal storage systems generally use readily available materials with high specific heat capacities such as water, earth, and stone Phase change materials such as paraffin wax and Glauber's salt are other thermal storage media These materials are inexpensive, readily available, and can deliver heat at domestically useful temperatures (approximately 64°C) Solar energy can be stored at high temperatures using molten salts Salts are an effective storage medium because they are low-cost, have a high specific heat capacity and can deliver heat at temperatures compatible with conventional power systems Off-grid systems have traditionally used rechargeable batteries to store excess electricity With grid-tied systems, excess electricity can be sent to the transmission grid Net metering programs give these systems a credit for the electricity they deliver to the grid This credit offsets electricity provided from the grid when the system cannot meet demand, effectively using the grid as a storage mechanism Pumped-storage hydroelectricity systems store energy in the form of water pumped from a lower elevation reservoir to a higher elevation one when energy is available The energy is recovered when demand is high by releasing the water to run through a hydroelectric power generator • Solar energy is used commonly for heating, cooking, and even in the desalination of seawater, in works by trapping the sun's rays into solar cells where this sunlight is then converted into electricity Other methods include using sunlight that hits parabolic mirrors to heat water (producing steam), or simply opening a rooms blinds or window shades to allow entering sunlight to passively heat a room .1.5.2 Applications of solar technology Four-fifths of the sun’s energy falls on the oceans and drives the water cycle Evaporation from the sea causes rain to fall on the land, resulting in the global hydropower resource The remaining fifth of the sun’s energy falls on the land and is still about 2,000 times greater than the total world energy demand The main technologies that have been developed to capture the solar energy are Passive Solar, Solar Thermal, Photovoltaic modules, and Concentrating Solar Power (CSP) systems • Passive Solar refers to the way in which buildings are designed consciously to heat space This method can provide up to 70% of the building’s energy requirements simply by using design and solar Physics Module 1: Energy 20 orientation By installing large glass windows on right surfaces, one gains large amounts of solar energy To avoid excessive heat, either overhanging balconies are installed or trees are planted nearby (The benefit of trees is that they reduce sunlight in the summer, but in the winter, when the leaves have fallen and the sun is lower, they allow the light to come in.) • Solar Thermal refers to the use of solar energy to heat water A solar water heater is simply water pipes that are painted black to improve heat absorption The pipes are small in diameter, ensuring that there is a large surface area of water exposed to the sun Then, the pipes are placed in a small greenhouse, which acts to keep them insulated Solar water heaters are facing the sun to maximize gain • The Photovoltaic Effect refers to the generation of electricity from sunlight in a solid-state device with photovoltaic cells as its basic building blocks A photovoltaic cell, commonly called a solar cell or PV cell, is a device used to convert solar energy directly into electrical power As mentioned above, photovoltaic cells are the basic building blocks of a photovoltaic Figure A diagrams illustrating the operation of a basic photovoltaic (PV) cell system Individual cells can vary in size from about centimeter (1/2 inch) to about 10 centimeters (4 inches) across However, one cell produces only or watts, which is not enough for most applications To increase power output, cells are electrically connected into a packaged weather-tight module Modules can be further connected to form an array The term array refers to the entire generating plant, whether it is made up of one or several thousand modules The number of modules connected together in an array depends on the amount of power output needed Most current technology photovoltaic modules are about 10 percent efficient in converting sunlight Further research is being conducted to raise this efficiency to 20 percent • Photovoltaic cells, like batteries, generate direct current (DC) which is generally used for small loads (electronic equipment) such as watches, calculators, and lighted road signs When DC power from photovoltaic cells is used for commercial applications or sold to electric utilities using the electric grid, it must be converted into alternating current (AC) using inverters, solid state devices that convert DC power into AC power • Figure illustrates the operation of a basic photovoltaic (PV) cell made of semiconductor materials, such