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SolarSynGas: Results from a Virtual Institute developing Materials and Key Components for Solar Thermochemical Fuel Production

Roeb, Martin and Sattler, Christian and Pitz-Paal, Robert and Feldmann, Claus and Borchardt, Günter and Steinfeld, Aldo (2015) SolarSynGas: Results from a Virtual Institute developing Materials and Key Components for Solar Thermochemical Fuel Production. In: Solar Paces 2015 Book of Abstracts. SolarPACES 2015, 13.-16. Okt. 2015, Kapstadt, Südafrika.

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Abstract

The Helmholtz Virtual Institute (VI) SolarSynGas brings together expertise from solar energy research and materials science to develop metal oxide based redox materials and to integrate them in a suitable way into related process technologies for two-step thermochemical production of hydrogen and carbon monoxide from water and CO2. One of the foci of experimental investigation was exploring the impact of doping on the feasibility of ceria-based materials – mainly by Zr-doping. The results indicate that a certain Zr-content enhances the reducibility and therefore the splitting performance. Increasing the Zr-content to x = 0.15 improved the specific CO2-splitting performance by 50% compared to pure ceria. This finding agrees with theoretical studies attributing the improvements to lattice modification caused by the introduction of Zr4+. Thermogravimetric relaxation experiments and equilibrium oxygen isotope exchange experiments with subsequent depth profiling analysis were carried out on ceria. As a result the reduction reaction of even dense samples of pure ceria with a grain size of about 20 μm is surface reaction controlled. The structure of the derived expression for the apparent activation energy suggests that the chemical surface exchange coefficient should show only a very weak dependence on temperature for ceria doped with lower valence cations. A solar receiver reactor exhibiting a foam-type reticulated porous ceramics made of ceria was tested. It could be shown that applying dual-scale porosity to those foams with mm-size pores for effective radiative heat transfer during reduction and μm-size pores within its struts for enhanced kinetics during oxidation allows enhancing the performance of the reactor significantly. Also a particle process concept applying solid-solid heat recovery from redox particles in a high temperature solar thermochemical process was analysed that uses ceramic spheres as solid heat transfer medium. This concept can be implemented into any particle reactor and offers sufficiently high heat recovery rates and thus high overall system efficiencies. A detailed model to calculate the performance of the concept in consideration of temperature dependent material data and several other influencing factors was developed. It was found that the molar flow ratio needs to be optimized regarding the contact time and the heat recovery rate only increases slightly over a contact time of τ=10s. The system reaches a heat recovery rate over 70% in case of six stages, connected in a quasi-counter-current principle.

Item URL in elib:https://elib.dlr.de/99213/
Document Type:Conference or Workshop Item (Speech)
Title:SolarSynGas: Results from a Virtual Institute developing Materials and Key Components for Solar Thermochemical Fuel Production
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Roeb, MartinMartin.roeb (at) dlr.deUNSPECIFIED
Sattler, Christianchristian.sattler (at) dlr.deUNSPECIFIED
Pitz-Paal, Robertrobert.pitz-paal (at) dlr.deUNSPECIFIED
Feldmann, ClausKITUNSPECIFIED
Borchardt, GünterTU ClausthalUNSPECIFIED
Steinfeld, AldoETH ZürichUNSPECIFIED
Date:16 October 2015
Journal or Publication Title:Solar Paces 2015 Book of Abstracts
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:solar syn-gas, hydrogen, concentrated solar, redox cycles, thermochemical cycles, water Splitting, CO2 splitting
Event Title:SolarPACES 2015
Event Location:Kapstadt, Südafrika
Event Type:international Conference
Event Dates:13.-16. Okt. 2015
Organizer:SolarPACES
HGF - Research field:Energy
HGF - Program:Renewable Energies
HGF - Program Themes:Concentrating Solar Systems (old)
DLR - Research area:Energy
DLR - Program:E SF - Solar research
DLR - Research theme (Project):E - Solar Process Technology (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Solar Research > Solare Verfahrenstechnik
Deposited By: Sattler, Prof. Dr. Christian
Deposited On:06 Nov 2015 15:03
Last Modified:06 Nov 2015 15:03

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