Chapter 18:Chapter 18:Renewable EnergyRenewable Energy

Holt, Rinehart and Holt, Rinehart and WinstonWinston

Environmental ScienceEnvironmental Science

Water

Sun

Wind Geothermal

Sunshine State StandardsSunshine State Standards SC.B.1.4.5: SC.B.1.4.5: Different forms of Energy – Different forms of Energy –

Advantages and Disadvantages (Advantages and Disadvantages (AAAA)) SC.B.1.4.7: SC.B.1.4.7: Conservation of Energy (Conservation of Energy (CSCS)) SC.G.2.4.5: SC.G.2.4.5: Human Activity and Energy Flow Human Activity and Energy Flow

((AAAA))

Section 1:Section 1:

Renewable Energy TodayRenewable Energy Today

ObjectivesObjectives ListList six forms of renewable energy, and compare six forms of renewable energy, and compare

their advantages and disadvantages.their advantages and disadvantages. DescribeDescribe the difference between passive solar the difference between passive solar

heating, active solar heating, and photovoltaic heating, active solar heating, and photovoltaic energy.energy.

DescribeDescribe the current state of wind energy the current state of wind energy technology.technology.

ExplainExplain the differences in biomass fuel use the differences in biomass fuel use between developed and developing nations.between developed and developing nations.

DescribeDescribe how hydroelectric energy, geothermal how hydroelectric energy, geothermal energy, and geothermal heat pumps work.energy, and geothermal heat pumps work.

Renewable EnergyRenewable Energy

Renewable energyRenewable energy - - from sources that are from sources that are constantly being formed.constantly being formed.

Types of renewable energy includes:Types of renewable energy includes:• solar energysolar energy• wind energywind energy• the power of moving waterthe power of moving water• EarthEarth’’s heats heat

Remember, all sources of energy, including Remember, all sources of energy, including renewable sources, affects the environment.renewable sources, affects the environment.

Solar Energy—Solar Energy—Power from the SunPower from the Sun

Nearly all renewable energy comes Nearly all renewable energy comes directly or indirectly from the sun.directly or indirectly from the sun.

Direct solar energy is used every Direct solar energy is used every day, like when the sun shines on a day, like when the sun shines on a window and heats the room.window and heats the room.

Solar energy can also be used Solar energy can also be used indirectly to generate electricity in indirectly to generate electricity in solar cells.solar cells.

Passive Solar HeatingPassive Solar Heating Passive solar heatingPassive solar heating - - the use of sunlight to the use of sunlight to

heat buildings directly.heat buildings directly.

In the Northern Hemisphere, south facing In the Northern Hemisphere, south facing windows receive the most solar energy.windows receive the most solar energy.

Therefore, passive solar buildings have large Therefore, passive solar buildings have large windows that face south.windows that face south.

Active Solar HeatingActive Solar Heating Active solar heatingActive solar heating - -

the gathering of solar the gathering of solar energy by collectors energy by collectors that are used to heat that are used to heat water or heat a building.water or heat a building.

More than 1 million More than 1 million homes in the United homes in the United States use active solar States use active solar energy to heat water.energy to heat water.

Solar collectors, usually Solar collectors, usually mounted on a roof, mounted on a roof, capture the suncapture the sun’’s s energy.energy.

Photovoltaic CellsPhotovoltaic Cells Photovoltaic cellsPhotovoltaic cells - -

solar cells that convert solar cells that convert the sunthe sun’’s energy into s energy into electricity.electricity. They have no moving They have no moving

parts, and they run on parts, and they run on nonpolluting power nonpolluting power from the sun.from the sun.

They produce a very They produce a very small electrical current. small electrical current.

Meeting the electricity Meeting the electricity needs of a small city needs of a small city would require covering would require covering hundreds of acres with hundreds of acres with solar panels.solar panels.

Photovoltaic CellsPhotovoltaic Cells Solar cells require extended periods of sunshine to Solar cells require extended periods of sunshine to

produce electricity. produce electricity. This energy is stored in batteries, which supplies electricity This energy is stored in batteries, which supplies electricity

when the sun is not shining.when the sun is not shining.

Currently, solar cells provide energy for more than 1 Currently, solar cells provide energy for more than 1 million households in developing countries, where million households in developing countries, where energy consumption is minimal and electricity energy consumption is minimal and electricity distribution networks are limited.distribution networks are limited.

Wind PowerWind Power Energy from the sun warms Energy from the sun warms

the Earththe Earth’’s surface s surface unevenly, which causes air unevenly, which causes air masses to flow in the masses to flow in the atmosphere.atmosphere.

