Renewable Energy Sources

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
Radiation Cloud form Chernobyl on April 27th

• http//www.worldprocessor.com/53.htm

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?
Wind
Biomass
Solar
Geothermal
From the Oceans
Hydroelectric

• http//zebu.uoregon.edu/2001/ph162/l14.html

7
Today Production Cost of Electricity
(in the U.S. in 2002)
25-50
Cost, /kW-hr
6-7
5-7
6-8
2.3-5.0
1-4
Nate Lewis, Caltech
8
Energy Costs
0.05/kW-hr
Europe
Brazil
www.undp.org/seed/eap/activities/wea
Nate Lewis, Caltech
9
Wind Energy Potential in the USA
10
Electric Potential of Wind
In 1999, U.S consumed 3.45 trillion kW-hr
of Electricity 0.39 TW
http//www.nrel.gov/wind/potential.html
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
Electric Potential of Wind

• 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 earths land surface is class
  3 (250-300 W/m2 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 gt 20
  km offshore now)

Nate Lewis, Caltech
13
Electric Potential of Wind

• 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)

Nate Lewis, Caltech
14
Solar Cell
Ken Pedrotti, EE80T (winter quarter)
15
Solar Intensity

• http//www.wipp.carlsbad.nm.us/science/energy/sola
  rpower.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
Hydroelectric Energy Potential

• 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

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 earths
  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
22
Energy from the Oceans?
Currents
Thermal Differences
Tides
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
Biomass Energy Potential

• 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

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

Solar 1, Barstow California 1993
Future Solar Farm?
www.fantascienza.net/femino/ MCCALL/MCCALL13.html
Ken Pedrotti, EE80T (winter quarter)
americanhistory.si.edu/.../ images/gallry53.htm
30
Solar Energy Potential

• 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

Nate Lewis, Caltech
31
Solar Thermal, 2001

• 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
• (DS) 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)

Nate Lewis, Caltech
32
Solar Land Area Requirements

• 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.)

Nate Lewis, Caltech
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Solar Land Area Requirements
3 TW
Nate Lewis, Caltech
34
Solar Land Area Requirements
6 Boxes at 3.3 TW Each
Nate Lewis, Caltech
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Solar Power Sattelites
                                                
                                  One suggestion
for energy in the future is to
Ken Pedrotti, EE80T (winter quarter)
36
Biomass Energy Potential
Global Bottom Up

• 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

Nate Lewis, Caltech