1. Renewable-energy Use in the United States

2. Solar Energy

3. Principles of Solar Energy Constant Abundant Free Everlasting Drawback Dilute

4. Using Solar Energy Collection Conversion Storage Cost- effectiveness

5. Solar Heating Systems Active: moves water or air with pumps and blowers Passive: moves water or air with natural convection currents or gravity

6. Solar Heating of Water: Flat-plate Solar Collector Acts like a greenhouse 1.Light energy goes in 2.Converted into heat energy (infrared) 3.Heat energy is trapped 4.Heat is transferred to circulating water

7. Solar Water Heaters

8. Passive Solar Space Heating

9. Solar Production of Electricity Photovoltaic Cell

10. Photovoltaic Cell (PV) Mostly made of silicon –Silicon form 4-bonds with other atoms –Silicon crystal is a poor conductor

11. Silicon Crystal All electrons are fixed in bonds –Poor conductor “Doping” silicon crystals with impurities makes silicon a better conductor –Semiconductor

12. Silicon Doping N-type –Add phosphorus Has extra electron in outer orbit Donates electrons easily –Negatively charged P-type –Add Boron Has one less electron in outer orbit Accepts electrons easily –Positively charged

13. PV Cell Electric field (electrical potential or voltage) is generated when N and P silicon are in contact Electrons move from N to P silicon at contact point Electric field is generated Once electric field is produced electrons cannot pass from N to P silicon –Acts like a diode (electrical one-way valve) N-type P-type

14. PV cell in Action Photons (packets of light energy) are absorbed cause electrons to be freed Electrons move from P to N but cannot go back to the P side directly Electrons flow through the wire back to the P side N-type P-type

15. What about at night? Energy stored in batteries Net metering –Special meter that can run backwards –Generate energy “currency” during the day and use the it at night

16. Efficiency Only 15-25% efficient –All or nothing effect Threshold amount on energy required to knock off an electron –Reflection at surface –Resistance generated on N-side –DC current must be converted to AC current

17. Concentrating Solar Power PV power plants Solar-trough collectors Power towers Dish-engine system

18. The Solar-trough Collector

19. How the Solar-trough Collector Works The curved reflector focuses sunlight on and heats oil in the pipe. Heated oil used to boil water and generate steam for driving a conventional turbogenerator.

20. Power Tower

21. Solar Dish Engine System

22. Disadvantages of Solar Energy Technologies Expense Only works during the day Requires backup energy sources, e.g., batteries Some climates not sunny enough

23. Indirect Solar Energy Hydropower Wind power Biomass energy

24. Hydropower: Drawbacks Limited to certain geographical areas Ecological impacts above and below dam Disruption of communities

25. Wind Power

26. Pros –Small environmental degradation –Clean energy Cons –Limited to certain geographical areas –Aesthetics –Low megawatt output –Noise

27. Long Island Wind Park South shore off Jones Beach and Robert Moses Park Proposed 1999

28. View from Robert Moses Park

29. View from Jones Beach

30. Benefits Provide electricity to 44,000 homes Saves 13.5 million barrels yearly

31. Ecological Impact? Disruption of benthic environment –2.7 acres support base –14.3 acres cable –Small area effected Migratory Birds –Multiple European studies – safe to migrating birds

32. Biomass Energy – All produce CO 2 Burning firewood Burning wood/corn pellets Burning wastes Burning biogas (methane)

33. Geothermal Energy: Benefits or Drawbacks? Pros –Consistent source –No pollution Cons –Limited to certain geographical area

35. Geothermal Heat Pump System

36. Tidal Power Pros –Consistent source –No pollution Cons –Very expensive –Effects ecology of shoreline Rance river in France

37. Tidal Power

38. Wave Power Pros –No pollution –Consistent source –Minimal environmental impact Cons –Expensive to install and connect to power grid

39. Shoreline Devices

40. Shoreline Device

42. Offshore Device

45. Renewable Energy and Transportation Biofuels: ethanol and biodiesel Hydrogen: the fuel for the future

46. Hydrogen–Oxygen Fuel Cell Electrophoresis –Produces hydrogen and oxygen gas –Electric field passed through water splits water (H 2 O) into hydrogen and oxygen Fuel Cell –Electrophoresis run in reverse

47. Fuel Cells: Benefits or Drawbacks? Pros –Substitute for fossil fuels –No pollution!!! Cons –Production –Portability –Distribution system