Idea Transcript
Solar Energy Challenges and Opportunities George Crabtree Materials Science Division Argonne National Laboratory
with with
Nathan Nathan Lewis, Lewis, Caltech Caltech Arthur Arthur Nozik, Nozik, NREL NREL Michael Michael Wasielewski, Wasielewski, Northwestern Northwestern Paul Paul Alivisatos, Alivisatos, UC-Berkeley UC-Berkeley
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 solar energy - solar electric - solar fuels - solar thermal
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World Energy Demand 2100: 40-50 TW 2050: 25-30 TW
25.00 World Energy Demand
20.00
total
energy gap ~ 14 TW by 2050 ~ 33 TW by 2100
TW
15.00 industrial
10.00
developing
5.00
50
US ee/fsu
0.00 1990
2010
2030
30
gas
%
1970
World Fuel Mix 2001
oil
40
coal
20
nucl renew
10 0
85% fossil
EIA Intl Energy Outlook 2004 http://www.eia.doe.gov/oiaf/ieo/index.html
Hoffert et al Nature 395, 883,1998
Fossil: Supply and Security When Will Production Peak? Bbbl/yr
50 40 30 20
World Oil Production
2037
gas: beyond oil coal: > 200 yrs
2016
2% demand growth ultimate recovery: 3000 Bbbl
10 1900
1950
2000
2050
production peak demand exceeds supply price increases geo-political restrictions
2100
EIA: http://tonto.eia.doe.gov/FTPROOT/ presentations/long_term_supply/index.htm R. Kerr, Science 310, 1106 (2005)
World Oil Reserves/Consumption 2001
uneven distribution ⇒ insecure access http://www.eere.energy.gov/vehiclesandfuels/facts/2004/fcvt_fotw336.shtml
OPEC: Venezuela, Iran, Iraq, Kuwait, Qatar, Saudi Arabia, United Arab Emirates, Algeria, Libya, Nigeria, and Indonesia
2
Fossil: Climate Change CO2 CH4 (ppmv) (ppmv)
275
+ 4
0
600
250 225 200
500
- 4
400
- 8
300
100 400 200 300 Thousands of years before present (Ky BP) Climate Change 2001: T he Scientific Basis, Fig 2.22
J. R. Petit et al, Nature 399, 429, 1999 Intergovernmental Panel on Climate Change, 2001 http://www.ipcc.ch
N. Oreskes, Science 306, 1686, 2004 D. A. Stainforth et al, Nature 433, 403, 2005
0
1.5
380
-- CO2 -- Global Mean Temp
360 340
1.0 0.5
320
0
300
- 0.5
280 260
- 1.0
240
1000
1200
1600 1400 Year AD
1800
Temperature (°C)
175
Relaxation time transport of CO2 or heat to deep ocean: 400 - 1000 years
ΔT relative to present (°C)
300
-- CO2 -- CH4 -- ΔT
700
Atmospheric CO2 (ppmv)
325
CO2 in 2004: 380 ppmv
800
- 1.5
2000
The Energy Alternatives Fossil
energy gap ~ 14 TW by 2050 ~ 33 TW by 2100
Nuclear
Renewable
Fusion
10 TW = 10,000 1 GW power plants 1 new power plant/day for 27 years
no single solution diversity of energy sources required
3
Renewable Energy Solar
energy gap ~ 14 TW by 2050 ~ 33 TW by 2100
1.2 x 105 TW on Earth’s surface 36,000 TW on land (world) 2,200 TW on land (US)
Wind
Biomass
2-4 TW extractable
5-7 TW gross (world) 0.29% efficiency for all cultivatable land not used for food
Tide/Ocean Currents 2 TW gross
Hydroelectric 4.6 TW gross (world)
Geothermal
1.6 TW technically feasible 0.6 TW installed capacity
9.7 TW gross (world) 0.6 TW gross (US)
0.33 gross (US)
(small fraction technically feasible)
Solar Energy Utilization H2O N CH3 N HN H N N
h+
O2 CO2
sugar natural photosynthesis
Solar Electric .0002 TW PV (world) .00003 TW PV (US) $0.30/kWh w/o storage
1.5 TW electricity (world) $0.03-$0.06/kWh (fossil)
O2 CO2
H2, CH4 CH3OH
H NC O
e-
H2O
artificial photosynthesis
Solar Fuel 1.4 TW biomass (world) 0.2 TW biomass sustainable (world)
11 TW fossil fuel (present use) ~ 14 TW additional energy by 2050
50 - 200 °C space, water heating
500 - 3000 °C heat engines electricity generation process heat
Solar Thermal
0.006 TW (world)
2 TW space and water heating (world)
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BES Workshop on Basic Research Needs for April 21-24, 2005 Solar Energy Utilization Workshop Chair: Nathan Lewis, Caltech Co-chair: George Crabtree, Argonne
