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Energy

Chapter 13

Three big ideas • Energy resources should be evaluated by… potential

supplies, net energy they provide, and their environmental impacts.

• Using a mix of renewable energy sources can drastically reduce pollution, greenhouse gas emissions, and biodiversity losses.

• A sustainable energy future will require sharply reducing energy waste, using a mix of environmentally friendly renewable energy resources, and including the harmful environmental costs of energy resources in their market prices.

WHAT IS NET ENERGY AND WHY IS IT IMPORTANT?

Section 13-1

Basic science: Net energy is the only energy that really counts

• The usable amount of high-quality energy available from a given quantity of an energy resource is its net energy yield: the total amount of useful energy available from an energy resource minus the energy needed to make it available to consumers.

• We can express net energy as the ratio of energy produced to the energy used to produce it. As the ratio increases, the net energy also rises. When the ratio is less than 1, there is a net energy loss.

Net energy ratios for various energy systems over their estimated lifetimes differ widely

Fig. 13-2a, p. 301

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Figure 13.2 science: Net energy ratios for various energy systems over their estimated lifetimes differ widely: the higher the net energy ratio, the greater the net energy available (Concept 13-1). Question: Based on these data alone, which two resources in each category should we be using?

Fig. 13-2b, p. 301

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Fig. 13-2c, p. 301

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Fig. 13-2d, p. 301

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Energy resources with low or negative net energy need help to compete in the marketplace

• Any energy resource with a low or negative net energy ratio cannot compete in the open marketplace with other energy alternatives with higher net energy ratios unless it receives financial support from the government (taxpayers) or other outside sources of funding. – For example, the low net energy yield for the nuclear

power fuel cycle is one reason why many governments throughout the world must heavily support nuclear power financially to make it available to consumers at an affordable price.

WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF FOSSIL FUELS?

Section 13-2

Fossil fuels supply most of our commercial energy

• The direct input of solar energy produces several other forms of renewable energy resources that: wind, flowing water, and biomass.

• Most commercial energy comes from extracting and burning nonrenewable energy resources obtained from the earth’s crust. – 87% from carbon-containing fossil fuels (oil, natural

gas, and coal). – 6% from nuclear power. – 8% from renewable energy resources—biomass,

hydropower, geothermal, wind, and solar energy.

Energy use by source throughout the world and US in 2009

We depend heavily on oil

• Crude oil (petroleum), is a black, gooey liquid consisting of hundreds of different combustible hydrocarbons along with small amounts of sulfur, oxygen, and nitrogen impurities. – Also known as conventional oil and as light or sweet

crude oil. – Oil, coal, and natural gas are called fossil fuels

because they were formed from the decaying remains (fossils) of organisms that lived millions of years ago.

• When the rate of crude oil production starts declining it is referred to as peak production for the well.

We depend heavily on oil

• Global peak production is the point in time when we reach the maximum overall rate of crude oil production for the whole world.

• After extraction, crude oil is transported to a refinery by pipeline, truck, or ship (oil tanker).

• Crude oil is heated to different boiling points in a complex process called refining to separate it into different layers, such as petrochemicals.

When crude oil is refined, many of its components are removed at various levels

How long might supplies of conventional crude oil last?

• Crude oil is now the single largest source of commercial energy in the world.

• Proven oil reserves are identified deposits from which conventional crude oil can be extracted profitably at current prices with current technology.

• Geologists project that known and projected global reserves of conventional crude oil will be 80% depleted sometime between 2050 and 2100. The remaining 20% will likely be too costly to remove.

How long might supplies of conventional crude oil last?

• Options include: – look for more oil. – use less oil. – waste less oil. – use other energy resources.

OPEC controls most of the world’s crude oil supplies

• 13 countries make up the Organization of Petroleum Exporting Countries (OPEC). – In 2010, OPEC holds about 77% of the world’s

proven crude oil reserves. – OPEC’s members are Algeria, Angola, Ecuador,

Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela.

• The U.S. has only about 2% of the world’s proven oil reserves. China has only 1.1%, India has 0.4%, and Japan has no oil reserves.


• Currently, the world’s largest producers of oil are, in order, Russia, Saudi Arabia, and the U.S. Energy experts project that by about 2020, Iraq will become the world’s third largest oil producer.

