Basic Research Needs for Solar Energy Utilization - Office of ...

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A. Marti and A. Luque (Eds.), Next Generation Photovoltaics: High Efficiency through Full Spectrum Utilization. Institute of Physics, Bristol, UK (2004). R. Memming, Semiconductor Electrochemistry. Wiley-VCH, Weinheim, Germany (2001). National Academy of Engineering, Board on Energy and Environmental Systems, The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs. The National Academies Press, Washington, D.C. (2004). A.J. Nozik and R. Memming, “Physical Chemistry of Semiconductor-liquid Interfaces,” J. Phys. Chem. 100, 13061 (1996). A.J. Nozik, “Photoelectrochemistry: Applications to Solar Energy Conversion,” Annual Rev. I 29, 189 (1978). PV Energy Systems, PV News. P.D. Maycock (Ed.), Warrenton, Va. (2004). R.T. Ross and A.J. Nozik, “Efficiency of Hot-carrier Solar Energy Converters,” J. Appl. Phys. 53, 3813 (1982). W. Shockley and H.J. Queisser, “Detailed Balance Limit of Efficiency of p-n Junction Solar Cells,” J. Appl. Phys. 32, 510 (1961). T. Surek, “Crystal Growth and Materials Research in Photovoltaics,” J. Crystal Growth 275, 292 (2005). C.W. Tang, “2-Layer Organic Photovoltaic Cell,” Appl. Phys. Lett. 48, 183 (1986). G. Yu, J. Gao, J.C. Hummelen, F. Wudl, and A.J. Heeger, “Polymer Photovoltaic Cells: Enhanced Efficiencies via a Network of Internal Donor-acceptor Heterojunctions,” Science 270, 1789 (1995). 32
BASIC RESEARCH CHALLENGES FOR SOLAR FUELS Because of the day/night variation of the solar resource, the practical use of solar energy faces two overarching technological challenges: economically converting sunlight into useful energy, and storing and dispatching that converted energy to end users in an economical, convenient form. To provide base load power, solar electricity and any other solar energy conversion system will require a tightly integrated storage and distribution technology to provide energy to end users in accord with demand. Additionally, there must be a means to cost-effectively convert this energy into forms useful for transportation, residential, and industrial applications. Because these sectors currently use chemical fuels as their primary energy feedstock, one of the following three options must occur: (1) solar electricity must be converted into chemical fuels that could be used in the existing distribution and end-use infrastructure; (2) the distribution and end-use infrastructure must be converted to one that allows widespread, direct use of electricity, which also must be stored until use; or (3) solar energy must be directly converted into useful chemical fuels. Put simply, without cost-effective global transmission, storage, and/or fuel formation, solar electricity can only be a (large) niche market serving as a supplement for other primary sources of energy. Conversion of electricity into chemical fuels, through electrolysis of water to produce H2 and O2, is an existing technology. However, it is a very expensive method of making H2 (as discussed below), and the catalysts that are used in current electrolyzers cannot readily scale to the levels that would be needed to support a TW-level implementation of solar electricity use in H2 production. Direct production of fuels from sunlight is advantageous because it inherently provides a method for extracting energy during the night and for dispatching and distributing energy cost effectively in the existing infrastructure for use in the residential, industrial, and transportation sectors. The ability to use sunlight to produce CH4 or H2 from abundant, non-toxic resources such as CO2 and water, respectively, would revolutionize the economical, environmentally sound production of fuels. Photosynthetic solar energy conversion has produced the vast majority of the energy that fuels human society and sustains life on Earth. This global-scale, time-tested energy conversion and storage process produces all current biomass and, over geologic time, has produced all the fossil fuels available today. The drawback is that, with current plant types, a large-scale implementation of biomass as a primary energy source would require very large areas of land to make a material contribution to meeting current energy demands. Using the best-known plant for energy production, switchgrass, as an example, production of 10 TW of average power would require covering 10% of the land on Earth (i.e., essentially all of the cultivable land on Earth that is not currently used for agriculture) would have to be covered with biomass farms. Such a large deployment would also clearly stress our ability to provide fresh water to grow such crops; would constrain land use on a global scale; and would impose serious infrastructural constraints to effectively and constantly manage, harvest, and optimally exploit all of the crops over such a large land area. Hence, practical constraints dictate that (1) the efficiency of photosynthesis be increased so that less land area (likely by a factor of 5–10) is required and/or (2) that artificial photosynthetic systems be developed that either borrow components from natural systems or are inspired by the natural system’s components to produce useful chemical fuels directly from sunlight with higher efficiencies than the natural system and with an acceptably low cost. 33
Page 2 and 3: On the Cover: One route to harvesti
Page 4 and 5: Revisions, September 2005 p ix, par
Page 6 and 7: CONTENTS (CONT.) Appendix 4: Additi
Page 8 and 9: OEC oxygen-evolving complex PCET pr
Page 10 and 11: viii
Page 12 and 13: thin films, organic semiconductors,
Page 14 and 15: genetic sequencing, protein product
Page 17 and 18: INTRODUCTION The supply and demand
Page 19 and 20: showing promise to overcome them. T
Page 21: GLOBAL ENERGY RESOURCES 7
Page 24 and 25: energy can be exploited on the need
Page 27 and 28: BASIC RESEARCH CHALLENGES FOR SOLAR
Page 29 and 30: CONVERSION OF SUNLIGHT INTO ELECTRI
Page 31 and 32: PHYSICS OF PHOTOVOLTAIC CELLS Inorg
Page 33 and 34: Figure 4 Learning curve for PV prod
Page 35 and 36: Needs of Direct-gap, Thin-film Phot
Page 37 and 38: Figure 6 Current record efficiencie
Page 39 and 40: devices. The molecules and material
Page 41 and 42: Figure 8 Structure for high-efficie
Page 43 and 44: One critical property of the photoa
Page 45: PHOTOELECTROCHEMICAL STORAGE CELLS
Page 49 and 50: information about the proteins that
Page 51 and 52: convert it into H2 and liquid fuels
Page 53 and 54: charge separation ensures highly ef
Page 55 and 56: Efficient Photo-initiated Charge Se
Page 57 and 58: artificial RCs, have proven to be i
Page 59 and 60: CATALYSTS FOR CO2 REDUCTION Photo-d
Page 61 and 62: Upon photoexcitation, the electron
Page 63 and 64: (5) determining the physical and ch
Page 65 and 66: following challenges must be met: (
Page 67 and 68: A.F. Heyduk and D.G. Nocera, “Hyd
Page 69: J. Seth, V. Palaniappan, R.W. Wagne
Page 72 and 73: THREE TYPES OF CONCENTRATED SOLAR
Page 74 and 75: Solar Thermal to Electric Energy Co
Page 76 and 77: Tm = mean temperature Z = measure o
Page 78 and 79: control and further diode developme
Page 80 and 81: An overview of solar thermochemical
Page 82 and 83: for electron and phonon band struct
Page 84 and 85: coefficient. The thermal conductivi
Page 86 and 87: J.J. Greffet, R. Carminati, K. Joul
Page 89 and 90: CROSS-CUTTING RESEARCH CHALLENGES B
Page 91 and 92: ange of time and length scales span
Page 93 and 94: Research Issues Advances in the syn
