Environmental science module 2 notes


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Environmental science module 2 notes

  1. 1. Module 2 Energy and the Environment
  2. 2. It exists in several forms  According to the law of conservation of energy total energy of a system remains constant although the energy can be transferred into another form.
  3. 3. Type of Energy  The names of energy are related to: a) The way the energy is perceived e.g. mechanical, electrical, light. b) The way the energy is transported e.g. thermal c) The origin of the energy e.g. nuclear, solar, wind.
  4. 4.  Since energy can neither be created nor destroyed, the sum of energies which enter a process must be equal to the sum of energies resulting from this process.
  5. 5. Names of energy  Potential energy aka Stored energy  Kinetic energy aka Energy of motion  Chemical energy  Mechanical energy  Thermal Energy aka heat energy  Solar energy  Light energy  Electromagnetic Energy (EMR)
  6. 6. Names of Energy con’t  Electrical Energy  Nuclear energy aka Atomic energy
  7. 7. The basic use of energy measurement is the Joule (J) Symbol name Value in Joules Equivalent KJ Kilojoules 1000 J (103 J) Maximum amt of solar radiation received by 1sq of earth in one seemed MJ mega joules 1000,000 J( 106 J) Kinetic energy of one tonne vehicle moving out at 160 Km/h GJ Giga joules 1000,000,000 J (109 J) 6GJ is about the amount of potential chemical energy in a barrel of oil when it is combusted.
  8. 8. The Basic use of energy measurement is the joule (J) Symbol Name Value in Joules Equivalent TJ Tera joule 1,000,000,000,000 J (1012 J) 60 Tj were released by the atomic bomb which was droppedon Hiroshima.
  9. 9. Work  The deffinition of work says nothing about the time taken during which work was done.  E.g a person does the same amt of work when he carries something up a flight of stairs, whether he runs or not, But, he is more tired when ge runs. Therefore, to distinguish these cases, the concept of power was introduced.
  10. 10. Power  Is defined as the rate of doing work .  Power= work done/time taken  The unit of power measurement is Watt (W)
  11. 11. Watt (W) Symbol Name Value in watts Equivalent KW Kilowatts 1,000 W (103 W) Largest industrial light bulb of 1.8 house power MW Megawatt 1,000.000 W (106 W) Enough to play a night game at a stadium- 1300hp GW Gigawatt 1,000,000,000W (109W) Enough to power a major city for a day.
  12. 12. Energy Conversions  Example  Heating water with a burner  Photosynthesis  Internal combustion Energine  Power station  Nuclear Power
  13. 13. Non renewable energy Sources  Fossil Fuels e.g coal, oil,natural gas. Peat(from waterlogged marshland)  Carbon Dioxide (CO2)  Sulphur Dioxide (SO2)  Nitrogen Oxide (NO)
  14. 14. Non Renewable energy sources cont’d  Major fossil fuels Coal OIL Natural gas Peat
  15. 15. Nuclear Power  There are two types of nuclear reactions  1) nuclear fission  2)nuclear fusion  Nuclear fission Nuclei of atoms are split, releasing energy. This process occurs in a)atomic bombs nuclear reactons. b) Nuclear reactions.
  16. 16. Nuclear Fusion  Nuclei of atoms joined or fused together This happends under very hot conditions . The sun like all other stars creates heat and light , through nuclear fusion. In the sun, hydrogen nuclei fuse to form helium.
  17. 17. Nuclear Fission  Uranium is the main fuel used in nuclear fission because it splits easily when bombarded by neutrons once a uranium molecule is split, multiple neutrons are released.  The “free” neutrons are used to split other uranium molecules. This is called a chain reaction.
  18. 18. Functioning of a nuclear Power plant. Enriched uranium is formed into 2.5cm pellets 2. Pellets are arranged into long, hollow, metal rods. 3. Rods are collected together into bundles. 4. Rods are submerged in water inside a pressure vessel( the water acts as a coolant) 1.
  19. 19. Outside a Nuclear Power Plant  Due to harmful radiation extra precautions are required in the construction design of nuclear power plants. 1. Hence there is an outer steeled vessel which houses the reactor core, all the equipment used to fuel + maintain the reactor. This steal barrier serves as a barrier to prevent leakage of any radioactive gases or fluids from the plant.
  20. 20. Reactor Types Boiling water reactors/BWR 2. High temperature gas cooled reactor/ HTGCR 3. Process Inherent Ultimate Safety reactor PLUS 4. Pressurised Water reactors 1.
  21. 21. Uranium conversation+ enrichment  Uranium oxide is a raw mined product which cannot be used as fuel for a nuched reactor.  Additional processing is required. Only ).7% of naturally-occuring uranium is “fissile” (capable of undergoing fission. This fissile isotype form is called Uranium 235 (U-235). The rest of the deposit is made up of U-138 most reactors need the concentration of U-235 to be above 3.5-5%. This is achieved by a process call Enrichment which requires uranium to be gaseous.
