1 A. Shakouri 3/25/2009 Overview of Renewable Energy Sources Ali Shakouri Baskin School of...

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A. Shakouri 3/25/2009

Overview of Renewable Energy Sources

Ali ShakouriBaskin School of Engineering

University of California Santa Cruzhttp://quantum.soe.ucsc.edu/

Philips Research Lab, Eindhoven, Netherlands; 25 March 2009

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34%

8%

28%

6%

Share of WorldTotal

24%

38%

26%

23%

7%

6%

US Department of Energy; Energy Information Administration (2007)

World Marketed Energy Use by Fuel Type 1980-2030

13TW

2050: 25-30TW

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A. Shakouri 3/25/2009US Energy Consumption

DOE Energy Information Administration (2007)

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Martin Green, UNSW

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PV

1980 1990 2000 2010 2020

100

80

60

40

20

0

CO

E c

en

ts/k

Wh

Cost of Renewable EnergyLevelized cents/kWh in constant $2000

Wind

1980 1990 2000 2010 2020

CO

E c

en

ts/k

Wh

40

30

20

10

0

10

8

6

4

2

0

CO

E c

en

ts/k

Wh Geothermal

1980 1990 2000 2010 2020

Source: NREL Energy Analysis OfficeThese graphs are reflections of historical cost trends NOT precise annual historical data.Updated: October 2002

Biomass

1980 1990 2000 2010 2020

15

12

9

6

3

0

CO

E c

en

ts/k

WhSolar thermal

1980 1990 2000 2010 2020

70

60

50

40

30

2010

0

CO

E c

en

ts/k

Wh

Keith Wipke, NREL

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1,000,0001,000,000

100,000100,000

10,00010,000

1,0001,000

1010

100100

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1 Billion 1 Billion TransistorsTransistors

808680868028680286

i386i386i486i486

PentiumPentium®®

KK

PentiumPentium®® II II

’’7575 ’’8080 ’’8585 ’’9090 ’’9595 ’’0000 ’’0505 ’’1010

PentiumPentium®® III IIIPentiumPentium®® 4 4

’’1515

Microprocessor Evolution

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McMasters & Cummings, Journal of Aircraft, Jan-Feb 2002

Airplane Speed/Efficiency Evolution

US Energy Intensity (MJ) per available seat km

@ 160kg payload/seat

NLR-CR-2005-669;Peeters P.M., Middel J., Hoolhorst A.

Airplane Speed

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Vaclav Smil,Energy at the Crossroads, 2005

Felix’s forecasts of US energy consumption in year 2000 (early 1970’s)

Coal

Oil

Natural gas

Nuclear

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• 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 is class >3 => 50 TW Practical: 2 TW potential (4% utilization)

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

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A. Shakouri 3/25/2009Turbine Sizes

Trend toward bigger turbine sizesHelge Aagaard Madsen, DTU Riso

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http://www.eere.energy.gov/

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A. Shakouri 3/25/2009Offshore Wind Farm

Nysted, Denmark A. Shakouri 11/25/2008

EE 181 Renewable Energies in PracticeCA-Denmark Summer Program

2008

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A. Shakouri 3/25/2009Geothermal 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

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A. Shakouri 3/25/2009Energy from the Oceans?

Tides

Currents Thermal Differences

Ken Pedrotti, UCSC

Waves

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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

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Amount of land needed for 20 TW at 1% efficiency:

9% of land

Chris Somerville, UC Berkeley

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Farrell et al. (Science 311, 2006)

Corn Ethanol Greenhouse Gas Emission

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Steve Koonin, BP

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Dan Kammen, Berkeley

Biofuels

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Bioenergy and Sustainable Development, Ambuj D. Sagar, Sivan KarthaAnnual Review of Environment and Resources, Vol. 32: 131-167 (November 2007)

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• Theoretical: 1.2x105 TW solar energy potential

• Practical: ≈ 600 TW solar energy potential

• Onshore electricity generation potential of ≈60 TW (10%

conversion efficiency):

• Photosynthesis: 90 TW

• Generating 12 TW (1998 Global Primary Power) requires

0.1% of Globe = 5x1011 m2 (i.e., 5.5% of U.S.A.)

