Fossil Fuels A.S – 8.3.5

What are fossil fuels? Non-renewable energy sources that are derived from plants and animals that lived hundreds of millions of years ago Non-renewable energy sources that are derived from plants and animals that lived hundreds of millions of years ago In general, deceased plant and animal matter is converted into fossil fuels through exposure to high temperatures and high pressures In general, deceased plant and animal matter is converted into fossil fuels through exposure to high temperatures and high pressures Examples: Examples: Coal Coal Natural Gas Natural Gas Oil Oil

Coal Decaying plant matter, when buried under sediment, eventually forms peat (very moist, compact) Decaying plant matter, when buried under sediment, eventually forms peat (very moist, compact) Further compaction, over time, forces the moisture out of the peat—forms a layer of lignite Further compaction, over time, forces the moisture out of the peat—forms a layer of lignite More compression (compaction), and more moisture is removed, forming a layer of soft coal (bituminous) More compression (compaction), and more moisture is removed, forming a layer of soft coal (bituminous) Higher pressure and higher temperatures cause the bituminous coal to metamorphose into hard coal (anthracite) Higher pressure and higher temperatures cause the bituminous coal to metamorphose into hard coal (anthracite)

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Oil Derived from the remains of plants and animals that once lived in oceans—up to 200 million years ago Derived from the remains of plants and animals that once lived in oceans—up to 200 million years ago Organisms died, sank to the ocean bottom, and were covered with sediment (prevents rapid decomposition because they are not exposed to oxygen) Organisms died, sank to the ocean bottom, and were covered with sediment (prevents rapid decomposition because they are not exposed to oxygen) Decay occurs slowly, forms carbon-rich compounds that mix with the sediment. Pressure from more sediment above causes the compound and sediment mixture to form shale (“source rock”) Decay occurs slowly, forms carbon-rich compounds that mix with the sediment. Pressure from more sediment above causes the compound and sediment mixture to form shale (“source rock”)

Oil More pressure from layers above the source rock cause the organic matter to transform into oil. More pressure from layers above the source rock cause the organic matter to transform into oil. Liquid oil finds its way into porous rock layers (like sandstone and limestone)—these rocks are known as “Reservoir rocks” because they store the oil Liquid oil finds its way into porous rock layers (like sandstone and limestone)—these rocks are known as “Reservoir rocks” because they store the oil A “Cap rock” is a layer of non-porous rock directly above the reservoir rock that prevents the oil from leaving that layer. A “Cap rock” is a layer of non-porous rock directly above the reservoir rock that prevents the oil from leaving that layer.

Oil Reserves Discovered reserves: an estimate of all known oil deposits with a “good probability of recovery” Discovered reserves: an estimate of all known oil deposits with a “good probability of recovery” Undiscovered resources: those areas that, based on geologic knowledge and estimates, have a good chance of being likely spots to find oil reserves. Undiscovered resources: those areas that, based on geologic knowledge and estimates, have a good chance of being likely spots to find oil reserves. Cumulative production: the term that refers to the estimate of all oil that has been produced historically up until now. Cumulative production: the term that refers to the estimate of all oil that has been produced historically up until now.

Natural Gas Formed at the same time as oil Formed at the same time as oil At higher temperatures, relatively more gas is formed than oil…at lower temps, more oil than gas is formed At higher temperatures, relatively more gas is formed than oil…at lower temps, more oil than gas is formed Typically gets trapped above the layer of oil and below the cap rock when there is a “fold” in the Earth’s rock layers Typically gets trapped above the layer of oil and below the cap rock when there is a “fold” in the Earth’s rock layers Cleaner burning than coal or oil Cleaner burning than coal or oil Colorless, odorless in its natural form…power companies add odor in order to detect leaks Colorless, odorless in its natural form…power companies add odor in order to detect leaks

