ESC110 CHAPTER TWELVEENERGY

Chapter Twelve Readings & ObjectivesRequired ReadingsCunningham & Cunningham, Chapter Twelve: EnergyAt the end of this lesson, you should be able to:

•summarize our current energy sources and explain briefly how our energy compares with that of other people in the world;

•analyze the resources and reserves of fossil fuels in the world;

•evaluate the costs and benefits of using coal, oil, and natural gas;

•understand how nuclear reactors work, why they are dangerous, and how they might be made safer;

•appreciate the opportunities for energy conservation available to us;

•understand how active and passive systems capture solar energy, and how photovoltaic collectors generate electricity;

•comprehend the promise and problems of using biomass as an energy source; and,

•explain how hydropower, wind, and other energy from the earth’s forces can contribute to our energy supply.

Chapter Twelve Key Terms

active solar systems page 286 of text

chain reaction 281

control rods 281

energy 275

fossil fuels 275

fuel assembly 281

fuel cells 290

gasohol 293

"green pricing” 290

high-level waste repository 255

joule (J) 275

monitored, retrievable storage 283

nuclear fission 281

passive heat absorption 286

power 275photovoltaic cell 288Proven-in-place reserves 277

reformer 290

wind farms 294

work 275

Chapter Twelve Topics

• Energy Sources and Uses (Oil & Arctic National Wildlife Refuge)

• Fossil Fuels• Nuclear Power• Energy Conservation (Hybrid Autos)• Solar Energy• Fuel Cells• Biomass• Energy From the Earth’s Forces• What’s Our Energy Future?

PART 1: ENERGY SOURCES AND USES

• Work is the application of force through a distance.• Energy is the capacity to do work.• Power is the rate of flow of energy, or the rate at

which work is done.– A small calorie is the metric measure of energy necessary to heat

1 gram of water 1oC, whereas a British Thermal Unit (BTU) is the energy needed to heat 1 pound of water 1oF

– A joule is the amount of work done by a force needed to accelerate 1 kilogram 1 meter per second per second. Another definition for joule is the force of an electrical current of 1 amp/second through a resistance of 1 ohm.

Worldwide Commercial Energy Production

How We Use Energy• What are the commercial uses of energy?

– Industry uses 38%;

– Residential and commercial buildings use 36%; and,

– Transportation uses 26%.

• Half of all energy in primary fuels is lost during conversion to more useful formsm while being shipped or during use.– Nearly two-thirds of energy in coal being burned to generate

electricity is lost during thermal conversion in the power plant. Another 10% is lost during transmission and stepping down to household voltages.

• Natural gas is the most efficient fuel.– Only 10% of its energy content is lost during shipping and

processing. Ordinary gas-burning furnaces are about 75% efficient. High-economy furnaces can be 95% efficient.

Energy Use Trends• A general trend is for

higher energy use to correlate with a higher standard of living

• In an average year, each person in the U.S. and Canada consumes more than 300 times the amount of energy consumed by a person in one of the poorest countries of the world; however,

• Several European countries have higher living standards than the U.S., yet they use about half as much energy.

Per Capita Energy Use & GNP

U.S. Energy Flow, 1999

Quantities in Quadrillion BTUs.

PART 2: FOSSIL FUELS• Fossil fuels are organic chemicals created by living

organisms that were buried in sediments millions of years ago and transformed to energy-rich compounds.

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

CoalOilNatural Gas

Recoverable Oil Reserves

Coal Reserves

Natural Gas Reserves

Coal Extraction and Use• Mining is 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 are billions of dollars

• 900 million tons of coal are burned in the U.S. for electric power generation. As a result, multiple pollutants are released such as:– Sodium Dioxide (18 million metric tons)

– Nitrogen Oxides ( 5 million metric tons)

– Particulates (4 million metric tons)

– Hydrocarbons (600,000 metric tons)

– Carbon Dioxide (1 trillion metric tons)

Oil Extraction and Use• The countries of the Middle East control two-thirds of all

proven-in-place oil reserves. Saudi Arabia has the most.• The U.S. has already used up about 40% of its original

recoverable petroleum resource.• Oil combustion creates substantial air pollution.• Drilling causes soil and water pollution.• Often oil contains a high sulfur level. Sulfur is corrosive, thus

the sulfur is stripped out before oil is shipped to market.• Oil is primarily used for transportation providing > 90% of

transportation energy.• Resources and proven reserves for the year 2000 are 650

billion barrels (bbl). 800 bbl remain to be discovered or are currently not recoverable.