Solar Energy Potential

Nate Lewis, Caltech

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A. Shakouri 3/25/2009World Insolation

12 TW

6.0-6.9

4.0-4.9

2.0-2.9

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BoyleRenewable

Energy Sources

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Chris Somerville, UC Berkeley


From: Basic Research Needs for Solar Energy Utilization, DOE 2005

Potential of Carbon Free Energy Sources

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Vaclav SmilEnergy at the

Crossroads

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Specific Energy (Wh/kg)

Spe

cific

Pow

er (

W/k

g)

Combustion Engine

Energy Storage Options

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RejectedEnergy 61%

Lawrence Livermore National Lab., http://eed.llnl.gov/flow

Power ~3.3TW

1.3TW


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Biomass

Petroleum

Coal

Waste Energy

India’s Energy Consumption 2005

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A. Shakouri 3/25/2009Direct Conversion of Heat into ElectricityDirect Conversion of Heat into Electricity

)(

)()( 2

2

tyconductivithermal

tyconductivielectricalSeebeckZ

k

SZ

V~ S T

Electrical Conductor

Hot Cold

Efficiency function of thermoelectric figure-of-merit (Z)

Rload = RTE internal

T

VS

Seebeck coefficient(1821)

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Power Generation Efficiencies of Different Technologies

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

400 600 800 1000 1200

ZTm=0.5ZTm=1ZTm=2ZTm=3Carnot limit

Op

tima

l effi

cie

ncy

Thot

(K)

0.5

En

erg

y C

on

ve

rsio

n E

ffic

ien

cy

3

1

2

Carnot

Solar/ Rankine

Geothermal/ Organic Rankine

ZTavg=20Coal/ Rankine

Cement/ Org. Rankine

Solar/ Stirling

C. Vining 2008

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Radioisotope Thermoelectric Generators

(Voyager, Galileo, Cassini, …)

• 55 kg, 300 We, ‘only’ 7 % conversion efficiency

• But > 1,000,000,000,000 device hours without a single failure

B-doped Si0.78Ge0.22

P-doped Si0.78Ge0.22

B-doped Si0.63Ge0.36

P-doped Si0.63Ge0.36

Hot Shoe (Mo-Si)

Cold Shoe

n-type legp-type leg

SiGe unicoupleCronin Vining, ZT Services

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Which Materials To Choose for TE Modules?Which Materials To Choose for TE Modules?

SS2

Free carrier concentration

Thermal Conductivity

Lattice contribution

Electronic contribution

Seebeck Electrical Conductivity

Insulator Semiconductor Metal

For almost all materials, if doping is increased, electrical conductivity increases but Seebeck coefficient is reduced. Similarly ↔

ZT= S2/

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A. Shakouri 3/25/2009Microrefrigerators on a chip

Featured in Nature Science Update, Physics Today, AIP April 2001

• Monolithic integration on silicon• Tmax~4C at room temp. (7C at 100C)

UCSC, UCSB, HRL Labs

Relative Temp. (C)

50m1 µm

Hot Electron

Cold Electron

Nanoscale heat transport and microrefrigerators on a chip; A. Shakouri, Proceedings of IEEE, July 2006

J. Christofferson

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Hot Electron Filters in Hot Electron Filters in Metal/Semiconductor NanocompositesMetal/Semiconductor Nanocomposites

Assume: lattice=1W/mK, mobility ~10 cm2/Vs

Even with only modestly low lattice thermal conductivity and electron mobility of typical metals, ZT > 5 is theoretically possible

Fermi energy eV (↔ free electron concentration)

Planar Barrier

Metal/Semiconductor Nanostructure

• Need lattice-compatible composites with appropriate barrier heights

D. Vashaee, A. Shakouri;

Physical Review Letters, 2004

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ErAs Semi-metal Nanoparticles imbedded in InGaAs Semiconductor Matrix

ErAs dots are lattice-matched and incorporate without any visible defects in InGaAs despite different crystal structures (Cubic vs. Zinc-blende)

