Research Papers

Coupled Concentrating Optics, Heat Transfer, and Thermochemical Modeling of a 100-kWth High-Temperature Solar Reactor for the Thermal Dissociation of ZnO

[+] Author and Article Information
W. Villasmil

Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland;
Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland

T. Cooper

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland

E. Koepf, A. Meier

Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland

A. Steinfeld

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
e-mail: aldo.steinfeld@ethz.ch

1Corresponding author.

Manuscript received August 7, 2016; final manuscript received November 9, 2016; published online December 22, 2016. Assoc. Editor: Wojciech Lipinski.

J. Sol. Energy Eng 139(2), 021015 (Dec 22, 2016) (13 pages) Paper No: SOL-16-1358; doi: 10.1115/1.4035330 History: Received August 07, 2016; Revised November 09, 2016

This work reports a numerical investigation of the transient operation of a 100-kWth solar reactor for performing the high-temperature step of the Zn/ZnO thermochemical cycle. This two-step redox cycle comprises (1) the endothermal dissociation of ZnO to Zn and O2 above 2000 K using concentrated solar energy, and (2) the subsequent oxidation of Zn with H2O/CO2 to produce H2/CO. The performance of the 100-kWth solar reactor is investigated using a dynamic numerical model consisting of two coupled submodels. The first is a Monte Carlo (MC) ray-tracing model applied to compute the spatial distribution maps of incident solar flux absorbed on the reactor surfaces when subjected to concentrated solar irradiation delivered by the PROMES-CNRS MegaWatt Solar Furnace (MWSF). The second is a heat transfer and thermochemical model that uses the computed maps of absorbed solar flux as radiation boundary condition to simulate the coupled processes of chemical reaction and heat transfer by radiation, convection, and conduction. Experimental validation of the solar reactor model is accomplished by comparing solar radiative power input, temperatures, and ZnO dissociation rates with measured data acquired with the 100-kWth solar reactor at the MWSF. Experimentally obtained solar-to-chemical energy conversion efficiencies are reported and the various energy flows are quantified. The model shows the prominent influence of reaction kinetics on the attainable energy conversion efficiencies, revealing the potential of achieving ηsolar-to-chemical = 16% provided the mass transport limitations on the ZnO reaction interface were overcome.

Copyright © 2017 by ASME
Topics: Solar energy
Your Session has timed out. Please sign back in to continue.


