Transcript Renewable and Alternative Energy Sources

RENEWABLE AND
ALTERNATIVE ENERGY
SOURCES
Mrs. Paul
Environmental Science
Chapter 17 (pgs. 264-283)
Renewable Energy Today

Renewable Energy: energy from sources constantly
being formed.
 Include:
solar energy, wind energy, water energy,
Earth’s heat.
 Even renewable energy affects the environment.
Solar Energy


Solar energy: energy from the sun; absorbed by plants
and used as fuel.
Sun
Medium-sized star.
 Radiates energy from nuclear fusion reaction in its core.





High temperatures cause hydrogen nuclei to fuse, forming helium
nuclei and a loss of mass occurs. Lost mass converted to heat and
light energy.
Only little bit (2-billionth) of energy reaches Earth.
All renewable energy comes from the sun.
Energy reaches us as visible light and infrared
radiation.

Pros
 Free,
clean, nonpolluting.
 Savings on fuel bills
 Collected energy can be stored.

Cons
 Energy
source is not constant (limited sunlight on cloudy
or rainy days, none at night).
Passive Solar Heating


Passive solar heating: sun’s energy is collected,
stored, and distributed naturally in an enclosed
dwelling.
Not used to produce electricity.
 Example:
Northern Hemisphere-windows facing south
receive most solar energy; passive solar buildings have
windows facing south.
 Energy
enters windows and warms the house!
 Heat released slowly at night.
 Buildings
must be well insulated with thick walls and
floors to prevent heat loss.
 Oriented to sun’s yearly movement.
Passive Solar Features:
Active Solar Heating

Active solar heating: energy from sun gathered by
collectors and used to heat water or buildings.
 Solar
collectors capture sun’s energy.
 Liquid heated as it passes through collectors.
 Hot liquid pumped through heat exchanger, which heats
water for building.

Photovoltaic cells: solar cells; convert the sun’s energy
into electricity, using thin wafers of semiconductor
material.
No moving parts, electric current generated when electrons
on negative side move to positively charged side.
 Nonpolluting
 Produce little electrical current, need extended sunshine to
produce electricity (stored in batteries when not shining).
 Energy production from solar cells has doubled every 4
years from 1985.

Wind Power-Cheap and Abundant


Wind: movement of air masses as Earth’s surface is
warmed unevenly by the sun.
Wind power: converts the movement of wind into
electric energy.
 Wind
turbines are cost effective and can by constructed
quickly.

Aerogenerators: windmills used to generate
electricity; also called wind turbine generators.
Wind Farms

Wind farms: large arrays of wind turbines.
 Take
up little space.
 Land can still be used for farming.
Biomass-Power from Living Things

Biomass Fuel: organic material that is used as an
energy source.
 Renewable
 Ex:
wood, dung, plant material.
 Wood
 Used
for heating and cooking
 Renewable
 Careful-can lead to habitat loss, deforestation, soil erosion;
pollution from burning
 Methane
 Produced
when bacteria decompose organic wastes.
 Burned to generate heat or electricity
 Alcohol
 Can
be made from fermenting fruit or agricultural waste.
 Gasohol (gasoline and ethanol) produces less pollution.
Hydroelectricity-Power from Moving
Water

Hydroelectric energy: energy produced from
moving water.
 Dam
across river to hold back water.
 Water released to turn a turbine.
 Motion of turbine transferred to coils of wire inside
generators. Coils spin in magnetic field.
 Benefits:
 Inexpensive
to operate
 No air pollution
 Last long
 Disadvantages:
 Dam
changes river flow.
 Resevoir floods habitat above the dam.
 Water flow below dam is reduced.
 Dam failure can kill or injure people.
 Modern
Trends
 Micro-hydropower:
electricity produced in a small stream
without having to build a big dam.

Energy from the Tides
 Generate
electricity similarly to how generated in river.
 Turbine must be able to turn in BOTH directions.
Geothermal Energy-Power from the
Earth


Geothermal Energy: energy from heat in the Earth’s
crust; can be used to generate electricity.
Geothermal heat pump: a loop of piping that
circulates a fluid underground, using the stable
underground temperatures to warm and cool homes.

Enough heat present in the earth to melt rock.
 Magma:
 When
molten rock.
it reaches the surface it is called lava.
Alternative Energy and Conservation


Alternative energy: energy sources that are still in
development.
To become viable, source must prove to be cost
effective, and environmental effects must be
acceptable.

Tidal Power
 Movement
of water in oceans caused by gravitational
attraction between the sun, Earth and moon.
 Marked by rising and falling of sea level.
 As tide rises, water trapped behind the dam. Released
to turn turbine and generate electricity.
 High cost to build, not many good locations.

Ocean Thermal Energy Conversion (OTEC)
 Warm
surface water is used to boil sea water in a
vacuum chamber. The water turns to steam and turns a
turbine, generating electricity.
 Pumping the water up uses about 1/3 of the generated
electricity.

Hydrogen
 Burned
as a fuel.
 When burned, it combines with oxygen to form water.
 Current production of hydrogen is not efficient and a
LOT of hydrogen is needed to produce energy.