In,GaAs

Er

1nm

• “Random” ErAs particles ~ 2-3 nm

• Size is invariant to growth conditions

J. Zide et al. UCSB/UCSC

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Beating the Alloy Limit in Thermal Conductivity Beating the Alloy Limit in Thermal Conductivity ErAs:InErAs:In0.530.53GaGa0.470.47AsAs

Phonon scattering by ErAs nanoparticles 3-fold reduction in thermal conductivity beyond the alloy limit

InGaAs

0.3% ErAs:InGaAs

3% ErAs:InGaAs

6% ErAs:InGaAs

Nanoparticle

W. Kim et al. UCB/UCSB/UCSC

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A. Shakouri 3/25/2009Module Power generation results

140 m/140 m AlN

400 elements (10-20 microns ErAs:InGaAlAs thin films, 120x120m2)

G. Zeng, J. Bowers, et al. (UCSB, UCSC) Appl. Physics Letters 2006

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100 120 140

10 m module

20 m module

Ou

tpu

t P

ow

er (

W/c

m2)

T (K)

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A. Shakouri 3/25/2009Summary

• Significant amount of energy produced in the world is wasted in the form of heat (61% is US)

• Thermoelectric effects can be engineered via nanomaterials – Modify the average energy of moving electrons– Selective scattering of phonons w.r.t electrons

• Micro refrigerators on a chip (silicon based)• Localized cooling, Cooling power density > 500 W/cm2

• Metal semiconductor nanocomposites for direct conversion of heat into electricity

• Potential to reach 20-30% conversion efficiencies

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A. Shakouri 3/25/2009 A. Shakouri 11/25/2008

Nate Lewis, Caltech

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A. Shakouri 3/25/2009Plan B for EnergySeptember 2006; Scientific American; W. Wayt Gibbs

• WAVES AND TIDES (Reality factor 5)

• HIGH-ALTITUDE WIND (Reality factor 4)

• NANOTECH SOLAR CELLS (Reality factor 4)

• DESIGNER MICROBES (Reality factor 4)

• NUCLEAR FUSION (Reality factor 3)

• SPACE-BASED SOLAR (Reality factor 3)

• A GLOBAL SUPERGRID (Reality factor 2)

• SCI-FI SOLUTIONS (Reality factor 1)

– Cold Fusion and Bubble Fusion– Matter-Antimatter Reactors

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A. Shakouri 3/25/2009Can Renewables Save the World?

• Fossil fuels have excellent energy characteristics. • Wind/ geothermal are among the cheapest of

renewables. There is potential for significant growth but they can not solve our energy problem.

• Solar energy has the potential to provide all our energy needs.– Currently expensive; it is intermittent.

• Currently no clear options for large scale energy storage

• Biomass has the potential to provide part of transportation energy needs – Cellulosic biofuels and algaes are interesting but they

have not demonstrated large scale/long term potential. One has to consider the full ecosystem impact (water, food, etc.).

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John Bowers, UCSB

World Average

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Can Renewables Save the World?

• If our goal is to have a planet where everybody has a level of life similar to developed countries, energy need is enormous and it is not clear if we can do this by working on the supply side alone.

• Energy efficiency is important but it is not enough.• We need to consider changes in lifestyle, city

planning and social structure (transportation, lodging, grid).

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S. Koonin, Chief Scientist BPnrg.caltech.edu

Oil Resources

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Source: Hansen, Clim. Change, 68, 269, 2005.

400,000 years of greenhouse-gas & temperature history based on bubbles trapped in Antarctic ice

Last time CO2 >300 ppm was 25 million years ago.

John P. Holdren, 2006

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EE80J Renewable Energy SourcesSpring 2009, Also Summer 2009• Energy, power and thermodynamics• Home energy audit• Power plants, nuclear power• Solar energy • Wind energy, hydropower, geothermal • Biomass, hydrogen, fuel cells • Economics, Environmental and

Societal Impacts

CA/Denmark summer school (UCSC, UC Davis, UC Merced, Techn. Univ. Denmark, Roskilde) –Extensive field trips

EE181J Renewable Energies in Practice (July-August 2009)

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