Steinfeld, A. , 2005, “ Solar Thermochemical Production of Hydrogen––A Review,” Sol. Energy, 78(5), pp. 603–615. [CrossRef]
Abanades, S. , Charvin, P. , Flamant, G. , and Neveu, P. , 2006, “ Screening of Water-Splitting Thermochemical Cycles Potentially Attractive for Hydrogen Production by Concentrated Solar Energy,” Energy, 31(14), pp. 2805–2822. [CrossRef]
Romero, M. , and Steinfeld, A. , 2012, “ Concentrating Solar Thermal Power and Thermochemical Fuels,” Energy Environ. Sci., 5(11), pp. 9234–9245. [CrossRef]
Wurzbacher, J. A. , Gebald, C. , Piatkowski, N. , and Steinfeld, A. , 2012, “ Concurrent Separation of CO2 and H2O From Air by a Temperature-Vacuum Swing Adsorption/Desorption Cycle,” Environ. Sci. Technol., 46(16), pp. 9191–9198. [CrossRef] [PubMed]
Choi, S. , Gray, M. L. , and Jones, C. W. , 2011, “ Amine-Tethered Solid Adsorbents Coupling High Adsorption Capacity and Regenerability for CO2 Capture From Ambient Air,” ChemSusChem, 4(5), pp. 628–635. [CrossRef] [PubMed]
Steinfeld, A. , 2002, “ Solar Hydrogen Production Via a Two-Step Water-Splitting Thermochemical Cycle Based on Zn/ZnO Redox Reactions,” Int. J. Hydrogen Energy, 27(6), pp. 611–619. [CrossRef]
Perkins, C. , and Weimer, A. , 2004, “ Likely Near-Term Solar-Thermal Water Splitting Technologies,” Int. J. Hydrogen Energy, 29(15), pp. 1587–1599. [CrossRef]
Loutzenhiser, P. G. , Meier, A. , and Steinfeld, A. , 2010, “ Review of the Two-Step H2O/CO2-Splitting Solar Thermochemical Cycle Based on Zn/ZnO Redox Reactions,” Materials (Basel), 3(11), pp. 4922–4938. [CrossRef]
Muhich, C. L. , Evanko, B. W. , Weston, K. C. , Lichty, P. , Liang, X. , Martinek, J. , Musgrave, C. B. , and Weimer, A. W. , 2013, “ Efficient Generation of H2 by Splitting Water With an Isothermal Redox Cycle,” Science, 341(6145), pp. 540–542. [CrossRef] [PubMed]
Roeb, M. , Neises, M. , Monnerie, N. , Call, F. , Simon, H. , Sattler, C. , Schmücker, M. , and Pitz-Paal, R. , 2012, “ Materials-Related Aspects of Thermochemical Water and Carbon Dioxide Splitting: A Review,” Materials (Basel), 5(12), pp. 2015–2054. [CrossRef]
Loutzenhiser, P. G. , and Steinfeld, A. , 2011, “ Solar Syngas Production From CO2 and H2O in a Two-Step Thermochemical Cycle Via Zn/ZnO Redox Reactions: Thermodynamic Cycle Analysis,” Int. J. Hydrogen Energy, 36(19), pp. 12141–12147. [CrossRef]
Schunk, L. O. , and Steinfeld, A. , 2009, “ Kinetics of the Thermal Dissociation of ZnO Exposed to Concentrated Solar Irradiation Using a Solar-Driven Thermogravimeter in the 1800–2100 K Range,” AIChE J., 55(6), pp. 1497–1504. [CrossRef]
Perkins, C. , Lichty, P. , and Weimer, A. W. , 2007, “ Determination of Aerosol Kinetics of Thermal ZnO Dissociation by Thermogravimetry,” Chem. Eng. Sci., 62(21), pp. 5952–5962. [CrossRef]
Schunk, L. O. , Lipiński, W. , and Steinfeld, A. , 2009, “ Ablative Heat Transfer in a Shrinking Packed-Bed of ZnO Undergoing Solar Thermal Dissociation,” AIChE J., 55(7), pp. 1659–1666. [CrossRef]
