Chapter 19 Energy resources19.1 Electricity is a convenient form of energy

Fig 19.1 basic anatomy of an electric generator. Electricity is generated in a looped wire as the wire rotates through a magnetic field. This motion causes electrons in the wire to slosh back and forth. Because the electrons are moving, they possess kinetic energy and so have the capacity to do work

electron

turbine

Metal ion

armature

Multiple wire loops

magnet

water

steam

Energy source

19.2 Fossil fuels are a widely used but limited energy source38% from petroleum, 30 % from coal, 20% from natural gas

Fig 19.2 fossil-fuel deposits are not distributed evenly throughout the world, for instance, as percent of the world’s recoverable petroleum deposits are in the middle east, along with 34 percent of recoverable natural-gas deposits. North America is relatively poor in petroleum and natural gas but has a bit more than one-fourth of the world’s supply of coal

North America coal 26.1%

petroleum 6.2% natural gas 5.0%

South and central America

coal 2.2% petroleum 8.6% natural gas 4.3%

Europe coal 12.4%

petroleum 2.0% natural gas 3.5%

Africa coal 6.2%

petroleum 7.2% natural gas 7.7%

Former Soviet Union coal 23.4%

petroleum 6.3% natural gas 38.7%

Asia Pacific coal 29.7%

petroleum 4.3% natural gas 7.0%

Middle East coal 6.2%

petroleum 65.4% natural gas 33.8%

Fig 19.3 typical molecular structure of coal, petroleum and natural gas

Coal petroleum Natural gas

Coal is the filthiest fossil fuelCoal contains sulfur, toxic heavy metals, and radioactive isotopes.Extracting coal from the ground is harmful to human health and to the environment.The coal can be purified by floatation (浮选 ).Sulfur dioxide produced from the burning of coal can be removed by scrubber (气体洗涤器 ).

Fig 19.7 a scrubber is used to remove most of the sulfur dioxide

created when coal is burned

Scrubbed gas to atmosphere

Spray tower

CaCO3

CaSO4 to solid-waste

disposal site

Effluents from coal-fired

power plant

containing SO2

• Petroleum is the king of fossil coal.• Natural gas is the purest fossil fuel.• Natural gas contains little amount of sulfur.

It burns at lower temperature, producing less NO.

• The efficiency to generate electricity by using gas turbine can be as high as 47%.

• Natural gas can be methane, which is safer, and propane.

19.3 There are two forms of nuclear energy (Nuclear fission, 核裂变； Nuclear fusion, 核聚变 )

Fig 19.11 nuclear fission involves the splitting apart of large atomic nuclei. Nuclear fusion involves the coming together of small nuclei

Nuclear fission

Nuclear fusion

Nuclear fission generates some of our electricity

Fig 19.12 percentage of electricity generated from nuclear fission reactors in selected countries (April, 2001)

Nuclear wastes: Storage is a problem.AccidentThe number of nuclear power station has been decreasing.

Fig 19.14 in 1986, a meltdown occurred at this nuclear power plant in Chernobyl, Ukraine. Because there was no containment building, large amounts of radioactive material were released into the environment, three people died outright and dozens more died from radiation sickness within a few weeks . Thousands who were exposed to high levels of radiation stand an increased risk of cancer. Today, 10,000 square kilometers of land remains contaminated with high levels of radiation

Nuclear fusion is a potential source of clean energyMagnetic field and laser are used to the fusion reaction.Cost to build the power station is very high.

Fig 19.16 a fusion reactor called the Large Helical Device is being built and tested by researchers in Japan. These coils create a magnetic field that contain the hot ionized gas within which nuclear fusion takes place

19.5 Water can be used generate electricityHydroelectric power comes from the kinetic energy of flowing waterTemperature differences in the ocean can generate electricityGeothermal energy comes from the Earth’s interiorThe energy of ocean tides can be harnessed

Fig 19.22 about 50 percent of the electricity generated in iceland is from geothermal sources. This is the blue lagoon, a warm pool created from the effluent of the hydrothermal power plant visible in the background

19.6 Biomass is chemical energy

Fig 19.23 Gasohol is gasoline containing an alcohol additive. The alcohol provides an octane boost, allowing an engine to run more efficiently with less pollution. If the alcohol is produced from biomass grown within a nation, there is the added benefit of a reduced dependence on foreign oil

19.7 Energy can be harnessed from sunlightSolar energy can be easily collected.

Fig 19.25 (a) a solar energy collector is covered with glass to provide a greenhouse effect: sunlight passing into the box is converted to infrared radiation, which cannot escape. (b) most solar energy collectors are located on rooftops. The collectors are painted black to maximize the absorption of solar heat. The rooftop collector shown here is used for warming an outdoor swimming pool

Cold waterBlack interior

Warm water

Glass plate

Wind power is cheap

Fig 19.29 about 4000 wind turbines at the Tehachapi site in Southern California supply 626 megawatts of electricity

Photovoltaics convert sunlight directly to electricity

Fig 19.33 (a) the four valence electrons in a silicon atom can form four bonds. The fifth valence electron of arsenic is unable to participate in bonding in the silicon lattice, and so remains free. Silicon that contains trace amounts of arsenic (or any other element whose atoms have five valence electrons) is called n-type silicon. (b) boron has only three valence electrons for bonding with four silicon atoms. One boron-silicon pair therefore lacks an electron for covalent bonding. Silicon containing trace amounts of boron (or any other elements whose atoms have three valence electrons) is called p-type silicon.

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

As

Si

Si

Si

Si

Si

Si

As

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

B

B

Si

Si

Si

Si

Si

Si

Arsenic’s extra valence electron

Boron’s missing valance electron

Fig 19.36 sunlight is converted to electrical energy as it pushes electrons through the external wire from the n-type silicon to the p-type silicon

sunlight

p-type wafer n-type wafer

• 19.8 Our future economy should be based on hydrogen

• Fuel cells produce electricity from fuel

• Photovoltaic cells can be used to produce hydrogen from water