Panel Chairs
Arthur Nozik, NREL: Solar Electric Mike Wasielewski, NU: Solar Fuel Paul Alivisatos, UC-Berkeley: Solar Thermal Topics
Photovoltaics Photoelectrochemistry Bio-inspired Photochemistry Natural Photosynthetic Systems Photocatalytic Reactions Bio Fuels Heat Conversion & Utilization Elementary Processes Materials Synthesis New Tools
Plenary Speakers
Pat Dehmer, DOE/BES Nathan Lewis, Caltech Jeff Mazer, DOE/EERE Marty Hoffert, NYU Tom Feist, GE
Charge
To identify basic research needs and opportunities in solar electric, fuels, thermal and related areas, with a focus on new, emerging and scientifically challenging areas that have the potential for significant impact in science and technologies.
200 participants
universities, national labs, industry US, Europe, Asia EERE, SC, BES
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 hour than 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 today’s 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 http://www.sc.doe.gov/bes/reports/abstracts.html#SEU
• Basic and applied science should couple seamlessly
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Solar Energy Challenges
Solar electric Solar fuels Solar thermal Cross-cutting research
Solar Electric • Despite 30-40% growth rate in installation, photovoltaics generate less than 0.02% of world electricity (2001) less than 0.002% of world total energy (2001) • Decrease cost/watt by a factor 10 - 25 to be competitive with fossil electricity (without storage) • Find effective method for storage of photovoltaic-generated electricity
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Cost of Solar Electric Power 100
$0.10/Wp
$0.20/Wp
$0.50/Wp
Efficiency %
80 Thermodynamic limit at 1 sun
60 $1.00/Wp
40 Shockley - Queisser limit: single junction
20
module cost only double for balance of system
$3.50/Wp
100
200
300
400
I: bulk Si II: thin film dye-sensitized organic
500
Cost $/m2
III: next generation
competitive electric power: $0.40/Wp = $0.02/kWh competitive primary power: $0.20/Wp = $0.01/kWh
assuming no cost for storage
Revolutionary Photovoltaics: 50% Efficient Solar Cells present technology: 32% limit for • single junction • one exciton per photon • relaxation to band edge
lost to heat
3V
3I
Eg
nanoscale formats
multiple junctions
multiple gaps
multiple excitons per photon
hot carriers
rich variety of new physical phenomena challenge: understand and implement
7
Organic Photovoltaics: Plastic Photocells O
)n (
polymer donor MDMO-PPV
O
fullerene acceptor PCBM
OMe O
donor-acceptor junction
opportunities inexpensive materials, conformal coating, self-assembling fabrication, wide choice of molecular structures, “cheap solar paint” challenges low efficiency (2-5%), high defect density, low mobility, full absorption spectrum, nanostructured architecture
Solar Energy Challenges
Solar electric Solar fuels Solar 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
Leveraging Photosynthesis for Efficient Energy Production • photosynthesis converts ~ 100 TW of sunlight to sugars: nature’s fuel • low efficiency (< 1%) requires too much land area
Modify the biochemistry of plants and bacteria - improve efficiency by a factor of 5–10 - produce a convenient fuel methanol, ethanol, H2, CH4
chlamydomonas moewusii
10 µ
hydrogenase 2H+ + 2e- ⇔ H2 switchgrass -
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
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Smart Matrices for Solar Fuel Production • Biology: protein structures dynamically control energy and charge flow • Smart matrices: adapt biological paradigm to artificial systems
hν
energy
charge
hν
energy
charge
smart matrices carry energy and charge