Natural Gas Consumption

• Proven world reserves and resources of natural gas equal 3,200 trillion cubic feet. This equals a 60 year supply at present usage rates.

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

• Problems: difficult to ship across oceans, to store in large quantities, and much waste from flaring off.

•World’s third largest commercial fuel (23% of global energy used).

•Produces half as much CO2 as equivalent amount of coal.

•Most rapidly growing used energy source.

PART 3: NUCLEAR POWER

• President Dwight Eisenhower, 1953, “Atoms for Peace” speech.– Eisenhower predicted that nuclear-powered electrical generators would provide

power “too cheap to meter.”

– Between 1970-1974, American utilities ordered 140 new reactors, but 100 were subsequently canceled.

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

• Construction costs and safety concerns have made nuclear power much less attractive than was originally expected. – Electricity from nuclear power plants was about half the price of coal in 1970,

but twice as much in 1990.

How Do Nuclear Reactors Work• The common fuel for nuclear reactors is U235 that occurs

naturally (0.7%) as a radioactive isotope of uranium.• U235 is enriched to 3% concentration as it is processed into

cylindrical pellets (1.5 cm long). The pellets are stacked in hollow metal rods (4 m long).

• 100 rods are bundled together into a fuel assembly. Thousands of these fuel assemblies are bundled in the reactor core.

• When struck by neutrons, radioactive uranium atoms undergo nuclear fission, releasing energy and more neutrons.This result triggers a nuclear chain reaction.

• This reaction is moderated in a power plant by neutron-absorbing solution (Moderator).

• Control Rods composed of neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate.

• Water or other coolant is circulated between the fuel rods to remove excess heat.

Nuclear fission occurs in the core of a nuclear reactor

Kinds of Reactors

• 70% of nuclear power plants are pressurized water reactors (PWRs). Water is circulated through the core to absorb heat from fuel rods. The heated water is then pumped to a steam generator where it heats a secondary loop. Steam from the secondary loop drives a high-speed turbine making electricity.

• Both reactor vessel and steam generator are housed in a special containment building. This prevents radiation from escaping and provides extra security in case of accidents. Under normal operations, a PWR releases little radioactivity.

Reactor Design

Chernobyl1986

Three Mile Island 1979

Radioactive Waste Management• Production of 1,000 tons of uranium fuel typically generates

100,000 tons of tailings and 3.5 million liters of liquid waste.– Now approximately 200 million tons of radioactive waste exists in

piles around mines and processing plants in the U.S.• About 100,000 tons of low-level waste (clothing) and about 15,000

tons of high-level (spent-fuel) waste in the US.– For past 20 years, spent fuel assemblies have been stored in deep

water-filled pools at the power plants. (designed to be temporary).– Many internal pools are now filled, and a number plants are storing

nuclear waste in metal dry casks outside.• A big problem associated with nuclear power is the disposal of

wastes produced during mining, fuel production, and reactor operation.– U.S. Department of Energy announced plans to build a high-level

waste repository near Yucca Mountain Nevada in 1987.– Cost is $10-35 billion, and earliest opening date is 2010.– This allows the government to monitor & retrieve stored uranium.

PART 4: ENERGY CONSERVATION

Hybrid gas-electric automobile

ENERGY CONSERVATION– 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, however, discouraged further conservation.

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. Energy gains can be made by orienting homes to gain passive solar energy in the winter.

To be effective with domestic energy conservation buying energy-efficient appliances and using innovative ways to insulate your home can significantly cut your energy consumption. To left is earth-sheltered house in Taos, New Mexico - an effective way to insulate your house.

PART 5: SOLAR ENERGY • Photosynthesis• Passive solar heat is using

absorptive structures with no moving parts to gather and hold heat. Greenhouse design

• Active solar heat is when a system pumps a heat-absorbing medium through a collector, rather than passively collecting heat in a stationary object. Water heating consumes 15% of US domestic energy budget.

Mean solar energy striking the upper atmosphere is 1,330 watts per square meter. The amount reaching the earth’s surface is 10,000 times > all commercial energy used annually. Until recently, this energy source has been too diffuse and low intensity to capitalize for electricity production.

