World Energy Sources, Fossil Fuel Power Production, and Nuclear Power. By Henry Aoki, Nathan Carroll, Cameron Fudeh and Casey Lee-Foss

Transcription

1 World Energy Sources, Fossil Fuel Power Production, and Nuclear Power By Henry Aoki, Nathan Carroll, Cameron Fudeh and Casey Lee-Foss

2 Part 1: World Energy Sources and Fossil Fuel Power Production

3 Different Sources of Energy Fossil Fuels: Hydrocarbons built up over time Nuclear Fission: Splits Uranium for power (can also do plutonium) Solar: Harvests sunlight Wind: Harvests wind Hydroelectric: Harvests water currents Geothermal: Harvests energy from beneath surface of Earth Nuclear Fusion: Not yet energy-positive

4 Renewable vs. Nonrenewable Energy Renewable Replenish easily or rely on very large energy sources (sun, geothermal) Non-Renewable Do not replenish on a small enough timescale Includes nuclear power and fossil fuels

5 Energy Density and How it Influences Fuel Choice Energy Density: Energy per unit of volume Uranium: 1,546,000,000 Megajoules/Litre Gasoline: 36 Megajoules/Litre Natural Gas: Megajoules/Litre Source:

6 World Use of Energy Sources Fossil Fuels: 82% Nuclear: 5% Renewables (Solar, Hydro, wind, etc.): 13% Source:

7 Advantages and Disadvantages of Fossil Fuels Advantages Easy to access Easy to use Disadvantages Non-renewable Reduces air quality (note China) Climate Change debacle

8 Advantages and Disadvantages of Solar power Advantages Renewable (relies on sun) Use for arid desert areas Disadvantages Cloud Cover Expensive to use on wide scale

9 Advantages and Disadvantages of Wind Power Advantages Renewable Room for growth in industry Disadvantages Reliant on wind (offshore installations face difficulties) Relatively expensive

10 Why Fossil Fuels Are So Commonly Used Fossil fuels popularity can be traced back to the Industrial Revolution, when coal was found to be more efficient than charcoal or wood, and also readily abundant. Source:

11 Specific Energy of Fossil Fuels Fossil Fuel Energy Unit/Mass Coal 24 MJ/kg Diesel 46 MJ/kg Natural Gas 53.6 MJ/kg Source:

12 Fossil Fuel Transportation and Storage: Advantages and Disadvantages Pros Transport Storage Cons Some can be Risk of oil spills, often produced domestically have to be brought overseas High energy density Highly volatile Source:

13 Efficiency of Coal, Petroleum and Natural Gas Power Plants Coal 33% Petroleum 31% Natural Gas 42% Sources: cfm?id=107&t=3

14 Environmental Problems with Extracting and Burning Fossil Fuels Mining destroys habitats, poses dangers for workers. CO2 is emitted from burning fossil fuels. Source:

15 Sankey Diagrams: Coal Nearly all coal is used for electric power, though a small amount is exported, and even less is used industrially. Some coal (1.4%) is lost in production. Source:

16 Sankey Diagrams: Natural Gas Energy used is very closely split between industrial sectors and electric power. Residential and commercial use is also notable. Notable amounts of energy are lost when the natural gas is refined, approximately 14%. Source:

17 Sankey Diagrams: Petroleum While the majority of coal is used in transportation (as fuel for cars, buses, etc.) there is a sizable amount used industrially, about 35% the size of transport. Small amounts of petroleum are lost during conversion to fuels, less than 0.3%. Source:

18 Part 2: Nuclear Power

19 Nuclear Chain Reactions After a fission reaction occurs, a few neutrons are released. These neutrons can strike another nucleus, cause it to become unstable and break apart. Source: hyperphysics.phy-astr.gsu.edu/hbase/nucene/fission.html

