NateLewis_Symposium2009

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April 18-21, 2005

Basic Research Needs for

Solar Energy Utilization

Basic Research Needs for

Solar Energy UtilizationReport of the Basic Energy Sciences Workshop on Solar Energy

Utilization

Report of the Basic Energy Sciences Workshop on Solar Energy

Utilization

Nathan S. LewisDivision of Chemistry and ChemicalEngineering

California Institute of Technology

Pasadena, CA 91125

with

George Crabtree, Argonne

Arthur Nozik, NRELMike Wasielewski, NU

Paul Alivisatos, UC-Berkeley

Nathan S. LewisDivision of Chemistry and ChemicalEngineering

California Institute of Technology

Pasadena, CA 91125

with

George Crabtree, Argonne

Arthur Nozik, NRELMike Wasielewski, NU

Paul Alivisatos, UC-Berkeley


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BES Workshop on Basic Research Needs forSolar Energy Utilization April 21-24, 2005

Workshop Chair: Nathan Lewis, CaltechCo-chair: George Crabtree, Argonne

Panel ChairsArthur Nozik, NREL: Solar ElectricMike Wasielewski, NU: Solar Fuel

Paul Alivisatos, UC-Berkeley: Solar Thermal

Plenary Speakers

Pat Dehmer, DOE/BESNathan Lewis, CaltechJeff Mazer, DOE/EEREMarty Hoffert, NYU

Tom Feist, GE

200 participantsuniversities, national labs, industry

US, Europe, AsiaEERE, SC, BES

ChargeTo identify basic researchneeds and opportunities in solar

electric, fuels, thermal andrelated areas, with a focus on

new, emerging and scientifically

challenging areas that have thepotential for significant impact

in science and technologies.

TopicsPhotovoltaics

PhotoelectrochemistryBio-inspired Photochemistry

Natural Photosynthetic SystemsPhotocatalytic Reactions

Bio Fuels

Heat Conversion & UtilizationElementary ProcessesMaterials Synthesis

New Tools


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Basic Research Needs for Solar Energy

The Sun is a singular solution to our future energy needs- capacity dwarfs fossil, nuclear, wind . . .

- sunlight delivers more energy in one hourthan the earth uses in one year

- free of greenhouse gases and pollutants- secure from geo-political constraints

Enormous gap between our tiny use

of solar energy and its immense potential- Incremental advances in todays technology

will not bridge the gap

- Conceptual breakthroughs are needed that come

only from high risk-high payoff basic research

Interdisciplinary research is required

physics, chemistry, biology, materials, nanoscience

Basic and applied science should couple seamlessly


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World Energy Demand

EIA Intl Energy Outlook 2004

http://www.eia.doe.gov/oiaf/ieo/index.html

0

10

20

30

40

50

%

World Fuel Mix 2001oil

gas coal

nucl renew

85% fossil

2100: 40-50 TW2050: 25-30 TW

0.00

5.00

10.00

15.00

20.00

25.00

1970 1990 2010 2030

TW

World Energy Demand total

industrial

developing

US

ee/fsu

energy gap

~ 14 TW by 2050~ 33 TW by 2100

Hoffert et al Nature 395, 883,1998


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The Energy Gap

~ 14 TW of additional power by 2050 ~ 33 TW of additional power by 2100

2004 capacity: 13 TW

fossil energyafter oil production peaks, switch to gas and coal

capture/store 22 Gtonnes of CO2/yr (current emissions)

12,500 km3 at atmospheric pressure = volume of Lake Superior

600 times CO2 injected in oil wells/yr to spur production

100 times the natural gas drawn in and out of geologic storage/yr to smoothdemand

20,000 times CO2 stored/yr in Norways Sleipner offshore reservior

no leaks: 1% leak rate nullifies storage in 100 yrs

nuclear energy14,000 1 GWe fission reactors - 1 new reactor/day for 38 years


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Renewable Energy

Solar1.2 x 105 TW at Earth surface

>> 600 TW practical

Biomass5-7 TW grossall cultivatableland not used

for food

Hydroelectric

Geothermal

Wind2-4 TW extractable

4.6 TW gross1.6 TW technically feasible0.9 TW economically feasible0.6 TW installed capacity

12 TW gross over landsmall fraction recoverable

Tide/OceanCurrents2 TW gross

energy gap~ 14 TW by 2050~ 33 TW by 2100


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Solar Energy Utilization

Solar Electric Solar Fuel Solar Thermal

.001 TW PV$0.30/kWh w/o storage

CO2

sugar

H2O

O2

e-

h

+NCO

NCH3

N

N

N

NHH

H

naturalphotosynthesis

artificialphotosynthesis

50 - 200 Cspace, water

heating

500 - 3000 Cheat engines

electricity generationprocess heat

1.5 TW electricity$0.03-$0.06/kWh (fossil)

1.4 TW solar fuel (biomass)

~ 14 TW additional energy by 2050

0.002 TW

11 TW fossil fuel(present use) 2 TWspace and water

heating

H2O

O2CO2

H2, CH4CH3OH


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Solar Energy Challenges

Solar electricSolar fuels

Solar thermalCross-cutting research


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Solar Electric

Despite 30-40% growth rate in installation,

photovoltaics generate

lessthan 0.1% of our electricitylessthan 0.01% of total energy

Decrease cost/watt by a factor 10 - 20 to becompetitive with fossil electricity (without storage)

