Sources of Energy

1. Sources of Energy pp.145-151

2. Nearly all the energy on Earth comes originally from the sun. • Plants get energy for photosynthesis from sunlight. • Animals get energy from food, including plants. • Over time plant and animal remains changed into coal, oil and natural gas. • Photovoltaics change solar power directly into electricity • Heat from sunlight creates wind, which windmills change into electricity or mechanical energy.

3. Fossil Fuels Coal, oil and natural gas are called fossil fuels because they take millions of years to be created, like fossils. Fossil fuels are nonrenewable resources because we are using them much faster than they can be replaced. They will run out! Burning fossil fuels releases pollution into the air.

4. Fossil Fuels Coal comes from plants alive millions of years ago. Oil and natural gas come from animals and bacteria from millions of years ago.

5. Nuclear Energy Nuclear energy comes from releasing the energy that holds the nucleus of a uranium atom together. This releases lots of heat (thermal energy). The nuclear fuel is still radioactive for millions of years after it’s removed from the power plant.

6. Hydroelectricity Uses the potential energy of water to generate electricity. The water has to be stored by a dam. Then it passes through the dam’s generators. Hydroelectricity is a renewable resource because the source can be replaced.

7. Inexhaustible Resources Inexhaustible means they can never run out! Examples include solar power, wind power and geothermal energy. These are also called alternative resources.

8. Geothermal Energy • Underground temperature stays same year round • Power plants pump water deep down to be heated to steam to generate electricity. • Home Heat Pumps • In summer: underground cooler than house so pump water down to cool it, then pump through house • In winter: underground hotter than house so pump water down to heat it, then pump through house

9. Inexhaustible Resources Solar Power Wind Power Geothermal • From sunlight • Depends on weather • Expensive • Passive solar uses light to heat water • Photovoltaics change light energy into electricity • From underground heat • No pollution • Expensive • From kinetic energy of wind • Depends on weather • No pollution • Not pretty to look at • Can kill birds that fly into windmill

10. Notes • Nearly all the energy on Earth comes originally from the sun • Coal, oil and natural gas are called fossil fuels. • Nonrenewable resources are used faster than they can be replaced. (Examples: coal, oil, natural gas) • Renewable resources can be replaced. (Example: hydroelectricity) • Inexhaustible resources can never run out! (Examples: solar, wind, geothermal energy) • Photovoltaics change sunlight to electric energy.

11. Fossil Fuels Advantages • We already use them • Portable

12. Fossil Fuels Advantages Disadvantages Limited amounts left Need large amounts of fuel Releases lots of pollution Leaves lots of ash/residue • We already use them • Portable

13. Nuclear Energy Advantages • Uses small amounts of fuel • No air pollution • Releases large amounts of energy

14. Nuclear Energy Advantages Disadvantages Limited amounts of uranium Leaves radioactive waste • Uses small amounts of fuel • No air pollution • Releases large amounts of energy

15. Hydroelectricity ADVANTAGES • No pollution • Available on demand

16. Hydroelectricity ADVANTAGES Disadvantages Can harm fish swimming upstream Drought can lower water level too low to generate power Expensive to build • No pollution • Available on demand

17. Solar Power Advantages • Inexhaustible • No pollution

18. Solar Power Advantages Disadvantages Need sunlight (night, clouds) Expensive Needs large spaces • Inexhaustible • No pollution

19. Wind Power Advantages • No pollution

20. Wind Power Advantages Disadvantages Depends on weather Needs large spaces Can kill birds Not pretty to look at • No pollution

21. Geothermal Energy Advantages • Available 24/7 • No pollution

22. Geothermal Energy Advantages Disadvantages Not available everywhere Expensive • Available 24/7 • No pollution

23. Sources of Energy • Nearly all the energy on Earth comes originally from the sun • Coal, oil and natural gas are called fossil fuels. • Nonrenewable resources are used faster than they can be replaced. (Examples: coal, oil, natural gas) • Renewable resources can be replaced. (Example: hydroelectricity) • Inexhaustible resources can never run out! (Examples: solar, wind, geothermal energy) • Photovoltaic cells change sunlight directly into electricity.