Fossil FuelsFossil Fuels

A.S. 8.3.1 – 8.3.5A.S. 8.3.1 – 8.3.5

What are fossil fuels?What are fossil fuels? Non-renewable energy sources that are derived Non-renewable energy sources that are derived

from plants and animals that lived hundreds of from plants and animals that lived hundreds of millions of years agomillions of years ago

In general, deceased plant and animal matter is In general, deceased plant and animal matter is converted into fossil fuels through exposure to converted into fossil fuels through exposure to high temperatures and high pressureshigh temperatures and high pressures

Examples:Examples: CoalCoal Natural GasNatural Gas OilOil

CoalCoal

Decaying plant matter, when buried under sediment, Decaying plant matter, when buried under sediment, eventually forms peat (very moist, compact)eventually forms peat (very moist, compact)

Further compaction, over time, forces the moisture Further compaction, over time, forces the moisture out of the peat—forms a layer of ligniteout of the peat—forms a layer of lignite

More compression (compaction), and more moisture More compression (compaction), and more moisture is removed, forming a layer of soft coal (bituminous)is removed, forming a layer of soft coal (bituminous)

Higher pressure and higher temperatures cause the Higher pressure and higher temperatures cause the bituminous coal to metamorphose into hard coal bituminous coal to metamorphose into hard coal (anthracite)(anthracite)

Images from: www.theviewfromthepeak.net

OilOil

Derived from the remains of plants and animals that Derived from the remains of plants and animals that once lived in oceans—up to 200 million years agoonce lived in oceans—up to 200 million years ago

Organisms died, sank to the ocean bottom, and were Organisms died, sank to the ocean bottom, and were covered with sediment (prevents rapid decomposition covered with sediment (prevents rapid decomposition because they are not exposed to oxygen)because they are not exposed to oxygen)

Decay occurs slowly, forms carbon-rich compounds Decay occurs slowly, forms carbon-rich compounds that mix with the sediment. Pressure from more that mix with the sediment. Pressure from more sediment above causes the compound and sediment sediment above causes the compound and sediment mixture to form mixture to form shaleshale (“source rock”) (“source rock”)

OilOil More pressure from layers above the source More pressure from layers above the source

rock cause the organic matter to transform into rock cause the organic matter to transform into oil.oil.

Liquid oil finds its way into porous rock layers Liquid oil finds its way into porous rock layers (like sandstone and limestone)—these rocks (like sandstone and limestone)—these rocks are known as “Reservoir rocks” because they are known as “Reservoir rocks” because they store the oilstore the oil

A “Cap rock” is a layer of non-porous rock A “Cap rock” is a layer of non-porous rock directly above the reservoir rock that prevents directly above the reservoir rock that prevents the oil from leaving that layer.the oil from leaving that layer.

Oil ReservesOil Reserves

Discovered reservesDiscovered reserves: an estimate of all known : an estimate of all known oil deposits with a “good probability of oil deposits with a “good probability of recovery”recovery”

Undiscovered resourcesUndiscovered resources: those areas that, : those areas that, based on geologic knowledge and estimates, based on geologic knowledge and estimates, have a good chance of being likely spots to have a good chance of being likely spots to find oil reserves.find oil reserves.

Cumulative productionCumulative production: the term that refers to : the term that refers to the estimate of all oil that has been produced the estimate of all oil that has been produced historically up until now.historically up until now.

Natural GasNatural Gas Formed at the same time as oilFormed at the same time as oil At higher temperatures, At higher temperatures,

relatively more gas is formed relatively more gas is formed than oil…at lower temps, more than oil…at lower temps, more oil than gas is formedoil than gas is formed

Typically gets trapped above Typically gets trapped above the layer of oil and below the the layer of oil and below the cap rock when there is a “fold” cap rock when there is a “fold” in the Earth’s rock layersin the Earth’s rock layers

Cleaner burning than coal or oilCleaner burning than coal or oil Colorless, odorless in its natural Colorless, odorless in its natural

form…power companies add form…power companies add odor in order to detect leaksodor in order to detect leaks

Natural GasNatural Gas

Typical Composition of Natural Gas

Methane CH4 70-90%

Ethane C2H6

0-20%Propane C3H8

Butane C4H10

Carbon Dioxide CO2 0-8%

Oxygen O2 0-0.2%

Nitrogen N2 0-5%

Hydrogen sulphide H2S 0-5%

Rare gases Ar, He, Ne, Xe trace

Natural Gas Uses…Natural Gas Uses…

According to the EIA, According to the EIA, approximately 22% of US approximately 22% of US Natural gas is used for Natural gas is used for residential energy residential energy