Fletcher, E. A. , 1999, “ Solarthermal and Solar Quasi-Electrolytic Processing and Separations: Zinc From Zinc Oxide as an Example,” Ind. Eng. Chem. Res., 38(6), pp. 2275–2282. [CrossRef]
Müller, R. , and Steinfeld, A. , 2008, “ H2O-Splitting Thermochemical Cycle Based on ZnO/Zn-Redox: Quenching the Effluents From the ZnO Dissociation,” Chem. Eng. Sci., 63(1), pp. 217–227. [CrossRef]
Gstoehl, D. , Brambilla, A. , Schunk, L. O. , and Steinfeld, A. , 2008, “ A Quenching Apparatus for the Gaseous Products of the Solar Thermal Dissociation of ZnO,” J. Mater. Sci., 43(14), pp. 4729–4736. [CrossRef]
Kogan, A. , and Kogan, M. , 2002, “ The Tornado Flow Configuration—An Effective Method for Screening of a Solar Reactor Window,” ASME J. Sol. Energy Eng., 124(3), pp. 206–214. [CrossRef]
Koepf, E. E. , Lindemer, M. D. , Advani, S. G. , and Prasad, A. K. , 2013, “ Experimental Investigation of Vortex Flow in a Two-Chamber Solar Thermochemical Reactor,” ASME J. Fluids Eng., 135(11), p. 111103. [CrossRef]
Koepf, E. , Villasmil, W. , and Meier, A. , 2015, “ High Temperature Flow Visualization and Aerodynamic Window Protection of a 100-kWth Solar Thermochemical Receiver-Reactor for ZnO Dissociation,” Energy Procedia, 69, pp. 1780–1789. [CrossRef]
Perkins, C. , 2008, “ Thermal ZnO Dissociation in a Rapid Aerosol Reactor as Part of a Solar Hydrogen Production Cycle,” Int. J. Hydrogen Energy, 33(2), pp. 499–510. [CrossRef]
Koepf, E. , Advani, S. G. , Steinfeld, A. , and Prasad, A. K. , 2012, “ A Novel Beam-Down, Gravity-Fed, Solar Thermochemical Receiver/Reactor for Direct Solid Particle Decomposition: Design, Modeling, and Experimentation,” Int. J. Hydrogen Energy, 37(22), pp. 16871–16887. [CrossRef]
Möller, S. , and Palumbo, R. , 2001, “ Solar Thermal Decomposition Kinetics of ZnO in the Temperature Range 1950–2400 K,” Chem. Eng. Sci., 56(15), pp. 4505–4515. [CrossRef]
Koepf, E. , Villasmil, W. , and Meier, A. , 2016, “ Pilot-Scale Solar Reactor Operation and Characterization for Fuel Production Via the Zn/ZnO Thermochemical Cycle,” Appl. Energy, 165, pp. 1004–1023. [CrossRef]
Chambon, M. , Abanades, S. , and Flamant, G. , 2010, “ Design of a Lab-Scale Rotary Cavity-Type Solar Reactor for Continuous Thermal Dissociation of Volatile Oxides Under Reduced Pressure,” ASME J. Sol. Energy Eng., 132(2), p. 021006. [CrossRef]
Villasmil, W. , Brkic, M. , Wuillemin, D. , Meier, A. , and Steinfeld, A. , 2013, “ Pilot Scale Demonstration of a 100-kWth Solar Thermochemical Plant for the Thermal Dissociation of ZnO,” ASME J. Sol. Energy Eng., 136(1), p. 011017. [CrossRef]
Klausner, J. F. , Li, L. , Singh, A. , Yeung, N. A. , Mei, R. , Hahn, D. , and Petrasch, J. , 2014, “ The Role of Heat Transfer in Sunlight to Fuel Conversion Using High Temperature Solar Thermochemical Reactors,” 15th International Heat Transfer Conference (IHTC), Kyoto, Japan, Aug. 10–15, Paper No. IHTC15-KN28.
Coray, P. , Lipiński, W. , and Steinfeld, A. , 2010, “ Experimental and Numerical Determination of Thermal Radiative Properties of ZnO Particulate Media,” ASME J. Heat Transfer, 132(1), p. 012701. [CrossRef]
