VCE Environmental Science - Unit 3 - Energy


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VCE Environmental Science - Unit 3 - Energy

  1. 1. Unit 3 Environmental Science: Energy
  2. 2. . <ul><li>Energy is the capacity to perform work and is measured in joules : </li></ul><ul><li>1 joule (J) </li></ul><ul><li>1 000 joules = 1 kilojoule (kJ) </li></ul><ul><li>1 000 000 joules = 1 megajoule (MJ) </li></ul><ul><li>1 000 000 000 joules = 1 gigajoule (GJ) </li></ul><ul><li>1 000 000 000 000 joules = 1 terajoule (TJ) </li></ul><ul><li>1 000 000 000 000 000 joules = 1 petajoule (PJ) </li></ul><ul><li>1 000 000 000 000 000 000 joules = 1 exajoule (EJ) </li></ul><ul><li>A joule is a very small amount of energy. A person requires about 1J per second for normal body functions. </li></ul><ul><li>Power is the amount of energy available or used over a given time: </li></ul><ul><li>power (watts) = energy (joules) [One watt is one joule/sec] </li></ul><ul><li>time (seconds) [energy = mass (kg) x 9.8 ( gravity ) x height (m)] </li></ul><ul><li>The energy rating of appliances is given in watts. A 100 watt globe, when switched on, consumes 100 joules per second. </li></ul><ul><li>Q. 1 - 4 </li></ul>
  3. 3. <ul><li>Some different types of energy include: </li></ul><ul><li>(gravitational) potential energy : the energy associated with an object’s position </li></ul><ul><li>kinetic energy : the energy associated with the movement of matter. It depends on its mass and its speed </li></ul><ul><li>mechanical energy : when a force moves an object. </li></ul><ul><li>electromagnetic (or radiant or light) energy : flows from one place to another in the form of rays. Ultraviolet, visible light, infra-red light, gamma rays, X-rays, television and radio waves and heat are examples </li></ul><ul><li>chemical energy : a form of potential energy due to the relative position of atoms and their electrons in the molecules that make up substances. It is released by reactions, such as combustion </li></ul><ul><li>electrical energy : such as that of lightning, a battery or appliance resulting from the existence of charged particles creating a current </li></ul><ul><li>nuclear energy : the energy between the strong bonds within the nucleus of atoms, released through fusion or fission </li></ul><ul><li>thermal energy : the energy of heat from one substance to a cooler one </li></ul><ul><li>Q. 5 - 6 </li></ul>
  4. 4. Types of energy energy kinetic energy potential energy solar radiant energy chemical energy electrical energy wind energy gravitational energy nuclear energy thermal energy
  5. 5. Conversion of energy <ul><li>Energy can be converted or transformed from one type of energy to another, and so by be put into a state useful to humans: </li></ul>kinetic energy potential energy river water dam water source of power
  6. 6. Conversion of energy <ul><li>Energy can be converted or transformed from one type of energy to another, and so by be put into a state useful to humans: </li></ul>potential energy kinetic energy coal heat
  7. 7. Conversion of energy <ul><li>The sun’s energy is transformed, by nuclear fusion of hydrogen in the sun, into thermal and light energy. It directly provides energy for many processes on earth, including natural processes such as photosynthesis and elements of the weather. </li></ul>
  8. 8. Conversion of energy <ul><li>As the hammer is raised up it has potential energy. </li></ul><ul><li>As the hammer falls this is converted into kinetic energy. </li></ul><ul><li>This is then converted into mechanical energy to drive the nail into the timber. Some of the energy is also converted to heat and sound. </li></ul>
  9. 9. Conversion of energy <ul><li>The potential energy stored in water can be converted to mechanical energy in a waterwheel (to grind grain for example) or in a turbine to produce hydroelectric power. </li></ul>
  10. 10. Conversion of energy <ul><li>A light bulb converts electrical energy to light and heat. Electrical appliances convert electrical energy into various different forms of energy. </li></ul>
  11. 11. Conversion of energy <ul><li>In the internal combustion engine of a car, the combustion of the chemical energy in petrol produces mechanical energy to propel the car. </li></ul><ul><li>In a coal-fired power plant, the chemical energy in the coal is used, through combustion and the production of steam, to drive the turbines which produce electrical energy. </li></ul>
  12. 12. Conversion of energy <ul><li>Photosynthesis converts energy from the sun into chemical energy for plant processes. </li></ul><ul><li>By eating plant food, humans convert this chemical energy into food which provides us with energy. </li></ul>
