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Renewable Energy Sources
Ali ShakouriElectrical Engineering Department
University of California Santa Cruzhttp://quantum.soe.ucsc.edu/
EE80S
Sustainability Engineering and Practice
October 17, 2007
The Sun Source of our Energy supply
Ken Pedrotti, EE80T (winter quarter)
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)
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)
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)
Are there Sustainable Solutions?
• http://zebu.uoregon.edu/2001/ph162/l14.html
Solar Biomass Wind
Hydroelectric Geothermal From the Oceans
(in the U.S. in 2002)
1-4 ¢ 2.3-5.0 ¢ 6-8 ¢ 5-7 ¢
Today: Production Cost of Electricity
0
5
10
15
20
25
Coal Gas Oil Wind Nuclear Solar
Cost6-7 ¢
25-50 ¢
Cos
t , ¢
/kW
-hr
Nate Lewis, Caltech
Energy Costs
0
2
4
6
8
10
12
14
$/GJ
Coal Oil Biomass ElectB
razi
l Eur
ope
$0.05/kW-hr
www.undp.org/seed/eap/activities/wea
Nate Lewis, Caltech
Wind Energy Potential in the USA
Electric Potential of Wind
http://www.nrel.gov/wind/potential.html
In 1999, U.S consumed3.45 trillion kW-hr ofElectricity =0.39 TW
Nate Lewis, Caltech
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)
• 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/m2 at 50 m) or greaterIf 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
• 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
Solar Cell
Ken Pedrotti, EE80T (winter quarter)
Solar Intensity
• http://www.wipp.carlsbad.nm.us/science/energy/solarpower.htm
Ken Pedrotti, EE80T (winter quarter)
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
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
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)
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)
Geothermal Energy Potential
Ken Pedrotti, EE80T (winter quarter)
Geothermal Energy Potential
• Mean terrestrial geothermal flux at earth’s surface 0.057 W/m2
• 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 well 500 MW• Needs drilling technology breakthrough (from exponential $/m to linear $/m) to become economical)
Nate Lewis, Caltech
Energy from the Oceans?
Tides
Currents Thermal Differences
Waves
Ken Pedrotti, EE80T (winter quarter)
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
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)
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)
Global: Top Down
• Requires Large Areas Because Inefficient (0.3%)
• 3 TW requires ≈ 600 million hectares = 6x1012 m2
• 20 TW requires ≈ 4x1013 m2
• Total land area of earth: 1.3x1014 m2
• Hence requires 4/13 = 31% of total land area
Biomass Energy Potential
Nate Lewis, Caltech
Conservation
Aerogel Thermal Insulation
EE80J (spring quarter)
Prius Power Train
Ken Pedrotti, EE80T (winter quarter)
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)
• Theoretical: 1.2x105 TW solar energy potential
(1.76 x105 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
• 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
• 1.2x105 TW of solar energy potential globally
• Generating 2x101 TW with 10% efficient solar farms requires
2x102/1.2x105 = 0.16% of Globe = 8x1011 m2 (i.e., 8.8 % of
U.S.A)
• Generating 1.2x101 TW (1998 Global Primary Power) requires
1.2x102/1.2x105= 0.10% of Globe = 5x1011 m2 (i.e., 5.5% of
U.S.A.)
Solar Land Area Requirements
Nate Lewis, Caltech
Solar Land Area Requirements
3 TW
Nate Lewis, Caltech
Solar Land Area Requirements
6 Boxes at 3.3 TW Each
Nate Lewis, Caltech
Solar Power Sattelites
One suggestion for energy in the future is to
Ken Pedrotti, EE80T (winter quarter)
• Land with Crop Production Potential, 1990: 2.45x1013 m2
• Cultivated Land, 1990: 0.897 x1013 m2
• Additional Land needed to support 9 billion people in 2050: 0.416x1013 m2
• Remaining land available for biomass energy: 1.28x1013 m2
• 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
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