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Topic 8: Energy, power, climate change 8.2 World energy sources

Topic 8: Energy, power, climate change 8.2 World energy sources. 8.2.1 Identify different world energy sources. 8.2.2 Outline and distinguish between renewable and non-renewable energy sources. 8.2.3 Define the energy density of a fuel.

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Topic 8: Energy, power, climate change 8.2 World energy sources

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  1. Topic 8: Energy, power, climate change8.2 World energy sources 8.2.1 Identify different world energy sources. 8.2.2 Outline and distinguish between renewable and non-renewable energy sources. 8.2.3 Define the energy density of a fuel. 8.2.4 Discuss how choice of fuel is influenced by its energy density. 8.2.5 State the relative proportions of world use of the different energy sources that are available. 8.2.6 Discuss the relative advantages and disadvantages of various energy sources.

  2. CO2 CO2 CO2 Topic 8: Energy, power, climate change8.2 World energy sources Identify different world energy sources. We can divide our energy sources into two categories: Sun-derived, and Non-sun-derived. Sun-Derived Energy Sources Fuels Non-fuels Fuels are “burned” Coal Solar Energy Oil Hydroelectric Gas Wind CO2 Wood Wave Biomass Photovoltaic Non-Sun-Derived Energy Sources Fuels Fuels “burned” Non-fuels Hydrogen Tidal Uranium Geothermal Chemical Chemical

  3. Energy diagram for the US. Most of our energy comes from sun-derived fuels. 3.2 +23.2 +23.0 +39.2 = 88.6%

  4. Sun-Derived Energy Sources Fuels Non-fuels Coal Solar Energy Oil Hydroelectric Gas Wind Wood Wave Biomass Photovoltaic Non-Sun-Derived Energy Sources Fuels Non-fuels Hydrogen Tidal Uranium Geothermal Chemical Chemical Topic 8: Energy, power, climate change8.2 World energy sources Outline and distinguish between renewable and non-renewable energy sources. Renewable resources can be replaced in a reasonable amount of time (or are not depleted).

  5. Topic 8: Energy, power, climate change8.2 World energy sources Define the energy density of a fuel. Energy density is how much energy you can get per kilogram from a fuel. EXAMPLE: Coal has an energy density of 32.5 MJ/kg. If a city has a coal-fired power plant that needs to produce 30.0 MW of power, and it has an efficiency of 25%, how many kilograms of coal are needed per day? SOLUTION: Since efficiency = output / input 0.25 = 30.0 MW / input input = 120 MW But 1 day = 243600 s = 86400 s so that input = (120 MJs-1)(86400 s) = 10368000 MJ. Thus input = (10368000 MJ)(1 kg / 32.5 MJ) = 320000 kg.

  6. Topic 8: Energy, power, climate change8.2 World energy sources Define the energy density of a fuel. Energy density is how much energy you can get per kilogram from a fuel. PRACTICE: If coal is transported in rail cars having a capacity of 1.5 metric tons, how many cars per day must supply the power plant of the previous example? SOLUTION: From the previous example we calculated that we need 320000 kg of coal per day. Since a metric ton is 1000 kg, we have (320000 kg )/(1.5  1000 kg / car) or 213 cars d-1!

  7. Topic 8: Energy, power, climate change8.2 World energy sources Define the energy density of a fuel. Most of our energy comes from fuels. Here is the energy yield of various fuels: Fuel Fuel Type Energy Density (MJ/kg) Protons Nuclear 300,000,000 Uranium-235 Nuclear 90,000,000 Petrol Fossil 46.9 Diesel Fossil 45.8 Biodiesel Fossil 42.2 Crude Oil Fossil 41.9 Coal Fossil 32.5 Sugar Fossil 17.0 Wood Fossil 17.0 Cow Dung Fossil 15.5 Household Waste Fossil 10.0

  8. Topic 8: Energy, power, climate change8.2 World energy sources Define the energy density of a fuel. PRACTICE: If a nuclear power plant powered by uranium-235 has the same output and the same efficiency as the coal-fired plant of the previous example, how many kg of nuclear fuel will it burn per day? Per year? SOLUTION: From the previous example we calculated that we need 10368000 MJof energy per day. Thus (10368000 MJ)/(1 kg / 90000000 MJ) or 0.1152 kg d-1! This is only 42 kg y-1.

  9. Topic 8: Energy, power, climate change8.2 World energy sources Discuss how choice of fuel is influenced by its energy density. PRACTICE: Explain why it is advantageous to have a submarine which is nuclear powered, as opposed to diesel powered. SOLUTION: There are two main reasons: (1) Nuclear reactors don’t use oxygen, so the sub can stay under water for months at a time. (2) Nuclear fuel is extremely compact for the amount of energy it contains. Thus the sub can cruise far before refill.

  10. Topic 8: Energy, power, climate change8.2 World energy sources State the relative proportions of world use of the different energy sources that are available. You should have a good idea of these percentages, from memory. Fossil fuels CO2

  11. Topic 8: Energy, power, climate change8.2 World energy sources State the relative proportions of world use of the different energy sources that are available.

  12. Topic 8: Energy, power, climate change8.2 World energy sources State the relative proportions of world use of the different energy sources that are available. PRACTICE: Sun makes biomass through photosynthesis. Biomass gathers and grows over time. Biomass buried under great pressure and heat. Biomass becomes coal, oil and natural gas over eons. Coal, oil and natural gas are extracted. Coal, oil and natural gas are used as fuels.

  13. Topic 8: Energy, power, climate change8.2 World energy sources Discuss the relative advantages and disadvantages of various energy sources Renewable energy is better than non-renewable because it will not run out. Oil and gas are better than coal because they burn more efficiently and produce less CO2. Coal is cheaper and more plentiful than gas and oil. Nuclear power does not produce CO2. Hydroelectric is useful to have in a grid because it can be used to store extra energy. Burning biomass alleviates landfills. Nuclear waste lasts for thousands of years. Renewable energy sources like wind turbines and photovoltaic cells depend on the weather conditions and have small output.

  14. Topic 8: Energy, power, climate change8.2 World energy sources Discuss the relative advantages and disadvantages of various energy sources. PRACTICE: Proved reserves are resources that we are sure we can obtain. Production means actual reserves that have been obtained and placed on the market. Use the table to estimate how long oil reserves might last. SOLUTION: Expectancy = Reserves / Production = 1200.7109/29.6109 = 40.6 years FYI This is an estimate because both numbers are subject to yearly change.

  15. Topic 8: Energy, power, climate change8.2 World energy sources Discuss the relative advantages and disadvantages of various energy sources. PRACTICE: The machine shown is called the “Bay View Bob” and can produce enough power on Lake Michigan waves to power a cell phone. Give reasons why this might not be a good way to produce energy?

  16. Topic 8: Energy, power, climate change8.2 World energy sources Discuss the relative advantages and disadvantages of various energy sources. PRACTICE: Wind power doesn’t produce greenhouse gas. Wind power is a renewable resource. Wind depends on the weather. 2 GW / 0.8 MW = 2500 turbines required.

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