  13. 13. Conversion of energy <ul><li>Methane has chemical energy due to the arrangement of carbon and hydrogen atoms within its molecules. This can be converted to other forms of energy through combustion, which involves the reaction of the substance with oxygen. </li></ul><ul><li>CH 4 + 2O 2 2H 2 O + CO 2 + heat </li></ul><ul><li>methane + oxygen water + carbon dioxide + heat </li></ul>
  14. 14. Conversion of energy <ul><li>Respiration is a chemical reaction within the cells of our body involving the combustion of glucose stored in ATP (adenosine triphosphate) to produce energy to move our muscles. This is also converted through combustion. </li></ul><ul><li>C 6 H 12 O 6 + 6O 2 6H 2 O + 6CO 2 + energy </li></ul><ul><li>glucose + oxygen water + carbon dioxide + energy </li></ul>
  15. 15. Conversion of energy <ul><li>A diver standing on the board has potential energy, but this is converted into kinetic energy, and then into the movement of water and sound as she hits the water. </li></ul><ul><li>The diver also uses chemical energy in her cells, stored as carbohydrates and lipids, and released as energy when they react with oxygen when she uses her muscles to leap off the board. </li></ul>
  16. 16. Conversion of energy <ul><li>Heat is a form of energy, in thermal energy. Heat is produced when kinetic energy is transferred between molecules. </li></ul><ul><li>All molecules are in constant motion, and heat makes them move or vibrate faster. The high kinetic energy of a flame will be transferred to the molecules of a saucepan and its contents placed over the flame. </li></ul><ul><li>Temperature is a way of measuring the amount of heat/thermal energy in an object. </li></ul>
  17. 17. Conversion of energy <ul><li>Thermal energy, or heat, can also cause a change of state. For example, to melt ice, the molecules need to gain sufficient energy to break the bonds between the molecules for the solid to melt. Similarly, heat is required to turn liquid into a gas, such as steam. </li></ul>
  18. 18. Conversion of energy <ul><li> on conversion of energy </li></ul><ul><li>Q. 7 - 15 </li></ul>
  19. 19. Conversion of energy <ul><li>Thermal energy can be transmitted by: </li></ul><ul><li>conduction: heat is transmitted directly from atom to atom, and requires direct physical contact between the two substances. The heat flows from the hotter object to the cooler one. Metals are good conductors, while wood, air and water a poor conductors. </li></ul><ul><li>convection: transmits heat by transporting groups of molecules from place to place within a fluid substance. Convection occurs in fluids such as water and air. </li></ul><ul><li>radiation: the transfer of heat energy through electromagnetic waves or photons, without the involvement of a physical substance in the transmission. Radiation can transmit heat through a vacuum. </li></ul>
  20. 20. Endothermic and exothermic reactions <ul><li>Chemical reactions which exert heat (create or release energy) are called exothermic reactions . </li></ul><ul><li>eg: the combustion of matter </li></ul><ul><li> the setting of concrete </li></ul><ul><li>respiration </li></ul><ul><li> </li></ul><ul><li>Chemical reactions which absorb heat (ie: absorb energy) are called endothermic reactions </li></ul><ul><li>eg: photosynthesis </li></ul><ul><li> the depressurising of pressure cans </li></ul><ul><li>instant cold packs (ammonium nitrate and water) </li></ul><ul><li> </li></ul>
  21. 21. <ul><li>The laws regarding energy is amalgamated into the </li></ul><ul><li>Laws of Thermodynamics </li></ul>
  22. 22. The First Law of Thermodynamics: the law of conservation of energy <ul><li>Energy can be transformed from one form to another, and work is the process that brings about this change </li></ul><ul><li>The Law of Conservation of Energy states that energy cannot be created or destroyed. It can be transformed from one form to another as well as transferred from one body to another but the total energy remains the same . </li></ul><ul><li>(The Law of Conservation of Energy should be distinguished from efforts to conserve energy) </li></ul><ul><li>Energy cannot be created or destroyed – but it can be converted into different forms: </li></ul><ul><li>total energy quantity in = total energy quantity out </li></ul>
