Potential Applications of Concentrated Solar Photons (1991) / Chapter Skim
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2 Review and Evaluation of Various Application Areas
2 Review and Evaluation of Various Application Areas
Pages 11-47
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From page 11... ...
, under appropriate conditions, a wide spectrum of organic, haloorganic, and metallo-organic compounds found as dilute con~ninants of well water, aquifers, and surface waters or as components of industrial and domestic wastewater effluents or waste disposal site leachates. These chemical processes, collectively referred to as advanced oxidation processes (AOPs)
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From page 12... ...
. In wastewater treatment the last step in the process is often used to effect removal of trace residuals; such "polishing" operations typically involve' feed streams of clear or nearly clear water with only trace contaminant levels and may be regarded as ideal streams for advanced oxidation technologies, applicable after most contaminants have been removed by the cheaper, larger-scale proven technologies such as carbon adsorption or biological treatment.
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From page 13... ...
Parabolic trough concentrators, developed originally for capturing direct solar photons for thermal energy storage, have recently been examined as a solar photoreactor configuration. Scales of collector trough area in published reports include 0.45 m2 in Australia [101, several square meters at the Solar Energy Research Institute (SERI)
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From page 14... ...
Conclusion 3: Photocatalysis represents an emerging process chemistry, but it is not currently an industrial water treatment practice. Economics Large-scale water treatment by advanced oxidation processes has been estimated to cost as little as $0.10 ptg in a very large, hypothetical, ozone-peroxide water treatment process operating on an "easy" challenge, the mineralization of 0.2 ppm trichloroethylene [241.
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Solar concentrator design is well developed, to the point where commercial-scale, off-theshelf parabolic concentrators are conveniently available, and engineering models for predicting the usable flux of concentrated solar photons are in use at SERI [111.
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reactor design, including coupling between intrinsic kinetics and mass transfer (especially for immobilized catalysts) and illumination supply level and spatial distributions within the reactor from direct, diffuse, and concentrated solar sources.
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Workshop on Potential Applications of Concentrated Solar Photons, NRC, Nov. 7-8, 1990, Golden, Colo.
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"Cost and Performance Projections for Solar Water Detoxification Systems." Presented at the Workshop on Potential Applications of Concentrated Solar Photons, NBC, Nov. 7-8, 1990, Golden, Colo., and ASME International Solar Energy Meeting, Reno, Nev., March 17-22, 1991.
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From page 19... ...
. The potential applications of solar energy for waste treatment are those in which solar collectors can supply the temperatures needed for destruction at a cost competitive with other energy sources or in which the enhancement of destruction by photolytic reactions is sufficient to compensate for differentials In the energy cost.
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From page 20... ...
lo_ ~ 20% Feed PreD. Treatment Unit \ POTENTIAL APPLICATIONS OF CONCENTRATED SOLAR PHOTONS OPERATIONS: Energy __ .
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From page 21... ...
At higher temperatures the fractional conversion of tetrachlorobiphenyl to tetrachlorod~benzofuran was as high as 0.01 in the absence of irradiation but below detection [units for the run with 95 suns. Solar processes have a potential benefit over thermal processes of a reduction of the reaction temperature required to achieve a given destruction efficiency, with a reduction in the concentration of undesirable by-products as well.
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From page 22... ...
and secondary reactions. Issues of interest on the effect of temperature and pressure on the photochemical reactions include: the extent of the shift in the absorption spectra to longer wavelengths with increasing temperature; the approach to thermal equilibrium of the excited Fibrotic states; the dependence on temperature of the excited deactivation rates; the wa~eelength dependence of reactivity and the role of forbidden and repulsive states in photoreactirity; die importance of oxidation of excited states; the elucidation of the reaction pathways; and the effectiveness of radical producing photoinitiators and energy or electron transfer sensitizers.
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From page 23... ...
SOURCE: [3~. Photocatalytic Destruction of Airborne Organics Over Semiconductors at Near Ambient Temperatures In heterogeneous photocatalysis the reactants are oxidized by valence band holes that are generated in semiconductors irradiated with photons having energies in excess of the bandgap of the solid.
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From page 24... ...
Catalytic Steam Reforming The advantages of using catalytic steam reforming for waste destruction are reduction of the reaction temperature needed to achieve a given destruction level and elimination of undesirable by-products through selectivity of the catalysts. The process is endothermic, and solar energy can be used to heat the catalyst surface directly, reducing the potential of gas-phase pyrolysis 100 a_ t', 1 ~ ._ A: i_ E ~1 ~ - o 0 _ .- o .
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From page 25... ...
Bench-scale experiments are also needed to study the destruction efficiency of complex mixtures; to test interesting operating conditions suggested by the kinetic modeling studies; and to evaluate other potential applications of solar energy in waste treatment, such as that of carbon regeneration. The concept of using both
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From page 26... ...
"High Temperature Photochemistry Educed by Concentrated Solar Radiation." Workshop on Potential Applications of Concentrated Solar Photons, NRC, Nov. 7-8, 1990, Golden, Colo.