as silicon, used in the microelectronics industry When sunlight strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material If electrical conductors are attached to the positive and negative sides of this material, forming an electrical circuit, the electrons can be captured in the form of an electric current - that is, electricity This electricity can then be used to power a load such as a light bulb (here) or a small electric device It is this kind of electricity that powers space satellites Physics Module 1: Energy 21 • The most common photovoltaic (PV) cell is made mostly from silicon, the earth’s second most abundant element Special panels of photovoltaic cells capture light from the sun and convert it directly into electricity PV generators operate with no moving parts, noise, or pollution This makes them a very appropriate renewable energy source for urban areas Over the past few years, there has been rapid progress in the development of PV cells, increasing their efficiency while decreasing their cost and weight Worldwide sales of PV modules have increased dramatically over the past few years, from 35 peak megawatts/year (35 MW/year) in 1988 to 83 MW/year in 1995 PV cells played an essential part in the success of early commercial satellites and they remain vital to the telecommunication infrastructure today • Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam The concentrated light is then used as a heat source for a conventional power plant A wide range of concentrating technologies exists; the most developed are the solar trough, parabolic dish, and solar power tower These methods vary in the way they track the sun and focus light In all these systems, a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage A solar trough consists of a linear parabolic reflector that concentrates light Figure 10 Solar troughs are the most widely onto a receiver positioned along the deployed and cost-effective CSP technology reflector's focal line The reflector is made to follow the sun during the daylight hours by tracking along a single axis Trough systems provide the best land-use factor of any solar technology An example of solar troughs is given in Figure 10 A parabolic dish system consists of a stand-alone parabolic reflector that concentrates light onto a receiver positioned at the reflector's focal point The reflector tracks the sun along two axes Parabolic dish systems give the highest efficiency among CSP technologies The Stirling solar dish combines a parabolic concentrating dish with a Stirling heat engine which normally drives an electric generator The advantages of Stirling solar technology over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime A Stirling engine has an approximate mean time before failure (MTBF) of 25 years A solar power tower uses an array of tracking reflectors to concentrate light on a central receiver atop a tower Power towers are less advanced than trough systems but offer higher efficiency and better energy storage capability • Beside those mentioned above, other devices and equipment using solar energy have been recently developed They include solar vehicles (cars, boats, etc.), solar distillation systems which are used to make saline or brackish water potable, and solar cookers that use sunlight for cooking, drying and pasteurization, etc Physics Module 1: Energy 22 `1.6 Other energy sources 1.6.1 Wind energy • Wind energy is the energy obtained from wind People harness the power of the wind to propel the blades of wind turbines The rotation of turbine blades is converted into electrical current by means of an electrical generator In the older windmills, wind energy was used to turn mechanical machinery to physical work, like crushing grain or pumping water Wind towers are usually built together on wind farms Today, electrical currents are harnessed by large scale wind farms that are used by electrical grids as well as by small individual turbines for providing electricity to isolated locations or individual homes In 2005, the worldwide capacity of wind-powered generators was 58,982 megawatts, and their production made up less than 1% of world-wide electricity use • Wind power plants, or wind farms, are clusters of wind machines used to produce electricity A wind farm usually has dozens of wind machines scattered over a large area Large scale wind farms are typically connected to the local electric power transmission network, while smaller ones are used to provide electricity to isolated locations • Wind power has advantages and disadvantages as shown below: Advantages Wind power produces no pollutions that can contaminate the environment Since no chemical processes take place, like in the burning of fossil fuels; in wind power generation, there are no harmful by-products left over Farming and grazing can still take place on land occupied by wind turbines Wind farms can be built off-shore Wind, used as a