Find effective method for storageof photovoltaic-

generated electricity


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Cost of Solar Electric Power

competitive electric power: $0.40/Wp = $0.02/kWh

competitive primary power: $0.20/Wp = $0.01/kWh

assuming no cost for storage

I: bulk Si

II: thin filmdye-sensitizedorganic

III: next generationCost $/m2

$0.10/Wp $0.20/Wp $0.50/Wp

Efficiency%

20

40

60

80

100

100 200 300 400 500

$1.00/Wp

$3.50/Wp

Thermodynamic

limit at 1 sun

Shockley - Queisserlimit: single junction

module cost onlydouble for balance of system


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Revolutionary Photovoltaics: 50% Efficient Solar Cells

present technology: 32% limit for single junction one exciton per photon relaxation to band edge

multiple junctions multiple gaps multiple excitonsper photon

3 I

hot carriers

3 V

rich variety of new physical phenomenaunderstand and implement

Eg

lost toheat


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Organic Photovoltaics: Plastic Photocells

opportunitiesinexpensive materials, conformal coating, self-assembling fabrication,

wide choice of molecular structures, cheap solar paint

challengeslow efficiency (2-5%), high defect density, low mobility, full

absorption spectrum, nanostructured architecture

donor-acceptor junction

polymer donorMDMO-PPV

fullerene acceptorPCBM

O

O

(

)n

O

OMe

O

OMe


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Large Area Si Rod ArraysLarge Area Si Rod Arrays

Large area arrays (> 1 cm2)transferred in one piece.


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Solar electric

Solar fuelsSolar thermal

Cross-cutting research


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Solar Fuels: Solving the Storage Problem

Biomass inefficient: too much land area.

Increase efficiency 5 - 10 times

Designer plants and bacteria for designer fuels:

H2, CH4, methanol and ethanol

Develop artificial photosynthesis


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Leveraging Photosynthesis for Efficient Energy Production

photosynthesis converts ~ 100 TW of sunlight to sugars: natures fuel low efficiency (< 1%) requires too much land area

Modify the biochemistry of plants and bacteria

- improve efficiency by a factorof 510

- produce a convenient fuel

methanol, ethanol, H2, CH4

Scientific Challenges- understand and modify genetically controlled biochemistry that limits growth- elucidate plant cell wall structure and its efficient conversion to ethanol or other fuels- capture high efficiency early steps of photosynthesis to produce fuels like ethanol and H2- modify bacteria to more efficiently produce fuels

- improved catalysts for biofuels production

hydrogenase2H+ + 2e- H2

switchgrass

10

chlamydomonas moewusii


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Efficient Solar Water Splitting

demonstrated efficiencies 10-18% in laboratory

Scientific Challenges cheap materials that are robust in water

catalysts for the redox reactions at each electrode

nanoscale architecture for electron excitation

transfer

reaction

+

-

H2O2


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NanorodbasedMembraneOffersSeveralAdvantages

TandemjunctionsystemIncreasedlightabsorptionNanorod

geometryorthogonalizes

directionsof

lightabsorptionandcarriercollectionLongnanorods

canabsorballincidentlight

Carriersneedonlytravelradially

tothenanorod

sidewallstobeseparatedandcollectedGreaterflexibilityinmaterialsselection

Potentialcandidates:WO3

andSi


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o ar- owere a a ys s or ueFormation

hydrogenase2H+ + 2e- H2

10

chlamydomonas moewusii

2 H2O

O2

4e-

4H+

CO2

HCOOHCH3OHH2, CH4

Cat Cat

oxidation reduction

photosystem II


20/32

Solar electric

Solar fuels




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Solar Thermal

heat is the first link in our existing energy networks solar heat replaces combustion heat from fossil fuels

solar steam turbines currently produce the lowest cost solar electricity

challenges:new uses for solar heatstore solar heat for later distribution

fuel heatmechanical

motion electricity

space heat

process heat


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Solar Thermochemical Fuel Production

high-temperature hydrogen generation500 C - 3000 C

Scientific Challengeshigh temperature reaction kinetics of

- metal oxide decomposition- fossil fuel chemistry

robust chemical reactor designs and materials

fossil fuels

gas, oil, coal

SolarReforming

SolarDecomposition

SolarGasification

CO2, CSequestration

Solar H2

concentrated solarpower

Solar ReactorMxOy

x M +y/2 O2

Hydrolyser

x M + y H2O

MxOy + yH2

H2

M

MxOy

MxOy

H2O

1/2O2

concentratedsolar power

A. Streinfeld, Solar Energy, 78,603 (2005)


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Thermoelectric Conversion

TAGS

0 200 400 600 800 1000 1200 1400RT

2.5

1.5

0.5

ZT

CsBi4

Te6

Bi2Te3

LaFe3CoSb12

Zn4Sb3

Si Ge

PbTe

Temperature (K)