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MATERIALS PROCESSING AND SYNTHESIS* Brief Description Concentrated photons generated from electric arc and solar sources using parabolic mirrors (searchlights)
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From page 28... ...
Therefore, applications of potential concentrated solar photons will~most likely be related to thermal processing and synthesis. Status of Technology In assessing the potential applications of concentrated solar photons useful for the synthesis and processing of materials, it is relevant to compare He characteristics of concentrated .cal~r radiation .
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From page 29... ...
The committee does not foresee that conventional process methods will be replaced in the next few decades. Potential Applications Possible applications of concentrated solar photons for He processing and synthesis of matenals generally follow conventional applications areas, and very few have been reported or investigated.
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From page 30... ...
3. Specific materials processes or synthesis technologies that could be improved or made more economical through the use of concentrated solar photons (rather than CO2 lasers, high-intensity arc concentrators, or plasmas)
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From page 31... ...
"Materials Processing Using Highly Concentrated Solar Radiation." Proceedings of the 25~ Intersociety Energy Conversion Engineenng Conference (P.A. Nelson, W.W.
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Several photochemical processes are used in industrial applications. For example, photochemical reactions such as the photobromination of diethylcarbonate (Astra Pharmaceuticals)
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From page 33... ...
Very recently we have witnessed several exciting new discoveries [7,8l, but it is loo early to know if and when industrial applications will follow. Thermal-Asszsted Photochemistry Specific to concentrated solar photons is the abundance of thermal photons present simultaneously with the higher-energy visible and near-W photons used photochemically.
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From page 34... ...
. For testing promising new technologies, at some time it may be useful to have available at SERI a user facility where concentrated solar photons are available to evaluate potential applications.
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From page 35... ...
'the Biotechnology of Cultivating Dunaliella Rich in Beta Carotene: From Basic Research to Industrial Production," from the Workshop on Potential Acolicaiions of Concentrated Solar Photons, NRC, Nov. 7-8, 1990, Golden, Colo.
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From page 36... ...
Solar energy is a very convenient energy source in locations such as earth orbit for applications in communications, power transmission, and laser propulsion. Solar-pumped laser systems based on gas lasers have been designed, and the basic concepts have been demonstrated [4-61.
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From page 37... ...
While CO2 lasers have been the most efficient electrically pumped lasers used for materials processing, they have not been efficiently pumped by solar energy. For space applications, considerable emphasis has been applied to the iodine laser, which in recent years has been tailored to achieve absorption bands matching the solar spectrum.
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From page 38... ...
A potential advantage of blackbody pumping is that the collected solar energy is stored in the blackbody during periods of interruption of the solar flux, during which laser operation might continue, perhaps with the infusion of substitute fonns of heating of the blackbody during long interruptions. Blackbody pumping of YAG lasers has been proposed.
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From page 39... ...
Recommendation: The development of materials designed for lasing using the solar spec~n, but operating at wavelengths and scalable to power levels Mat have commercial potential, represents a productive area for research. Very high temperatures can be achieved in concentrated solar systems, suggesting the idea of infrared lasers based on blackbody cavity pumping [5l, which takes advantage of the wide-wavelength region of the solar spectrum.
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From page 40... ...
Lees, J.H. "Solar Pumped Lasers and Then Applications." Submitted at He Workshop on Potential Applications of Concentrated Solar Photons, NRC, Nov.
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From page 41... ...
. However, the combination of capital costs to provide the concentrated solar energy and the elaborate and expensive plants required to carry out the chemical processes places a heavy financial burden on this approach to a clean and renewable energy economy.
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From page 42... ...
JS SOLAR ENERGY CONVERSION TECHNOLOGIES ptRECT HYDROG£N EN£RGY PROC)
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From page 43... ...
of several reactions (photochemical, thermochemical, electrochemical) presents certain advantages with respect to solar energy utilization as it embraces both the heat generated In a solar reactor and the high-energy photons available.
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From page 44... ...
,¢ ~ ~^ ~ ~^ ~ ~^ I ~ ~-~ ~- ~ AO ~ Certain H2 production processes have reached maturity to possible commercial exploitation: (1) steam reforming of natural gas, (2)
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From page 45... ...
. Development and Commercialization of New Technologies As in the cases of coal, oil, and even nuclear energy, whose technical and economic develop ment started some 35 years ago and which nonetheless contribute only 4 percent of the primary energy consumption worldwide, solar energy and solar fuels will require time for R&D, and for introduction to the marketplace and adaptation to the worldwide established energy system
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From page 46... ...
Conclusion: The feasibility of steam reforming and CO2 reforming of methane has been exam~ned using solar concentrators ~n several counmes. Recommendations Recommendation: Research in high-temperature photochemical processes might explore Me use of high solar fluxes in presently energy-demanding industrial processes, such as biomass conversion and hydrogeneraiion of biomass using H2O as the hydrogen source followed by thermal cracking to obtain bunk chemicals and fuels.
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From page 47... ...
"Thermal, ThermalcheIriical, and Hybnd Solar Hydrogen Production." Submitted at the Workshop on Potential Applications of Concentrated Solar Photons, NBC, Nov. 7-8, 1990, Golden, Cola.
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