2. 8.2.1Identify different world energy sources. 8.2.2Outline and distinguish between renewable and non-renewable energy sources. 8.2.3Define the energy density of a fuel. 8.2.4Discuss how choice of fuel is influenced by its energy density. 8.2.5State the relative proportions of world use of the different energy sources that are available. 8.2.6Discuss the relative advantages and disadvantages of various energy sources. Topic 8: Energy, power, climate change 8.2 World energy sources

3. Identify different world energy sources.  We can divide our energy sources into two categories: Sun-derived, and Non-sun-derived. Topic 8: Energy, power, climate change 8.2 World energy sources Sun-Derived Energy Sources FuelsNon-fuels  Coal  Oil  Gas  Wood  Biomass  Solar Energy  Hydroelectric  Wind  Wave  Photovoltaic Non-Sun-Derived Energy Sources FuelsNon-fuels  Hydrogen  Uranium  Tidal  Geothermal  Chemical Fuels are “burned” Fuels “burned” CO 2

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

5. 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). Topic 8: Energy, power, climate change 8.2 World energy sources Sun-Derived Energy Sources FuelsNon-fuels  Coal  Oil  Gas  Wood  Biomass  Solar Energy  Hydroelectric  Wind  Wave  Photovoltaic Non-Sun-Derived Energy Sources FuelsNon-fuels  Hydrogen  Uranium  Tidal  Geothermal  Chemical

6. Define the energy density of a fuel.  Energy density is how much energy you can get per kilogram from a fuel. Topic 8: Energy, power, climate change 8.2 World energy sources 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.

7. Define the energy density of a fuel.  Energy density is how much energy you can get per kilogram from a fuel. Topic 8: Energy, power, climate change 8.2 World energy sources 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 !

8. Define the energy density of a fuel.  Most of our energy comes from fuels. Here is the energy yield of various fuels: Topic 8: Energy, power, climate change 8.2 World energy sources FuelFuel TypeEnergy Density (MJ/kg) ProtonsNuclear300,000,000 Uranium-235Nuclear90,000,000 PetrolFossil46.9 DieselFossil45.8 BiodieselFossil42.2 Crude OilFossil41.9 CoalFossil32.5 SugarFossil17.0 WoodFossil17.0 Cow DungFossil15.5 Household WasteFossil10.0

9. Define the energy density of a fuel. Topic 8: Energy, power, climate change 8.2 World energy sources 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 MJ of energy per day.  Thus (10368000 MJ)/(1 kg / 90000000 MJ) or 0.1152 kg d -1 !  This is only 42 kg y -1.

10. Discuss how choice of fuel is influenced by its energy density. Topic 8: Energy, power, climate change 8.2 World energy sources 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.

11. 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. Topic 8: Energy, power, climate change 8.2 World energy sources Fossil fuels CO 2

12. Topic 8: Energy, power, climate change 8.2 World energy sources State the relative proportions of world use of the different energy sources that are available.

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

14. 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 CO 2.  Coal is cheaper and more plentiful than gas and oil.  Nuclear power does not produce CO 2.  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. Topic 8: Energy, power, climate change 8.2 World energy sources

15. Discuss the relative advantages and disadvantages of various energy sources. Topic 8: Energy, power, climate change 8.2 World 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  10 9 /29.6  10 9 = 40.6 years Fuel (and unit) Proved reserves in 2005 Production in 2005 Coal (10 9 tonnes) 909.15.85 Oil (10 9 barrels) 1200.729.6 Gas (10 12 m 3 ) 179.82.76 FYI  This is an estimate because both numbers are subject to yearly change.

16. Discuss the relative advantages and disadvantages of various energy sources. Topic 8: Energy, power, climate change 8.2 World 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?

17. Discuss the relative advantages and disadvantages of various energy sources. Topic 8: Energy, power, climate change 8.2 World 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.