We experience the We experience the movement of these air movement of these air masses as wind.masses as wind.

Wind power, which converts Wind power, which converts the movement of wind into the movement of wind into electric energy, is the electric energy, is the fastest growing energy fastest growing energy source in the world.source in the world.

Wind FarmsWind Farms

Wind turbines are used to capture the Wind turbines are used to capture the energy from the wind.energy from the wind.

Wind Wind Farms - large arrays of wind turbines.Farms - large arrays of wind turbines. Supply electricity to thousands of homes.Supply electricity to thousands of homes. In windy rural areas, small wind farms with 20 or In windy rural areas, small wind farms with 20 or

fewer turbines are also becoming common.fewer turbines are also becoming common.

The cost of wind power has been The cost of wind power has been steadily falling as wind turbines steadily falling as wind turbines

have become more efficient.have become more efficient.

An Underdeveloped ResourceAn Underdeveloped Resource

Scientists estimate that the windiest spots on Scientists estimate that the windiest spots on Earth could generate more than ten times the Earth could generate more than ten times the energy used worldwide.energy used worldwide.

In the future, the electricity may be used on the In the future, the electricity may be used on the wind farm to produce hydrogen from water.wind farm to produce hydrogen from water.

Today, all of the large energy companies are Today, all of the large energy companies are developing plans to use more wind power.developing plans to use more wind power.

Biomass—Power from Living Biomass—Power from Living ThingsThings

Biomass fuelBiomass fuel - - consists of plant material, consists of plant material, manure, or any other organic matter that is manure, or any other organic matter that is used as an energy source.used as an energy source.

Fossil fuels can be thought of as biomass Fossil fuels can be thought of as biomass energy sources, although they are energy sources, although they are nonrenewable.nonrenewable.

Renewable biomass fuels, such as wood and Renewable biomass fuels, such as wood and dung, are major sources of energy in dung, are major sources of energy in developing countries.developing countries.

More than 1/2 of all wood cut in the world is More than 1/2 of all wood cut in the world is used as fuel for heating and cooking.used as fuel for heating and cooking.

Biomass—Power from Living Biomass—Power from Living ThingsThings

Biomass—Power from Living Biomass—Power from Living ThingsThings

Although materials like wood are a Although materials like wood are a renewable resource, if trees are cut renewable resource, if trees are cut down faster than they grow, the down faster than they grow, the resulting habitat loss, deforestation, resulting habitat loss, deforestation, and soil erosion can be severe.and soil erosion can be severe.

In addition, harmful air pollution may In addition, harmful air pollution may result from burning wood and dung.result from burning wood and dung.

MethaneMethane When bacteria decompose organic wastes, When bacteria decompose organic wastes,

one byproduct is methane gas.one byproduct is methane gas.

Methane can be burned to generate heat Methane can be burned to generate heat or electricity.or electricity.

In China, more than 6 million households In China, more than 6 million households use biogas digesters to ferment manure use biogas digesters to ferment manure and produce gas for heating and cooking.and produce gas for heating and cooking.

Some landfills in the U.S. generate Some landfills in the U.S. generate electricity by using the methane from the electricity by using the methane from the decomposition of trash.decomposition of trash.

AlcoholAlcohol

Liquid fuels can also be derived from Liquid fuels can also be derived from biomass.biomass.

Example: ethanol, an alcohol, can be made Example: ethanol, an alcohol, can be made by fermenting fruit or agricultural waste. by fermenting fruit or agricultural waste.

GasoholGasohol - a blend of gasoline and - a blend of gasoline and ethanol.ethanol. Gasohol produces less air pollution than fossil Gasohol produces less air pollution than fossil

fuels.fuels. Some states require the use of gasohol in Some states require the use of gasohol in

vehicles as a way to reduce air pollution.vehicles as a way to reduce air pollution.

Hydroelectricity—Power from Hydroelectricity—Power from Moving WaterMoving Water

Hydroelectric energyHydroelectric energy - - electrical energy electrical energy produced by falling water.produced by falling water.

It accounts for 20% of the It accounts for 20% of the worldworld’’s electricity.s electricity.

Large hydroelectric power Large hydroelectric power plants have a dam that is plants have a dam that is built across a river to hold built across a river to hold back a reservoir of water.back a reservoir of water.

The water in the reservoir The water in the reservoir is released to turn a is released to turn a turbine, which generates turbine, which generates electricity.electricity.

