ch 12 energy energy sources and uses coal - oil - natural gas nuclear power conservation solar...

Ch 12 Energy• Energy Sources and Uses• Coal - Oil - Natural Gas• Nuclear Power• Conservation• Solar Energy

– Photovoltaic Cells

• Fuel Cells• Energy From Biomass• Energy From Earth’s Forces

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Fossil Fuels

• Fossil fuels - organic chemicals that were created by living organisms millions of years ago, buried in sediments, and transformed into energy- rich compounds

• Because fossil fuels take so long to form, they are essentially nonrenewable resources.

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Coal Extraction and Use• Mining - dangerous to

humans and the environment

• Coal burning releases large amounts of air pollution, and is the largest single source of acid rain in many areas.

• Economic damages - billions of dollars

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Oil Extraction and Use• The largest supply of proven-in-place oil is in

Saudi Arabia.

• The countries of the Middle East control two-thirds of all known oil reserves.

• The U.S. has already used up about 40% of its original recoverable petroleum resource.

• Problems:– Combustion - substantial air pollution– Drilling - soil and water pollution– Controversies – Arctic National Wildlife Refuge,

California coast6

Crude Oil Prices

Today

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Natural Gas Consumption

• Natural gas produces only half as much CO2 as an equivalent amount of coal.

• Problems: – difficult to ship

across oceans or to store in large quantities

– Flaring off - wasted

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Nuclear Power

• “Atoms for Peace” in 1953 by Eisenhower (produce enough power ‘to cheap to monitor’)

• Nuclear power now produces only about 7% of the U.S. energy supply.

• Problems have made nuclear power much less attractive than was originally expected :

– construction costs and

– safety concerns and….

– waste disposal.10

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Nuclear EnergyTwo types of nuclear power & both involve

rearranging the structure of the atom.– Fission - splitting of a radioactive isotope of a heavy

element into daughter products (smaller atoms) with the release of energy

– Fusion - joining of isotopes of a light element into a heavier element with the release of energy.

• All commercial energy generation is run by fission.

• The Sun generates heat and light by fusion.

• Some nuclear weapons use fusion reactions but controlled fusion is still in the developmental stage.

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Chernobyl - 1986

Three Mile Island - 1979

Accidents????

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Nuclear Wastes

• One of the most difficult problems associated with nuclear power is the disposal of wastes produced during mining, fuel production, reactor operation, and decommissioning of reactors.

• Ocean dumping – until 1970?

• Radioactive mine wastes, mill tailings

• Dry cask storage

• High-level waste repository - Yucca Mountain, NV

• Monitored, retrievable storage?

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1965+ - former Soviet Union disposed of 18

nuclear reactors (7 w/ fuel in the Kara Sea)

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• Hanford buried radioactive waste which began leaking.

• Nuclear testing peaks in 1950-60s. Trees absorb cesium and accumulates in wood.

Plant roots absorbed the radioactive material and transported it to the ground surface.

Wood ash can be radioactive – 100X higher cesium than other environmental samples.

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ENERGY CONSERVATION

• Utilization Efficiencies– Most potential energy in fuel is lost as

waste heat.– In response to 1970’s oil prices,

average US automobile gas-mileage increased from 13 mpg in 1975 to 28.8 mpg in 1988.

–Falling fuel prices of the 1980’s discouraged further conservation.

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Find more non-

renewable oil?

Eg, Arctic National Wildlife Refuge

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Hybrid gas-

electric engines

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Energy Conversion Efficiencies

• Energy Efficiency is a measure of energy produced compared to energy consumed.– Household energy losses can be reduced by

one-half to three-fourths by using better insulation, glass, protective covers, and general sealing procedures.(Indoor Pollution?)• Orient homes to gain advantage of passive

solar gain in the winter.21

Mesa Verde NP (SW USA) – many energy efficient features

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Domestic Energy Efficiency

Earth-sheltered house in Taos, New Mexico

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Buying energy-efficient appliances can cut your energy consumption considerably.

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Renewable Energies:SOLAR ENERGY

• Average amount of solar energy arriving on top of the atmosphere is 1,330 watts per square meter.– Amount reaching the earth’s surface is

10,000 times more than all commercial energy used annually.• Until recently, this energy source has been

too diffuse and low intensity to capitalize for electricity. 25

Solar Energy

• Passive Solar Heat - Using absorptive structures with no moving parts to gather and hold heat.– Greenhouse Design

• Active Solar Heat - Generally pump heat- absorbing medium through a collector, rather than passively collecting heat in a stationary object.

