Energy

Fossil-Fuel Dependence

• Fossil fuels– Petroleum, natural gas, coal

• Currently, fossil fuels supply about 88 percent of the world’s commercial energy needs

Oil

35%Coal

29%

Gas

24%

Nuclear5%

Hydro6% Wind, etc.

1%

Negative Impacts of Fossil Fuels

• Mountaintop removal for coal extraction

• Water pollution from extracting tar sands

• Air pollution & global climate change from burning carbon-based fuels

• We are too much dependent on fossil fuels

Mountaintop Removal in Appalachia

• Typically, the whole top of a mountain ridge is scraped off to access buried coal

• Waste rock is pushed into nearby valleys

Could We Get All the Power We

Need From Renewable Sources?

• As you’ll learn in more detail later in this chapter, the

total global potential for wind and solar energy is

approximately 8,200 TW (terawatts).

• Even though much of that supply is far out to sea or

other inaccessible places, the easily available power

from renewable resources is more than 50 times our

current global energy consumption.

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How Do We Use Energy?

• Industry is the largest energy use sector• Transportation uses about 2/3 of all oil

(data from DOE 2010)

Transportation

28%

Industrial

31%

Residential

Customers

22%

Commercial

Customers

19%

Mining, milling, smelting, forging of primary metalsChemistry industry etc.

Space heating Air conditioning Lighting Water heating

Motor vehicles

Fossil Fuels

• Fossil fuels are organic (carbon-based) compounds derived from decomposed plants, algae, and other organisms buried in rock layers for hundreds of millions of years.

• Most of the richest deposits date to about 286 million to 360 million years ago, when the Earth’s climate was much warmer and wetter than it is now.

Coal Resources Are Vast

• World coal deposits are vast, ten times greater than

conventional oil and gas resources combined.

• Almost all the world's coal is in North America, Europe and

Asia and just three countries, the United States, Russia,

and China, account for two-thirds of all proven reserves.

• The total resource is estimated to be 10 trillion metric tons.

If all this coal could be extracted, this would amount to

several thousand years’ supply.

• But coal mining is a dirty, dangerous activity. Underground

mines are notorious for cave-ins, explosions, and lung

diseases, such as black-lung suffered by miners. Surface

mines leave huge holes where coal has been removed and

vast piles of discarded rock and soil.12-8

Coal Burning

• Every year the roughly one billion tons of coal burned in the

U.S. releases carbon dioxide (CO2) � global warming

• Coal also contains toxic impurities, such as mercury, arsenic,

chromium, and lead, which are released into the air during

combustion.

• It’s possible to make either gas or liquid fuels out of coal, but

these processes are even dirtier and more expensive than

burning the coal directly.

New Plants Could Be Cleaner

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Have We Passed Peak Oil?

• We have already used more

than 0.5 trillion bbl—almost

half of proven oil reserves.

• Competition has already

raised oil prices, from

around $15 per barrel in

1993 to more than $150 per

barrel in 2008.

Global Oil Reserves

• Proven oil reserves. • 12 countries account for 91%• Middle Eastern countries have more than half of world supplies• Source: data from U.S. DOE 2008

Dependence on Foreign Oil

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Oil drilling rig Deepwater Horizon exploded and sank in the Gulf of Mexico.Ruptured pipelines gushed up to 6 million gallons of crude oil per day for more than a month, contaminating hundreds of kilometers of Gulf Coast and killing huge numbers of creatures

High Efficiency Cars Can Help

Reduce Dependence on Foreign Oil

• Conservation can make a big difference.

• Transportation accounts for over 40% of U.S.

oil use.

• Vehicle efficiency can have a substantial

influence in overseas oil dependence

Oil Shales and Tar Sands Contain

Huge Amounts of Petroleum

• The World Energy Council estimates that oil shales, tar sands,

and other unconventional deposits contain ten times as much

oil as liquid petroleum reserves.

