Section 10.3

Renewable Energy Sources

Renewable Energy Sources

• Renewable resource

as it is used : is an energy source that is replaced nearly as quickly

• 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

electric energy —(solar cell)—a device that is used to convert solar energy into

• 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

generate electricity can be used to

• 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

energy needs —renewable organic matter

• Can be burned in the presence of oxygen to

convert stored chemical energy to thermal

• Burning biomass—probably the oldest use of

natural resources for meeting human energy

Innovation Paper

• What is an innovation? – An innovation is a CHANGE AGENT • Something that promotes/introduces/encourages

change YOUR ASSIGNMENT!!