  23. 23. The Second Law of Thermodynamics: the law of increase of entropy <ul><li>Entropy is a measure of the disorder within a system. The more disordered the system, the higher the entropy. The Law of Increase of Entropy states that the total entropy of any system tends to increase over time, as there is a natural tendency towards greater disorder through energy transformations. The disorder of a system increases because, at each stage, some of the energy is dissipated, usually in the form of heat. </li></ul><ul><li>Put simply, the result of the first two laws of thermodynamics is that, while the quantity of energy does not change during a conversion, the quality of energy is degraded. Less useful energy is available with each successive energy conversion: </li></ul><ul><li>total energy quality in > total energy quality out </li></ul>
  24. 24. Energy efficiency <ul><li>Energy is dissipated, most often as heat, with every conversion from higher quality energy to lower quality. Energy efficiency is the measure of the amount of useful energy as a proportion of total energy expended: </li></ul><ul><li> energy efficiency (%) = useful energy output x 100 </li></ul><ul><li>total energy input </li></ul><ul><li>eg: a car engine has an energy efficiency of 10% - it converts only 10% of the total energy used as petrol to useful energy to move the car. The remaining 90% is ‘lost’ to heat, friction and sound. </li></ul><ul><li>The Law of Increase of Entropy means no energy conversion is 100% efficient. The more steps in the energy conversions process, the lower the energy efficiency. </li></ul><ul><li>Q.16 - 18 </li></ul>
  25. 25. Energy efficiency <ul><li>In a coal-fired power plant the chemical energy in the coal is converted into electrical energy for use in industry and homes, but much of the energy in the coal is dissipated in the form of sound and heat to the infrastructure used to process, store and transport the electricity as well as the surrounding air. </li></ul>
  26. 26. Energy efficiency <ul><li>Coal chemical energy kinetic energy produce transmission space </li></ul><ul><li>extraction (to create steam) (to turn turbine) electrical energy heating </li></ul><ul><li>energy dissipated </li></ul>
  27. 27. Energy efficiency <ul><li>Coal chemical energy kinetic energy produce transmission space </li></ul><ul><li>extraction (to create steam) (to turn turbine) electrical energy heating </li></ul><ul><li>To calculate the energy efficiency: </li></ul><ul><li>1. Convert the energy efficiency at each step to a proportion eg: 50% = 0.5 </li></ul><ul><li>2. Multiple the proportions together </li></ul><ul><li>3. Multiply the final answer by 100 </li></ul><ul><li>(0.93 x 0.3 x 0.9) x 100 = 25.11% </li></ul><ul><li>Q. 19 </li></ul>Mining: 93% efficiency Power generation: 30% efficiency Powerlines: 90% efficiency
  28. 28. Energy efficiency <ul><li>An ordinary incandescent light globe, for example, turns only about 20% of the energy used into light, wasting the remaining 80% as heat. </li></ul><ul><li>A car typically wastes about 60 – 80% of the fuel used to propel the vehicle, mostly through the exhaust pipe and friction within the engine, the transmission and the road. </li></ul><ul><li>The energy efficiency of the conversion between trophic levels in food chains varies from 5 – 20%. </li></ul><ul><li>The human body wastes about 80% of the energy it ingests as food. </li></ul><ul><li>Q. 20 - 23 </li></ul>
  29. 29. Energy resources <ul><li>Energy resources are fuels or resources which can be processed or harnessed to provide useful energy for humans. </li></ul><ul><li>Energy resources vary in: </li></ul><ul><li> - their accessibility and abundance </li></ul><ul><li> - the amount of useful energy that can be derived from them </li></ul><ul><li> - the energy lost in transformations </li></ul><ul><li> - the energy required to harness or extract, process and redistribute them </li></ul><ul><li>Fuels are energy resources which are substances containing chemical energy that is released when oxidised, most commonly through combustion. Once a fuel is used, it cannot be used again. </li></ul>
  30. 30. Energy resources <ul><li>Society needs energy resources to facilitate many activities in industry and in their homes. Energy resources may be renewable or non-renewable. </li></ul><ul><li>Non-renewable source are those that exist in limited deposits and cannot be replaced within scales relevant to human lifetimes. We consider them finite as they take very long geologic time scale to be replaced, and they are being used at a rate faster than that at which they are being formed. They include fossil fuels such as coal, natural gas and petroleum, as well as uranium for nuclear energy. </li></ul><ul><li>There are limited quantities of these energy resources on Earth, though their relative abundance varies. It is also suggested additional reserves are yet to be found, or are available, but not currently accessible. </li></ul>
