1. Chapter 7 Resources and Energy 7.3 Renewable Energy
EARTH & SPACE SCIENCE
Chapter 7 Resources and Energy
7.3 Renewable Energy

2. 7.3 Renewable Energy Objectives
Explain how geothermal energy may be used as a substitute for fossil fuels.
Compare passive and active methods of harnessing energy from the sun.
Explain how water and wind can be harnessed to generate electricity.

3. Introduction
The world’s supply of fossil fuels, if current use continues, may be used up in as little time as the next 200 years.
Renewable resources are natural resources that can be replaced at the same rate or faster than they are being used.

4. Geothermal Energy
In areas where subterranean water flows through rocks heated by nearby magma or the hot gases of magma, the water becomes heated as it flows through rocks.
The heat energy generated in this way is known as geothermal energy.
Water may even be pumped down into hot rocks to be converted into steam that can drive turbines and generate electricity.
In Iceland, 85% of homes are heated by geothermal energy.

5. Solar Energy
Solar energy is radiation emitted by the sun and received by Earth.
Global energy needs can be met by the amount of energy the Earth receives from the sun every 15 minutes.
The key to utilizing solar energy is figuring out how to capture and store solar energy.
For heating homes and buildings, solar energy capture can be passive or active.

6. Solar Energy
A passive system does not use moving parts and is based on the building having windows that face the sun.
No moving parts are used
Sunlight enters the house and warms the interior by being captured by the building material and slowly radiated out
An active system uses solar collectors that circulate a medium in tubes through a box usually placed on the roof and routes the energy from the collectors through the rest of the building.

7. Passive Solar Energy

8.
Active Solar Energy

9. Solar Energy
Photovoltaic cells are active systems that convert solar energy directly into electricity.
Photovoltaic cells are commonly used for calculators and other objects requiring small amounts of energy.

10. Energy from Moving Water
Hydroelectric energy is electricity derived from the use of water falling to turn turbines for the generation of electricity.
Moving water has been used for centuries as a source for energy such as with grist mills.
About 11% of the energy generated in the U.S. comes from hydroelectric energy.
A large dam holds back water in a reservoir or impoundment and channels it through a narrow opening allowing the water to run downhill.

11. Alabama Power’s Weiss Dam in Cherokee Co, AL

12. Energy from Moving Water
As the water runs downhill, it is directed through turbines that are turned in order to convert the kinetic energy of the moving water into electrical energy.
Using tidal water to turn turbines is also a form of hydroelectric energy.
The impoundment of water, however, does alter the nature of aquatic ecosystems and can have a detrimental effect on the wildlife in the affected area.

13. Energy From Biomass
Plant debris, manure, sawdust, and other organic wastes are called biomass.
More than half of the trees cut down globally are burned for fuel for heating and cooking.
Methane and alcohol can also be produced from biomass and used as an energy source.

14. Energy From Wind
The sun heats the Earth’s surface unevenly resulting in density and pressure differences in the atmosphere.
The resulting convection currents are more commonly called wind.
Wind turbines convert the wind energy into mechanical energy which is converted to electrical energy.
Small wind-driven generators can be used to meet the energy needs of a single home.

15. Energy From Wind
On a larger scale, wind farms may consist of hundreds of large wind turbines used to meet the electricity needs of an entire community.
Locations where wind is not consistently blowing are not prime locations for such alternative energy.

16. Summary
In short, geothermal energy is heat energy that can be used as a direct heat source or converted into electricity via steam turning an electrical generator.
Solar energy can be used as a direct heat source or converted straight to electricity by use of solar cells.
Water and wind movement can be used to turn turbines to move a coil of wires in a magnetic field which produces an electrical current.