Hydroelectricity—Power from Hydroelectricity—Power from Moving WaterMoving Water

The Benefits of Hydroelectric The Benefits of Hydroelectric EnergyEnergy

Hydroelectric dams are expensive to build, but relatively Hydroelectric dams are expensive to build, but relatively inexpensive to operate.inexpensive to operate.

Unlike fossil fuel plants, hydroelectric dams do not Unlike fossil fuel plants, hydroelectric dams do not release air pollutants that cause acid precipitation.release air pollutants that cause acid precipitation.

Hydroelectric dams also tend to last much longer than Hydroelectric dams also tend to last much longer than fossil fuel-powered plants.fossil fuel-powered plants.

Dams also provide other benefits such as flood control Dams also provide other benefits such as flood control and water for drinking, agriculture, industry, and and water for drinking, agriculture, industry, and recreation.recreation.

Disadvantages of Hydroelectric Disadvantages of Hydroelectric EnergyEnergy

A dam changes a riverA dam changes a river’’s flow, which can have far-s flow, which can have far-reaching consequences.reaching consequences.

A reservoir floods large areas of habitat above the A reservoir floods large areas of habitat above the dam. dam. Water flow below the dam is reduced, which disrupts Water flow below the dam is reduced, which disrupts

ecosystems downstream.ecosystems downstream. Example: many salmon fisheries of the NW U.S. have been Example: many salmon fisheries of the NW U.S. have been

destroyed by dams that prevent salmon from swimming destroyed by dams that prevent salmon from swimming upriver to spawn.upriver to spawn.

Modern TrendsModern Trends

While in developing countries the construction While in developing countries the construction of large dams continues, in the U.S., the era of of large dams continues, in the U.S., the era of large dam construction is probably over.large dam construction is probably over.

Micro-hydropowerMicro-hydropower- electricity produced in a - electricity produced in a small stream without having to build a big small stream without having to build a big dam.dam. The turbine may even float in the water, not The turbine may even float in the water, not

blocking the river at all.blocking the river at all. Much cheaper than large hydroelectric dam Much cheaper than large hydroelectric dam

projects, and it permits energy to be generated projects, and it permits energy to be generated from small streams in remote areas.from small streams in remote areas.

Geothermal Energy—Power from Geothermal Energy—Power from the Earththe Earth

In some areas, deposits of water in the In some areas, deposits of water in the EarthEarth’’s crust are heated by geothermal s crust are heated by geothermal energy.energy.

Geothermal energyGeothermal energy - energy produced by - energy produced by heat within the Earth.heat within the Earth. The U.S. is the worldThe U.S. is the world’’s largest producer of s largest producer of

geothermal energy.geothermal energy. ItIt’’s considered a renewable resource, the water s considered a renewable resource, the water

that is used must be managed carefully so that that is used must be managed carefully so that it is not depleted.it is not depleted.

Geothermal Energy—Power from Geothermal Energy—Power from the Earththe Earth

Geothermal power plants generate Geothermal power plants generate electricity using the following stepselectricity using the following steps

• Steam rises through a wellSteam rises through a well• Steam drives turbines, which generate electricitySteam drives turbines, which generate electricity• Leftover liquid is pumped back into the hot rockLeftover liquid is pumped back into the hot rock

The leftover liquid, water, is returned to The leftover liquid, water, is returned to EarthEarth’’s crust because it can be reheated by s crust because it can be reheated by geothermal energy and used again.geothermal energy and used again.

Geothermal Energy—Power from Geothermal Energy—Power from the Earththe Earth

Geothermal Heat Pumps: Energy Geothermal Heat Pumps: Energy for Homesfor Homes

More than 600,000 homes in the U.S. are More than 600,000 homes in the U.S. are heated and cooled using geothermal heat heated and cooled using geothermal heat pumps.pumps.

Geothermal heat pumpGeothermal heat pump uses stable uses stable underground temperatures to warm and underground temperatures to warm and cool homes because the temperature of cool homes because the temperature of the ground is nearly constant year-round.the ground is nearly constant year-round.

A heat pump is simply a loop of piping that A heat pump is simply a loop of piping that circulates a fluid underground.circulates a fluid underground.

Geothermal Heat Pumps: Energy Geothermal Heat Pumps: Energy for Homesfor Homes

In the summer, the ground is cooler than air and the fluid cools the home.

In the winter, the ground is warmer than air, and the fluid warms the home.

Section 2:Section 2:

Alternative Energy and Alternative Energy and ConservationConservation

ObjectivesObjectives DescribeDescribe three alternative energy technologies. three alternative energy technologies.