Lipiński, W. , Thommen, D. , and Steinfeld, A. , 2006, “ Unsteady Radiative Heat Transfer Within a Suspension of ZnO Particles Undergoing Thermal Dissociation,” Chem. Eng. Sci., 61(21), pp. 7029–7035. [CrossRef]
Li, L. , Chen, C. , Singh, A. , Rahmatian, N. , AuYeung, N. , Randhir, K. , Mei, R. , Klausner, J. F. , Hahn, D. , and Petrasch, J. , 2016, “ A Transient Heat Transfer Model for High Temperature Solar Thermochemical Reactors,” Int. J. Hydrogen Energy, 41(4), pp. 2307–2325. [CrossRef]
Villasmil, W. , Meier, A. , and Steinfeld, A. , 2013, “ Dynamic Modeling of a Solar Reactor for Zinc Oxide Thermal Dissociation and Experimental Validation Using IR Thermography,” ASME J. Sol. Energy Eng., 136(1), p. 011015. [CrossRef]
Schunk, L. O. , Lipiński, W. , and Steinfeld, A. , 2009, “ Heat Transfer Model of a Solar Receiver-Reactor for the Thermal Dissociation of ZnO—Experimental Validation at 10 kW and Scale-Up to 1 MW,” Chem. Eng. J., 150(2–3), pp. 502–508. [CrossRef]
PROMES-CNRS, 2013, “ Mega Watt Solar Furnace (MWSF),” Le Centre national de la recherche scientifique, Paris, accessed May 7, 2013, http://www.promes.cnrs.fr/index.php?page=mega-watt-solar-furnace
Trombe, F. , and Le Phat Vinh, A. , 1973, “ Thousand kW Solar Furnace, Built by the National Center of Scientific Research, in Odeillo (France),” Sol. Energy, 15(1), pp. 57–61. [CrossRef]
Petrasch, J. , 2010, “ A Free and Open Source Monte Carlo Ray Tracing Program for Concentrating Solar Energy Research,” ASME Paper No. ES2010-90206.
Johnston, G. , 1995, “ On the Analysis of Surface Error Distributions on Concentrated Solar Collectors,” ASME J. Sol. Energy Eng., 117(4), pp. 294–296. [CrossRef]
Gardon, R. , 1960, “ A Transducer for the Measurement of Heat-Flow Rate,” ASME J. Heat Transfer, 82(4), pp. 396–398. [CrossRef]
Kribus, A. , Vishnevetsky, I. , Yogev, A. , and Rubinov, T. , 2004, “ Closed Loop Control of Heliostats,” Energy, 29(5–6), pp. 905–913. [CrossRef]
Moüller, S. , and Palumbo, R. , 2001, “ The Development of a Solar Chemical Reactor for the Direct Thermal Dissociation of Zinc Oxide,” ASME J. Sol. Energy Eng., 123(2), pp. 83–90. [CrossRef]
Touloukian, Y. , and DeWitt, D. P. , 1972, Thermal Radiative Properties: Nonmetallic Solids, Thermophysical Properties of Matter, Vol. 8, IFI/Plenum, New York.
ASTM, 2013, “ Standard Tables for Reference Solar Spectral Irradiance: Direct Normal and Hemispherical on 37 deg Tilted Surface,” American Society for Testing and Material, West Conshohocken, PA, Standard No. ASTM G173–03. http://rredc.nrel.gov/solar/spectra/am1.5/astmg173/astmg173.html
Roine, A. , 1997, “ Outokumpu HSC Chemistry 5.0,” Outokumpu Research, Pori, Finland.
Siegel, R. , and Howell, J. , 2002, Thermal Radiation Heat Transfer, Taylor and Francis, New York.
Siegel, R. , 1973, “ Net Radiation Method for Enclosure Systems Involving Partially Transparent Walls,” Washington, DC, NASA Report No. TN D-7384.