• However, this costly, energy-intensive extraction only

becomes economically justified when oil prices rise above

about $50 per barrel.

• There are severe environmental costs, though. A typical plant

creates about 15 million m3 of toxic sludge, releases 5,000

tons of greenhouse gases, and consumes billions of liters of

water each year.12-15

Natural Gas

• Natural gas is the world’s third largest commercial fuel

• Because natural gas produces only half as much CO2 as an

equivalent amount of coal, substitution could help reduce

global warming.

• Russia has nearly one-quarter of known natural gas reserves

and accounts for about 35% of all global production.

• The total ultimately recoverable natural gas resources in the

world are estimated to be 10,000 10,000 trillion ft3. Current

gas reserves represent roughly a 60-year supply at present

usage rates.

Special Refrigerated Ships Transport

Liquefied Natural Gas (LNG)

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Gas is compressed and liquefied At -160 oC the liquid takes up about 1/600th the volume of gasAn explosion of one these ships would release about as much energy as a medium-size atomic bomb

Nuclear Power

• In 1953 President Dwight Eisenhower announced that the

United States would build nuclear-powered electrical

generators to provide clean, abundant energy

• Today there are about 440 reactors in use worldwide, 104 of

these in the United States.

• Half of the U.S. plants (52) are more than 30 years old and are

thus approaching the end of their expected operational life.

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Nuclear Reactors in Southern California

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Two nuclear reactors at the San Onofre Nuclear Generating Station (SONGS) sit near San Diego

How Do Nuclear Reactors Work?

• Radioactive uranium atoms

are unstable—that is, when

struck by a high-energy

subatomic particle called a

neutron, they undergo

nuclear fission (splitting),

releasing energy and more

neutrons.

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Nuclear Reactor Design

• 70% of the world’s nuclear plants are pressurized water

reactors (PWR).

• Water circulates through the core, absorbing heat as it cools

the fuel rods. This primary cooling water is heated to 317°C

(600°F) and reaches a pressure of 2,235 psi.

• It is then pumped to a steam generator, where it heats a

secondary water-cooling loop.

• Steam from the secondary loop drives a high-speed turbine

generator that produces electricity. 12-21

Pressurized Water Nuclear Reactor

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Pressurized water nuclear reactor. Water is superheated and pressurized as it flows through the reactor core. Heat is transferred to non-pressurized water in the stream generator. The stream drives the turbogenerator to produce electricity

We Lack Safe Storage for

Radioactive Waste

• One of the most difficult

problems associated with

nuclear power is the

disposal of wastes produced

during mining, fuel

production, and reactor

operation.

• How these wastes are

managed may ultimately be

the overriding obstacle to

nuclear power.12-23

We Lack Safe Storage for

Radioactive Waste

• In 1987 the U.S. Department of Energy announced plans to

build the first high-level waste repository on a barren desert

ridge under Yucca Mountain, Nevada.

• Waste was to be buried deep in the ground, where it was

hoped it would remain unexposed to groundwater and

earthquakes for the thousands of years required for the

radioactive materials to decay.

• However, President Obama cut off funding for the project in

2009 after 20 years of research and $100 billion in exploratory

drilling and development.12-24

Energy Conservation

• Much of the energy we consume is wasted.

• Our ways of using energy are so inefficient that most potential

energy in fuel is lost as waste heat.

• Conservation involves technology innovation as well as changes in

behavior, but we have met these challenges in the past.

• In 2010, the Obama administration mandated an average fleet fuel

efficiency of 35.5 mpg (14.6 km/l) for cars and light trucks by 2016.

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What Can You Do?

Steps to Save Energy and Money

1. Live close to work and school, or near transit routes, so you can minimize

driving.

2. Ride a bicycle, walk, and use stairs instead of elevators.

3. Keep your thermostat low in winter and high in summer. Fans are cheaper

to run than air conditioners.

4. Buy fewer disposable items; producing and shipping them costs energy.

5. Turn off lights, televisions, computers, and other appliances when not

needed.