fuel, is free and nonpolluting and produces no emissions or chemical wastes Wind energy as a power source is favored by many environmentalists as an alternative to fossil fuels, as it is plentiful, renewable, widely distributed, clean, and produces lower greenhouse gas emissions Disadvantages Wind power is intermittent Consistent wind is needed for continuous power generation If wind speed decreases, the turbine lingers and less electricity is generated Large wind farms can have a negative effect on the scenery Figure 11 A diagram of a wind machine for electricity generating (a wind generator) • Currently, more than 20,000 wind turbines are used for generating electricity around the Physics Module 1: Energy 23 world and over a million for pumping water Countries such as Denmark, Germany, Britain, and Spain have installed numerous wind systems in order to help meet some of their energy requirements • A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill If the mechanical energy is then converted into electricity, the machine is called a wind generator Figure 11 shows a diagram of a modern wind generator • The blades of the turbine are attached to a hub that is mounted on a turning shaft The shaft goes through a gear transmission box where the turning speed is increased The transmission is attached to a high speed shaft which turns a generator that makes electricity • In order for a wind turbine to work efficiently, wind speeds usually must be above 12 to 14 miles per hour Wind has to have this speed to turn turbines fast enough to generate electricity The turbines usually produce about 50 to 300 kilowatts of electricity each • If the wind speed gets too high, the turbine has a brake that will keep the blades from turning too fast and being damaged • Operating a wind power plant is not as simple as just building a windmill in a windy place Wind plant owners must carefully plan where to locate their machines One important thing to consider is how fast and how much the wind blows As a rule, wind speed increases with altitude and over open areas with no windbreaks Good sites for wind plants are the tops of smooth, rounded hills, open plains or shorelines, and mountain gaps 1.6.2 Hydroelectric energy • Hydro means "water" So, hydroelectric energy is electrical energy generated using water power In a hydroelectric power plant, potential energy (or the "stored" energy in a reservoir) becomes kinetic energy This mechanical energy is then turned into electrical energy Hydroelectric energy is a renewable resource Figure 12 shows a diagram of a hydroelectric power plant Physics Module 1: Energy 24 Figure 12 A diagram of a typical hydroelectric power plant From the figure: water is stored behind a dam in a reservoir There is a water intake This is a narrow opening to a tunnel which is called the penstock Water pressure (from the weight of the water and gravity) forces the water through the penstock and onto the blades of a turbine The moving water pushes the blades and turns the turbine The turbine spins due to the force of the water The turbine is connected to an electrical generator inside the powerhouse The generator produces electricity which travels over long-distance power lines to homes and businesses • Therefore, we see that hydroelectric energy comes from the falling water; the force of falling water is used to drive turbine-generators to produce electricity Hydroelectric power plants produce more electricity than any other alternative energy sources • Hydroelectric energy source offers many advantages over other energy sources It is, however, facing unique environmental challenges Advantages Hydroelectric energy is fueled by water, therefore it is a clean fuel source Hydroelectric power plants not pollute the air like power plants that burn fossil fuels, such as coal or natural gas Generally, hydroelectric energy is a domestic source of energy Hydroelectric energy relies on the water cycle, which is driven by the sun, thus it is a renewable power source Hydroelectric energy is generally available as needed; people can control the flow of water through the turbines to produce electricity on demand Hydroelectric power plants provide benefits in addition to clean electricity Impoundment hydroelectric power plants create reservoirs that offer a variety of recreational opportunities, notably fishing, swimming, and boating Most hydroelectric power plant installations are required to provide some public access to the reservoir to allow the public to take advantage of these opportunities Other benefits may include water supply and flood control Physics Module 1: Energy 25 Disadvantages Fish populations can be impacted if fish cannot migrate upstream past impoundment dams to spawning grounds, or if they cannot migrate downstream to the ocean Hydroelectric power plants can impact water quality and flow Hydroelectric power plants can cause low dissolved oxygen