• Since 1984, production of conventional crude oil from proven reserves has exceeded new oil discoveries. Since 2005, global crude oil production has generally leveled off. Of the world’s 64 major oil fields, 54 are now in decline.


• According to some analysts, in order to keep using conventional oil at the projected increasing rate of consumption, we must discover proven reserves of conventional oil equivalent to the current Saudi Arabian supply every 5 years. Most oil geologists say this is highly unlikely.

Crude oil use has advantages and disadvantages

Using crude oil has advantages and disadvantages

• Extraction, processing, and burning of nonrenewable oil and other fossil fuels have severe environmental impacts. – Land disruption. – Air pollution. – Greenhouse gas emissions. – Water pollution. – Loss of biodiversity.

Using crude oil has advantages and disadvantages

• Oil spills cause catastrophic damage. – In 2010, the BP Company’s Deepwater Horizon oil-

drilling rig exploded, spilling an estimated 679 million liters (180million gallons) of crude oil into U.S. Gulf Coast waters.

– In 1989, the oil tanker Exxon Valdez ran aground and spilled 42 million liters (11 million gallons) of oil into Alaskan waters.

– More than 2.5 times the estimated amount of crude oil spilled in the 2010 Gulf Coast disaster has been spilled from off the coast of Nigeria with little media attention.

Will heavy oil be a useful resource?

• Oil shale is rock that contains a solid combustible mixture of hydrocarbons called kerogen which can be processed to produce shale oil.

• Producing shale oil requires large amounts of water and has a low net energy and a very high environmental impact.

• Estimated potential global supplies of unconventional shale oil are about 240 times larger than estimated global supplies of conventional crude oil.

• Shale has a low net energy yield so would require subsidies to compete on the open market, and shale extraction would have a high environmental impact, causing severe land disruption, high water use, and high CO2 emissions when produced and burned.

Shale oil can be extracted from oil shale rock

Using heavy oil from oil shale and tar sands as energy source has advantages and disadvantages

Natural gas is a useful and clean-burning fossil fuel

• Natural gas is a mixture of gases of which 50–90% is methane (CH4). – Has high net energy. – Versatile fuel that can be burned to heat indoor space

and water, propel vehicles and produce electricity. – Lies above most reservoirs of crude oil. – When a natural gas field is tapped, propane and

butane gases are liquefied and removed as liquefied petroleum gas (LPG).

– Cleanest-burning among the fossil fuels, releasing much less CO2 per unit of energy than coal, crude oil, and synthetic crude oil from tar sands and oil shale.

Using conventional natural gas has advantages and disadvantages

Use of fracking to extract natural gas is controversial

• Hydraulic fracturing, or fracking, pumps water mixed with sand and some toxic chemicals underground to fracture deep rock and free up natural gas stored there. – The gas flows out, along with a toxic slurry of water,

salts, toxic heavy metals, and naturally occurring radioactive materials that is stored in tanks and holding ponds.

– Drillers maintain that fracking is necessary for exploiting this reserve at a reasonably low cost, and they argue that no groundwater contamination directly due to fracking has ever been recorded.


– Scientists and citizens point out that there is no guarantee that sharply increasing use of the process will not contaminate groundwater or that holding ponds and tanks used to store the toxic slurry will not leak and pollute rivers and streams.

– People who rely on aquifers and streams in these areas for their drinking water have little protection from pollution of their water supplies that might result from natural gas drilling.


• Natural gas can be transported as liquefied natural gas (LNG). However, LNG has a low net energy yield, as more than a third of its energy content is used to process it and to deliver it to users.

• The long-term global outlook for conventional natural gas supplies is better than for crude oil.

• Potential sources of unconventional natural gas include coal bed methane gas and methane hydrate, but environmental impacts and cost may limit their use.

Coal is a plentiful but dirty fuel

• Coal is a solid fossil fuel formed from the remains of land plants that were buried 300–400 million years ago and exposed to intense heat and pressure over those millions of years.

• Coal is burned in power plants to generate about 42% of the world’s electricity, and burned in industrial plants to make steel, cement, and other products.

• The three largest coal-burning countries are China, the U.S., and India.

• Coal is plentiful and cheap.