6. Line-dry your laundry.

7. Recycle.

8. Cut back on meat consumption; if every American ate 20 percent less meat,

we would save as much energy as if everyone used a hybrid car.

9. Buy some of your food locally, to reduce energy in shipping.

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Green Building Can Cut

Energy Costs by Half

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Cogeneration Makes Electricity

from Waste Heat

• One of the fastest growing sources of new energy is

cogeneration, the simultaneous production of both electricity

and steam or hot water in the same plant.

• By producing two kinds of useful energy in the same facility,

the net energy yield from the primary fuel is increased from

30–35 percent to 80–90 percent.

• Interest in this technology is growing. The EPA estimates that

cogeneration could produce almost 20 percent of U.S.

electrical use, or the equivalent of 400 coal-fired plants.

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Wind Energy

• In China’s efforts to reduce dependence on fossil fuel

imports, wind power has been the principal focus.

• Relative to other alternative sources, wind is cheap

and available almost everywhere.

• Wind turbines have a small footprint, so they don’t

displace farming and other land uses.

• How people feel about a wind farm depends on their

views about energy alternatives, whether it earns

money for their community, and which particular

view is obstructed by the turbines.

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U.S. Wind Resources by Region

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Wind Energy is Our

Fastest Growing Renewable

• It is estimated that wind

could produce about 50

times the total capacity

of all nuclear power

plants now in operation.

• Wind farms are large

concentrations of wind

generators producing

commercial electricity.12-31

Do Wind Turbines Have any

Negative Impacts?

• Often wind farms are built where wind and weather make

homes or other development unattractive. But they can

interrupt the view in remote areas and destroy a sense of

isolation and natural beauty.

• Bird and bat kills have been reported in some places.

• As wind turbines have proliferated, neighbors who live close

by often complain about noise and flickering shadows from

the blades.

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Solar Energy

• The Sun is a giant nuclear furnace in space, constantly bathing

our planet with a free energy supply.

• Until recently, this tremendous infusion of energy has been in

a form that has been too diffuse and low in intensity to be of

much use except for environmental heating and

photosynthesis.

• Next Figure shows solar energy levels over the United States

for typical summer and winter days.

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Average Daily Solar Radiation

in the Continental U.S.

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unit: 1 cal/cm2

Passive Solar Absorbs Heat;

Active Solar Pumps Heated Fluids

• Passive Solar uses thick adobe or stone walls to

absorb daytime heat and release it gradually at night.

• Active solar pumps a heat-absorbing fluid medium

(rather than stationary medium) through a relatively

small collector and then transfers the heat to create

hot water or heat the air in the home.

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Concentrating Solar Energy

Generates Electricity• Solar thermal energy can also be used to generate

electricity.

• Concentrating trough systems use long rows of

parabolic mirrors to heat a transfer fluid to

temperatures as high as 400°C.

• The hot liquid is pumped to a central plant, where it

heats water to produce steam that spins a turbine to

produce electricity.

• California’s Mojave Desert has solar thermal facilities

with over 300 MW of installed capacity.

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Solar Thermal Electric Plant

in California Desert

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Concentrating Solar Energy

Generates Electricity• Another type of concentrating solar power uses

thousands of heliostats—mirrors that track the sun—

to focus sunlight on a boiler sitting atop a tower.

• Steam from the boiler drives a turbine as do other

thermal systems.

• BrightSource recently signed a contract with

Southern California Edison to build more than 1,300

MW of solar electric capacity in the Mojave desert

over the next decade. 12-38

Solar Thermal Electric

Plant Using Heliostats

12-39

Photovoltaic Cells Generate

Electricity Directly

• Photovoltaic cells capture solar energy and convert it

directly to electrical current by separating electrons

from their parent atoms and accelerating them

across a one-way electrostatic barrier.

• Over the past 25 years, the efficiency of energy

captured by photovoltaic cells has increased from

less than 1% of incident light to more than 10%.

