1. 10.1 The Status of Renewable Energy
Currently, alternative energy sources supply almost 13% of the world’s total energy.
Some studies suggest these sources could provide half of the world’s energy needs by 2050.
Renewable sources will become much more important as fossil fuel supplies become more expensive.
Biomass conversion
Hydroelectric power
Solar energy
Wind energy
Tidal power

2. 10.2 Major Kinds of Renewable Energy
Renewable energy as a share of total energy consumption (World 2006)

3. Biomass Conversion
Biomass is produced by green plants that convert sunlight into plant material
Biomass is still the predominant form of energy used by people in less-developed countries.
It accounts for 10% of world energy use.
Sources:
Fuelwood
Municipal and industrial wastes
Agricultural crop residues and animal wastes

4. Biomass Conversion
In less-developed countries, fuelwood has been a major energy source for centuries.
Fuelwood is the primary energy source for nearly half the world’s population.
It is a source of air pollution and particulate matter.

5. Biomass Conversion Environmental impact of biomass
Habitat and biodiversity loss
1.3 billion people cannot obtain wood, or harvest it faster than it grows.
Much forest has been destroyed in Asia and Africa.
Desertification has increased in these regions.
Air pollution
Burning wood produces air pollution.
Smoke, particulates, carbon monoxide, and hydrocarbons contribute to ill health.

6. Hydroelectric Power
Hydroelectric power is created when flowing water is captured and turned into electricity.
Damming a river and storing water in a reservoir is the most common method.
The potential for developing hydroelectric power is best in mountainous regions and large river valleys.

7. Hydroelectric Power
Hydroelectric power currently supplies 16% of world’s electricity.
In South and Central America, 65% of electricity used comes from hydroelectric power.
Norway gets 99% of its electricity and 65% of all its energy from hydroelectric power.

8. Hydroelectric Power
Reservoir construction causes significant environmental and social damage.
Loss of farmland or forest land due to flooding
Community relocation
Prevention of fish migrations
Trapping of silt fills in reservoir and stops flow of nutrients downstream
Mercury accumulation

9. Hydroelectric Power
Hydroelectric power plant.

10. Solar Energy
Solar energy can generate electricity in two different ways.
Steam can be created to drive a turbine.
Photovoltaic cells can generate electricity directly.
Currently the most successful design is the parabolic trough which heats oil in pipes. The heat is transferred to water to make steam and run a turbine.

11. Solar Energy
Solar heating designs

12. Solar Energy
Solar generation of electricity

13. Solar Energy
Improving solar cell efficiency while holding down the cost per cell is very important
Solar electricity is 20 cents per kilowatt-hour, more than electricity from the power plant.
They are silent, produce no emissions, and use no fuel other than sunlight, but thermal systems use large amounts of land to position the mirrors.

14. Solar Energy
Photovoltaic shingles

15. Wind Energy
Wind Power
Some areas are better suited than others, and winds are variable. Wind energy must be coupled with other sources of energy.
Less than 1% of total worldwide electrical production is from wind.
Only 1% of U.S. electricity is from wind. 20% could be generated by 2030.
Wind turns blades of windmill which turns a turbine, generating electricity

16. Wind Energy There are some negative effects from wind generators:
The moving blades produce noise and some consider the windmills visual pollution.
Moving blades are hazardous to birds, although newer windmills have slower-moving rotors that many birds find easier to avoid.
Vibrations from generators can cause structural damage.

17. Tidal Power Tidal Power
The gravitational forces of the moon and sun cause ocean water to bulge out. Tides form as the Earth rotates through this bulge.
As water flows from a higher level to a lower level, it can be used to spin an electricity-generating turbine.
Since tidal changes of roughly 16 feet (5 m) are needed to produce practical amounts of power, suitable sites are limited.
Best sites are narrow bays where water is forced in and out quickly.

18. Tidal power generation