Increasing moisture content Increasing heat and carbon content

Peat (not a coal)

Lignite (brown coal)

Bituminous (soft coal)

Anthracite (hard coal)

Heat Heat Heat

Pressure Pressure Pressure

Partially decayed plant matter in swamps and bogs; low heat content

Low heat content; low sulfur content; limited supplies in most areas

Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content

Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas

Stepped Art Fig. 13-12, p. 310


• Mining and burning coal have severe impacts on the earth’s air, water, land, climate, and human health. – Coal-burning power and industrial plants are among

the largest emitters of the greenhouse gas CO2. – Coal burning emits trace amounts of toxic and

radioactive materials. – Burning coal produces a highly toxic ash that must be

safely stored, essentially forever. – China uses three times as much coal as the U.S. and

it has become the world’s leading emitter of CO2 and of sulfur dioxide.

This power plant burns pulverized coal to boil water and produce steam that spins a turbine to

produce electricity.

CO2 emissions vary with different energy resources


– Coal is cheap but most of the harmful environmental and health costs are not included in the price.

– The clean coal campaign. • Powerful U.S. coal companies and utilities oppose

measures. • Publicity campaign built around the misleading

notion of clean coal. – Burn coal more cleanly by adding costly air pollution

control devices. – There is no such thing as clean coal.

Coal has advantages and disadvantages

WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF NUCLEAR ENERGY?

Section 13-3

How does a nuclear fission reactor work?

• Nuclear power plant is a highly complex and costly system designed to perform a relatively simple task: to boil water to produce steam that spins a turbine and generates electricity.

• A controlled nuclear fission reaction is used to provide the heat. – The fission reaction takes place in a reactor. – Light-water reactors (LWRs) produce 85% of the world’s

nuclear-generated electricity (100% in the U.S.). – The fuel for a reactor is made from uranium ore mined

from the earth’s crust, then enriched and processed into pellets of uranium dioxide.


• Pellets are packed into fuel rods which are then grouped into fuel assemblies and placed in the core of a reactor.

• Control rods are moved in and out of the reactor core to regulate the amount of power produced.

• A coolant, usually water, circulates through the reactor’s core to remove heat, which keeps fuel rods and other materials from melting and releasing massive amounts of radioactivity into the environment.


• A containment shell surrounds the reactor core to keep radioactive materials from escaping into the environment in case there is an internal explosion or a melting of the reactor’s core.

• Light water reactors are highly inefficient; the net energy loss is about 82%, without taking into account the energy needed to dismantle a plant at the end of its life and transport and store its radioactive materials for thousands of years.

A water-cooled nuclear power plant

What is the nuclear fuel cycle?

• A nuclear power plant is only one part of the nuclear fuel cycle, which also includes the mining of uranium, processing and enriching the uranium to make fuel, using it in the reactor, safely storing the resulting highly radioactive wastes for thousands of years until their radioactivity falls to safe levels, and retiring the highly radioactive plant by taking it apart and storing its high- and moderate-level radioactive material safely for thousands of years.

What is the nuclear fuel cycle?

– In addition to a nuclear power plant, the nuclear fuel cycle includes:

• mining uranium. • processing and enriching the uranium to make fuel. • using it in the reactor. • safely storing the resulting highly radioactive wastes

for thousands of years until their radioactivity falls to safe levels.

• retiring the highly radioactive plant by taking it apart. • storing its high- and moderate-level radioactive

material safely for thousands of years.

Nuclear fuel cycle

Storing spent radioactive fuel rods presents risks

• High-level radioactive wastes consist mainly of spent fuel rods and assemblies.

• After 3–4 years in a reactor, spent fuel rods are removed and stored in a deep pool of water contained in a steel-lined concrete basin for cooling.

• After about 5 years of cooling, the fuel rods can be stored upright on concrete pads in sealed dry-storage casks made of heat-resistant metal alloys and concrete.

Storing spent radioactive fuel rods presents risks

• Stored spent radioactive fuel rods are vulnerable to terrorist acts.

• Storage pools and dry casks at 68 nuclear power plants in 31 U.S. states are especially vulnerable to sabotage or terrorist attack.

• Critics call for construction of much more secure structures to protect spent-fuel storage pools and dry casks.