  31. 31. Energy resources <ul><li>Renewable energy falls into two categories: those that are infinite and are available irrespective of the rate of use, and those that are renewable as long as their rate of use does not exceed the rate at which they are replenished. Infinite resources are inexhaustible sources of energy such as solar energy, wind, tidal and wave power and geothermal energy. Renewable energy sources which could be depleted if their rate of use is unsustainable include the power or running water, such as hydro-power, and wood and biofuels. </li></ul>
  32. 32. Energy resources Q.24 energy sources non-renewables renewables infinite energy resources finite renewable energy resources fossil fuels other non-renewable fuels
  33. 33. Energy resources <ul><li>Electricity is produced when a fuel is used to drive generators or turbines. An electric generator is a device for converting mechanical energy into electrical energy. Electricity is the flow of electrons. All matter is made up of atoms, and within the nucleus of each atom are protons (+ charged) and neutrons (uncharged). The nucleus is surrounded by negatively charged electrons. When an outside force upsets the balancing force between protons and neutrons an atom may gain or lose an electron. When this occurs the free movement of these electrons creates an electric current. A large generator within a power plant have a magnet at the end of a rotating shaft, and when the magnet rotates it induces an electric current. Steam, created by the combustion of fuel, forces the blades of the turbine to move. </li></ul>
  34. 34. Energy resources <ul><li>Coal: </li></ul><ul><li>Australia has about 8% of the world’s coal. </li></ul><ul><li>Electricity in Australia is mainly generated from coal. Australia now has a national grid (which is really actually only Q’ld, NSW, Victoria, ACT, SA and Tasmania) which means power is shared across these states. Most of the power used in Australia comes from coal: about 30% is from brown coal and 55% from black coal. </li></ul><ul><li>Victoria’s main coal reserves are brown coal accessed from open cut mines in the Latrobe Valley in Gippsland. The power plants generating power for the state are also mostly located in the Latrobe Valley. They operate around the clock all year. </li></ul><ul><li>Electricity is heavily used by industry, transport (suburban trains and trams) and for residential uses. </li></ul><ul><li>In terms of electricity use, society has ‘peak’ energy requirements as well as ‘base load’ energy requirements. </li></ul><ul><li>Extreme weather conditions increase energy needs. </li></ul>Brown coal Black coal
  35. 35. Coal <ul><li>The energy density of coal is 6.67 kW·h/kg. The typical efficiency of coal power plants is about 30%, so of the 6.67 kW·h of energy per kilogram of coal, 30% of that (ie: 2.0 kW·h/kg) can successfully be turned into electricity; the rest is waste heat. So coal power plants generate approximately 2.0 kW·h of energy for each kilogram of coal burnt. </li></ul><ul><li>Running a 100 watt computer for one year requires 876 kW·h (100 W × 24 h/day × 365 {days in a year} = 876000 W·h = 876 kW·h). Converting this power usage into coal consumption, it takes 438 kg of coal to power a computer for one full year. </li></ul><ul><li>Coal is about 50% carbon, so a 100W computer creates 219 kg carbon each year. </li></ul><ul><li>However, one should also take into account transmission and distribution losses caused by resistance and heating in the power lines, which is about 5–10%, depending on distance from the power station and other factors. </li></ul><ul><li>(For more on coal and electricity: ) </li></ul>
  36. 36. Energy resources <ul><li>Petroleum: </li></ul><ul><li>Petroleum is used to make a wide range of products, including plastics, paint and bitumen, as well as a range of fuels, such as petrol, diesel, kerosene, oil and LP gas. </li></ul><ul><li>About 75% of petroleum in Australia is used for transport. </li></ul><ul><li>Petroleum, or crude oil, is refined into various fractions through distillation to produce a wide range of products. </li></ul><ul><li>Australia has its own petroleum reserves, including in Bass Strait and on the Northwest Shelf of WA, but it also imports crude oil. </li></ul>
