Download Section 10.3

Section 10.3
Renewable Energy Sources
Renewable Energy Sources
• Renewable resource: is an energy
source that is replaced nearly as quickly
as it is used
• Solar energy is a renewable resource
than can provide a source of energy for
the foreseeable future
• Even if a small fraction of solar energy
could be used, it would greatly reduce
consumption of fossil fuels
Solar Cells
• Photovoltaic cells—(solar cell)—a device
that is used to convert solar energy into
electric energy
• Solar cells are made of two layers of
semiconductor materials between two
layers of conducting metal
• The process of converting radiant
energy from the Sun directly to
electricity is about 7-11% efficient
Using Solar Energy
• Producing electricity using solar cells is
more expensive on a large scale than
use of non-renewable fuel
• Cost /kwH for fossil-fuel power- $ .8
• Cost/kwH for solar cell power--$ .28
• Disadvantages:
– Electricity generated by solar cells must be
stored in batteries
– However: lg. amts of energy are needed to
manufacture batteries/
– Lg. batteries contain heavy metals; i.e.
lead; --environmental hazards
Hydroelectricity
• Hydroelectricity—electricity produced
from the energy of moving water
• Currently, about 8% of electrical
energy used in the US is produced by
hydroelectric power plants
• Hydroelectric power plants—Efficient
way to produce electricity w/almost no
pollution
• After initial costs of building dams,
hydroelectric plants—relatively cheap
More on Hydroelectricity
• Disadvantages:
Artificial dams can disturb the balance of
natural ecosystems
ex: fish migration upstream may be
blocked by some dams
Some water sources suitable for a
hydroelectric power plant are not near
the people needing the power
Energy from the Tides
• Gravity of the Moon and Sun causes
bulges in Earth’s oceans-tides
• Hydroelectric power can be generated
by ocean tides
– Tide comes in/moving water spins a turbine
that generates electricity
– Low tide/water behind the dam flows back
out to the ocean, spinning turbines and
generating electric power
Harnessing the Wind
• Windmills—can use the energy of the
wind to generate electricity
• Only a few places on Earth consistently
have enough wind to rely on wind
power to meet energy needs
• Windmills are only about 20% efficient
More on Windmills
• Advantages
– Don’t pollute
– Don’t consume any resources
Disadvantages:
-can disrupt migration patterns of some birds
-can be noisy
Energy from inside Earth
• Geothermal energy:
• The thermal energy that is contained in
hot magma
– In some places, Earth’s crust has cracks or
thin spots that allow magma to rise near
the surface
– This produces hot springs/geysers, etc.
• Ex: Old Faithful
**In some areas, the hot water can be pumped
into houses to provide heat
Geothermal Power Plants
• Geothermal energy can be used to
generate electricity
• Steam is converted to electrical energy
• The efficiency of geothermal power
plants is about 16 percent
• However: use of geothermal energy is
limited to areas where magma is
relatively close to the surface
Alternative Fuels
• More than 2/3 of the petroleum used in
the US powers cars and other vehicles
• Other options: electric cars/hydrogen
gas as an alternative fuel/????
• Biomass fuels:
– Biomass—renewable organic matter
• Can be burned in the presence of oxygen to
convert stored chemical energy to thermal
energy
• Burning biomass—probably the oldest use of
natural resources for meeting human energy
needs
Innovation Paper
• What is an innovation?
– An innovation is a CHANGE AGENT
• Something that promotes/introduces/encourages
change
YOUR ASSIGNMENT!!