Nuclear power cycle to produce energy has advantages and disadvantages

Dealing with high-level radioactive wastes produced by nuclear power is a difficult problem

• High-level radioactive wastes consist mainly of spent fuel rods and assemblies from commercial nuclear power plants and dismantled plants, and assorted wastes from the production of nuclear weapons.

• Spent fuel rods can be processed to remove radioactive plutonium, as is done with some of the other radioactive wastes we produce.

• Reduces the storage time from up to 240,000 to about 10,000 years.

Dealing with high-level radioactive wastes produced by nuclear power is a difficult problem

• Deep burial in a geologically acceptable underground repository is the safest and cheapest way to store these and other high-level radioactive wastes.

• All worn-out nuclear plant plants will have to be dismantled and their high-level radioactive materials will have to be stored safely for thousands of years.

Can nuclear power lessen dependence on imported oil and help reduce projected global warming?

• Nuclear power advocates contend it will: – Reduce oil dependency. – Reduce or eliminate CO2 emissions and reduce the

threat of projected climate change. • Dissenters claim that

– While nuclear power plants do not produce greenhouse gasses, the nuclear fuel cycle does.

– Increased use of nuclear power in the U.S. will make the country dependent on imports of uranium.

– While nuclear emissions are much lower than those from coal-burning power plants, they still contribute to projected atmospheric warming and climate change.

Nuclear Power Is Not Expanding Very Rapidly

• 1950s prediction was that by the year 2000 at least 1,800 nuclear power plants would supply most of the world’s electricity.

• Some 441 commercial nuclear reactors in 31 countries produce only 6% of the world’s commercial energy and 14% of its electricity.

• Nuclear power is now the world’s slowest-growing form of commercial energy.

Experts Disagree about the Future of Nuclear Power

• Opposition to Nuclear Power. – Nuclear power industry could not exist without

support from governments and taxpayers. – In the U.S., the government provides huge

subsidies, tax breaks, and loan guarantees to the nuclear industry, and accident insurance guarantees, because insurance companies have refused to fully insure any nuclear reactor.

– Public concerns about the safety of nuclear reactors.

Some critics of nuclear power say any new generation of nuclear power plants should beet all of these criteria; so far, none do

Support for Nuclear Power

• Governments should continue funding research, development, and pilot-plant testing of potentially safer and cheaper second-generation reactors.

• New advanced light-water reactors (ALWRs) have built-in safety features designed to make explosions and releases of radioactive emissions almost impossible.

• Replace today’s uranium-based reactors with new ones based on the element thorium which are less costly and safer, and would cut the amount of nuclear waste generated in half.

Support for Nuclear Power

• Develop nuclear fusion – A nuclear change at the atomic level in which the nuclei

of two isotopes of a light element such as hydrogen are forced together at extremely high temperatures until they fuse to form a heavier nucleus, releasing energy in the process

– No risk of a meltdown or of a release of large amounts of radioactive materials, and little risk of the additional spread of nuclear weapons. In addition to generating electricity, fusion power could be used to destroy hazardous wastes, and it could have many other uses.

WHY IS ENERGY EFFICIENCY AN IMPORTANT ENERGY RESOURCE?

Section 13-4

We waste huge amounts of energy

• Energy efficiency is the measure of how much work we can get from each unit of energy we use.

• Roughly 84% of all commercial energy used in the U.S. is wasted. – About 41% of this energy is unavoidably lost because

of the degradation of energy quality imposed by the second law of thermodynamics.

– The other 43% is wasted unnecessarily, mostly due to the inefficiency of incandescent light bulbs, industrial motors, most motor vehicles, coal and nuclear power plants, and numerous other energy-consuming devices.

– Poorly insulation and building design also contribute.

We waste huge amounts of energy

• Reducing energy waste is the most efficient way to provide more energy, reduce pollution and environmental degradation, and slow climate change. – Widely used devices that waste large amounts of

energy unnecessarily: • Incandescent light bulbs: use only about 5% to produce light.

The other 95% is wasted as heat. • The internal combustion engine, which propels most motor

vehicles and wastes about 80% of the energy in its fuel. • A nuclear power plant, wastes about 65% of the energy in its

nuclear fuel. • A coal-fired power plant wastes about 66% of its energy.