Bi2Te3/Sb2Te3superlattice

PbTe/PbSesuperlattice

LAST-18AgPbAgPb1818SbTeSbTe2020

figure of merit: ZT ~ (/) T

ZT ~ 3: efficiency ~ heat engines

no moving parts

Scientific Challenges

increase electrical conductivitydecrease thermal conductivity

nanoscale architecturesinterfaces block heat transport

confinement tunes density of statesdoping adjusts Fermi level

nanowire superlattice

thermal gradient electricity


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Solar electricSolar fuels




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Molecular Self-Assembly at All Length Scales

Scientific Challenges- innovative architectures for coupling light-harvesting, redox, and catalytic components

- understanding electronic and molecular interactions responsible for self-assembly

- understanding the reactivity of hybrid molecular materials on many length scales

The major cost of solar energy conversion is materials fabrication

Self-assembly is a route to cheap, efficient, functional production

biological physical


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Defect Tolerance and Self-repair

Understand defect formation

in photovoltaic materials and

self-repair mechanisms inphotosynthesis

Achieve defect tolerance andactive self-repair in solar

energy conversion devices,

enabling 2030 year operation

the water splitting protein in Photosystem IIis replaced every hour!


27/32

Nanoscience

N

theory and modeling

multi-node computer clustersdensity functional theory10 000 atom assemblies

manipulation of photons, electrons, and molecules

quantum dot solar cells

artificialphotosynthesis

naturalphotosynthesis

nanostructuredthermoelectrics

nanoscale architectures

top down lithographybottom up self-assemblymulti-scale integration

characterization

scanning probeselectrons, neutrons, x-rays

smaller length and time scales

Solar energy is interdisciplinary nanoscience

TiO2nanocrystals

adsorbeddye

liquidelectrolyte

conductingglass

transparent

electrode


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Perspective

The Energy Challenge~ 14 TW by 2050~ 33 TW by 2100

13 TW in 2004

Solar Potential125,000 TW at earths surfaceat least 600 TW practical

Breakthrough basic research neededSolar energy is a young science

- spurred by 1970s energy crises

- fossil energy science spurred by industrial revolution - 1750s

solar energy horizon is distant and unexplored


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Preview

Grand energy challenge- double demand by 2050, triple demand by 2100

Sunlight is a singular energy resource- capacity, environmental impact, geo-political security

Breakthrough research directions for mature solarenergy- solar electric

- solar fuels

- solar thermal


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Fossil: Supply and Security

EIA: http://tonto.eia.doe.gov/FTPROOT/

presentations/long_term_supply/index.htm

1900 1950 2000 2050 2100

Bbbl/yr

10

20

30

40

50World OilProduction

2016

2037

2% demand growth

ultimate recovery:

3000 Bbbl

When Will Production Peak?

gas: beyond oil

coal: > 200 yrsproduction peak

demand exceeds supply

price increasesgeo-political restrictions

World Oil Reserves/Consumption2001

OPEC: Venezuela, Iran, Iraq, Kuwait, Qatar, Saudi Arabia,

United Arab Emirates, Algeria, Libya, Nigeria, and Indonesiahttp://www.eere.energy.gov/vehiclesandfuels/facts/2004/fcvt_fotw336.shtml

unequal supply insecure access


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Fossil: Climate Change

Relaxation time

transport of CO2or heat to deepocean: 400 - >3000 years

Intergovernmental Panel on Climate Change, 2001http://www.ipcc.ch

N. Oreskes, Science306, 1686, 2004

D. A. Stainforth et al, Nature433, 403, 2005

Climate Change 2001: T he Scientific Basis, Fig 2.22

12001000 1400 1600 1800 2000

240

260

280

300

320

340

360

380

Year AD

Atmosp

heric

CO

2(ppmv)

Temperature(C)

- 1.5

- 1.0

- 0.5

0

0.5

1.0

1.5

-- CO2-- Global Mean Temp300

400

500

600

700

800

- 8

- 4

0

+ 4

400 300 200 100Thousands of years before present

(Ky BP)

0

Trelative

to

present(

C)

CH4(ppmv)

-- CO2-- CH4--

T

325

300

275

250

225

200

175

CO2(ppmv)

CO2in 2004: 380 ppmv


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photosystem II

Biology: protein structures dynamically control energy and charge flow Smart matrices: adapt biological paradigm to artificial systems

Scientific Challenges engineer tailored active environments with bio-inspired components

novel experiments to characterize the coupling among matrix, charge, and energy

multi-scale theory of charge and energy transfer by molecular assemblies

design electronic and structural pathways for efficient formation of solar fuels

Smart Matrices for Solar Fuel Production

h

chargechargeenergy energy

h

smart matrices carryenergy and charge

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