Environmental Science
Renewable/Alternative
Energy Sources
Lecture Notes
Biomass Energy
Biomass = garbage from organisms
 Dead trees, branches, yard
clippings, left-over crops, wood
chips, bark and sawdust from
lumber mills (even manure)
 Trash that can't be recycled 
landfill  using biomass for fuel
cuts down landfill space
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Biomass to Electricity
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60 million tons of biomass (amount
produced by most states) 2,000
megawatts of electricity (enough for 2
million homes!)
How biomass works:
1. Biomass collected in trucks 
taken to biomass power plant
2. Biomass burned boils water 
steam turns turbogenerators
Landfill Gas
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Biomass also “tapped” at landfills (LANDFILL
GAS):
1. Garbage decomposes  methane gas
2. Pipelines collect methane gas  burned
in power plants to make electricity
Also done on animal farms: Manure
decomposes  methane gas  burned at
farm to make energy
Using biomass does NOT add to global
warming (unlike fossil fuels). WHY NOT??
Turning Landfill Gas into Energy (4")
The Future of Biomass
Biomass is renewable because
plant biomass can be regrown
Another use of biomass is ethanol,
a liquid alcohol fuel
– Ethanol used in cars designed to use
alcohol fuel instead of gasoline
– Alcohol can also be mixed with
gasoline to reduce dependence on oil
Geothermal Energy
• "Geo" = earth "thermal" = heat
• Below earth’s crust, top layer of mantle
is hot liquid rock called magma
• For every 328 feet below ground,
temperature ↑5.4oF. At 10,000 feet
below ground, the temperature is hot
enough to boil water.
• Deep under the surface, hot water can
reach temperatures more than 300oF
(water boils at 212oF). It doesn't turn
to steam because it is not in contact
with the air.
• What are geysers? (Old Faithful
pictured on the right)
Geothermal Today
 In U.S., geothermally heated water is used in
swimming pools and health spas
 In Southern California, hot water from
underground is used to heat buildings during
winter. Hot water runs through miles of
insulated pipes to public buildings.
 In Iceland, many buildings/swimming pools
are heated with geothermal hot water. The
country has at least 25 active volcanoes and
many hot springs and geysers.
Geothermal Heating (1")
Geothermal Electricity
 Underground steam  electricity in
geothermal power plant
1. Holes drilled in ground & pipes
lowered into steam
2. Steam comes up pipes
3. Steam spins turbine blades and
generator to make electricity
4. Steam cooled off in cooling
tower and pumped back
underground to be reheated by
earth
 California's geothermal power plants
produce about 1/2 of world's
geothermally generated electricity
(enough for 2 million homes)
Geothermal Electric
Power Plant (4.5")
Hydro Power
 Moving water kinetic energy electricity
 First used to turn wooden wheels
attached to grinding wheels to grind (or
mill) flour or corn
 Water can either go over the top of the
wheel (see photograph at right), or the
wheel can be placed in the moving
river. The flow of the river turns the
wheel at the bottom (see moving
graphic in the upper right)
Hydroelectricity
 Hydroelectric power  kinetic
energy of moving water  electricity
 Dams built across large rivers
 Hydro power today is found in
mountainous areas of states where
there are lakes or reservoirs and along
rivers
 Washington state leads nation in
hydroelectricity 87% is produced by
hydroelectric facilities
How a Hydro Dam Works
1. Water behind dam flows
through intake pipe called
penstock.
2. Water pushes against
blades in a turbine.
3. Turbine spins generator
to produce electricity.
Electricity travels via
electric lines to homes,
schools, factories and
businesses.
Hydroelectricity (2")
Ocean Energy
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3 basic ways to tap the ocean for its energy:
1. ocean's waves
2. ocean's high and low tides
3. temperature differences in the water
Wave Energy
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Moving waves  Kinetic energy
Wave Energy Video
Wave turbine:
1. Wave rises into chamber
2. Rising water forces air out of chamber
3. Moving air spins turbine to turn a generator
4. When wave goes down, air flows through
turbine and back into chamber through doors that
are normally closed
Most wave-energy systems are very small and can be
used to power a warning buoy or small light house
Tidal Energy
Tidal Electricity Generation Animation (1")
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Tides come into shore and are trapped in
reservoirs behind dams. When tide drops,
water behind dam is let out just like a
hydroelectric power plant
An increase of at least 16 feet between low
to high tide is needed for tidal energy to
work
Only a few places where this tide change
occurs around the earth. One plant in
France makes enough energy from tides
(240 megawatts) to power 240,000 homes.
Ocean Thermal Energy Conversion
(OTEC)
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Uses temperature differences in ocean
Sun warms surface water more than deep
water
Ocean's warm surface water is used to heat a
fluid with a low-boiling point, such as
ammonia
Steam turns turbine activates generator to
produce electricity
OTEC Video (4")
Renewable Energy Pro’s
1. No shortage of renewable energy
from the sun, wind and water and
even stuff usually thought of as
garbage (biomass). (Sunlight falling on
the United States in one day contains more than
twice the energy we consume in an entire year.
California has enough wind gusts to produce 11
percent of the world's wind electricity.)
2. Less pollution
3. Renewable energy resource
development  new jobs for people
and less oil we must buy from foreign
countries.
4. Continued research has made
renewable energy more affordable than
25 years ago. (The cost of wind energy
has dropped from 40¢ per kilowatt-hour to
less than 5¢. The cost of solar electricity,
through photovoltaics has dropped from
more than $1/kilowatt-hour in 1980 to
20¢/kilowatt-hour today.)
Renewable Energy Con’s
 TAKES UP A LOT OF LAND:
1. Solar thermal energy (often huge mirrors)
needs large tracts of land as a collection
site.
2. Average wind farm requires 17 acres of
land to produce one megawatt of electricity,
enough electricity for 750 - 1,000 homes.
However, farms and cattle grazing can use the
same land under the wind turbines.
3. Environment also impacted when
constructing power plants, roads, transmission
lines and transformers.
EVEN THOUGH A RENEWABLE POWER
PLANT DOESN’T RELEASE AIR POLLUTION
OR USE FOSSIL FUELS, IT CAN STILL HAVE
A NEGATIVE IMPACT ON THE
ENVIRONMENT:
1. Making PV cells uses toxic chemicals.
2. Wind farms could cause erosion in
desert areas. Most often, winds farms
affect the natural view because they tend
to be located on or just below ridgelines.
Bird deaths also occur due to collisions
with wind turbines and wires.
3. Dams used in hydroelectric power
cause farmland and forests to flood.
Downstream, dams change the chemical,
physical and biological characteristics of
the river and land.