  22. 22. Fuel Fabrication  Generally available in the form of ceramic pallets encased in metal tubes called rods.
  23. 23. Functioning of a nuclear power plant.  Used Fuel Made up of approximately: 94% U-238, 1% U-235, 1% Plutonium,4% fission particles.  In a reprocessing facility, used fuel is separated into 3 components namely: uranium forms, plutonium, waste.
  24. 24. Important nuclear terms  Critical mass-averge one free neutron hits another U- 235 nucleus, then the masss of the uranium is said to be critical and exist at stable temperature.  Sub-critical mass – Less than one of the free neutrons hits another U-235. Eventually fission will end and source power stops.  Super-critical mass- more than one of the free neutrons hits another U-235 nucleus. This causes the reactor to heat up.
  25. 25. Nuclear Power Issues  Transportation  Reactor safety  Terrorism  Worker+ publia Exposure to radiation  Contamination  Radioactive waste disposal  Thermal pollution  Decommissioning
  26. 26. Renewable energy  Biomass  Hydroelectric  Wind energy  Solar energy  Geothermal energy  Tidal Energy
  27. 27. Biomass Biomass – includes all biological waste and there are several sources of biomass 1. Fuel wood 2. Municipal waste and industrial waste 3. Agricultural crop residue and animal waste. 4. energy plantations. N.B Anaerobic disasters produces biomass which consist of methane and carbon dioxide.
  28. 28. Environmental issues of Biomass as an energy source •Air pollution •Habitat and Biodiversity Loss •Carbon dioxide and global warming •Effects on food Production •Crop residues and Animal waste
  29. 29. Hydroelectric power/ Hydropower Hydropower – flowing water creates energy that can be captured and turned into electricity. Sources include a) Darms > most common method b) Streams> Store areas of the world c) Canals N.B Development potential of Hydropower is best in mountainous areas + large rivers valleys. Use of hydropower is expected to increase.
  30. 30. Environmental Issues of hydropower as an energy source. •Fish migration •Loss of Natural Habitats and reduction in fish species Diversity •Volume of water •Sediment Deposits
  31. 31. Solar Power The sun provides a supply of energy which far exceeds the worlds demands There are 3 main methods of utilising solar energy as follows: 1. Passive Heating System> suns energy converted directly to heat. E.g drying clothes. 2.Active solar systems > heat is transferred from the collection site to the place of use, requirements include; solar collector, Pump, Pipe System for transfer. 3.Solar generating electricity. E.g domestic water heating
  32. 32. Solar Power continued >Photo Volture Cells PV These are solid state semi – conducter devices which convert light directly into electricity. Characteristics: •Usually made of silicon with some trace elements. •Once installed, a PV system needs little to no maintenance, just cleaning most PV systems come with storage better (Os) • Produce no pollutants
  33. 33. Environmental issues of Solar Power as an Energy Source 1. Supply 2. Land Use 3. Manufactor, Installation and disposal
  34. 34. Environmental issues of wind Power as an energy source •Location of wind fields •Supply •Land use •Noise and Visual Pollution •Wildlife
  35. 35. Geothermal Energy Defined as heat contained below the earths surface Geothermal energy can be contained in 2 ways •Geologically active areas: where hot magma reaches the earths surface •Geologically in active areas: in these spots, geothermal pumps are used to extract heat from the earths and transfer it to buildings.
  36. 36. Environmental issues of Geothermal Power as an energy source •Air Pollutions •Water Pollution •Chemicals •Safe Disposal of Hazadous Waste •Location of plant •Land Subsidence
  37. 37. Tidal Power There are Two high and two low tides everyday. Certain coastal areas (bays + inlets) experience higher tides than others because of their geographical features.
  38. 38. Environmental issues of Tidal Power as an energy source Environmental. Construction of dam across a bay or estuary causes negative impacts on •Aquatic and shoreline Ecosystems •Navigation •Recreation
  39. 39. Limiting Factors Affecting Energy Use 1. Technology 2. Geographical 3. Reliability of Supply 4. Cost of Production 5. Energy Policy of a Country 6. Social Factors
  40. 40. Factors affecting electrical generating capacity and demand. Generating Rates Demand Patterns Load Patterns + supply characteristics Intermittent Energy Sources Although hydroelectric power is seasonable predictable and controllable, solar and wind power are only available when whether permits.
  41. 41. Methods of supply meeting Demand • Load levelling. This involves moving demand from peak periods to times when the demand is low. This is done by: 1. Peak shaving 2. Smart Grid 3. Energy Storage