Energy Resources Introduction

Transcription

1 Energy Resources Introduction 1

2 Overview Forms of Energy Renewable and Non Renewable Energy Resources A Brief look at Thermodynamics 2

3 Forms of Energy Form of Energy Description Primary Energy Sources Kinetic & Potential Energy Kinetic: ½mv 2 Potential: mgh Hydro Wind Wave Tidal Heat Movement of atoms and molecules Geothermal Energy Temperature difference Electrical Energy Volts and Amps. The flow of electrons Electromagnetic Radiation Radio waves / micro waves/ infra red / visible light/ UV/X-rays Solar Energy Chemical Energy Nuclear Energy Energy released when atoms combine into compounds. Energy locked within the nucleus: Fission / Fusion Combustible Fuels: Gas, Oil, Coal, Wood, Biofuels Fission Reactors (Uranium / Plutonium) 3

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5 Renewable Energy Boyle, Everett & Ramage: renewable energy sources are continuously replenished by natural processes Renewable sources are essentially flows of energy whereas the fossil and nuclear fuels are in essence stocks of energy Boyle, Everett Ramage 2003 Energy Systems and Sustainability Oxford Univerity Press The above definition does not cover the production of energy from waste which is often considered a form of renewable energy. A broader definition which would include waste would be: Renewable Energy sources are those which are replenished at a faster rate than they are consumed. Questions: Which of the sources of primary energy in previous chart are considered renewable? Energy * can neither be created or destroyed so where does the replenishment come from? Why is it considered renewable energy when I burn a biofuel which is the product of plant material but not considered renewable energy when I burn coal which is a natural product of plant material? Is nuclear energy a renewable energy source? What about nuclear fusion (energy from Hydrogen available from water)? What about fast breeder reactors? *According to the theory of special relativity we should substitute the term Mass/Energy for the word Energy 5

6 Non-Renewable Energy Resources 2005 Annual Production in ZettaJoules Data Source: World Energy Council: 2007 Survey of World Energy Reserves Total Annual Production ZettaJoules Uranium 5% Coal Natural Gas Coal 32% 23% Crude Oil Extra Heavy Oil 0% Natural Bitumen 0% Shale Oil 0% Crude Oil 40% Shale Oil Natural Bitumen Extra Heavy Oil Natural Gas Uranium 6

7 Exercise: When will we run out? Resource Proved Recoverable Units Reserves end Annual Production Energy Reserves to Conversion ProductionFactor (to RatioJoules) Energy Reserves (J) Annual Production (J) Bituminous Mtonnes E E E+20 Sub-Bituminous Mtonnes E E E+19 Lignite Mtonnes E E E+19 Total Coal E E E+20 Crude Oil+Gas liquids Million Barrels E E E+20 Shale Oil Million Barrels E E E+16 Natural Bitumen Million Barrels E E E+18 Extra Heavy Oil Million Barrels E E E+19 Total Oil E E E+20 Natural Gas Billion m E E E+20 Shale Gas Billion m E E+21 Total Gas E E E+20 Uranium ktonnes E E E+19 Global Total 7.51E E+20 Global R/P Ratio Figures from 2010 Survey of Energy Reserves by The World Energy Council. Available from Kevin Gaughan 7

8 Notes Conversion Factors Coal / Oil / Gas from Uranium Boyle Everett Ramage Assuming natural Uranium with 0.72% by weight U235 BER state that 1kg U235 undergoing complete fission will produce 82x10E12j of energy. Shale gas reserves estimate from (6 March 2012) 6,622 trillion cubic feet economically recoverable 1 trillion cubic feett = cubic metres Note IEA estimate for regular natural gas is much lower than WEC estimate but considers far fewer countries 8

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10 A Brief Look at Thermodynamics First Law: Energy can neither be created or destroyed Second Law: Entropy (disorder) is always increasing Heat will only flow from hot to cold unless you feed extra energy in The maximum efficiency 9CArnot Efficiency) of any heat based engine is limited by the temperature difference. Third Law: The lowest possible temperature is absolute zero (-273 C) Question: An open cycle gas turbine has a flame temperature of 1200 C and an exhaust temperature of 500 C. Calculate the theoretical maximum possible efficiency of this turbine. (Answer 47%. For comparisons real open cycle gas turbines currently have efficiencies of around 40% while combined cycle turbines which extract further heat from the exhaust in a second turbine have efficiencies of up to 60%) T Maximum Efficiency= 1 T Temperatures measured inkelvin K = Centigrade+ 273 c h 10

11 Implications of Second Law Mechanisms exist to convert energy from any form into any other eg Wind turbine converts kinetic energy into electricity / A boiler converts chemical energy into heat / A battery converts chemical energy into electricity. Many forms of energy can be converted with very high efficiency (90% +) but converting heat to another form is inherently inefficient (constrained by second law). In thermodynamic terms electricity, kinetic energy and chemical energy can be said to have low entropy (low disorder) while heat has high entropy (high disorder). If the desired output energy is not heat then avoiding a heat step will generally reduce losses and improve efficiency ( eg electric cars are more efficient than internal combustion engine) Although batteries and fuel cells can convert chemical energy directly into electricity there are as yet no practical means for converting the major fossil fuels into other energy forms without going through a combustion stage inherently inefficient. Question: For each of the principle sources of primary energy discuss ways that it may be converted into different energy types and identify whether a heat step is involved. 11