IdentifyIdentify two ways that hydrogen could be used a two ways that hydrogen could be used a fuel source in the future.fuel source in the future.

ExplainExplain the difference between energy efficiency the difference between energy efficiency and energy conservation.and energy conservation.

DescribeDescribe two forms of energy-efficient two forms of energy-efficient transportation.transportation.

IdentifyIdentify three ways that you can conserve three ways that you can conserve energy energy in your daily life.in your daily life.

Alternative EnergyAlternative Energy To achieve a future where energy use is sustainable, To achieve a future where energy use is sustainable,

we must make the most of the energy sources we we must make the most of the energy sources we already have and develop new sources of energy.already have and develop new sources of energy.

Alternative energyAlternative energy - describes energy that does not - describes energy that does not come from fossil fuels and that is still in come from fossil fuels and that is still in development.development.

For an alternative energy source to become a viable For an alternative energy source to become a viable option for the future, the source must be proven to option for the future, the source must be proven to be cost effective.be cost effective.

Also, the environmental effects of using the energy Also, the environmental effects of using the energy source must be acceptable.source must be acceptable.

Tidal PowerTidal Power A tidal power plant works A tidal power plant works

much like a hydroelectric much like a hydroelectric dam.dam.

As the tide rises, water As the tide rises, water enters a bay behind a dam. enters a bay behind a dam. The gate then closes at high The gate then closes at high

tide.tide. At low tide, the gate opens and At low tide, the gate opens and

the water in the bay rushes the water in the bay rushes through, spinning a turbine that through, spinning a turbine that generates electricity.generates electricity.

Although tidal energy is Although tidal energy is renewable and nonpolluting, renewable and nonpolluting, it will not become a major it will not become a major energy source in the future.energy source in the future. The cost of building and The cost of building and

maintaining tidal power plants maintaining tidal power plants is high, and there are few is high, and there are few suitable locations.suitable locations.

Ocean Thermal Energy Ocean Thermal Energy ConservationConservation

Ocean thermal energy conservationOcean thermal energy conservation (OTEC) (OTEC) is the use of temperature differences in is the use of temperature differences in ocean water to produce electricity. ocean water to produce electricity.

An OTEC plant produces energy using the An OTEC plant produces energy using the following steps:following steps:

• Warm surface water is boiled in a vacuum Warm surface water is boiled in a vacuum chamber.chamber.

• This produces a steam that drives a turbine to This produces a steam that drives a turbine to generate electricity.generate electricity.

• Cold deep-ocean water will condense the steam.Cold deep-ocean water will condense the steam.• The steam turns into water that can be used The steam turns into water that can be used

again.again.

Ocean Thermal Energy Ocean Thermal Energy ConservationConservation

•The United States and Japan have experimented with OTEC power.

•OTEC plants are inefficient because 1/3 of the electricity the plant produces is used to pump cold water up from the deep ocean.

•The environmental effects of pumping large amounts of cold water to the surface are also unknown.

Hydrogen—A Future Fuel Source?Hydrogen—A Future Fuel Source?

Hydrogen can be burned as a fuel.Hydrogen can be burned as a fuel. It doesnIt doesn’’t contain carbon.t contain carbon. It doesnIt doesn’’t release pollutants associated with burning t release pollutants associated with burning

fossil fuels and biomass.fossil fuels and biomass.

Hydrogen gas (HHydrogen gas (H22) can be produced by using ) can be produced by using electricity to split molecules of water (Helectricity to split molecules of water (H22O).O).

Hydrogen fuel can be made from any material Hydrogen fuel can be made from any material that contains a lot of hydrogen.that contains a lot of hydrogen.

In the future, we may also be able to grow In the future, we may also be able to grow plants to produce hydrogen cost effectively.plants to produce hydrogen cost effectively.

The Challenge of Hydrogen FuelThe Challenge of Hydrogen Fuel

Hydrogen fuel takes a lot of energy to Hydrogen fuel takes a lot of energy to produce.produce.

If this energy came from burning fossil fuels, If this energy came from burning fossil fuels, generating hydrogen would be expensive generating hydrogen would be expensive and polluting.and polluting.

One alternative is to use electricity from One alternative is to use electricity from solar cells or wind power to split water solar cells or wind power to split water molecules to produce hydrogen.molecules to produce hydrogen.

Hydrogen could then be stored in Hydrogen could then be stored in pressurized tanks and transported in gas pressurized tanks and transported in gas pipelines. pipelines.