• New Amorphous silicon collectors can be made into

lightweight, paper-thin sheets that require much less

material than traditional crystalline silicon PV cells.

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How a Photovoltaic Cell Operates

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Rooftop Photovoltaic Array

• A photovoltaic array of

about 30–40 m2 will

generate enough

electricity for an

efficient house.

• There are more than

1,000 mi2 (2,590 km2) of

roofs suitable for

photovoltaic systems in

the United States!12-42

Hybrid Cars and Solar Arrays

• An intriguing option for storing electricity is in plug-in

hybrid vehicles, which could provide an enormous,

distributed battery array.

• You’d recharge your auto battery at night when

power plants have excess generating capacity. During

the day, your car would be plugged into a smart

meter that could sell electricity back to your utility if

prices rise.

• A few million mobile battery arrays could greatly help

smooth out power peaks and valleys.

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Water Power

• The invention of water turbines in the nineteenth

century greatly increased the efficiency of

hydropower dams. Much of the hydropower

development since the 1930s has focused on

enormous dams because of their efficiency of size.

• Water power is now only one-quarter of total

electrical generation, but the total world potential for

hydropower is estimated to be about 3 million MW.

• The energy derived from this source in 1994 was

equivalent to about 500 million tons of oil, or 8% of

the total world commercial energy consumption.

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Hydropower Dams

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Hydropower dams produce clean and renewable energy but can be socially and ecologically damaging

Unconventional Hydropower

Comes from Tides and Waves

• Ocean tides and waves also contain enormous

amounts of energy that can be harnessed to do

useful work.

• A tidal station works like a hydropower dam, with its

turbines spinning as the tide flows through them. A

high-tide/low-tide differential of several meters is

required to spin the turbines.

• Unfortunately, variable tidal periods often cause

problems in integrating this energy source into the

electric utility grid.

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The Pelamis Wave-Power Generator Now in

Operation Off the Coast of Portugal

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Geothermal Heat

• The Earth’s internal temperature can provide a useful

source of energy in some places.

• This geothermal energy is expressed in the form of

hot springs, geysers, and fumaroles.

• Iceland, which sits on a midocean ridge, has

abundant geothermal energy.

• Iceland has ambitious plans to be the first carbon-

neutral country, largely because the Earth’s heat

provides steam for heat and electric energy.

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Geothermal Heat Pumps Can

Heat and Cool Efficiently

• While few places have

geothermal steam, the

Earth’s warmth can help

reduce energy costs

nearly everywhere.

• Pumping fluids through

deeply buried pipes can

exchange temperatures

with the soil to efficiently

heat or cool a home.

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Fuel Cells

• Fuel cells are devices

that use ongoing

electrochemical

reactions to produce an

electrical current.

12-50

Fuel Cells in Long Island, NY

12-51

Long Island Power Authority has installed 75 stationary fuel cells to provide backup power

What Is Our Energy Future?

• Could we get all our electricity from renewable,

environmentally-friendly sources?

• Currently available wind, water, and solar

technologies could supply 100% of the world’s

energy by 2030 and completely eliminate all our use

of fossil fuels, according to Mark Jacobson from

Stanford University and Mark Delucchi from the

University of California, Davis

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Potential Renewable Energy Mix

for a Typical Day in California

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The wind doesn't blow all the time and the sun doesn't always shine in a given

location. But a smart balance of sources can even out shortages

A smart grid that transmits energy more efficiently and safely is a good investment

Conclusion

• Fossil fuels like oil, coal, and natural gas, remain our dominant

energy sources.

– But oil is being depleted

– coal causes environmental damage.

– Natural gas is abundant and cleaner than coal, so its

importance has been increasing.

• Nuclear power supplies a significant proportion of the

electricity in some countries, but storage of waste is a problem.

• Innovations in solar, wind, wave power, and other renewable

energy sources now make it possible to get all our energy from

these alternative technologies.

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