Harnessing Renewable Energy: Solar, Wind, and Water Power

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