levels in the water; a problem that is harmful to riverbank habitats Hydroelectric power plants can be impacted by drought When water is not available, hydroelectric power plants cannot produce electricity New hydroelectric power plant facilities impact the local environment and may compete with other uses for the land Those alternative uses may be more highly valued than electricity generation Humans, flora, and fauna may lose their natural habitats Local cultures and historical sites may also be impinged upon 1.6.3 Biomass energy • Biomass energy is the energy produced from plants and plant-derived materials which are made up of carbohydrates - organic compounds formed in growing plantlife Biomass fuels include wood and forest and mill residues, animal wastes, grains, agricultural crops, and aquatic plants Biomass comes in a variety of forms: wood, sawdust, straw, rape seed, dung, waste paper, household refuse, sewage, and many others These materials are used as fuel to heat water for steam or processed into liquids and gases, which can be burned to produce energy • Biomass energy is a renewable energy source because the growth of new plants and trees replenishes the supply • Biomass is found all around us It exists in trees, in grasses, and in oceans More specifically, biomass consists of all the earth’s living matter and is found in the thin surface layer, the biosphere Figure 13 Left panel: biomass is collected Right panel: a biomass power plant • How to obtain biomass energy is very simple, as shown in Figure 13 The waste wood, tree branches, and other scraps are gathered together in big trucks (left panel of Figure 13) The trucks bring the waste from factories and from farms to a biomass power plant Here the biomass is dumped into huge hoppers This is then fed into a furnace where it is burned The resulting heat is then used to boil water in the Physics Module 1: Energy 26 boiler, and the energy in the steam is used to turn the turbine of electricity generators at a biomass power plant (right panel of Figure 13) • The creation of electricity from biomass is a very promising renewable energy technology Biomass fuels - agricultural residues or crops grown specifically for energy production - replace the conventional fossil fuels in powering electric generators Apart from electricity, biomass can also be used to produce liquid fuels, gaseous fuels, and a variety of useful chemicals, including those currently manufactured from petroleum Biomass is an important store of energy for the earth because it is being continually replenished • Biomass energy has numerous environmental benefits Firstly, because biomass fuels produce practically no sulphur emissions, they are not responsible for the production of acid rain Secondly, although CO2 is a by-product of biomass combustion, the same amount of CO2 is absorbed during the growth period of the biomass, and therefore, no net carbon dioxide is produced, as long as it is cultivated and harvested in a sustainable and repeated cycle Thirdly, because fewer materials are sent to the landfills, the lives of the current landfills are prolonged Fourthly, the combustion of biomass produces less ash than that of coal, therefore reducing the cost of ash disposal and landfill space requirements Biomass ash can additionally be used to improve the soil on farm land Finally, crops of biomass need less fertilizer and herbicides, and they provide much more vegetative cover, thus protecting it against soil erosion and watershed quality deterioration Biomass crops also result in enhanced wildlife cover • In addition to their environmental benefits, biomass has economic benefits By the year 2010, it was predicted that over 13,000 megawatts of biomass energy could be obtained Thus, crops planted specifically for biomass energy would complement the existing crops of farmers instead of competing with them • Today, biomass accounts for about 14% of the world’s primary energy consumption Currently, most of biomass energy comes from wood residues from the forest industries or wood cut into firewood • Large-scale biomass development, however, does pose a number of challenges to biodiversity, land availability, water resources, and local pollution; all of which need to be carefully addressed when considering biomass an energy source The issue of fuel versus food is very complex and has been heavily debated In order to gain maximum benefit from biomass, it is important to encourage agricultural processes which optimize land-use in order to meet both needs 1.6.4 Fuel cells • Fuel cells are electrochemical devices that produce electricity through a chemical reaction The basic design of a fuel cell involves two electrodes on either side of an electrolyte (see Figure 14) Hydrogen and oxygen pass over each of the electrodes and through means of a chemical reaction, electricity, heat, and water are produced Hydrogen fuel is supplied to the