Klaus Afflerbach; Sandra Afflerbach; Reinhard Trettin; Wolfgang Krumm
Abstract
One major scientific challenge is a shift of the energy generation and utilization towards sustainability and efficiency. Therefore, thermochemical heat storage concepts offer a promising contribution as for example by integration in Concentrated Solar Power (CSP) applications. The reaction system Ca(OH)2/CaO ...
Read More
One major scientific challenge is a shift of the energy generation and utilization towards sustainability and efficiency. Therefore, thermochemical heat storage concepts offer a promising contribution as for example by integration in Concentrated Solar Power (CSP) applications. The reaction system Ca(OH)2/CaO is seen as a superior candidate but its poor powder properties yet hinder a technical implementation. The authors have recently proven, that these obstacles can be overcome by a persistent particle size stabilization of the pre-granulated storage material. Within the present study, the mechanical capsule material properties are improved by admixing of additives to the powdery precursor. By thermochemical conversion in a laboratory reactor, the cyclability and the suitability for moved reaction beds of the storage material is proven. The investigations are complemented by attrition tests on the most promising sample material and an encapsulated reference material. It is shown that the chemically enhanced encapsulation is a suitable approach to retain good flow properties and reduce attrition significantly. An encapsulated sample with an enhanced shell material composition containing 5%(w/w) of diatomaceous earth and 1%(w/w) of flux agent is found to be of superior stability over ten thermochemical cycles. A comparative macroscopic evaluation of the sample material after tenfold thermochemical cycling emphasizes the potential of this approach.
Sandra Afflerbach; Wolfgang Krumm; Reinhard Trettin
Abstract
Within the past decade, ecological issues accompanying energy generation and utilization have gained increasing interest, thereby creating a need for new scientific and technical solutions on the path to a sustainable energy future. Besides switching the basis of the electricity sector from fossil fuels ...
Read More
Within the past decade, ecological issues accompanying energy generation and utilization have gained increasing interest, thereby creating a need for new scientific and technical solutions on the path to a sustainable energy future. Besides switching the basis of the electricity sector from fossil fuels to renewables, also the heat sector is to be transformed. A major obstacle accompanying this energy transition is the temporal intermittency of power generation from renewables. However, these hurdles can be overcome by design of systems for energy storage and conversion. Within the growing field of solutions for thermal storage, thermochemical systems move into the focus as they provide comparably highest storage densities but at the same time also options for heat conversion. This concise review summarizes the background and the scope of possible applications discussed in recent literature. A focus is set on the identification and modification of new reaction systems, criteria for material selection are presented and different classes of reaction systems are discussed with regard to their operating temperature ranges. It is concluded, that an evaluation of possible use cases with precise definition of their respective thermal boundary conditions would be of high value for a purposeful continuation of future screening approaches.
Sandra Afflerbach; Reinhard Trettin
Abstract
A major scientific challenge for carbon neutral, environmental friendly future energy production is the development of renewable energy production to technological readiness. One example are solar thermal power plants. Since their energy generation is intermittent, they demand for a feasible storage ...
Read More
A major scientific challenge for carbon neutral, environmental friendly future energy production is the development of renewable energy production to technological readiness. One example are solar thermal power plants. Since their energy generation is intermittent, they demand for a feasible storage solution for which thermochemical reaction systems are considered. The present work subjects the thermochemical reaction system CaO / Ca(OH)2 and its structural-mechanical correlations impacting the powder bulk performance upon thermochemical cycling. On exemplified Ca(OH)2 crystals is shown, that during the first de- and rehydration process, the entire crystal morphology is disintegrated. The underlying mechanism is evaluated by theoretical considerations on the layered structure of Ca(OH)2 and validated by scanning electron microscopy (SEM) on the probed material before and after dehydration as well as after rehydration. The obtained findings are transferred to the technically relevant powdery storage material, where they are capable to explain the phenomenon of agglomeration, which is proven by measurement of secondary particle size distribution over a number of ten thermochemical reaction cycles. From SEM imaging performed on the samples it is found, that agglomerates consist of cohering smaller particles. The inferred insights can help to deduce necessary amendments of reactor design or material modification also for other thermochemical reaction systems.
)
)