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Kinetic Investigations of a Two-Step Thermochemical Water-Splitting Cycle Using Mixed Iron Oxides Fixed on Ceramic Substrates

Neises, Martina and Roeb, Martin and Schmücker, Martin and Sattler, Christian and Pitz-Paal, Robert (2008) Kinetic Investigations of a Two-Step Thermochemical Water-Splitting Cycle Using Mixed Iron Oxides Fixed on Ceramic Substrates. In: ASME 2nd International Conference on Energy Sustainability, ES2008-54093. Pinehurst Technologies, Inc.. ASME 2nd International Conference on Energy Sustainability, 2008-08-10 - 2009-08-14, Jacksonville, Fl (USA). ISBN 0-7918-3832-3.

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Abstract

A two-step thermochemical cycle for solar hydrogen production using mixed iron oxides as the metal oxide redox system has been investigated. A reactor concept has been developed in which the metal oxide is fixed on multi-channelled honeycomb ceramic supports capable of adsorbing solar irradiation. In the solar furnace of DLR in Cologne coated honeycomb structures were tested in a solar receiver-reactor with respect to their water splitting capability and their long term stability. The concept of this new reactor design has proven feasible and constant hydrogen production during repeated cycles has been shown. For a further optimization of the process and in order to gain reliable performance predictions more information about the process especially concerning the kinetics of the oxidation and the reduction step are essential. To examine the kinetics of the water splitting and the regeneration step a test rig has been built up on a laboratory scale. In this test rig small coated honeycombs are heated by an electric furnace. The honeycomb is placed inside a tube reactor and can be flushed with water vapour or with an inert gas. A homogeneous temperature within the sample is reached and testing conditions are reproducible. Through analysis of the product gas the hydrogen production is monitored and a reaction rate describing the hydrogen production rate per gram ferrite can be formulated. Using this test set-up, SiC honeycombs coated with a zinc-ferrite have been tested. The influences of the water splitting temperature and the water concentration on the kinetics of the water splitting step have been investigated. A mathematical approach for the reaction rate was formulated and the activation energy was calculated from the experimental data. An activation energy of 110 kJ/mole was found.

Document Type:Conference or Workshop Item (Speech)
Title:Kinetic Investigations of a Two-Step Thermochemical Water-Splitting Cycle Using Mixed Iron Oxides Fixed on Ceramic Substrates
Authors:
AuthorsInstitution or Email of Authors
Neises, MartinaUNSPECIFIED
Roeb, MartinUNSPECIFIED
Schmücker, MartinUNSPECIFIED
Sattler, ChristianUNSPECIFIED
Pitz-Paal, RobertUNSPECIFIED
Date:10 August 2008
Journal or Publication Title:ASME 2nd International Conference on Energy Sustainability
Refereed publication:Yes
In ISI Web of Science:No
Page Range:ES2008-54093
Editors:
EditorsEmail
ASME, UNSPECIFIED
Publisher:Pinehurst Technologies, Inc.
Series Name:ASME International Conferences on Energy Sustainability
ISBN:0-7918-3832-3
Status:Published
Keywords:solar, hydrogen, mixed iron oxide, hydrosol, kinetics
Event Title:ASME 2nd International Conference on Energy Sustainability
Event Location:Jacksonville, Fl (USA)
Event Type:international Conference
Event Dates:2008-08-10 - 2009-08-14
Organizer:American Society of Mechanical Engineers
HGF - Research field:Energy
HGF - Program:Renewable Energies
HGF - Program Themes:E SF - Solar research (old)
DLR - Research area:Energy
DLR - Program:E SF - Solar research
DLR - Research theme (Project):E - Solare Stoffumwandlung (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Technical Thermodynamics > Solar Research
Institute of Materials Research
Deposited By: Dr.rer.nat. Christian Sattler
Deposited On:21 Aug 2008
Last Modified:12 Dec 2013 20:32

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