Fuel CellsFuel Cells Fuel cellFuel cell - device that produces electricity chemically - device that produces electricity chemically

by combining hydrogen fuel with oxygen from the air.by combining hydrogen fuel with oxygen from the air.

When hydrogen and oxygen are combined, electrical When hydrogen and oxygen are combined, electrical energy is produced and water is the only byproduct.energy is produced and water is the only byproduct.

They can be fueled by anything that contains plenty of They can be fueled by anything that contains plenty of hydrogen, including natural gas, alcohol, or even hydrogen, including natural gas, alcohol, or even gasoline.gasoline.

Energy EfficiencyEnergy Efficiency

There are two main ways to reduce There are two main ways to reduce energy use:energy use:• lifestyle changeslifestyle changes• increases in energy efficiencyincreases in energy efficiency

Energy efficiencyEnergy efficiency - percentage of - percentage of energy put into a system that does energy put into a system that does useful work.useful work.

energy efficiency (in %) = energy energy efficiency (in %) = energy out/energy in out/energy in 100 100

Energy EfficiencyEnergy Efficiency Most of our devices Most of our devices

are fairly inefficient. are fairly inefficient. More than 40 percent More than 40 percent of all commercial of all commercial energy used in the energy used in the United States is United States is wasted.wasted.

Increasing efficiency Increasing efficiency may involve sacrifices may involve sacrifices or investments in new or investments in new technology. technology.

Efficient TransportationEfficient Transportation

The internal combustion engines that The internal combustion engines that power most vehicles do so power most vehicles do so inefficiently and produce air pollution.inefficiently and produce air pollution.

In the next 50 years, the design of In the next 50 years, the design of these engines may change radically these engines may change radically to meet the need for more efficient to meet the need for more efficient transportation.transportation.

Hybrid CarsHybrid Cars Hybrid cars are examples of energy-efficient Hybrid cars are examples of energy-efficient

vehicles.vehicles.

They use small, efficient gasoline engines most of They use small, efficient gasoline engines most of the time, but they also use electric motors when the time, but they also use electric motors when extra power is needed, such as while accelerating.extra power is needed, such as while accelerating.

They donThey don’’t cost much more than conventional t cost much more than conventional vehicles, they cost less to refuel, and they produce vehicles, they cost less to refuel, and they produce less harmful emissions.less harmful emissions.

Hybrid CarsHybrid Cars

Hybrid cars feature many efficient Hybrid cars feature many efficient technologies. technologies.

• They convert some energy of braking into They convert some energy of braking into electricity and store this energy in the battery.electricity and store this energy in the battery.

• The gasoline engine is sometimes shut off to The gasoline engine is sometimes shut off to save fuel, such as when the car is stopped at a save fuel, such as when the car is stopped at a red light.red light.

• They are aerodynamic in design and need They are aerodynamic in design and need less energy to accelerate.less energy to accelerate.

CogenerationCogeneration

CogenerationCogeneration - production of two - production of two useful forms of energy from the useful forms of energy from the same fuel source.same fuel source. Example: the waste heat from an Example: the waste heat from an

industrial furnace can power a steam industrial furnace can power a steam turbine that produces electricity.turbine that produces electricity.

Energy ConservationEnergy Conservation

Energy conservationEnergy conservation - process of saving - process of saving energy by reducing energy use and waste.energy by reducing energy use and waste.

This can occur in many ways, including This can occur in many ways, including using energy-efficient devices and wasting using energy-efficient devices and wasting less energy.less energy.

Cities and Towns Saving EnergyCities and Towns Saving Energy The town of Osage, Iowa, numbers 3,600 The town of Osage, Iowa, numbers 3,600

people. people.

This town saved more than $1 million each This town saved more than $1 million each year in energy because they found ways to year in energy because they found ways to conserve energy.conserve energy.

In addition to saving energy, the town has In addition to saving energy, the town has greatly improved its economy through energy greatly improved its economy through energy conservation.conservation.

Businesses have relocated to the area to take Businesses have relocated to the area to take advantage of low energy costs. Unemployment advantage of low energy costs. Unemployment rates have also declined.rates have also declined.

Conservation Around the HomeConservation Around the Home

The average household in the The average household in the U.S. spends more than $1,200 U.S. spends more than $1,200 on energy bills each year.on energy bills each year.

Unfortunately, much of the energy from Unfortunately, much of the energy from homes is lost through poorly insulated homes is lost through poorly insulated windows, doors, walls, and the roof.windows, doors, walls, and the roof.