anode (negative terminal) of the fuel cell while oxygen is supplied to the cathode (positive terminal) of the fuel cell Through a chemical reaction, the hydrogen molecules are split into electrons (e-) and protons (H+) which take different paths to the cathode The electrons are capable of taking a path other than through the electrolyte, which, when harnessed correctly, can produce electricity for a given load such as a light bulb The protons pass through the electrolyte and reunite with the electrons at the cathode At the cathode, electrons, protons, and oxygen molecules combine to form water - the harmless by-product which is exhausted This process is shown in Figure 14 Physics Module 1: Energy 27 • As a result, fuel cells are able to convert fuel directly into electricity without burning the fuel by combining stored hydrogen with oxygen from the air This bypasses the standard method of obtaining electricity from a fuel through combustion Fuel cells are able to offer high thermodynamic efficiency, quiet operation, near-zero pollutant emissions, and low maintenance requirements Fuel cells convert energy very efficiently, which helps conserve energy resources, and the only byproduct of this chemical process is pure water - a clear benefit for the environment Figure 14 A diagram depicting the operation of a fuel cell • There are several different types of fuel cells, and they are used for completely different applications Some are suitable for use in automobiles while others are more useful in the development of stationary electricity generation • A typical cell running at 0.7 V has an efficiency of about 50%, meaning that 50% of the energy content of the hydrogen fuel is converted into electrical energy and the remaining 50% will be converted into heat • In principle, a fuel cell operates like a battery Unlike a battery, however, a fuel cell does not run down or require recharging It will produce energy in the form of electricity and heat as long as fuel is supplied • Hydrogen fuel cell technology has numerous advantages Firstly, it is possible that no pollution will be produced Secondly, fuel cells are more efficient in their conversion of energy into electricity than any other power system They can convert energy with up to 80% efficiency Thirdly, fuel cells are nearly silent if they are operating normally, and they last significantly longer than the machines they replace Finally, fuel cells can be of any size, from small enough to fit in a golf cart to large enough to power an entire community, and are therefore very versatile Physics Module 1: Energy 28 References 1) Halliday, David; Resnick, Robert; Walker, Jearl (1999), Fundamentals of Physics, 7th ed., John Wiley & Sons, Inc 2) Feynman, Richard; Leighton, Robert; Sands, Matthew (1989), Feynman Lectures on Physics, Addison-Wesley 3) Serway, Raymond; Faughn, Jerry (2003), College Physics, 7th ed., Thompson, Brooks/Cole 4) Sears, Francis; Zemansky Mark; Young, Hugh (1991), College Physics, 7th ed., Addison-Wesley 5) Beiser, Arthur (1992), Physics, 5th ed., Addison-Wesley Publishing Company 6) Jones, Edwin; Childers, Richard (1992), Contemporary College Physics, 7th ed., Addison-Wesley 7) Alonso, Marcelo; Finn, Edward (1972), Physics, 7th ed., Addison-Wesley Publishing Company 8) Michels, Walter; Correll, Malcom; Patterson, A L (1968), Foundations of Physics, 7th ed., AddisonWesley Publishing Company 9) Hecht, Eugene (1987), Optics, 2th ed., Addison-Wesley Publishing Company 10) Eisberg, R M (1961), Modern Physics, John Wiley & Sons, Inc 11) Reitz, John; Milford, Frederick; Christy Robert (1993), Foundations of Electromagnetic Theory, 4th ed., Addison-Wesley Publishing Company 12) Priest, Joseph (1991), Energy: Principle, Problems, Alternatives, 4th ed., Addison-Wesley Publishing Company 13) Giambattista Alan; Richardson, B M; Richardson, R C (2004), College Physics, McGraw-Hill 14) Websites: http://csep10.phys.utk.edu/astr162/lect/energy/mass-energy.html http://www.oilcrisis.com/Youngquist/altenergy.htm http://www.cc.utah.edu/~ptt25660/tran.html http://www.oregon.gov/ENERGY/RENEW/Biomass/BiomassHome.shtmlhttp://www.oregon.go v/ENERGY/RENEW/Biomass/BiomassHome.shtml http://www.canadianencyclopedia.ca/index.cfm?PgNm=TCE&Params=A1ARTA0000758 http://www.biomassenergycentre.org.uk/portal/page?_pageid=76,15049&_dad=portal&_schema =PORTAL http://www.world-mysteries.com/sci_9.htm http://www.phy6.org/stargaze/Snuclear.htm http://www.edinformatics.com/math_science/alternative_energy/nuclear/nuclear_basics.htm http://en.wikipedia.org/wiki/Solar_energy http://www.energyquest.ca.gov/story/chapter15.html http://www.phy6.org/stargaze/Lsun7erg.htm http://www.grc.nasa.gov/WWW/Electrochemistry/doc/fuelcell.html http://www.gmi.edu/~altfuel/fcback.htm http://www.cynosura.org/index.php?option=com_content&view=article&id=64:introduction-tofuel-cell-technology&catid=10:khoahoc-congnghe&Itemid=80 Physics Module 1: Energy 29