How commercial energy flows through the US economy

Benefits of reducing energy waste

We can save energy and money in industry

• Industry accounts for about 30% of the world’s energy consumption, 33% in U.S., mostly for the production of metals, chemicals, petrochemicals, cement, and paper.

• Ways for industries to cut energy waste: – Cogeneration, combines two useful forms of energy (e.g.

steam and electricity), produced from the same fuel. – Save energy and money in industry by replacing energy-

wasting electric motors. – Recycling materials, such as steel and other metals, is a

third way for industry to save energy and money. – Switch incandescent lighting to higher-efficiency lighting.

We can save energy and money in transportation

• As a result of the 1973–1974 oil embargo imposed by OPEC, the U.S. government imposed higher fuel efficiency standards for new vehicles sold in the U.S. beginning in 1978.

• Between 1973 and 1985, average fuel efficiency for new vehicles sold in the U.S. rose sharply because of the corporate average fuel economy (CAFE) standards.

• Greatly increased sales of light trucks and SUVs lead to a decline in fuel efficiency in the U.S. between 1985 and 2005.

• Fuel economy standards for new vehicles in Europe, Japan, China, and Canada are much higher than are those in the U.S.

We can save energy and money in transportation

• In 2007, the U.S. Congress passed a law requiring new motor vehicles to have an average combined fuel efficiency of 15 kilometers per liter (35 miles per gallon) by 2020.

• One way to include more of the real cost of gasoline in its market price is through gasoline taxes.

• Government could encourage consumers them to buy more fuel-efficient vehicles with a fee-bate program in which buyers of inefficient vehicles would pay a high fee, and the resulting revenues would be given to buyers of fuel-efficient vehicles as rebates.

A comparison of the changes in fuel economy standards

More energy efficient vehicles are on the way

• Energy-efficient, gasoline-electric hybrid car. – A small gasoline-powered motor and an electric motor

used to provide the energy needed for acceleration and hill climbing.

– The most efficient models of these cars, such as the 2011 Toyota Prius, get a combined city/highway mileage of up to 22 kpl (51 mpg) and emit about 65% less CO2 per kilometer driven than a comparable conventional car emits.

– A newer option is the plug-in hybrid electric vehicle—a hybrid with a second and more powerful battery that can be plugged into an electrical outlet and recharged.

Hybrid vehicles


• The next superefficient car may be an electric vehicle that uses a fuel cell—a device that uses hydrogen gas (H2) as a fuel to produce electricity. Fuel cells are at least twice as efficient as internal combustion engines, have no moving parts, and require little maintenance.

• Fuel efficiency for all types of cars could nearly double if car bodies were made of ultralight and ultrastrong composite materials.


• Other ways to save energy in transportation include – shifting from diesel-powered to electrified rail systems – building accessible mass transit systems within cities – constructing high-speed rail lines between cities – encourage bicycle use by designating bike lanes on

highways and city streets – using video conferencing as an alternative to flying

employees to meetings.

We can design buildings that save energy and money

• Changes in building design and construction could save 30–40% of the energy used globally.

• Orienting a building so it can get more of its heat from the sun can save up to 20% of heating costs and as much as 75% when the building is well insulated and airtight.

• Green architecture, based on energy-efficient and money-saving designs, makes use of natural lighting, solar heating and cells, recycled wastewater, and energy-efficient appliances and lighting.

We can design buildings that save energy and money

• Super insulated houses in Sweden use 90% less energy for heating and cooling than typical American homes of the same size.

• Green building certification standards now exist in 21 countries, thanks to the efforts of the World Green Building Council.

• The U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program awards certificates to buildings that meet certain efficiency standards.

Thermogram showing heat losses

We can save energy and money in existing buildings

• Have an expert make an energy audit of a house or other building to suggest ways to improve energy efficiency. – Insulate the building and plug leaks. – Use energy-efficient windows. – Heat houses more efficiently. – Heat water more efficiently. – Use energy-efficient appliances. – Use energy-efficient lighting.

You can takes steps to save energy and money

Why are we still wasting so much energy and money?

• Common energy resources are artificially cheap, mainly due to government subsidies and prices do not include the harmful environmental and health costs.

• There are few large and long-lasting government tax breaks, rebates, low-interest and long-term loans, and other economic incentives for consumers and businesses to invest in improving energy efficiency.

