1. Renewable Energy Sources Ali Shakouri Electrical Engineering Department University of California Santa Cruz http://quantum.soe.ucsc.edu/ EE80S Sustainability Engineering and Practice October 17, 2007

2. The Sun Source of our Energy supply Ken Pedrotti, EE80T (winter quarter)

3. Nuclear Fission Heavy atomic nuclei can split giving rise to two smaller nuclei some extra particles. In a slow controlled reaction the energy that the particles fly off with is ultimately dissipated as heat and used to run a heat engine and a generator in a nuclear reactor. Ken Pedrotti, EE80T (winter quarter)

4. Fission suffers from some public relations problems Chernobyl Meltdown Aftermath http://www.worldprocessor.com/53.htm Radiation Cloud form Chernobyl on April 27th Ken Pedrotti, EE80T (winter quarter)

5. Nuclear Fusion Nuclear Fusion: Forget it, we aren't smart enough yet. But suppose we become smart enough in a few hundred years. Can adoption of sustainable energy technology get us to this point? http://zebu.uoregon.edu/2001/ph162/l1.html Ken Pedrotti, EE80T (winter quarter)

6. Are there Sustainable Solutions? http://zebu.uoregon.edu/2001/ph162/l14.html Solar Biomass Wind Hydroelectric GeothermalFrom the Oceans

7. (in the U.S. in 2002) 1-4 ¢ 2.3-5.0 ¢ 6-8 ¢ 5-7 ¢ Today: Production Cost of Electricity 6-7 ¢ 25-50 ¢ Cost, ¢/kW-hr Nate Lewis, Caltech

8. Energy Costs Brazil Europe $0.05/kW-hr www.undp.org/seed/eap/activities/wea Nate Lewis, Caltech

9. Wind Energy Potential in the USA

10. Electric Potential of Wind http://www.nrel.gov/wind/ potential.html In 1999, U.S consumed 3.45 trillion kW-hr of Electricity = 0.39 TW Nate Lewis, Caltech

11. Wind Energy Advantages: supplemental power in windy areas; best alternative for individual homeowner Disadvantages: Highly variable source; relatively low efficiency (30% ?); more power than is needed is produced when the wind blows; efficient energy storage is thus required http://www.bullnet.co.uk/shops/test/wind.htm Ken Pedrotti, EE80T (winter quarter)

12. Significant potential in US Great Plains, inner Mongolia and northwest China U.S.: Use 6% of land suitable for wind energy development; practical electrical generation potential of ≈0.5 TW Globally: Theoretical: 27% of earth’s land surface is class 3 (250-300 W/m 2 at 50 m) or greater If use entire area, electricity generation potential of 50 TW Practical: 2 TW electrical generation potential (4% utilization of ≥class 3 land area) Off-shore potential is larger but must be close to grid to be interesting; (no installation > 20 km offshore now) Electric Potential of Wind Nate Lewis, Caltech

13. Relatively mature technology Distribution system not now suitable for balancing sources vs end use demand sites Inherently produces electricity, not heat; perhaps cheapest stored using compressed air ($0.01 kW-hr) Electric Potential of Wind Nate Lewis, Caltech

14. Solar Cell Ken Pedrotti, EE80T (winter quarter)

15. Solar Intensity http://www.wipp.carlsbad.nm.us/science/energy/solarpower.htm Ken Pedrotti, EE80T (winter quarter)

16. Hydro Power Advantages: No pollution; Very high efficiency (80%); little waste heat; low cost per KWH; can adjust KWH output to peak loads; recreation dollars Disadvantages: Fish are endangered species; Sediment buildup and dam failure; changes watershed characteristics; alters hydrological cycle http://zebu.uoregon.edu/2001/ph162/l1.html

17. Globally Gross theoretical potential 4.6 TW Technically feasible potential 1.5 TW Economically feasible potential 0.9 TW Installed capacity in 1997 0.6 TW Production in 1997 0.3 TW (can get to 80% capacity in some cases) Source: WEA 2000 Hydroelectric Energy Potential Nate Lewis, Caltech

18. Hydrogen Burning Advantages: No waste products; very high energy density; good for space heating Disadvantages: No naturally occurring sources of Hydogren; needs to be separated from water via electrolysis which takes a lot of energy; Hydrogen needs to be liquified for transport - takes more energy. Is there any net gain? See EE80J (spring quarter)

19. Geothermal Advantages: very high efficiency; low initial costs since you already got steam 200C at 10km depth Disadvantages: non- renewable (more is taken out than can be put in by nature); highly local resource Ken Pedrotti, EE80T (winter quarter)

20. Geothermal Energy Potential Ken Pedrotti, EE80T (winter quarter)

21. Geothermal Energy Potential Mean terrestrial geothermal flux at earth’s surface 0.057 W/m 2 Total continental geothermal energy potential 11.6 TW Oceanic geothermal energy potential 30 TW Wells “run out of steam” in 5 years Power from a good geothermal well (pair) 5 MW Power from typical Saudi oil well500 MW Needs drilling technology breakthrough (from exponential $/m to linear $/m) to become economical) Nate Lewis, Caltech