Kitamura, R. , Pilon, L. , and Jonasz, M. , 2007, “ Optical Constants of Silica Glass From Extreme Ultraviolet to Far Infrared at Near Room Temperature,” Appl. Opt., 46(33), pp. 8118–8133. [CrossRef] [PubMed]
Modest, M. F. , 2003, Radiative Heat Transfer, Academic Press, Cambridge, MA.
Petrasch, J. , Coray, P. , Meier, A. , Brack, M. , Haüberling, P. , Wuillemin, D. , and Steinfeld, A. , 2007, “ A Novel 50 kW 11,000 Suns High-Flux Solar Simulator Based on an Array of Xenon Arc Lamps,” ASME J. Sol. Energy Eng., 129(4), pp. 405–411. [CrossRef]
Shackelford, J. F. , and Alexander, W. , 2001, Thermal Properties of Materials, CRC Press, Boca Raton, FL.
JAHM Software, 1999, “ MPDB,” JAHM Software, Inc., North Reading, MA.
RATH Group, 2012, “ ALTRA KVS High Temperature Vacuum Formed Boards and Shapes,” RATH, Inc., Newark, DE, accessed Oct. 18, 2012, http://www.rath-usa.com/kvs.php
Heraeus, 2013, “ Quartz Glass—Thermal Properties,” Heraeus, Hanau, Germany, accessed Oct. 18, 2012, http://www.heraeus-quarzglas.com
Promat, 2013, “ Promat Handbook—High Temperature Insulation,” Promat International, Tisselt, Belgium, accessed June 22, 2013, www.promat-hti.be
Olorunyolemi, T. , Birnboim, A. , Carmel, Y. , Wilson, O. C. , Lloyd, I . K. , Smith, S. , and Campbell, R. , 2004, “ Thermal Conductivity of Zinc Oxide: From Green to Sintered State,” J. Am. Ceram. Soc., 85(5), pp. 1249–1253. [CrossRef]
Knovel, 2012, “ Knovel Critical Tables (2nd Edition)—Thermodynamic Properties of Inorganic Substances,” Knovel, New York, accessed Oct. 20, 2012, http://www.knovel.com/web
Archer, D. G. , 1993, “ Thermodynamic Properties of Synthetic Sapphire (α-Al2O3), Standard Reference Material 720 and the Effect of Temperature-Scale Differences on Thermodynamic Properties,” J. Phys. Chem. Ref. Data, 22(6), p. 1441. [CrossRef]
Pankratz, L. , 1982, Thermodynamic Properties of Elements and Oxides, U.S. Bureau of Mines Bulletin, Washington, DC, p. 672.
Martienssen, W. , and Warlimont, H. , 2006, Springer Handbook of Condensed Matter and Materials Data, Springer, Berlin, Germany.
Dombrovsky, L. , Schunk, L. , Lipiński, W. , and Steinfeld, A. , 2009, “ An Ablation Model for the Thermal Decomposition of Porous Zinc Oxide Layer Heated by Concentrated Solar Radiation,” Int. J. Heat Mass Transfer, 52(11–12), pp. 2444–2452. [CrossRef]
Haring, H.-W. , 2007, Industrial Gas Processing, Wiley, New York.
L'vov, B. V. , 2001, “ The Physical Approach to the Interpretation of the Kinetics and Mechanisms of Thermal Decomposition of Solids: The State of the Art,” Thermochim. Acta, 373(2), pp. 97–124. [CrossRef]
Cussler, E. L. , 2009, Diffusion: Mass Transfer in Fluid Systems, Cambridge University Press, New York.
Ezbiri, M. , Allen, K. M. , Gàlvez, M. E. , Michalsky, R. , and Steinfeld, A. , 2015, “ Design Principles of Perovskites for Thermochemical Oxygen Separation,” ChemSusChem, 8(11), pp. 1966–1971. [CrossRef] [PubMed]
Hänchen, M. , Stiel, A. , Jovanovic, Z. R. , and Steinfeld, A. , 2012, “ Thermally Driven Copper Oxide Redox Cycle for the Separation of Oxygen From Gases,” Ind. Eng. Chem. Res., 51(20), pp. 7013–7021. [CrossRef]


