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.
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April 2017
Research-Article
Coupled Concentrating Optics, Heat Transfer, and Thermochemical Modeling of a 100-kWth High-Temperature Solar Reactor for the Thermal Dissociation of ZnO
W. Villasmil,
W. Villasmil
Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland;
Paul Scherrer Institute,
Villigen 5232, Switzerland;
Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Search for other works by this author on:
T. Cooper,
T. Cooper
Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
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E. Koepf,
E. Koepf
Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland
Paul Scherrer Institute,
Villigen 5232, Switzerland
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A. Meier,
A. Meier
Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland
Paul Scherrer Institute,
Villigen 5232, Switzerland
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A. Steinfeld
A. Steinfeld
Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
e-mail: aldo.steinfeld@ethz.ch
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
e-mail: aldo.steinfeld@ethz.ch
Search for other works by this author on:
W. Villasmil
Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland;
Paul Scherrer Institute,
Villigen 5232, Switzerland;
Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
T. Cooper
Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
E. Koepf
Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland
Paul Scherrer Institute,
Villigen 5232, Switzerland
A. Meier
Solar Technology Laboratory,
Paul Scherrer Institute,
Villigen 5232, Switzerland
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
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. Apr 2017, 139(2): 021015 (13 pages)
Published Online: December 22, 2016
Article history
Received:
August 7, 2016
Revised:
November 9, 2016
Citation
Villasmil, W., Cooper, T., Koepf, E., Meier, A., and Steinfeld, A. (December 22, 2016). "Coupled Concentrating Optics, Heat Transfer, and Thermochemical Modeling of a 100-kWth High-Temperature Solar Reactor for the Thermal Dissociation of ZnO." ASME. J. Sol. Energy Eng. April 2017; 139(2): 021015. https://doi.org/10.1115/1.4035330
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