22. Energy from the Oceans? Tides CurrentsThermal Differences Waves Ken Pedrotti, EE80T (winter quarter)

23. Ocean Thermal Energy Conversion Advantages: enormous energy flows; steady flow for decades; can be used on large scale; exploits natural temperature gradients in the ocean Disadvantages: Enormous engineering effort; Extremely high cost; Damage to coastal environments? Nate Lewis, Caltech

24. Tidal Energy Advantages: Steady source; energy extracted from the potential and kinetic energy of the earth-sun- moon system; can exploit bore tides for maximum efficiency Disadvantages: low duty cycle due to intermittent tidal flow; huge modification of coastal environment; very high costs for low duty cycle source Ken Pedrotti, EE80T (winter quarter)

25. Biomass Advantages: Biomass waste (wood products, sewage, paper, etc) are natural by products of our society; reuse as an energy source would be good. Definite co-generation possibilities. Maybe practical for individual landowner. Disadvantages: Particulate pollution from biomass burners; transport not possible due to moisture content; unclear if growing biomass just for burning use is energy efficient. Large scale facilities are likely impractical. Ken Pedrotti, EE80T (winter quarter)

26. Global: Top Down Requires Large Areas Because Inefficient (0.3%) 3 TW requires ≈ 600 million hectares = 6x10 12 m 2 20 TW requires ≈ 4x10 13 m 2 Total land area of earth: 1.3x10 14 m 2 Hence requires 4/13 = 31% of total land area Biomass Energy Potential Nate Lewis, Caltech

27. Conservation Aerogel Thermal Insulation EE80J (spring quarter)

28. Prius Power Train Ken Pedrotti, EE80T (winter quarter)

29. Solar Energy Advantages: Always there; no pollution Disadvantages: Low efficiency (5-15%); Very high initial costs; lack of adequate storage materials (batteries); High cost to the consumer www.fantascienza.net/femino/ MCCALL/MCCALL13.html americanhistory.si.edu/.../ images/gallry53.htm Solar 1, Barstow California 1993 Future Solar Farm? Ken Pedrotti, EE80T (winter quarter)

30. Theoretical: 1.2x10 5 TW solar energy potential (1.76 x10 5 TW striking Earth; 0.30 Global mean albedo) Energy in 1 hr of sunlight  14 TW for a year Practical: ≈ 600 TW solar energy potential (50 TW - 1500 TW depending on land fraction etc.; WEA 2000) Onshore electricity generation potential of ≈60 TW (10% conversion efficiency): Photosynthesis: 90 TW Solar Energy Potential Nate Lewis, Caltech

31. Roughly equal global energy use in each major sector: transportation, residential, transformation, industrial World market: 1.6 TW space heating; 0.3 TW hot water; 1.3 TW process heat (solar crop drying: ≈ 0.05 TW) Temporal mismatch between source and demand requires storage (  S) yields high heat production costs: ($0.03-$0.20)/kW-hr High-T solar thermal: currently lowest cost solar electric source ($0.12-0.18/kW-hr); potential to be competitive with fossil energy in long term, but needs large areas in sunbelt Solar-to-electric efficiency 18-20% (research in thermochemical fuels: hydrogen, syn gas, metals) Solar Thermal, 2001 Nate Lewis, Caltech

32. 1.2x10 5 TW of solar energy potential globally Generating 2x10 1 TW with 10% efficient solar farms requires 2x10 2 /1.2x10 5 = 0.16% of Globe = 8x10 11 m 2 (i.e., 8.8 % of U.S.A) Generating 1.2x10 1 TW (1998 Global Primary Power) requires 1.2x10 2 /1.2x10 5 = 0.10% of Globe = 5x10 11 m 2 (i.e., 5.5% of U.S.A.) Solar Land Area Requirements Nate Lewis, Caltech

33. Solar Land Area Requirements 3 TW Nate Lewis, Caltech

34. Solar Land Area Requirements 6 Boxes at 3.3 TW Each Nate Lewis, Caltech

35. Solar Power Sattelites One suggestion for energy in the future is to Ken Pedrotti, EE80T (winter quarter)

36. Land with Crop Production Potential, 1990: 2.45x10 13 m 2 Cultivated Land, 1990: 0.897 x10 13 m 2 Additional Land needed to support 9 billion people in 2050: 0.416x10 13 m 2 Remaining land available for biomass energy: 1.28x10 13 m 2 At 8.5-15 oven dry tonnes/hectare/year and 20 GJ higher heating value per dry tonne, energy potential is 7-12 TW Perhaps 5-7 TW by 2050 through biomass (recall: $1.5-4/GJ) Possible/likely that this is water resource limited Challenges: cellulose to ethanol; ethanol fuel cells Biomass Energy Potential Global: Bottom Up Nate Lewis, Caltech