Page 95 and 96: Advances across several science fro
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Figure 19 Transparent conductive el
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Carrier generation, relaxation, and
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E. Hutter and J.H. Fendler, “Expl
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PRIORITY RESEARCH DIRECTIONS Revolu
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RESEARCH DIRECTIONS Several paths e
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Multiple Energy Level Solar Cells I
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Strain Relaxation. Growth of layers
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the relevant elastic and inelastic
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A.J. Nozik, “Quantum Dot Solar Ce
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these new organic structures, and t
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Figure 30 Schematic diagram (right)
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carrier injection between the indiv
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108
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Figure 32 One important example of
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interface for charge separation. Fo
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• Light harvesting, • Advanced
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116
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Multicomponent structures are often
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REFERENCES A.J. Bard and M.A. Fox,
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PLANT PRODUCTIVITY AND BIOFUEL PROD
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een made in identifying and charact
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126
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SUMMARY OF RESEARCH DIRECTION The k
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developing multi-electron catalytic
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coupling in multi-cofactor-containi
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134
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low toxicity, and processibility. T
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8 electrons) are extremely limited.
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largely unknown are the fundamental
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nanostructure design, and developme
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ealize an efficient artificial phot
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Figure 46 Defect-tolerant solar cel
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equired 20-30 years of operation to
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H2SO4 at 1,130K, and the University
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the sequestration step, these solar
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P. von Zedtwitz and A. Steinfeld,
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The continued advances in energy- a
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for the detailed understanding and
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160
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A shortcoming of this approach is t
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of ~2.4 at 300K and quantum-dot PbT
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High-throughput Experimental Screen
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Solar Concentrators and Hot Water H
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G. Chen, M.S. Dresselhaus, J.-P. Fl
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Materials and Processing Methods to
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materials and fabrication approache
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multi-electron H2O and CO2 activati
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178
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180
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and quantum dots. Quantum dots are
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184
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186
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Flux (mA/eV.cm2 Flux (mA/eV.cm ) 2
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Table 1 Worldwide PV Module Product
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Amorphous Silicon. From its discove
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Table 2 Are There Enough Materials
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passivating window and back-surface
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R.R. King, C.M. Fetzer, K.M. Edmond
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currently accounting for only a sma
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Anaerobic Digestion One gasificatio
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Electrolysis is the process for bre
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alkaline electrolyzers require a mi
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maintenance costs of the small prod
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P. Courty, P. Chaumette, and C. Rai
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212
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periods and extend the system opera
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When ηopt < 1, Equation (2) become
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Receiver & Power Conversion Unit So
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Figure 77 General concept of solar-
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Other areas whose development could
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THERMOPHOTOVOLTAICS Thermophotovolt
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N. Benz and Th. Kuckelkorn, “A Ne
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R.A. Sherif, H.L. Cotal, R.R. King,
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230
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Sub-panelists Edmond Amouyal, Centr
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Terry Tritt, Clemson University Joh
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236
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Plenary Closing Session — Wednesd
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Panel 1C (Photoelectrochemistry)
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Agenda for Solar Fuels Breakout Ses
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Tuesday, April 19, 2005, 8:00 a.m.
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Wednesday, April 20, 2005, 8:00 a.m
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Wednesday, April 20, 2005, 8:00 a.m
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250
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R. Corkish, S. Kettemann, and J. Ne
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T. Polivka and V. Sundstrom, “Ult
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256
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258
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microscopy, 81, 85, 101, 155-157, 1
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