1. Chapter 19: Alternative Energy and the Environment

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

4. Introduction to Alternative Energy Sources
Total energy we are able to extract from alternative energy is enormous

5. Some Limitation of Renewable Energy
May not be available when we need it.
Daily and seasonal variation
To smooth out supply need energy storage systems
Not equally available in all locations
Solar energy more expense
Smaller subsidies
Compete with other land use

6. More Benefits of Alternative Energy
Associated with minimal environmental degradation
Do not increase atmospheric CO2
Will not cause climate change or raise sea levels
Lead time to build plants is short

7. Solar Energy
Total amount of solar energy reaching Earth’s surface is tremendous
10 weeks of solar energy equivalent to all known fossil fuel reserves

9. 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 in
Building a wall that absorbs heat during the day and releases it at night
Plant deciduous trees

12. Active Solar Energy systems that require mechanical power
Electric pumps to circulate air, water or other fluids from solar collectors to a location where heat is stored
Then pumped to where the energy is used

13. Solar Collectors Provide space heating or hot water
Usually flat glass covered plates over a black background where and absorbing fluid is circulating through tubes
A second type is evacuated tube collector
Each tube along with absorbing fluid pass through a larger tube

15. 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

17. 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

20. Solar Thermal Generators
Focus sunlight onto water-holding containers.
The water boils and is used to run conventional steam-drive electrical generators
Being built with very large output
Traditionally towers more recently devices built w/ many mirrors

24. 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

25. Converting Electricity from Renewable Energy to a Fuel that can be Burned and can Power Vehicles
Basically two choices:
Store electricity in batteries and use electrical vehicles
Transfer the energy in the electricity to a gaseous or liquid fuel.
hydrogen

26. Hydrogen Fuel
An electrical current can be used to separate water in top the hydrogen and oxygen.
Can be produced using solar and other renewable energy sources
Then transported in pipelines and held in tanks
Combustion product is water

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

30. Small-Scale Systems
The total amount of electrical power produced by running water from large dams will probably not increase in the coming years in the US.
Most dam sites already utilized
Small scale systems have potential in mountainous areas along streams.

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

32. Ocean Energy
A lot of energy is involved in the motion of waves, currents and tides in the ocean.
Difficult to harness
Storms destructive and water corrosive
Most successful tidal power
But very few areas w/ the right topography

33. Tidal Power
To harness a dam built across the entrance to a bay or estuary
Water held in or out of bay until significant difference in level will force water in or out running turbines
Has environmental impacts
Changes hydrology of bay
Restricts passage of fish
Changes habitat for birds and other organisms

35. Wind Power
Winds are produced when differential heating of Earth’s surface create air masses with differing heat contents and densities.
Potential energy from wind large
Problems w/ use because highly variable in time, place, and intensity.
Wind velocity often increases over hill tops or funneled through a mountain pass

37. Wind Power Wind energy is the cheapest form of alternate energy.
Less than natural gas and coal
Now used in many place including offshore

40. 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

41. 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

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

44. Biofuels Are biofuels a net benefit or disbenefit?
Using waste as a fuel is a good way to dispose of them
Firewood that regenerates naturally or in plantations that require little energy input will continue to be important sources of energy
Farming of crop to convert to liquid fuels is a poor source of energy

45. 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

46. 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

47. Geothermal Energy Natural heat from the interior of the 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

48. Geothermal Systems Areas of high heat flow occur at plate boundaries
Divergent and convergent plate boundaries
A common system, hydrothermal convection, transfers heat from depths to surface.
Using steam or hot water

50. 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

51. Geothermal Energy and the Environment
Problems include:
Considerable thermal pollution from hot wastewaters
May be saline or highly corrosive
On-site noise, emissions of gas and disturbance of land

52. 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)