1. Renewable Energy Sources
Section 10.3
Renewable Energy Sources

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. More on Windmills Advantages Don’t pollute Don’t consume any resources
Disadvantages:
-can disrupt migration patterns of some birds
-can be noisy

10. 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

11. 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

12. 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

13. Innovation Paper What is an innovation?
An innovation is a CHANGE AGENT
Something that promotes/introduces/encourages change
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