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THREE TYPES OF CONCENTRATED SOLAR “THERMAL” SYSTEMS direct & diffused sunlight cold water hot water Concentrated photovoltaic (CPV) system. Concentrated photovoltaics, although not a solar thermal process, is included in this survey because of the utilization of concentrators. cold input direct sunlight solar to thermal power conversion hot output concentrated sunlight optical concentrator 58 process heat direct sunlight heat to electricity or heat to chemical potential power conversion Low-temperature solar thermal systems. This system does not involve sunlight concentration, or occasionally may employ low-concentration (C ≤ 2). This system is suitable for home use where it usually heats hot water for direct use or home heating. photovoltaic power conversion concentrated sunlight optical concentrator electricity High-temperature solar thermal systems. Such systems require optical concentration of direct sunlight at a ratio varying from about 20 to several thousands, depending on the specific process and system involved. Concentrated solar thermal systems are large megawatt(electric) systems that can be used for electricity generation or fuel production. Central Receiver Systems. Central receiver systems contain an array of Fresnel reflectors (heliostats) with two axes of rotation. The common focus is stationary, located on a solar tower (Figure 14b). The two-axis tracking enables a higher concentration ratio and the higher operating temperatures and power conversion efficiency than those of the line focus configuration. However, as the system size increases, the optical efficiency (the ratio of sunlight capture to incident sunlight) declines. Thus, system optimization is required. Two 10-MWe facilities are situated in the United States near Barstow, California, and one 2.5-MWe facility is in Almaria, Spain. Present estimates of large-scale (>50-MW) facility costs are about $3/W (Sargent & Lundy 2003; Stoddard et al. 2005). A recent study (Pitz-Paal et al. 2005) indicates that the new developments discussed here should lead to a cost reduction of at least $0.5/W. Materials development aimed at high-temperature performance would impact efficiency.
Direct Sunlight Tubular Receiver Linear Collector Concentrated Sunlight a b c Rotational Axis Receiver & Power Conversion Unit Figure 14 Three types of solar concentrators utilizing (a) linear collectors that focus on tubular receiver, (b) central receiver (solar power tower) with heliostat field that tracks the sun, and (c) on-axis tracking system with parabolic dish concentrator On-axis Tracking Systems. On-axis systems, such as parabolic dish concentrators (Figure 14c), provide the highest optical efficiency of all the concentrating solar systems. Their main drawback is the concentrator size, which is limited by practical structural consideration. Recent progress in the development of small Brayton engines provides the option of using a dish/Brayton system as an alternative to the dish/Stirling system. Estimates of large-scale (>50-MW) dish/Stirling facility costs are about $2.5/W (Stoddard et al. 2005), although the current costs, based on several demonstration systems, are three to four times higher (Mancini et al. 2003). A recent study (Pitz-Paal et al. 2005) indicates that new developments in current areas of research can reduce cost by more than $0.5/W. Other estimates, by Stirling Energy Systems (Stoddard et al. 2005), suggest even a larger potential cost reduction. The uncertainty in all of these estimates is considered to be large. The development areas suggested in the Priority Research Directions should lead to the cost reductions required to make this technology competitive with conventional electricity production within five to ten years, assuming fossil fuels remain at present prices. 59 Receiver & Power Conversion Unit Solar Tower Structure Concentrated Sunlight Parabolic Dish Concentrator Heliostat Field Reflected Light Beams Heliostats
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On the Cover: One route to harvesti
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Revisions, September 2005 p ix, par
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CONTENTS (CONT.) Appendix 4: Additi
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OEC oxygen-evolving complex PCET pr
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viii
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thin films, organic semiconductors,
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genetic sequencing, protein product
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INTRODUCTION The supply and demand
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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 and 46: PHOTOELECTROCHEMICAL STORAGE CELLS
Page 47 and 48: BASIC RESEARCH CHALLENGES FOR SOLAR
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 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
Page 97 and 98: Figure 19 Transparent conductive el
Page 99 and 100: Carrier generation, relaxation, and
Page 101 and 102: E. Hutter and J.H. Fendler, “Expl
Page 103: PRIORITY RESEARCH DIRECTIONS Revolu
Page 106 and 107: RESEARCH DIRECTIONS Several paths e
Page 108 and 109: Multiple Energy Level Solar Cells I
Page 110 and 111: Strain Relaxation. Growth of layers
Page 112 and 113: the relevant elastic and inelastic
Page 114 and 115: A.J. Nozik, “Quantum Dot Solar Ce
Page 116 and 117: these new organic structures, and t
Page 118 and 119: Figure 30 Schematic diagram (right)
Page 120 and 121: 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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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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