Natural Gas Typical Composition of Natural Gas MethaneCH % EthaneC2H6C2H6 0-20% PropaneC3H8C3H8 ButaneC 4 H 10 Carbon DioxideCO 2 0-8% OxygenO2O % NitrogenN2N2 0-5% Hydrogen sulphideH2SH2S0-5% Rare gasesAr, He, Ne, Xetrace

Natural Gas Uses… According to the EIA, approximately 22% of US Natural gas is used for residential energy According to the EIA, approximately 22% of US Natural gas is used for residential energy Propane, used in barbecue grills, is a byproduct of natural gas processing Propane, used in barbecue grills, is a byproduct of natural gas processing

Historical Use of Fossil Fuels Coal: Coal: ~1000 BC: China ~1000 BC: China 18 th Century: Industrial Revolution 18 th Century: Industrial Revolution As industry spread, rate of energy usage increased As industry spread, rate of energy usage increased Industry tended to build in areas where fossil fuel supplies were already in abundance Industry tended to build in areas where fossil fuel supplies were already in abundance Infrastructure was developed/improved for transporting fossil fuels (i.e. coal) and the products made by industry Infrastructure was developed/improved for transporting fossil fuels (i.e. coal) and the products made by industry

Historical Use of Fossil Fuels Oil Oil 1960s—became more widely used than coal for general use, mainly because of growth in transportation and gasoline usage 1960s—became more widely used than coal for general use, mainly because of growth in transportation and gasoline usage Coal still more widely use for electrical power production… Coal still more widely use for electrical power production…

Advantages/Disadvantages? What are some benefits to the use of fossil fuels? What are some benefits to the use of fossil fuels? What are some disadvantages to the use of fossil fuels? What are some disadvantages to the use of fossil fuels? Homework for tomorrow: do a little research and come up with a list of 5-10 “pros” and 5-10 “cons” for the continued use of fossil fuels Homework for tomorrow: do a little research and come up with a list of 5-10 “pros” and 5-10 “cons” for the continued use of fossil fuels

Energy Transformations Solar Energy Electrical Energy KE of Turbines KE of Steam Thermal Energy Chemical energy in fossil fuels Chemical Energy in Plants Photosynthesis Compression Burning

Generation of Electricity Approximately 20% of the fossil fuels (primary energy) goes towards the generation of electrical energy (secondary energy) Approximately 20% of the fossil fuels (primary energy) goes towards the generation of electrical energy (secondary energy) Energy densities of the fuels used help determine how much electricity can be generated from the fossil fuels Energy densities of the fuels used help determine how much electricity can be generated from the fossil fuels Remember: Remember: Power = energy transferred per second Power = energy transferred per second Efficiency = Power output / Power supplied Efficiency = Power output / Power supplied

Efficiency of Power Stations Depends on the design of the power station Depends on the design of the power station Also depends on which type of fossil fuel is used to generate the electrical power. Also depends on which type of fossil fuel is used to generate the electrical power. Fossil Fuel Typical Efficiency Maximum Efficiency (as of 2006) Coal35%42% Natural Gas 45%52% Oil38%45%

Energy Densities The amount of energy, per kilogram, that a fuel source contains. The amount of energy, per kilogram, that a fuel source contains. If the conversion is 100% efficient, this is the amount that could be converted into usable energy If the conversion is 100% efficient, this is the amount that could be converted into usable energy What type of fuel source do you think has the highest energy density? What type of fuel source do you think has the highest energy density?

Energy Densities

Sample problem: At what rate (mass per hour) must coal be supplied to a 500. MW coal fired power station? At what rate (mass per hour) must coal be supplied to a 500. MW coal fired power station? Electrical power supply = 500 MW = 5.00 x 10 8 W Electrical power supply = 500 MW = 5.00 x 10 8 W Power released from the fuel = Power released from the fuel =

Rate of consumption of coal = Rate of consumption of coal =

Sustainable Development By definition: By definition: “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” What must be considered? What must be considered? Economic aspects Economic aspects Social aspects Social aspects Environmental aspects Environmental aspects