Title: Methodology to determine the apparent specific heat capacity of metal hydroxides for thermochemical energy storage
Language: English
Authors: Lager, Daniel 
Hohenauer, Wolfgang 
Knoll, Christian 
Weinberger, Peter 
Werner, Andreas
Category: Research Article
Issue Date: 2018
Journal: Journal of Thermal Analysis and Calorimetry
ISSN: 1388-6150
Thermochemical energy storage uses reversible thermochemical reactions to store and release heat, representing a promising technology for energy conservation and utilizing fluctuating renewable energy sources and waste heat. Many recent studies have focused on determination of the enthalpy of reaction of possible thermochemical materials (TCM) based on thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). So far, comparatively few attempts have been made to characterize the apparent specific heat capacity at constant pressure cappp(T) of the investigated TCM. The purpose of this study is to outline a measurement and analysis procedure to evaluate cappp(T) of powdery TCM. The procedure is presented focusing on two metal hydroxides Ca(OH)2 and Mg(OH)2. Preliminary TGA experiments were conducted to identify reaction-free temperature intervals and mass change. Starting from the metal hydroxide, subsequent DSC experiments with two consecutive heating and cooling cycles were carried out to determine cappp(T) of the initial hydroxide and the oxide product. Three separate DSC runs for each candidate enable an evaluation of measurement uncertainty, and cappp(T) results were compared to available literature data. Preliminary TGA experiments have shown that the applied heating rate β has a strong effect on the measured dehydration reaction. This result influences the consecutive cappp(T) interpretation of the metal hydroxides. Analysis of the measured cappp(T) data compared to literature show good agreement for both metal hydroxides and oxides. Overlapping endotherm effects, which are not part of cp(T), have to be considered for further thermal conductivity calculations.
Keywords: Thermochemical energy systems; Specific heat capacity; Thermochemical materials; Calcium hydroxide; Magnesium hydroxide
DOI: 10.1007/s10973-017-6883-2
Library ID: AC15321008
URN: urn:nbn:at:at-ubtuw:3-4922
Organisation: E302 - Institut für Energietechnik und Thermodynamik 
Publication Type: Article
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