• The U.S. government has done a poor job of encouraging fuel efficiency in motor vehicles and educating the public about the environmental and economic advantages of cutting energy waste.

• Inadequate energy-efficiency building codes and appliance standards.

WHAT ARE THE ADVANTAGES AND DISADVANTAGES OF USING RENEWABLE ENERGY RESOURCES?

Section 13-5

We can use renewable energy for many purposes

• Renewable solar energy comes directly from the sun or indirectly from wind, moving water, and biomass.

• Renewable energy can come from geothermal energy from the earth’s interior.

• Renewable energy could provide 20% of the world’s electricity by 2025 and 50% by 2050.

We can use renewable energy for many purposes

• Why renewable energy provides only 13% of the world’s energy and 8% in the U.S.: – Since 1950, government tax breaks, subsidies, and

funding for research and development of renewable energy resources have been much lower than those for fossil fuels and nuclear power.

– Although subsidies and tax breaks for fossil fuels and nuclear power have essentially been guaranteed for many decades, those for renewable energy in the U.S. have to be renewed by Congress every few years.

– Nonrenewable fossil fuels and nuclear power are artificially cheap.

We can heat buildings and water with solar energy

• Passive solar heating system absorbs and stores heat from the sun directly.

• Active solar heating system uses energy from the sun by pumping a heat-absorbing fluid through special collectors usually mounted on a roof or on special racks to face the sun.

Homes can be heated with passive or active solar systems

Heating a house with passive or active solar energy systems has advantages and disadvantages

We can cool buildings naturally • Open windows to take advantage of breezes and

use fans to keep the air moving. • A living roof can make a huge difference in keeping

a building cool. • Install superinsulation and high-efficiency windows. • Block the high summer sun with window overhangs

or awnings. • Use a light-colored roof to reflect as much as 80%

of the sun’s heat. • Use geothermal heat pumps for heating and

cooling.

We can concentrate sunlight to produce high-temperature heat and electricity

• Solar thermal systems use different methods to collect and concentrate solar energy in order to boil water and produce steam for generating electricity

• The net energy yield for solar thermal systems is only about 3%, which means that they need large government subsidies or tax breaks in order to compete in the marketplace with alternatives that have higher net energy yields.

• Inexpensive solar cookers focus and concentrate sunlight for cooking food and sterilizing water.

We can use sunlight directly to produce electricity

• Solar energy can be converted directly into electrical energy by photovoltaic cells, commonly called solar cells.

• Solar cells have no moving parts, are safe and quiet, and produce no pollution or greenhouse gases during operation.

• The material used in solar cells can be made into paper-thin rigid or flexible sheets that can be incorporated into roofing materials and attached to a variety of surfaces such as walls, windows, and clothing.

• Generating electricity with solar cells could become nearly as efficient as using coal-burning power plants without producing the air pollutants and climate-changing CO2 emitted by those plants.

Solar thermal power

Using solar energy to generate high-temperature heat and electricity has advantages and disadvantages

Using solar cells has advantages and disadvantages

We can produce electricity from falling and flowing water

• Hydropower uses the kinetic energy of flowing and falling water to produce electricity.

• Indirect form of solar energy because it is based on the evaporation of water, which is part of the earth’s solar-powered water cycle.

• Most common approach to harnessing hydropower is to build a high dam across a large river to create a reservoir.

• Hydropower is the world’s leading renewable energy source for the production of electricity. In order, the world’s top six producers of hydropower are China, Canada, Brazil, the U.S., Russia, and Norway.

We can produce electricity from falling and flowing water

• Some analysts expect that use of large-scale hydropower plants will fall slowly over the next several decades as many existing reservoirs fill with silt and become useless faster than new systems are built.

• Microhydropower generators are small floating turbines that use the power of flowing water to turn rotor blades, which spin a turbine to produce electric current. They provide electricity at a low cost with a very low environmental impact.

• Ocean tides and waves contain energy. Dams have been built across the mouths of some bays and estuaries to capture the energy in ocean water movement.

Large-scale hydropower has advantages and disadvantages

Using wind to produce electricity is an important step toward sustainability

• Wind turbines have been erected in large numbers at favorable sites to create wind farms

• Since 1990, wind power has been the world’s second fastest-growing source of energy after solar cells.

