1. Physics 08: Energy Power and Climate Change BY HEI MAN KWOK 12N03S

2. 8.1 ENERGY DEGRADATION AND POWER GENERATION

3. Energy is CONSERVERED Thermal Energy may be completely converted to work in a single process, but that continuous conversion of this energy into work requires a cyclical process and the transfer of some energy from the system Energy cannot be created or destroyed, it is conserved Energy Efficiency (EE) = Useful Energy Output (UE) / Total Energy Input (TE) [X100%]

4. Conversion of Thermal Energy Thermal energy may be completely converted to work in a single process but that continuous conversion of this energy into work requires a cyclical process the transfer of some energy from the system As it is impossible to take heat from a hot object and use it all to do work without losing some to the surroundings

5. Degraded Energy Energy becomes more spread out or disordered – degradation of energy Thermal energy is the most degraded form of energy Once energy becomes thermal energy we can never get it all back All energy will eventually turn to heat

6. All energy transfers must always lead to some thermal energy transferred to the surroundings Light blub – electrical energy to UE: light, NUE: heat Car Engine – chemical energy to UE: (kinetic), NUE: heat Electric motor lifting an object up – electrical energy to UE: mechanical lifting up an object, NUE: heat from friction

7. Sankey Diagram Sankey diagrams are used to visualize the flow of something, in this case energy

8. Generating Electricity Useful as it can be transported easily through wires Make use of a generator to convert mechanical energy to electrical energy Coils of wire are rotated in a magnetic field. This is called a dynamo

9. 8.2 WORLD ENERGY SOURCES

10. Identify different world energy sources TypeOriginRenewable? Coal – plants that died millions of years ago SunYes Oil – dead microorganismsSunYes Gas – dead microorganismsSunYes WoodSunYes Biomass -SunYes Nuclear Fission Fusion SolarSunYes HydroelectricSunYes WindSunYes WaveSunYes Tidal Geothermal

11. Renewable vs Non-Renewable Renewable Sources can be replenished within a human’s life time Non-Renewable Sources cannot be Non-renewable: rate of production of fuel much smaller than rate of usage; so fuel will be exhausted/run out; Non-Renewable Sources are burnt and produce carbon dioxide when burnt Renewable Sources are not burnt except for biomass and wood which are burnt

12. Energy Density of Fuels Energy Density – amount of energy that can be liberated per kg of fuel (J/kg) Fuel is a source of energy in a useful form U-235 has the highest energy density but infrastructure and running of nuclear plant is $$$ Natural gas has the highest energy density of the fossil fuels, oil then coal

13. Choice of fuel based on energy density Choices of fuel depends on the energy density as we want to choose fuels that are efficient (high energy density) and at low cost Fuels with high energy density costs less to transport – as they weigh less

14. Relative Proportions of energy source use 39% coal 19% gas 17% nuclear 16% hydro 7% oil 2% other

15. Renewable and Non-Renewable AdvantagesDisadvantages Renewable – non-finite source Sustainable Will never run out Minimal environmental impact Expensive Isn’t as energy efficient as non-renewable Unreliable and unstable supply Non-renewable – finite source Cheap and easy to use Stable supply – for now Very energy efficient Pollution – adds to global warming Not sustainable Hard, close to impossible to replace

16. Fuel - Coal

17. Fuel – Oil and Gas

18. Fossil Fuels Advantages Easy to construct fossil fuel power plant anywhere Fossil fuels available on all continents Easy to gain energy from – less technological demands compared to other energy sources Disadvantages Low energy density Contributes to the enhanced greenhouse effect Non-Renewable – the supplies will run out

19. Fuel – Wood and Biomass

20. Fuel – Nuclear Fuel Origin: NOT FROM THE SUN - Nuclear fuels are materials that have unstable nuclei and when those nuclei split thy give out energy Gives rise to waste material that is highly radioactive and hence difficult to dispose of Like coal, nuclear fuels such as uranium have to be extracted from the ground and then purified before use Non-Renewable Source

21. Nuclear Energy Advantages: Very high energy density Doesn’t contribute to the greenhouse effect Disadvantages: High set-up and running costs Produces hard to dispose of, highly radioactive nuclear waste Possibility of a reactor meltdown

22. Fuel – Fusion Fuel Fusion of two hydrogen molecules Non-renewable source

23. Sun – Solar Energy Mirrors to focus radiation to a point Create hot spot where energy can e used to power an engine that can do work Sun’s radiation can be turned directly into electricity using a photovoltaic cell

24. Solar Energy Advantages Widespread source everyone on the planet Can be harvested even in remote areas Doesn’t contribute to the enhanced greenhouse effect Disadvantages Cannot work at night Low energy output Irregular levels of output