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Underground massive heat storage unit

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High-Temperature Solar Energy 2828

Parabolic mirrors

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Fresh and salt water ponds to trap solar

radiation/heat

Average Daily Solar

Radiation

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Photovoltaic Cells• During the past 25 years, efficiency of

energy capture by photovoltaic cells has increased from less than 1% of incident light to more than 10% in field conditions, and 75% in laboratory conditions.– Invention of amorphous silicon collectors

has allowed production of lightweight, cheaper cells.

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Costs for alternativeand renewable energy sources have dropped in recent years.

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Storing Electrical Energy

• Electrical energy storage is difficult and expensive.– Lead-acid batteries are heavy and have

low energy density.• Typical lead-acid battery sufficient to store

electricity for an average home would cost $5,000 and weigh 3-4 tons.

– Pumped-Hydro Storage

– Flywheels

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Promoting Renewable Energy

• Distributional Surcharges– Small charge levied on all utility customers to help

finance research and development.

• Renewable Portfolio– Mandate minimum percentage of energy from

renewable sources.

• Green Pricing– Allow utilities to profit from conservation programs and

charge premium prices for energy from renewable sources.

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Fuel Cells

• Fuel cells - use ongoing electrochemical reactions to produce an electrical current

• Oxygen, hydrogen• Reformers• Efficiency- 70%

theoretically but practically around 40-45%?

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Fuel Cell Electric

Car

Typical fuel cell efficiency is 40-45%.

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Hydrogen fueling stations

BIOMASS• Wood provides less than 1% of US

energy, but provides up to 90% in poorer countries.– 1,500 million cubic meters of fuelwood

collected in the world annually.• Inefficient burning of wood produces smoke

laden with fine ash and soot and hazardous amounts of carbon monoxide (CO) and hydrocarbons.

– Produces few sulfur gases, and burns at lower temperature than coal.

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Fuel wood Crisis in Less-Developed Countries

• About 40% of the world’s population depends on firewood and charcoal as their primary energy source.

• Supplies diminishing• Half of all wood

harvested worldwide is used as fuel.

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Using Dung as Fuel

• Using dung as fuel deprives fields of nutrients and reduces crop production.

• When cow dung is burned in open fires, 90% of the potential heat and most of the nutrients are lost. 40

Swedish workers harvesting marsh reeds for biomass energy

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Using Methane as Fuel

Anaerobic Fermentation 43

Alcohol from Biomass

• Ethanol - grain alcohol• Methanol - wood alcohol• Gasohol - a mixture of gasoline and

alcohol - reduced CO emissions• Ethanol production could be a solution

to grain surpluses.• Both methanol and ethanol make good

fuel for fuel cells.

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Forest thinnings to methanol to fuel cells for electricity

Energy from the Earth’s Forces

• Water power produces 25% of the world’s electricity.

• Clean, renewable energy

• Dams - social and ecological damage

Hydropower

?

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Dam Drawbacks• Human Displacement• Ecosystem Destruction• Wildlife Losses• Large-Scale Flooding Due to Dam

Failures• Sedimentation• Herbicide Contamination• Evaporative Losses• Nutrient Flow Retardation• CO2 emissions 47

Wind Energy

• Wind power - advantages and disadvantages

• Wind farms - potential: Great Plains, seacoasts48

Wind Energy• Wind Farms - Large concentrations of

wind generators producing commercial electricity.– Negative Impacts:

• Interrupt view in remote places

• Destroy sense of isolation

• Potential bird kills

• Cannot place w/i 70 km of military airbases, etc

• Sources vary geographically 49

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Geothermal Energy

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• Have long life span,

• no mining needs, and

• little waste disposal.• Potential danger of noxious gases and • noise problems from steam valves.

5252

Tidal Energy

• Requires a high tide/low-tide differential of several meters• Saltwater flooding behind the dam and heavy siltation• Locations w/ large waves?

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Wave Power!!

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Ocean Thermal Electric Conversion (OTEC) Plant

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An Alternative

Energy Future?

5656

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Green Buildings to conserve energy

Summary:• Energy Sources and Uses

• Coal - Oil - Natural Gas

• Nuclear Power

• Conservation

• Solar Energy– Photovoltaic Cells

• Fuel Cells

• Energy From Biomass

• Energy From Earth’s Forces

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