Propane, used in barbecue Propane, used in barbecue grills, is a byproduct of grills, is a byproduct of natural gas processingnatural gas processing

Historical Use of Fossil FuelsHistorical Use of Fossil Fuels

CoalCoal:: ~1000 BC: China~1000 BC: China 1818thth Century: Industrial Revolution Century: Industrial Revolution

As industry spread, rate of energy usage increasedAs industry spread, rate of energy usage increased Industry tended to build in areas where fossil fuel Industry tended to build in areas where fossil fuel

supplies were already in abundancesupplies were already in abundance Infrastructure was developed/improved for transporting Infrastructure was developed/improved for transporting

fossil fuels (i.e. coal) and the products made by industryfossil fuels (i.e. coal) and the products made by industry

Historical Use of Fossil FuelsHistorical Use of Fossil Fuels

OilOil 1960s1960s—became more widely used than coal for —became more widely used than coal for

general use, mainly because of growth in general use, mainly because of growth in transportation and gasoline usagetransportation and gasoline usage

Coal still more widely use for electrical power Coal still more widely use for electrical power production…production…

Advantages/Disadvantages?Advantages/Disadvantages?

What are some benefits to the use of fossil What are some benefits to the use of fossil fuels?fuels?

What are some disadvantages to the use of What are some disadvantages to the use of fossil fuels?fossil fuels?

Homework for tomorrow:Homework for tomorrow: do a little do a little research and come up with a list of 5-10 research and come up with a list of 5-10 “pros” and 5-10 “cons” for the continued use “pros” and 5-10 “cons” for the continued use of fossil fuelsof fossil fuels

Energy TransformationsEnergy TransformationsSolar Energy

Electrical Energy

KE of Turbines

KE of Steam

Thermal Energy

Chemical energy in fossil fuels

Chemical Energy in PlantsPhotosynthesis

Compression

Burning

Generation of ElectricityGeneration of Electricity

Approximately 20% of the fossil fuels Approximately 20% of the fossil fuels (primary energy) goes towards the generation (primary energy) goes towards the generation of electrical energy (secondary energy)of electrical energy (secondary energy)

Energy densities of the fuels used help Energy densities of the fuels used help determine how much electricity can be determine how much electricity can be generated from the fossil fuelsgenerated from the fossil fuels

Remember:Remember: Power = energy transferred per secondPower = energy transferred per second Efficiency = Power output / Power suppliedEfficiency = Power output / Power supplied

Efficiency of Power StationsEfficiency of Power Stations Depends on the design of the power stationDepends on the design of the power station Also depends on which type of fossil fuel is used to Also depends on which type of fossil fuel is used to

generate the electrical power.generate the electrical power.

Fossil FuelFossil Fuel Typical EfficiencyTypical Efficiency Maximum Maximum Efficiency (as of Efficiency (as of 2006)2006)

CoalCoal 35%35% 42%42%

Natural GasNatural Gas 45%45% 52%52%

OilOil 38%38% 45%45%

Energy DensitiesEnergy Densities

The amount of energy, per kilogram, that a The amount of energy, per kilogram, that a fuel source contains.fuel source contains.

If the conversion is 100% efficient, this is the If the conversion is 100% efficient, this is the amount that could be converted into usable amount that could be converted into usable energyenergy

What type of fuel source do you think has the What type of fuel source do you think has the highest energy density?highest energy density?

Energy DensitiesEnergy Densities

Sample problem:Sample problem:

At what rate (mass per hour) must coal be At what rate (mass per hour) must coal be supplied to a 500. MW coal fired power supplied to a 500. MW coal fired power station?station? Electrical power supply = 500 MW = 5.00 x 10Electrical power supply = 500 MW = 5.00 x 1088 W W Power released from the fuel = Power released from the fuel =

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

Sustainable DevelopmentSustainable Development

By definition: By definition: ““Development that meets the needs of the present Development that meets the needs of the present

without compromising the ability of future without compromising the ability of future generations to meet their own needs.”generations to meet their own needs.”

What must be considered?What must be considered? Economic aspectsEconomic aspects Social aspectsSocial aspects Environmental aspectsEnvironmental aspects