1. Sources of Energy pp

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.
Coal comes from plants alive 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 kinetic energy of wind
Depends on weather
No pollution
Not pretty to look at
Can kill birds that fly into windmill
From underground heat
No pollution
Expensive

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 Limited amounts left We already use them
Disadvantages
Advantages
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 Uses small amounts of fuel No air pollution
Advantages
Uses small amounts of fuel
No air pollution
Releases large amounts of energy

14. Nuclear Energy Limited amounts of uranium Uses small amounts of fuel
Disadvantages
Advantages
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 Can harm fish swimming upstream No pollution
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 Inexhaustible No pollution Need sunlight (night, clouds)
Advantages
Disadvantages
Inexhaustible
No pollution
Need sunlight (night, clouds)
Expensive
Needs large spaces

19. Wind Power
Advantages
No pollution

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

21. Geothermal Energy
Advantages
Available 24/7
No pollution

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

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.
Fossil Fuels
Advantages
Disadvantages
Already being used
Limited amounts left
Portable
Causes much pollution
Nuclear Energy
Advantages
Disadvantages
No air pollution
Radioactive waste for millions of years
Need just small amount of fuel
Limited amount of uranium
Get large amount of energy

24. Hydroelectricity
Advantages
Disadvantages
No pollution
Can harm fish
Always available
Drought can lower water too far
Expensive
Need large amounts of space
Solar Power
Advantages
Disadvantages
No pollution
Not available at night or cloudy days
Inexhaustible
Expensive
Needs large amounts of space

25. Wind Power
Advantages
Disadvantages
No pollution
Depends on weather
Needs large amounts of space
Can kill birds
Not pretty to look at
Geothermal Power
Advantages
Disadvantages
Reliable
Not available everywhere
No pollution
Expensive