25. Sun – Hydroelectric Power Energy can be made to do work as water runs down the mountain Collects water in dams then releases it to change from GPE into kinetic to spin Calculate the total energy stored in a reservoir 1km above the bottom of the dam

26. Hydroelectric Energy Advantages Highly efficient Doesn’t contribute to the enhanced greenhouse effect Low running costs Disadvantages Causes flooding and droughts Dams to be built Dams can break and release of water can cause significant damage

27. Sun – Wind Power Sun heats the atmosphere causing the air to become less dense and move upwards Air movements combined with the rotation of the earth cause winds KE in the moving air can be used to turn a turbine and produce electricity

28. Wind Power Advantages Doesn’t contribute to the enhanced greenhouse effect Many possible sites for construction Can work in remote areas Disadvantages Creates noise pollution High setup and maintenance costs

29. Sun – Wave Power Production of waves due to disturbed water by the movement of air As the wave spreads out, so will their energy, arriving at beaches all around the world Energy can be used to turn power turbines and produce energy

30. Wave Power Advantages Very high potential energy output Doesn’t contribute to the enhanced greenhouse effect Disadvantages High maintenance due to easy damage from the power of waves Hard to build

31. Non-Sun – Tidal Power Tides are produced by the gravitational force from the moon Movement of water from tides can be used to drive turbines and produce energy Ducts sit on surface of the water and oscillate Oscillating water column

32. Non-Sun – Geothermal Energy Earth’s crust moves against each other and friction between the rocks creates heat Water runs into cracks in these rocks and turns into steam and forms geysers on the earth’s surface This explosive energy can be used to produce electricity

33. 8.3 FOSSIL FUEL POWER PRODUCTION

34. Historical and Geographical reasons for the widespread use of Fossil Fuels The invention of the steam engine – used to transport goods with wood or coal as fuel Industrialisation (industrial revolution) lead to a higher rate of energy usage Leading to industry being developed near large deposits of fossil fuels

35. State two reasons why most of the world’s energy consumption is provided by fossil fuels. wide availability / a great deal available; ease of transportation; power stations can be built close to the source; high energy density;

36. Energy Density of fossil fuel with respect to the demands of power stations

37. Relative advantages and disadvantages associated with the transportation and storage of fossil fuels AdvantagesDisadvantages Inflammable, no danger (coal)Combustion dangers of flammable (oil and natural gas) Infrastructure presentBulky takes up space in tanks (oil and natural gas); piles (coal) Heavy (oil, natural gas and coal) hence costly to transport

38. Overall efficiency of power stations Coal: 30% efficient Oil: 40% efficient Gas: 50% efficient; but when wasted heat used to heat houses 80%

39. Environmental problems Recovery of fossil fuels: opencast mining of coal is damaging to the environment; oil spills also affect aquatic ecosystems Use in power stations: produces Carbon Dioxide

40. How electricity is produced Chosen fossil fuel is burned The heat from the burning fuel is used to boil water The water turns to steam The steam turns a turbine which is connected to the generator Generator produces electricity Chemical → heat → kinetic → electrical

41. 8.4 NON-FOSSIL FUEL POWER PRODUCTION – NUCLEAR POWER

42. Nuclear Fission (splitting) Nucleus of Uranium-235 splits by collision with a neutron to produce 2 daughter nuclei and a small number of neutrons (3) This process releases energy due to the difference in mass between the products and reactants The neutrons produced by one fission can strike other U-235 nuclei creating a chain reaction

43. Nuclear Fission (splitting)

44. Chain Reaction? Neutrons (about 3) are emitted which can collide with/hit other uranium nuclei; Start new fission processes which in turn will lead to more and so on;

45. Nuclear Reactor When fission process is used as an energy source to generate electricity – the chain reaction must be controlled: Outer Shell - Lead Control Rods – Boron Fuel Rods – Uranium Moderator – Graphite

46. Control Rods Made of boron Placed between rods of nuclear fuel Absorbs some of the neutrons Moveable, adjustable – so there are just enough neutrons to keep the chain reaction going Lowered = decreased rate of reaction Raised = increased rate of reaction

47. Moderator Usually made out of water, Graphite or heavy water (water with heavier isotopes) Reduces the speed of neutrons, so the Control Rods have enough time to absorb it – can sustain a chain reaction involving U-235

50. Outline why the enhanced greenhouse effect may result in an increase in the temperature of the Earth’s surface. (because of increased greenhouse gases) atmosphere absorbs more (IR) energy and heats up; atmosphere radiates in all directions; Earth’s surface absorbs some of this extra (IR) radiation hence temperature increases;

51. 51% absorbed at surface 6% reflected by atmosphere 20% reflected by clouds Albedo: fraction of incoming 30% reflected into the