• Wind turbines can be interconnected in arrays of tens to hundreds. These wind farms or wind parks can be located on land or offshore.

• In 2009, a Harvard University study estimated that wind power has the potential to produce 40 times the world’s current use of electricity.


• Benefits: – Wind is widely distributed and inexhaustible – Wind power is mostly carbon-free and

pollution-free. – A wind farm can be built within 9 to 12

months and expanded as needed. – Homeowners can also use small and quiet

wind turbines to produce their own electricity. – Wind power has a moderate-to-high net

energy ratio.


• Areas with the greatest wind power potential are often far from cities so may require controversial upgrading and expansion of electrical grid systems.

• Winds can die down and thus require a backup source of power, such as natural gas, for generating electricity.

• Some people in populated areas oppose wind farms as being unsightly and noisy.

• In windy parts of the U.S. Midwest and in Canada, farmers and ranchers are paid royalties for each wind turbine located their land and can still grow crops or graze cattle.

Wind power has advantages and disadvantages

We can produce energy by burning solid biomass

• Biomass consists of plant materials (such as wood and agricultural waste) and animal wastes that can be burned directly as a solid fuel or converted into gaseous or liquid biofuels.

• Solid biomass is burned mostly for heating and cooking, but also for industrial processes and for generating electricity.

We can produce energy by burning solid biomass

– Wood, wood wastes, charcoal (made from wood), animal manure.

– In agricultural areas, crop residues (such as sugarcane stalks, rice husks, and corn cobs) and animal manure are collected and burned.

– About 2.7 billion people in 77 less-developed countries face a fuelwood crisis and are often forced to meet their fuel needs by harvesting wood faster than it can be replenished.

– Plant fast-growing trees, shrubs, and perennial grasses in biomass plantations, but this can deplete soil nutrients and deplete or degrade biodiversity.

Solid biomass has advantages and disadvantages

We can convert plants and plant wastes to liquid biofuels

• Liquid biofuels such as biodiesel (produced from vegetable oils) and ethanol (ethyl alcohol produced from plants and plant wastes) are being used in place of petroleum-based diesel fuel and gasoline.

• Advantages of biofuels: – While oil resources are concentrated in a small

number of countries, biofuel crops can be grown almost anywhere, and thus they help countries to reduce their dependence on imported oil.


– If these crops are not used faster than they are replenished by new plant growth, there is no net increase in CO2 emissions, unless existing grasslands or forests are cleared to plant biofuel crops.

– Biofuels are easy to store and transport through existing fuel networks and can be used in motor vehicles at little or no additional cost.

• The two most water-intensive ways to produce a unit of energy are irrigating soybean crops to produce biodiesel fuel and irrigating corn to produce ethanol.


• An alternative to corn ethanol is cellulosic ethanol, which is produced from inedible cellulose that makes up most of the biomass of plants. – In this process, enzymes are used to help convert the

cellulose from widely available inedible cellulose materials such as leaves, stalks, and wood chips to sugars that are processed to produce ethanol.

– A plant that could be used for cellulosic ethanol production is switchgrass, a tall perennial grass native to North American prairies that grows faster than corn.

– Affordable chemical processes for converting cellulosic material to ethanol are still being developed and are possibly years away.

Advantages and disadvantages of liquid biofuels

We can get energy by tapping the earth’s internal heat

• Geothermal energy is heat stored in soil, underground rocks, and fluids in the earth’s mantle.

• A geothermal heat pump system can heat and cool a house by exploiting the temperature differences between the earth’s surface and underground almost anywhere in the world at a depth of 3–6 meters (10–20 feet). – Most energy-efficient, reliable, environmentally clean,

and cost-effective way to heat or cool a space. It produces no air pollutants and emits no CO2.


• Drill wells into hydrothermal reservoirs of geothermal energy to extract steam or hot water, which is used to heat homes and buildings, provide hot water, grow vegetables in greenhouses, raise fish in aquaculture ponds, and spin turbines to produce electricity. – The U.S. is the world’s largest producer of

geothermal electricity from hydrothermal reservoirs.


• Deep geothermal energy stored in hot, dry rock found 5 or more kilometers (3 or more miles) underground almost everywhere. – Tapping just 2% of this source of geothermal

energy in the U.S. could produce more than 2,000 times the country’s current annual use of electricity.