20 Controlled vs. Uncontrolled Nuclear Fission Controlled Uncontrolled Controlled nuclear fission provides a way to control neutrons to prevent or control the chain reaction process. Uncontrolled nuclear fission does not moderate or control neutrons to limit subsequent chain reactions from occurring. Example: Nuclear Power Plant s Control Rods Example: Atomic Bomb A nuclear power plant utilizes neutron absorbing control rods that can control the rate at which nuclear chain reactions occur. This limits the rate at which energy is released from the chain reaction to a safe level. An atomic bomb releases a deadly amount of energy because it does not control the nuclear chain reaction. edu/physical_chemistry/nuclear_chemistry/fission_and_fusion/nuclear_chain_reactions#uncontrolled_chain_r

21 Fuel Enrichment Gas Centrifuge Fuel enrichment is the process of separating isotopes to use only the isotopes that are desirable for nuclear energy. The uranium isotope used in most nuclear reactors is U235. However, when uranium is mined, only approximately 0.7% of the atoms are U235. U235 is enriched either through gaseous diffusion through a membrane or using a gas centrifuge Gaseous Diffusion

22 Energy Transformations at a Nuclear Power Station The fission reaction transforms nuclear energy into heat energy. The heat energy is used to change water into steam. This steam gains kinetic energy to powers steam turbines and generators which transforms the kinetic energy into electrical energy. Source:

23 The Moderator and Control Rods Moderator Nuclear fission does not occur if the neutron that is making the nucleus unstable is not a slow neutron. A moderator is a substance that lowers the kinetic energy of the neutron. The most common moderators are water, graphite and water with deuterium atoms. The neutrons collide with the moderators and lose kinetic energy, making them viable for fission. Control Rods Control rods are neutron absorbing material that are used to control the nuclear reactor s rate of fission. A common material used in control rods is boron. They separate the fuel rods which contain the material that will be fissioned. They can also be used to put the reactor into a state which will eventually stop the chain reaction. Source:

24 The Heat Exchanger The fission reaction produces heat which increases the kinetic energy of water. This water is run through a heat exchanger which increases the kinetic energy of separate water which becomes steam. This steam powers a turbine. The advantage of using the heat exchanger is that the turbine will not come in contact with radioactive material. Source:

25 Production of Plutonium-239 Plutonium 239 (Pu-239) is created using Uranium 238 (U-238) and a nuclear reactor. In the reactor, a neutron is added to the U-238 atom, making it into U-239. As a result of radioactive decay, over the course of 23 minutes, a neutron is converted into a proton, so the U-239 becomes Neptunium 239 (NP-239). For another 2.3 days, another neutron becomes a proton. The Np-239 decays into Pu-239. Sources: EPA.gov, laradioactivite.com

26 Importance of Plutonium-239 Pu-239 is able to undergo nuclear chain reactions and has a half-life of about 24,000 years. For these reasons, it is very useful both as a fuel and as a weapon. Source: Chemicool.com

27 Safety Issues/Risks with Nuclear Power Production Cooling system failure can lead to a complete or partial meltdown of the core, which would release dangerous amounts of radiation into the surrounding environment. The most dangerous meltdowns were Three Mile Island, Chernobyl, and Fukushima. After the nuclear fuel has been used up, there is the question of where to put the waste, which will remain dangerously radioactive for tens of thousands of years. Sources: greenpeace.org, world-nuclear.org

28 Problems with Using Nuclear Fusion for Energy We have not yet developed a way to use nuclear fusion for energy on a large scale. It is difficult to build a reactor that can withstand and control the enormous amounts of energy that are released from nuclear fusion. The research and development of nuclear fusion as an energy source is very expensive. In addition to being used as an energy source, nuclear fusion can also be used to create hydrogen bombs. Sources: cnn.com, howstuffworks.com

29 Energy Flow/Sankey Diagrams Sources: sankey-diagrams.com, schoolphysics.co.uk

30 Possible Solutions to the Problems with Nuclear Power Continue research and development of fusion; the byproduct of fusion is non-radioactive helium. Enact higher safety design standards so that there will not be another explosion, such as the one at Chernobyl. Build new nuclear power plants in locations where they will be able to withstand natural disasters so there will not be another Fukushima accident. Sources: EFDA.org, world-nuclear.org