  37. 37. Energy resources <ul><li>Natural gas: </li></ul><ul><li>Natural gas makes up about 20% of Australia’s energy use. It is most commonly used for cooking and heating water and space in homes, and is used extensively in industry for heating and manufacturing. It can also be used to generate electricity, such as at Newport power station. </li></ul><ul><li>Natural gas reserves usually occur with oil reserves. It consists mostly of methane, but it also contains ethane, propane and butane. </li></ul><ul><li>The combustion of natural gas is a relatively clean process compared to that of other fossil fuels, and often entails less energy transformations, so it is more efficient in delivering energy. </li></ul><ul><li>Areas which do not have access to piped natural gas may use bottled gas. </li></ul>
  38. 38. Energy resources <ul><li>Uranium: </li></ul><ul><li>Uranium is a finite , but non-fossil fuel energy resource. </li></ul><ul><li>Uranium occurs as an ore which must be milled and enriched in nuclear reactors, where fission produces thermal energy to turn a turbine to generate electricity. </li></ul><ul><li>Presently, it is used to generate energy through fission (splitting) within the nucleus of uranium atoms, though it is hoped that one day nuclear fusion may provide an even more efficient and cleaner resource </li></ul><ul><li>While uranium produces 15% of the world’s electricity, no electricity in Australia is generated by nuclear power, despite the fact we have about 20% of the world’s uranium ore reserves. </li></ul><ul><li>There are a number of environmental and societal concerns regarding the use of nuclear power, including the long lifetime of the intractable radio-active waste it produces as a by-product, the safety issue relating to its extraction, processing, use and transport, and the fact the fuel it produces can be used for nuclear weapons as well as nuclear power. </li></ul><ul><li>While nuclear power does not produce greenhouse gas emissions itself, the extraction, processing and transport of the substance involved the use of fossil fuels. </li></ul>
  39. 39. Energy resources <ul><li>Renewable energy sources: </li></ul><ul><li>Australia’s use of renewable energy sources is quite low. </li></ul><ul><li>Flat plate solar collectors are used to heat water for domestic hot water supplies. The use of solar collectors for electricity generatation, photovoltaic cells, is low, as it is quite costly compared to the cost of grid electricity. </li></ul><ul><li>Wind farms are becoming more common in Australia, and they contribute electrical energy to the national grid. </li></ul><ul><li>Hydroelectricity provides about 10% of Australia’s electricity needs by mainly supplementing the national grid for peak demand, as they can be brought in and out of operation quickly and easily. This includes the Snowy River scheme on the Vic-NSW border, and a number of schemes in Tasmania. </li></ul>
  40. 40. Energy resources <ul><li>Biomass energy are energy resources derived from living matter. It may include organic material from forests, agriculture, animal and plant waste and landfill. </li></ul><ul><li>Biomass includes: </li></ul><ul><li>fuels formed by the fermentation of organic material to produce ethano l and methanol , which is used as an extender for petrol for transport </li></ul><ul><li>biodiesel formed from oils, which can be used as fuel for vehicles, generators etc </li></ul><ul><li>biogas which can be used in place of natural gas </li></ul><ul><li>wood is an example of a biomass energy resource. About 30% of the world’s population derive most their fuel needs for cooking and heating from wood. </li></ul>
  41. 41. Energy is used to power our societies. Power for society industry transportation utilities mining milling smelting forging glass bricks cement plastics paper cars trains ships aircraft pipelines space heating water heating air conditioning lighting electrical appliances
  42. 42. E nergy resources <ul><li>Because reserves of some commonly used fuels is dwindling and the use of many fuels has detrimental impacts on the environment and society, it is important to reduce our reliance on these energy resources. This can be achieved by: </li></ul><ul><li>improve the design of appliances, vehicles and infrastructure </li></ul><ul><li>to improve energy efficiency and reduce energy needs </li></ul><ul><li>change human behaviour so that less energy is consumed </li></ul><ul><li>reduce our reliance on the fuels which have negative </li></ul><ul><li>impacts, particularly fossil fuels, by using more alternative </li></ul><ul><li>sources of fuel </li></ul>Q.25 - 40
  43. 43. <ul><li> </li></ul>