Underground massive heat storage unit

High-Temperature Solar Energy•Parabolic mirrors (left) are curved reflective surfaces that collect light and focus it onto a concentrated point. It involves two techniques:

–Long curved mirrors focus on a central tube containing a heat-absorbing fluid.–Small mirrors arranged in concentric rings around a tall central tower track the sun and focus light on a heat absorber on top of the tower where molten salt is heated to drive a steam-turbine electric generator.

Photovoltaic Solar Energy

• 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.

• Photovoltaic cells capture solar energy and convert it directly to electrical current by separating electrons from parent atoms and accelerating them across a one-way electrostatic barrier.– Bell Laboratories - 1954

• 1958 - $2,000 / watt• 1970 - $100 / watt• 2002 - $5 / watt

Photovoltaic energy -solar energy converteddirectly to electricalcurrent

Transporting & 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

Costs for alternative and renewable energy sources have dropped in recent years. Nuclear energy costs have increased the most.

•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.

Promoting Renewable Energy

PART 6: FUEL CELLS• Fuel cells use ongoing electrochemical

reactions to produce electrical current• Fuel cells provide direct-current

electricity as long as supplied with hydrogen and oxygen.

• Hydrogen is supplied as pure gas, or a reformer can be used to strip hydrogen from other fuels.

• Fuel cells run on pure oxygen and hydrogen produce only drinkable water and radiant heat.

• Reformer releases some pollutants, but far below conventional fuel levels.

• Fuel cell efficiency is 40-45%.• Positive electrode (cathode) and

negative electrode (anode) separated by electrolyte which allows charged atoms to pass, but is impermeable to electrons. Electrons pass through external circuit, and generate electrical current.

PART 7: BIOMASS

Fuelwood Crisis• Currently, about half of worldwide annual wood

harvest is used as fuel.– Eighty-five percent of fuelwood is harvested in

developing countries.• By 2025, worldwide demand for fuelwood is expected to be

twice current harvest rates while supplies will have remained relatively static.

• About 40% of world population depends on firewood and charcoal as their primary energy source.– Of these, three-quarters do not have an adequate supply.

• Problem intensifies as less developed countries continue to grow.

– For urban dwellers, the opportunity to scavenge wood is generally nonexistent.

Fuelwood 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.

Using Dung as Fuel

• Where other fuel is in short supply, people often dry and burn animal dung.

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

• 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.

Using Methane As a Fuel

Alcohol from Biomass

• Ethanol (grain alcohol) production could be a solution to grain surpluses but thermodynamic considerations question it being practical on a sustainable basis. Gasohol (a mixture of gasoline and alcohol) reduces CO emissions when burned in cars. Ethanol raises octane ratings, and helps reduce carbon monoxide emissions in automobile exhaust.

• Methanol (wood alcohol)• Both methanol and ethanol make good fuel for fuel

cells.

PART 8: ENERGY FROM EARTH'S FORCES

• Water power produces 25% of the world’s electricity and it is clean, renewable energy.

• Dams cause social and ecological damage.

WindGeothermalTidalWaveHydropower

• Hydropower– By 1925, falling water generated 40% of world’s electric power.

• Hydroelectric production capacity has grown 15-fold, but fossil fuel use has risen so rapidly that now hydroelectric only supplies one-quarter of electrical generation.

• Total world hydropower potential estimated about 3 million MW.– Currently use about 10% of potential supply.

• Energy derived from hydropower in 1994 was equivalent to 500 million tons of oil. Much of recent hydropower development is in very large dams.

• Drawbacks to dams include:– Human Displacement– Ecosystem Destruction– Wildlife Losses– Large-Scale Flooding Due to Dam Failures– Sedimentation– Herbicide Contamination– Evaporative Losses– Nutrient Flow Retardation

Wind Energy

• Wind power - advantages and disadvantages• Wind farms - potential exists in Great Plains, along seacoasts and Eastern

Washington

http://www.awea.org/projects/washington.html

This energy source involves the use of high-pressure, high-temperature steam fields that exist below the earth’s surface.

Geothermal Energy

Tidal & Wave Energy•Ocean tides and waves contain enormous amounts of energy that can be harnessed.

–Tidal Station - Tide flows through turbines, creating electricity. It requires a high tide/low-tide differential of several meters.–Main worries are saltwater flooding behind the dam and heavy siltation.–Stormy coasts with strongest waves are often far from major population centers.

Part 9:An Alternative Energy Future?

Average Daily Solar Radiation

Solar radiation units of the legend are langleys [a langley = 1 calorie/cm2 (3.69Btu/ft2)]