Grahic Jump Location
Fig. 1

Schematic of the 100-kWth solar thermochemical reactor configuration

Grahic Jump Location
Fig. 2 Left

side-elevation view of the MegaWatt Solar Furnace (MWSF) of PROMES-CNRS, Odeillo, France. The heliostats, arranged in eight stepped terraces, track the sun and reflect the direct normal irradiation (DNI) onto a parabolic dish concentrator, which in turn focuses the sunrays into a receiving tower where the experimental platform is located. Right: north-facing front-elevation view of the MWSF showing the 36 heliostats (dark-shaded group, referred to as G36) used during the reactor experimental campaign. Heliostats are numbered according to the MWSF convention. Dimensions in meters.

Grahic Jump Location
Fig. 3

(a) Sun-tracking orientation of a heliostat, relative to the adopted heliostat-centered Cartesian coordinate system (x = west, y = south, z = zenith). The direction of an incident ray r is determined by the solar azimuth angle γs and altitude angle αs. Heliostat angles γn and αn are analogously defined: (b) Reflection of an incident ray on a differential surface area dS, showing the angular dispersion error θerr relative to the directions of a perfectly specular ray r′ and deviant ray r″.

Grahic Jump Location
Fig. 4

Left: locations of the 33 heat flux measurements (black dots) conducted at the focal plane of the MWSF for each of the G36 heliostats. The gray-shaded portion represents the 19-cm-diameter aperture area of the solar reactor. Dimensions in cm. Right: distribution map of solar radiative flux incident on the focal plane when irradiated by heliostat #47. The location of the peak flux (256 suns) is shown relative to the nominal focal point of the MWSF. The dashed circle delineates the perimeter of the aperture.

Grahic Jump Location
Fig. 5

Superposition of all 36 experimentally measured (left) and numerically computed (right) distribution maps of solar radiative flux incident on the focal plane of the MWSF

Grahic Jump Location
Fig. 6

(a) Comparison of the experimentally measured (solid lines) and numerically computed (dashed lines) solar radiative power and mean solar radiative flux incident on a circular aperture located at the focal plane of the MWSF. Solar radiative power delivered by G36 heliostats. (b) Computed daily evolution of the mean solar concentration ratio at the solar reactor's aperture Cmean during summer solstice (solid line), plotted along with the corresponding sun's path (dashed line). Simulations were performed for G36 heliostats and the shutter doors fully open.

Grahic Jump Location
Fig. 7

Distribution of circumferentially averaged solar fluxabsorbed on the surfaces of the solar reactor for G36 heliostats at solar noon of summer solstice (June 21) and DNI = 1000 Wm−2. The ticks around the reactor profile indicate the flux absorbed at the given positions in kW m−2. Orientation of the y-axis indicated in Fig. 2 (left).

Grahic Jump Location
Fig. 8

Schematic longitudinal half cross section of the 100-kWth solar reactor, showing the temperature measurement locations of the type-K and type-B thermocouples. The circled letters designate the various constituent materials considered in the reactor model: (a) Al2O3 bricks, (b) ALTRA KVS-184/400 insulation, (c) Promat Monalite M1-A insulation, (d) Al shell, (e) PORRATH FL32-12 firebricks, and (f) quartz glass.

Grahic Jump Location
Fig. 10

Parity plot of the computed amounts of ZnO dissociated versus the experimental amounts collected during the experimental runs #2–8. No ZnO was fed/dissociated during run#1.

Grahic Jump Location
Fig. 9

Modeled and measured solar reactor temperatures at the locations indicated in Fig. 8, for experimental runs 1–6 (see Table 4), plotted in the same order (a)–(f). Shown in the upper plots are the solar radiative power input Qsolar and the measured DNI. The vertical dotted lines indicate the points in time at which Qsolar ceased to be supplied.

Grahic Jump Location
Fig. 11

Circled markers: experimentally obtained mean solar-to-chemical energy conversion efficiencies of the 100-kWth solar reactor for runs #2–8 (including 8peak), as a function of the mean temperature of the ZnO bed [24]. Lines: modeled efficiency curves for the baseline case (dotted) and the optimized design schemes (dashed, dashed–dotted).

Grahic Jump Location
Fig. 12

Simulated cyclic evolution of the ZnO bed temperature, ZnO dissociation rate, and ηsolar-to-chemical, when subjecting the reactor to the indicated power profile Qsolar for four consecutive days. Indicated ηsolar-to-chemical values are daily averages.

Grahic Jump Location
Fig. 13

Numerically computed ηsolar-to-chemical curves for various values of the pre-exponential factor k0 of the Arrhenius kinetic law r‴=k0 exp(−Ea/R¯T)



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In