EARTH & SPACE EARTH & SPACE SCIENCESCIENCE

Chapter 7 Resources and EnergyChapter 7 Resources and Energy

7.3 Renewable Energy7.3 Renewable Energy

7.3 Renewable Energy Objectives7.3 Renewable Energy Objectives

Explain how geothermal energy may be Explain how geothermal energy may be used as a substitute for fossil fuels.used as a substitute for fossil fuels.

Compare passive and active methods of Compare passive and active methods of harnessing energy from the sun.harnessing energy from the sun.

Explain how water and wind can be Explain how water and wind can be harnessed to generate electricity.harnessed to generate electricity.

IntroductionIntroduction

The world’s supply The world’s supply of fossil fuels, if of fossil fuels, if current use current use continues, may be continues, may be used up in as little used up in as little time as the next time as the next 200 years.200 years.

Renewable Renewable resources are resources are natural resources natural resources that can be that can be replaced at the replaced at the same rate or same rate or faster than they faster than they are being used.are being used.

http://www.oceansatlas.org/unatlas/uses/transportation_telecomm/images

Geothermal EnergyGeothermal Energy

In areas where subterranean water flows In areas where subterranean water flows through rocks heated by nearby magma or the through rocks heated by nearby magma or the hot gases of magma, the water becomes heated hot gases of magma, the water becomes heated as it flows through rocks.as it flows through rocks.

The heat energy generated in this way is known The heat energy generated in this way is known as geothermal energy.as geothermal energy.

Water may even be pumped down into hot rocks Water may even be pumped down into hot rocks to be converted into steam that can drive to be converted into steam that can drive turbines and generate electricity.turbines and generate electricity.

In Iceland, 85% of homes are heated by In Iceland, 85% of homes are heated by geothermal energy.geothermal energy.

Solar EnergySolar Energy

Solar energy is radiation emitted by the Solar energy is radiation emitted by the sun and received by Earth.sun and received by Earth.

Global energy needs can be met by the Global energy needs can be met by the amount of energy the Earth receives from amount of energy the Earth receives from the sun every 15 minutes.the sun every 15 minutes.

The key to utilizing solar energy is figuring The key to utilizing solar energy is figuring out how to capture and store solar energy.out how to capture and store solar energy.

For heating homes and buildings, solar For heating homes and buildings, solar energy capture can be passive or active.energy capture can be passive or active.

Solar EnergySolar Energy

A passive system does not use moving parts A passive system does not use moving parts and is based on the building having windows and is based on the building having windows that face the sun.that face the sun. No moving parts are usedNo moving parts are used Sunlight enters the house and warms the interior by Sunlight enters the house and warms the interior by

being captured by the building material and slowly being captured by the building material and slowly radiated outradiated out

An active system uses solar collectors that An active system uses solar collectors that circulate a medium in tubes through a box circulate a medium in tubes through a box usually placed on the roof and routes the energy usually placed on the roof and routes the energy from the collectors through the rest of the from the collectors through the rest of the building.building.

http://www.urbanoptions.org/RenewableEnergy/SolarSpaceHeatingPassive.htm

Passive Solar Energy

http://pbisotopes.ess.sunysb.edu/classes/geo101-notes/ex-3-8.htm

Active Solar Energy

Solar EnergySolar Energy Photovoltaic cells are active systems that convert Photovoltaic cells are active systems that convert

solar energy directly into electricity.solar energy directly into electricity. Photovoltaic cells are commonly used for Photovoltaic cells are commonly used for

calculators and other objects requiring small calculators and other objects requiring small amounts of energy.amounts of energy.

http://science.nasa.gov/headlines/y2002/solarcells.htm

Energy from Moving WaterEnergy from Moving Water

Hydroelectric energy is electricity derived from Hydroelectric energy is electricity derived from the use of water falling to turn turbines for the the use of water falling to turn turbines for the generation of electricity.generation of electricity.

Moving water has been used for centuries as a Moving water has been used for centuries as a source for energy such as with grist mills.source for energy such as with grist mills.

About 11% of the energy generated in the U.S. About 11% of the energy generated in the U.S. comes from hydroelectric energy.comes from hydroelectric energy.

A large dam holds back water in a reservoir or A large dam holds back water in a reservoir or impoundment and channels it through a narrow impoundment and channels it through a narrow opening allowing the water to run downhill.opening allowing the water to run downhill.

http://www.janandpat.net/dams/southern/weissdam.htm

Alabama Power’s Weiss Dam in Cherokee Co, AL

Energy from Moving WaterEnergy from Moving Water

As the water runs downhill, it is directed through As the water runs downhill, it is directed through turbines that are turned in order to convert the turbines that are turned in order to convert the kinetic energy of the moving water into electrical kinetic energy of the moving water into electrical energy.energy.

Using tidal water to turn turbines is also a form Using tidal water to turn turbines is also a form of hydroelectric energy.of hydroelectric energy.

The impoundment of water, however, does alter The impoundment of water, however, does alter the nature of aquatic ecosystems and can have the nature of aquatic ecosystems and can have a detrimental effect on the wildlife in the affected a detrimental effect on the wildlife in the affected area.area.

Energy From BiomassEnergy From Biomass

Plant debris, manure, sawdust, and other Plant debris, manure, sawdust, and other organic wastes are called biomass.organic wastes are called biomass.

More than half of the trees cut down More than half of the trees cut down globally are burned for fuel for heating and globally are burned for fuel for heating and cooking.cooking.

Methane and alcohol can also be Methane and alcohol can also be produced from biomass and used as an produced from biomass and used as an energy source.energy source.

Energy From WindEnergy From Wind

The sun heats the Earth’s surface unevenly The sun heats the Earth’s surface unevenly resulting in density and pressure differences in resulting in density and pressure differences in the atmosphere.the atmosphere.

The resulting convection currents are more The resulting convection currents are more commonly called wind.commonly called wind.

Wind turbines convert the wind energy into Wind turbines convert the wind energy into mechanical energy which is converted to mechanical energy which is converted to electrical energy.electrical energy.

Small wind-driven generators can be used to Small wind-driven generators can be used to meet the energy needs of a single home.meet the energy needs of a single home.

Energy From WindEnergy From Wind On a larger scale, On a larger scale,

wind farms may wind farms may consist of hundreds consist of hundreds of large wind turbines of large wind turbines used to meet the used to meet the electricity needs of electricity needs of an entire community.an entire community.

Locations where Locations where wind is not wind is not consistently blowing consistently blowing are not prime are not prime locations for such locations for such alternative energy.alternative energy.

http://www.friendsofbruce.ca/Photos,Maps,Etc/links_page.html

SummarySummary

In short, geothermal energy is heat energy that In short, geothermal energy is heat energy that can be used as a direct heat source or can be used as a direct heat source or converted into electricity via steam turning an converted into electricity via steam turning an electrical generator.electrical generator.

Solar energy can be used as a direct heat Solar energy can be used as a direct heat source or converted straight to electricity by use source or converted straight to electricity by use of solar cells.of solar cells.

Water and wind movement can be used to turn Water and wind movement can be used to turn turbines to move a coil of wires in a magnetic turbines to move a coil of wires in a magnetic field which produces an electrical current.field which produces an electrical current.