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