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1
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84919317088
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Luz: Tomorrow's Energy Today (Luz International corporate literature), Kearney and Associates, 14022 Condesa Drive, Del Mar, CA 92014.
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3
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84919317087
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Radiative losses are proportional to the product and emittance and the fourth power of absolute temperature.
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4
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84919317086
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Luz reports a much higher concentration ratio, which results from their use of a non-standard definition of concentration. The usual definition is the ratio of aperture area to receiver area, which for Luz collectors is 23 to 25.
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5
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84919317085
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Diffuse radiation must be collected from a much larger angular segment of the sky than direct beam. There is an inverse relationship between the size of the angular acceptance angle and the concentration factor. An upper bound on the concentration C is given by C = 1/sin(θ) where θ is the half angle of acceptance. For a parabolic trough, C is less than this.
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6
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84919317084
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Next generation Luz plants were designed for direct steam generation, rather than using oil as a heat transfer fluid. A consortium of European and US utilities is exploring the possibility of continuing the development of direct steam generation technology.
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10
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84915970813
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The Potential of Renewable Energy: An Interlaboratory White Paper
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US Department of Energy
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(1990)
SERI/TP-260-3674, DE90000322
, pp. G-10
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12
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0010713935
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Barriers to Commercialization of Large-Scale Solar Electricity: Lessons Learned from the Luz Experience
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Sandia National Laboratories, US Department of Energy
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(1991)
SAND91-7014
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Lotker1
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13
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0038660440
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Solar Thermal Process Heat and Electricity Generation Performance and Costs for the ANU ‘Big Dish’ Technology: A Comparison with Luz System costs
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Energy Research Centre, Australian National University
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(1991)
Report EP-RR-57
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Kaneff1
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14
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84919317080
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At the equator the collector would be ground mounted, much like the Luz collector.
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15
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84919317079
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This is true for polar-axis orientation, but if any bias toward one season or another were undertaken for seasonal load matching, then annual performance would decrease.
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19
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84919317077
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As this article goes to press, the best laboratory specimen has yielded a preliminary measurement of 58. Hence, the performance of advanced solar collectors summarized in this article may be superseded by substantial improvements in the near future.
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20
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84919317076
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Water reaches the triple point above 370°C under saturation conditions, and assumes a single phase, not suitable for boiling heat transfer. The pumpless system should be transferable to large systems.
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21
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84919317075
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The quantity of diffuse radiation depends on the cloud cover, and varies by region. The associated performance increase is more pronounced in regions of lower insolation.
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24
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84919317072
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Hourly Insolation-Surface Meteorological Observations
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National Climate Center, Asheville, NC 28801
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(1979)
TD 9724
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SOLMET1
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25
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84919317071
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Annual system conversion efficiency from solar energy to steam would be around 54–60% (on an annual basis) in region 1 with vacuum insulated polar designs operating near 300°C.
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26
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84919317070
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Storage plants must compete with overall energy supply costs, whereas peaking plants compete only against high peak rates.
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27
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84919317069
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Engineering feasibility study for the Local Government Electricity association of NSW, Australia, The authors wish to apologize for citing a currently confidential report, but this is the only recent work known. This steam/air/steam rock bed system may be regarded as related to that described in the following two references, but was independently developed as the most cost effective and practical system and does not utilized sodium coolant or large temperature variations.
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(1991)
Solid Energy Storage System For Industrial Heat Applications
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Mills1
Morrison2
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29
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84919317067
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Comparative Ranking Solar Thermal Systems, Volume II Cost and Performance of Thermal Storage Concepts in Storage Systems, Phase 1
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5th Canadian edn, Solar Energy Research Institute, Golden, CO, These sodium/air/sodium system use much larger temperature swings than in the previous reference, and would not be suitable for polar axis trough storage.
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(1983)
SERI/TR-631-1283
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Dubberly1
Gormley2
Lang3
Liffengren4
McKenzie5
Porter6
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31
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84919317065
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Phase-Change Thermal Energy Storage
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5th Canadian edn, Solar Energy Research Institute (SERI), Golden, CO
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(1989)
SERI/TR-250-3516, DE89009426
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33
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84919317064
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This is obtained as follows: to 92.5 units of solar must be added 7.5 units of gas backup and 13 units of gas superheat. Solar fraction is 92.5/113 = 0.82 of total energy supplied.
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34
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84919317063
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This is a first approximation only, as this calculation implicitly assumes a given shape for the load curve, which in this case is the PG&E load curve in Figures 5 and 6.
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35
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84919317062
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Mostly laboratory models running at present, second stage steam cycle undemonstrated. Longevity and cost are uncertain, although some estimates of US4–5 ???/kWh have been recently made for the CSIRO fuel cell in Australia.
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36
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84919317061
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This procedure is acceptable as a first approximation, which is adequate for these preliminary calculations. This assumes that the exact same plant would be built in Charleston as in Fresno, although the Charleston plant may actually require somewhat more gas-fired capital equipment because a larger share of the energy is produced from gas. Also, gas is not necessarily available or inexpensive in all parts of region 2. A more accurate estimate would include several other refinements eg the replacement of PG&E's load profile with correct load profiles for utilities in region 2.
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38
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84919317060
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In levelized real terms, the average electricity generation cost - including intermediate and peak load electricity — is of course much higher than this.
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39
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84919317059
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Capital for solar power plants in the USA is currently quite expensive, if indeed it can be obtained at all. However, as political sentiment and environmental concerns mount to favour renewable energy development, these conditions could change in the relatively near future.
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40
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84919317058
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Variations in exchange rates would affect estimates.
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41
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84919317057
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Based on estimates carried out by the University of Sydney, Australia for an assumed 100 MW plant. Installed collector capital cost A$215 per square metre, using imported US stainless steel tubing (at 30% higher cost than in the USA), imported glass stock for evacuated tubes, and imported reflector material. This includes a 35% markup on large collector array sales. Costs in the USA may be lower because much of this material could be supplied locally. The power block would also be imported. It is believed that significant reductions in insulation costs and other components can be achieved.
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42
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84919317056
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Price quotation from Maxitherm Ltd, Sydney, Australia.
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43
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84919317055
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In practice, depending on detailed design considerations and the share of plant output from natural gas, other ways to incorporate gas backup could be utilized (eg combined cycle technology) if they led to better overall heat rates.
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44
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84919317054
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Securing America's Energy and Environmental Future: A Least Cost Strategy, Union of Concerned Scientists, Washington, DC, p 19.
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