III. RENEWABEL ENERGY
- renewable resources – a natural resource that can be
replaced at the same rate at which the resource is consumed
A. Geothermal Energy
1. energy produced by heat within the Earth
a. water flows beneath Earth’s surface
b. heated by nearby magma
c. the hot water, or resulting steam, is the source of a
large amount of energy
d. geothermal energy means “energy from the heat
of Earth’s interior”
2. wells are drilled to reach the hot water
3. water may be pumped down in hot rocks
4. the steam and hot water serve as a source of power to
drive turbines, which generate electricity
5. in Iceland, 85% of homes are heated by geothermal
energy
B. Solar Energy
1. energy received by Earth from the sun in form of
radiation
2. every 15 minutes, Earth receives enough energy from the
sun to meet the energy needs of the world for one year
3. converting solar energy into heat energy can be done in
two ways
a. passive system
1a. does not use moving parts
2a. sunlight enters the house and warms the building
materials
3a. stores sun heat to be used in the evening
b. active system
1b. use of solar collectors
2b. solar collector
aa. a box with a glass top
bb. commonly placed on the roof of houses
cc. water circulates through tubes
dd. provides heat and hot water
3b. photovoltaic cells
aa. an active system that converts solar energy
directly into electricity
bb. works well with small objects
cc. calculators
C. Energy from Moving Water
1. hydroelectric energy – electrical energy produced by the
flow of water
2. hydroelectric plant
a. 11% of electricity in the US comes from hydroelectric
b. massive dams hold back running water
c. water is channeled through the plant
d. water spins turbines which turn generators to
produce electricity
3. tides
a. water is trapped at high tide
b. released at low tide
c. when water is released, turbines are turned within
D. Energy from Biomass
1. biomass – plant material, manure or any organic matter
that is used as an energy source
2. more than 50% of trees cut down are used as fuel for
cooking and heating
3. bacteria produce methane that can be burned
4. ethanol also forms from bacteria that can be burned
E. Energy from Wind
1. wind – movement of air over Earth’s surface
2. wind turbines use the movement of air to convert wind
energy into mechanical energy, which is used to generate
electricity
3. wind farms – area that may have hundreds of giant wind
turbines