photosystem II
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
Efficient Solar Water Splitting O2
H2
+
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
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Solar-Powered Catalysts for Fuel Formation oxidation 2 H2O
reduction CO2
4e-
Cat
“uphill” reactions enabled by sunlight simple reactants, complex products
Cat
O2
4H+ multi-electron transfer coordinated proton transfer bond rearrangement
HCOOH CH3OH H2, CH4
spatial-temporal manipulation of electrons, protons, geometry
new catalysts targeted for H2, CH4, methanol and ethanol are needed Prototype Water Splitting Catalyst
Solar Energy Challenges
Solar electric Solar fuels Solar thermal Cross-cutting research
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Solar Thermal space heat fuel
mechanical motion
heat
electricity
process heat
•
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 heat store solar heat for later distribution
Solar Thermochemical Fuel Production high-temperature hydrogen generation 500 °C - 3000 °C
concentrated solar power Mx Oy
H2 O
concentrated solar power
Solar Reactor Mx Oy ⇒ x M + y/2 O2
M
fossil fuels gas, oil, coal
1/2 O2 Solar Reforming
Hydrolyser x M + y H2O ⇒ MxOy + y H2
Solar Solar Decomposition Gasification
H2
Mx Oy
Scientific Challenges
CO2 , C Sequestration
Solar H2
high temperature reaction kinetics of - metal oxide decomposition - fossil fuel chemistry robust chemical reactor designs and materials A. Streinfeld, Solar Energy, 78,603 (2005)
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Thermoelectric Conversion thermal gradient ⇔ electricity figure of merit: ZT ~ (σ /κ) T ZT ~ 3: efficiency ~ heat engines no moving parts
2.5
Scientific Challenges
PbTe/PbSe superlattice
increase electrical conductivity decrease thermal conductivity ZT
Bi2Te3/Sb2Te3 superlattice
1.5
Zn4Sb3 TAGS
nanowire superlattice
nanoscale architectures interfaces block heat transport confinement tunes density of states doping adjusts Fermi level
LAST-18 AgPb18SbTe20
Si Ge
LaFe3CoSb12
CsBi4Te6
PbTe
0.5 Bi2Te3
0
200 RT 400
600
800
Mercouri Kanatzidis
1000
1200
1400
Temperature (K)
Solar Energy Challenges
Solar electric Solar fuels Solar thermal Cross-cutting research
13
Molecular Self-Assembly at All Length Scales The major cost of solar energy conversion is materials fabrication Self-assembly is a route to cheap, efficient, functional production
physical biological
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
Defect Tolerance and Self-repair • Understand defect formation in photovoltaic materials and self-repair mechanisms in photosynthesis
the water splitting protein in Photosystem II is replaced every hour!
•Achieve defect tolerance and active self-repair in solar energy conversion devices, enabling 20–30 year operation
14
Nanoscience manipulation of photons, electrons, and molecules TiO2 nanocrystals
artificial photosynthesis
adsorbed quantum dots
N
liquid electrolyte
natural photosynthesis
quantum dot solar cells
nanoscale architectures
characterization
nanostructured thermoelectrics
theory and modeling
top-down lithography scanning probes multi-node computer clusters bottom-up self-assembly electrons, neutrons, x-rays density functional theory multi-scale integration smaller length and time scales 10 000 atom assemblies Solar energy is interdisciplinary nanoscience
Perspective The Energy Challenge ~ 14 TW additional energy by 2050 ~ 33 TW additional energy by 2100 13 TW in 2004
Solar Potential 125,000 TW at earth’s surface 36,000 TW on land (world) 2,200 TW on land (US)
Breakthrough basic research needed Solar 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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