1. Chapter 16: Alternative Energy and the Environment

2. Overview Introduction to Alternative Energy Sources Solar Energy
Converting Electricity from Renewable Energy into a Fuel for Vehicles
Water Power
Ocean Energy
Wind Power
Biofuels
Geothermal Energy

3. Introduction to Alternative Energy Sources
Nonrenewable alternative energy
Nuclear
Requires a mineral fuel mined from Earth
Geothermal
Heat is extracted faster than it is replenished
Renewable energy sources
Solar, fresh water, wind, ocean, and biofuels
All derive from the sun’s energy

5. Solar Energy
10 weeks of solar energy equivalent to all known fossil fuel reserves
Two types
Passive
Active

6. Passive Solar Energy
Promotes cooling in hot weather and retaining heat in cold weather
Methods include:
Overhangs that block summer sun but allow winter sun
Walls in buildings that absorbs heat during the day and releases it at night
Deciduous trees as landscaping

9. Active Solar Energy systems that require mechanical power
Electric pump circulate air, water or other fluids from solar collectors to a location where heat is stored
Additional pumps move heat to location where energy is converted and used

10. Solar Collectors Provide space heating or hot water
Flat Plate Collector
Flat, glass-covered plates over a black background where absorbing fluid is circulated through tubes
Evacuated tube collector
Each tube filled with absorbing fluid pass through a larger tube

11. Photovoltaic Converts sunlight directly into electricity
Made from thin layers of semiconductors and a solid-state electronic components with few or no moving parts
World’s faster growing source of energy

12. Photovoltaic Off the grid
Emerging as a major contributor to developing countries
Don’t have ability to build a electrical grid
Systems can power lights and televisions in small villages

14. Solar Thermal Generators
Focus sunlight onto water-holding containers
Traditionally built using solar power towers
Water boils and is used to run conventional steam-driven electrical generators
Built with very large output

15. Solar Thermal Generators
In newer facility
Mirrors focus solar energy onto pipes with heat-absorbing fluid

17. Solar Energy and the Environment
Generally low impact
One concern
Variety of metals, glass plastics, and fluids used in the manufacture and use of solar equipment
Production and accidental spills could release toxic materials

18. Converting Electricity from Renewable Energy to a Fuel that can be Burned and can Power Vehicles
Two choices:
Store electricity in batteries and use electric vehicles
Transfer the energy in the electricity to a gaseous or liquid fuel
Hydrogen

19. Hydrogen Fuel Hydrogen as power for fuel cells
Electric current separates water into hydrogen and oxygen
When H recombined with O, electrons flow between positive and negative poles
An electric current
H Can be transported in pipeline
Combustion product is water
Clean fuel

20. Water Power A form of stored solar energy
Long history
Waterwheels convert water power to mechanical energy
Today’s hydroelectric power plants
use water stored behind dams
Also produced through the process of pump storage

22. Small-Scale Systems
Electrical power produced by large dams will not increase
Most dam sites already utilized
Small scale systems have potential in mountainous areas along streams

23. Water Power and the Environment
Advantages
Water power is clean and efficient power
No burning of fuel, no radioactive waste
Disadvantages
Flood large tracts of land
Block fish migration
Trap sediment that would replenish beaches
Evaporative loss of water from reservoirs

24. Ocean Energy
High energy in motion of waves, currents and tides in the ocean
Difficult to harness
Storms destructive and water corrosive
Most successful = tidal power
Very few areas w/ the right topography

25. Tidal Power Dam built across the entrance to a bay or estuary
Water held in or out of bay until significant difference in level forces water in or out
This runs the turbines
Environmental impacts
Changes hydrology of bay
Restricts passage of fish
Changes habitat for birds and other organisms

26. Wind Power
Wind produced when differential heating of Earth’s surface create air masses with differing heat contents and densities
Wind energy is the cheapest form of alternative energy
Less than natural gas and coal
Now used in many place including offshore

27. Wind Power Problems Wind highly variable in time, place, and intensity
Wind velocity often increases over hill tops or funneled through a mountain pass

29. Wind Power and the Environment
Wind energy does have a few disadvantages
Kills birds
Use large areas of land
May degrade area’s scenic resources

30. Future of Wind Power Growing at approximately 30% per year
Nearly 10 times the growth rate of oil use
Created thousands of jobs and investment opportunities
Technology producing more efficient wind turbines

31. Biofuels and Human History
Energy from biomass is the oldest fuel used by humans.
Until end of 19th century major fuel source in the US
1 billion people in the world still use wood as primary source of energy for heat and cooking
Includes: firewood, cattle dung, peat

32. Biofuels Energy recovered from biomass-organic matter Three groups
Firewood
Organic wastes
Crops grown to be converted into liquid fuels

34. Biofuels and the Environment
Can pollute the air and degrade the land
World’s forests will decrease if our need for forest products and forest biomass fuel exceeds the productivity of the forests
Combustion of biomass-derived fuel generally release fewer pollutants then combustion of coal/gasoline
But burning urban waste can release heavy metals

35. Geothermal Energy Deep earth - high density
Energy from interior of earth
Mined and used to heat buildings and generate electricity
May be considered nonrenewable when rates of extraction are greater than rates of natural replenishment
Shallow earth - low density
Solar energy that has traveled to shallow depths

36. Geothermal Systems Areas of high heat flow occur at plate boundaries
Divergent and convergent plate boundaries
Hydrothermal convection- transfers heat from depths to surface
Using steam or hot water

38. Geothermal
Most groundwater can be considered a source of geothermal energy
Groundwater at a depth of 100m is 13oC or 55oF
In summer heat can be transferred to the cool water
In winter heat can be transferred from the water to the air

39. Geothermal Energy and the Environment
Problems:
Considerable thermal pollution from hot wastewaters
Water may be saline or highly corrosive
On-site noise
Emissions of gas
Disturbance of land

40. Future of Geothermal Energy
Could produce 10% of the electricity needed for the western US
Geohydrothermal
Could potentially provide four times that (10% of US total)