AP Environmental Science Ch 16 Notes
Introduction to Alternative Energy Sources
● Fossil fuels supply approximately 90% of the energy consumed by people. All other energy sources are
considered alternative energy and are divided into renewable energy and nonrenewable energy.
o Nonrenewable energy sources include nuclear energy (nonrenewable because it requires a mineral
fuel mined from Earth) and deep-earth geothermal energy (nonrenewable for the most part because
heat can be extracted from Earth faster than it is naturally replenished).
o Renewable energy sources include solar, freshwater (hydro), wind, low-density (near-surface)
geothermal, and biofuels.
Solar Energy
● Solar energy is absorbed at Earth’s surface at an average rate of 90,000 terawatts (9 x 10 16 watts), which is
about 7000 times the total global demand for energy.
● Solar energy is site-specific.
o Best states for solar energy: California, Nevada, Florida, Arizona, Texas, Utah
o Worst states for solar energy: New Jersey, Vermont, Delaware, Illinois, Indiana, Montana
● Solar energy may be passive or active.
o Passive solar energy uses architectural designs that enhance
the absorption of solar energy
o Active solar energy requires mechanical power, such as
electric pumps, to circulate air, water, or other fluids from
solar collectors to a location where the heat is stored and then
pumped to where the energy is used.
▪ Solar collectors are used to heat water (see diagram
to the right)
▪ Photovoltaics convert sunlight directly into electricity
using solar cells (photovoltaic cells); this is the world’s
fastest-growing source of energy. Modern solar cells
can convert as much as 20% of the sunlight they
receive into energy.
● Environmental trade-off: Solar power has a pretty low impact on the environment, but some of the substances
used in the manufacturing of solar equipment may cause environmental
problems through production and accidental release of toxic materials.
Solar plants also require land and may compete for it with other uses
(ex. the protection of certain species).
● Presidential fun facts: Carter put solar panels on the White House in
1980. Reagan had them taken down in 1986. Obama put up new ones
in 2013.
● http://youtu.be/iXiYJyPJu34
● A...different kind of solar power http://youtu.be/XFw7U7V1Hok
Converting Electricity from Renewable Energy into a Fuel for Vehicles
● Solar power can be stored as electricity in batteries. It can also be
transferred to a liquid or gaseous fuel; the simplest is hydrogen.
o An electrical current can be used to separate water into hydrogen
and oxygen, which are then stored in a fuel cell. Recombining the
hydrogen gas with oxygen from the air supplies a current that can
be used to run a motor. This is a “clean” fuel because the
combustion of hydrogen creates water as exhaust.
● http://youtu.be/yWqFHYeR-Tc
Water Power
● Water wheels—used to power grain mills, sawmills, and other machinery; have been used for centuries
● Hydroelectric power plants use the water stored
behind dams.
o About 10% of the total electricity
produced in the U.S. comes from
hydroelectric plants.
o Hydroelectric power plants produce
most of the electricity used in Norway
and Canada.
o Most good sites from dams have
already been used.
o Small-scale hydropower systems may
be more common in the future.
● Environmental issues
o Flooding land that could have other uses, blocking the migration of fish, increased evaporation of
water
● Three Gorges Dam
http://youtu.be/b8cCsUBYSkw
http://youtu.be/lpQYB2WOWDg
Wind Power
● Regions with the greatest potential for wind power are the Pacific Northwest coastal area, the coastal region of
the northeastern U.S., and a belt within the Great Plains extending from Texas through the Rocky Mountains
and the Dakotas.
● In any location, the wind’s direction, velocity, and duration may be quite variable, depending on local
topography and temperature differences in the atmosphere.
● Most of the small windmills used in the U.S. during the first half of the 20th century generated about 1 kW of
power. Modern wind turbines have a generating capacity of more than 1 million watts (over a MW), which is
enough for 500 modern U.S. homes.
● Today, wind energy is the cheapest form of alternative energy. Electricity produced from wind often costs less
than that from natural gas and coal.
● The United States, Germany, China, Spain, India, and Italy are the world’s leaders in wind power (in
descending order).
● Wind power is the second-fastest growing energy source.
● http://youtu.be/K2PvLKKvfyo
Geothermal Energy
● Geothermal energy uses circulating fluids to carry heat
energy from within the Earth to the surface. The fluids
boil, creating steam capable of turning a turbine.
Geothermal wells are rarely deeper than 3 km (the
deepest one is the Kola superdeep borehole in Russia
at 12.3 km).
● In the United States, most geothermal reservoirs of hot
water are located in the western states, Alaska, and
Hawaii.
● Leading geothermal countries include the U.S., the
Philippines, Mexico, Indonesia, and Italy. Iceland is
also well-known for geothermal power, which makes
up about 65% of its total energy use (hydropower
makes up another 20%). Iceland has 130 volcanic
mountains.
● http://youtu.be/XRAQrDduaU0