– Digging so deep into the earth’s crust is costly.

A geothermal heat pump system can heat or cool a house almost anywhere

Using geothermal energy has advantages and disadvantages

Will hydrogen save us?

• Focus is on fuel cells that combine H2 and oxygen gas (O2) to produce electricity and water vapor (2 H2 + O2→2 H2O).

• Use of hydrogen as a fuel would eliminate most of our outdoor air pollution problems.

• Greatly reduce the threat of projected climate change as long as the H2 is not produced with the use of fossil fuels or nuclear power.


• Three challenges in turning the vision of widespread use of hydrogen as a fuel into reality. – Hydrogen gas must be produced from elemental

hydrogen (H), which requires using other forms of energy; the amount of energy it takes to make this fuel will always be more than the amount we can get by burning it.

– Fuel cells are the best way to use H2 to produce electricity.

– Whether or not a hydrogen-based energy system produces less outdoor air pollution and CO2 than a fossil fuel system depends on how the H2 is produced.


• Possible uses of hydrogen fuel: – Fuel-cell cars, running on affordable H2

produced from natural gas, could be in widespread use by 2030 to 2050.

– Larger, stationary fuel cells could provide electricity and heat for commercial and industrial users.

– In homes, a fuel-cell stack about the size of a refrigerator could provide heat, hot water, and electricity.

Using hydrogen has advantages and disadvantages

HOW CAN WE MAKE THE TRANSITION TO A MORE SUSTAINABLE ENERGY FUTURE?

Section 13-6

Choosing energy paths

• Energy policies need to consider the future. – Usually takes at least 50 years and huge investments to

phase in new energy alternatives. • Creating energy policy involves trying to answer

the following questions for each alternative: – How much of the energy resource is likely to be

available in the near future (the next 25 years) and in the long term (the next 50 years)?

– What is the estimated net energy yield (p. 000) for the resource?

– What are the estimated costs for developing, phasing in, and using the resource?

Choosing energy paths – What government research and development subsidies

and tax breaks will be needed to help develop the resource?

– How will dependence on the resource affect national and global economic and military security?

– How vulnerable is the resource to terrorism? – How will extracting, transporting, and using the resource

affect the environment, the earth’s climate, and human health? How will these harmful costs be paid and by whom?

– Does use of the resource produce hazardous, toxic, or radioactive substances that must be safely stored for very long periods of time?


• Hard energy paths are based on increasing use of nonrenewable fossil fuels and nuclear energy.

• Soft energy paths are based on improving energy efficiency and increasing the use of various renewable energy resources.


• Three general conclusions of experts who have evaluated energy alternatives: – There will likely be a gradual shift:

• from large, centralized power systems such as coal and nuclear power plants to smaller, decentralized power systems such as household and neighborhood solar-cell panels, rooftop solar water heaters, and small natural gas turbines.

• from gasoline-powered motor vehicles to hybrid and plug-in electric cars.

• to fuel cells for cars and to stationary fuel cells for houses and commercial buildings.


– A combination of greatly improved energy efficiency and the temporary use of nonrenewable natural gas will be the best way to make the transition to a diverse mix of renewable energy resources over the next several decades

– Because of their still-abundant supplies and artificially low prices, we will continue using fossil fuels in large quantities.

Decentralized power system

Suggestions for transitioning to a more sustainable future

Economics, politics, and education can help us shift to more sustainable energy resources

• Governments can use three strategies to help stimulate or reduce the short-term and long-term use of a particular energy resource. – Keep the prices of selected energy resources

artificially low to encourage their use. – Keep the prices of selected energy resources

artificially high to discourage their use. – Governments can emphasize consumer

education.

Three big ideas • Energy resources should be evaluated by… potential

supplies, net energy they provide, and their environmental impacts.

• Using a mix of renewable energy sources can drastically reduce pollution, greenhouse gas emissions, and biodiversity losses.

• A sustainable energy future will require sharply reducing energy waste, using a mix of environmentally friendly renewable energy resources, and including the harmful environmental costs of energy resources in their market prices.

energy - northwest nazarene universitypeople.nnu.edu/jocossel/biol1040/biol1040...

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