GWC Solar2 1 06

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Solar Energy Challenges and Opportunities: 

Solar Energy Challenges and Opportunities with Nathan Lewis, Caltech Arthur Nozik, NREL Michael Wasielewski, Northwestern Paul Alivisatos, UC-Berkeley George Crabtree Materials Science Division Argonne National Laboratory


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

World Energy Demand: 

World Energy Demand EIA Intl Energy Outlook 2004 energy gap ~ 14 TW by 2050 ~ 33 TW by 2100 Hoffert et al Nature 395, 883,1998

Fossil: Supply and Security: 

Fossil: Supply and Security EIA: presentations/long_term_supply/index.htm R. Kerr, Science 310, 1106 (2005) When Will Production Peak? gas: beyond oil coal: > 200 yrs production peak demand exceeds supply price increases geo-political restrictions World Oil Reserves/Consumption 2001 OPEC: Venezuela, Iran, Iraq, Kuwait, Qatar, Saudi Arabia, United Arab Emirates, Algeria, Libya, Nigeria, and Indonesia uneven distribution  insecure access

Fossil: Climate Change: 

Fossil: Climate Change J. R. Petit et al, Nature 399, 429, 1999 Intergovernmental Panel on Climate Change, 2001 N. Oreskes, Science 306, 1686, 2004 D. A. Stainforth et al, Nature 433, 403, 2005 Climate Change 2001: T he Scientific Basis, Fig 2.22

The Energy Alternatives: 

The Energy Alternatives Fossil Nuclear Renewable Fusion energy gap ~ 14 TW by 2050 ~ 33 TW by 2100 10 TW = 10,000 1 GW power plants 1 new power plant/day for 27 years no single solution diversity of energy sources required

Renewable Energy: 

Renewable Energy Solar 1.2 x 105 TW on Earth’s surface 36,000 TW on land (world) 2,200 TW on land (US) Biomass 5-7 TW gross (world) 0.29% efficiency for all cultivatable land not used for food Hydroelectric Geothermal Wind 2-4 TW extractable 4.6 TW gross (world) 1.6 TW technically feasible 0.6 TW installed capacity 0.33 gross (US) 9.7 TW gross (world) 0.6 TW gross (US) (small fraction technically feasible) Tide/Ocean Currents 2 TW gross energy gap ~ 14 TW by 2050 ~ 33 TW by 2100

Solar Energy Utilization: 

Solar Energy Utilization .0002 TW PV (world) .00003 TW PV (US) $0.30/kWh w/o storage natural photosynthesis artificial photosynthesis 50 - 200 °C space, water heating 500 - 3000 °C heat engines electricity generation process heat 1.5 TW electricity (world) $0.03-$0.06/kWh (fossil) 1.4 TW biomass (world) 0.2 TW biomass sustainable (world) 0.006 TW (world) 11 TW fossil fuel (present use) 2 TW space and water heating (world)

BES Workshop on Basic Research Needs for Solar Energy Utilization: 

BES Workshop on Basic Research Needs for Solar Energy Utilization April 21-24, 2005 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 Plenary Speakers Pat Dehmer, DOE/BES Nathan Lewis, Caltech Jeff Mazer, DOE/EERE Marty Hoffert, NYU Tom Feist, GE 200 participants universities, national labs, industry US, Europe, Asia EERE, SC, BES Topics Photovoltaics Photoelectrochemistry Bio-inspired Photochemistry Natural Photosynthetic Systems Photocatalytic Reactions Bio Fuels Heat Conversion & Utilization Elementary Processes Materials Synthesis New Tools

Basic Research Needs for Solar Energy: 

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 Basic and applied science should couple seamlessly

Solar Energy Challenges: 

Solar Energy Challenges Solar electric Solar fuels Solar thermal Cross-cutting research

Solar Electric: 

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


Cost of Solar Electric Power I: bulk Si II: thin film dye-sensitized organic III: next generation module cost only double for balance of system


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 excitons per photon nanoscale formats


Organic Photovoltaics: Plastic Photocells 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 donor-acceptor junction polymer donor MDMO-PPV fullerene acceptor PCBM

Solar Energy Challenges: 

Solar Energy Challenges Solar electric Solar fuels Solar thermal Cross-cutting research

Solar Fuels: Solving the Storage Problem: 

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 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 hydrogenase 2H+ + 2e-  H2 switchgrass


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 smart matrices carry energy and charge


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

Solar-Powered Catalysts for Fuel Formation: 

Solar-Powered Catalysts for Fuel Formation new catalysts targeted for H2, CH4, methanol and ethanol are needed Prototype Water Splitting Catalyst multi-electron transfer coordinated proton transfer bond rearrangement “uphill” reactions enabled by sunlight simple reactants, complex products spatial-temporal manipulation of electrons, protons, geometry

Solar Energy Challenges: 

Solar electric Solar fuels Solar thermal Cross-cutting research Solar Energy Challenges

Solar Thermal: 

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 heat store solar heat for later distribution


Solar Thermochemical Fuel Production high-temperature hydrogen generation 500 °C - 3000 °C Scientific Challenges high temperature reaction kinetics of - metal oxide decomposition - fossil fuel chemistry robust chemical reactor designs and materials A. Streinfeld, Solar Energy, 78,603 (2005)

Thermoelectric Conversion: 

Thermoelectric Conversion figure of merit: ZT ~ ( /) T ZT ~ 3: efficiency ~ heat engines no moving parts Scientific Challenges increase electrical conductivity decrease thermal conductivity nanoscale architectures interfaces block heat transport confinement tunes density of states doping adjusts Fermi level nanowire superlattice thermal gradient  electricity Mercouri Kanatzidis

Solar Energy Challenges: 

Solar electric Solar fuels Solar thermal Cross-cutting research Solar Energy Challenges


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

Defect Tolerance and Self-repair: 

Defect Tolerance and Self-repair Understand defect formation in photovoltaic materials and self-repair mechanisms in photosynthesis Achieve defect tolerance and active self-repair in solar energy conversion devices, enabling 20–30 year operation the water splitting protein in Photosystem II is replaced every hour!


Nanoscience theory and modeling multi-node computer clusters density functional theory 10 000 atom assemblies manipulation of photons, electrons, and molecules quantum dot solar cells artificial photosynthesis natural photosynthesis nanostructured thermoelectrics nanoscale architectures top-down lithography bottom-up self-assembly multi-scale integration characterization scanning probes electrons, neutrons, x-rays smaller length and time scales


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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