018 Renewable Energy Alternatives Ch 16

1. Environment & Ecology 018 Renewable Energy Alternatives Ch 16

2. Central Case: Iceland moves toward a hydrogen economy Iceland aims to convert to an economy based completely on renewable energy. Geothermal Hydroelectric Hydrogen fuel Oil (import only) 81% renewable hydropower geothermal

3. Economies are powered by fossil fuels 80% of our energy comes from oil, coal, and natural gas

4. Nations vary in the renewables they use In the U.S., most renewable energy comes from hydropower and biomass.

5. The new renewables are growing fast

6. Rapid growth in renewables will continue • However, renewables receive little government help.

7. Biomass energy Biomass: organic material that makes up living organisms Biopower: biomass sources are burned, generating heat and electricity Biofuels: biomass sources are converted into fuels to power automobiles algae corn sugar cane

8. Biomass energy comes from many sources More than 1 billion people use wood from trees as their principal energy source.

9. Biofuels can power automobiles • Ethanol: produced as a biofuel by fermenting carbohydrate-rich crops • Ethanol is widely added to U.S. gasoline to reduce emissions. • Any vehicle will run well on a 10% ethanol mix. In 2007, the U.S. produced 30 billion L (6.5 million gal) of ethanol in 100 ethanol plants.

10. Cars can run on ethanol • Flexible fuel vehicles: run on 85% ethanol • But very few gas stations offer this fuel • Biodiesel: a fuel produced from vegetable oil, used cooking grease or animal fat • Some people use straight vegetable oil in their diesel engines. Bio-Beatle Rental on Maui

11. Drawbacks of biomass energy • Health hazards from indoor air pollution • Rapid harvesting can lead to deforestation, soil erosion, and desertification. • Growing crops exerts tremendous impacts on ecosystems. • Decreased biodiversity • Fertilizers and pesticides • Land is converted to agriculture. • Biofuel is competing with food production. • Corn supplies for food have dropped. • Substantial inputs of energy are required.

12. Hydroelectric power • Hydroelectric (hydro) power: uses the kinetic energy of moving water to turn turbines and generate electricity • The run-of-river approach generates energy without greatly disrupting the flow of river water.

13. A typical dam

14. Run of river Approach

15. Hydropower is clean and renewable • Hydropower’s advantages over fossil fuels for producing electricity: • It is renewable . • It is clean • Hydropower is efficient. • It has an EROI of 10:1

16. Hydropower has negative impacts • Damming rivers destroys riverine habitats. • Natural flooding cycles are disrupted. • Sediment deposition • Thermal pollution of downstream water • Reducing fish populations and aquatic biodiversity Fish ladder

17. Hydroelectric power is widely used • Nations with large rivers and economic resources have used dams. • But hydropower is not likely to expand. • Most of the world’s large rivers have already been dammed. • People have grown aware of the ecological impact of dams. Three-Gorge Dam in China

18. Solar energy • Passive solar energy: the most common way to harness solar energy • Buildings are designed to maximize direct absorption of sunlight in winter and keep cool in summer. • Active solarenergy collection: uses technology to focus, move, or store solar energy

19. Passive solar heating is simple and effective • Low south-facing windows maximize heat in the winter. • Overhangs shade windows in the summer.

20. Passive solar heating is simple and effective • Thermal mass: construction materials that absorb, store, and release heat • By heating buildings in winter and cooling them in summer, passive solar methods conserve energy and reduce costs.

21. Active solar energy collection • Flat plate solar collectors (solar panels): one active method for harnessing solar energy

22. Focusing solar rays magnifies energy In southern California, a power tower produces power for 10,000 households. • Solar cookers: simple, portable ovens that use reflectors to focus sunlight onto food • Power tower: mirrors concentrate sunlight onto receivers to create electricity

23. Photovoltaic cells generate electricity • Photovoltaic (PV) cells: collect sunlight and convert it into electrical energy • These are used with wind turbines and diesel engines. Bluenergy solar wind turbine

24. Photovoltaic cells generate electricity • Photovoltaic (photoelectric) effect: occurs when light strikes one of a pair of metal plates in a PV cell, causing the release of electrons, creating an electric current

25. Solar power is little used but fast growing • Solar energy was pushed to the sidelines by fossil fuels. • lack of investment • But grown 25%/year since 1971. • Solar energy is attractive in developing nations. • Where hundreds of millions don’t have electricity

26. Solar power offers many benefits • It’s long lasting. • It’s quiet, safe, contain no moving parts, and require little maintenance. • Net metering: PV owners can sell excess electricity to their local power utility • New jobs are being created. • Some federal tax credits.

27. Location is a drawback

28. Solar Power Hawaii

29. Modern wind turbines convert kinetic energy • Wind turbines: devices that turn wind energy into electricity • Towers are 40–100 m (131–328 ft) tall. • Higher is better to minimize turbulence and maximize wind speed.

30. Wind is the fastest-growing energy sector

31. Wind speeds are 20% greater over water than over land. There is less air turbulence over water than land. Costs to erect and maintain turbines in water are higher. But the stronger, less turbulent winds produce more power and make offshore wind more profitable. Currently, turbines are limited to shallow water. Offshore sites can be promising

32. Wind Power Hawaii

34. Wind produces no emissions. It doesn’t release any CO2,, SO2, NOx, mercury. It is more efficient. Turbines also use less water than conventional power plants. It can be used on many scales, from one turbine to hundreds. Farmers and ranchers can lease their land. Produces extra revenue Landowners can still use their land for other uses. Wind power has many benefits

35. Wind power has some downsides

36. U.S. wind-generating capacity Mountainous regions have the most wind capacity.

37. The origins of geothermal energy

38. Geothermal energy is greatest in the U.S. west

39. Hawaii Geothermal Resources

40. Puna Geothermal Venture

41. Geothermal power has benefits and limits • Benefits: • Reduces emissions • It does emit very small amounts of gases. • Limitations: • May not be sustainable • Water is laced with salts and minerals that corrode equipment and pollute the air. • Limited to areas where the energy can be trapped

42. Hydrogen Fuel • Electricity splits hydrogen atoms from oxygen atoms in water molecules: 2H2O  2H2 + O2 • Produces pure hydrogen

43. A hydrogen-fueled bus Hartford, CT

44. Other ways of obtaining hydrogen • Hydrogen can also be obtained from biomass and fossil fuels: CH4 + 2H2O  4H2 + CO2 • Results in emissions of carbon-based pollution • Whether a hydrogen-based energy system is environmentally cleaner than a fossil fuel system depends on how the hydrogen is extracted.

45. Costs and benefits of hydrogen and fuel cells • Drawbacks: • a lack of infrastructure and facilities, enormous expense, and hydrogen leakage could deplete stratospheric ozone • Benefits: • An unlimited supply that is clean and nontoxic to use • Few greenhouse gases and other pollutants are made • Is no more dangerous than gasoline in tanks • Cells are energy efficient, silent, non-polluting, and won’t need to be recharged

46. We can harness energy from the oceans • Tidal energy • Wave energy • OTEC

47. Tidal Energy La Rance tidal power plant at St. Malo, France.

48. Tidal Energy Tidal energy farm

49. Wave energy