Thermal energy storage: “How previous findings determine current research priorities”
Highlights
► The paper reviews the current applications and principles of heat energy storage. ► High temperature thermal storage is specifically considered. ► Latent heat and phase change materials are highlighted. ► Metal foams are considered to enhance thermal properties. ► Current knowledge and understanding leads to priorities for future research.
Introduction
The efficient use of energy is of growing importance and developing highly effective energy saving solutions are paramount in the current energy demand context. The objective of the current paper is to review the available information on the thermal energy storage (TES), in order to define the priority research objectives to complete the fundamentals needed for their widespread application. The review part of the paper specifically focuses upon (i) the underlying storage mechanisms and its potential, (ii) the essential materials and properties that delineate temperature ranges of application, and (iii) the illustration of particular solutions to high temperature thermal energy storage. After a brief description of thermal energy storage, the advantages of storing both sensible and latent heat are discussed. As a specific case, we show the effectiveness of storage involving latent heat and how it leads to the selection of a phase change material (PCM) for specific applications, whilst highlighting its appropriate characteristics, its current weaknesses, and the multiple solutions to improve the thermal properties of PCM. The selected solution involves a metal foam and a PCM, two materials that have been previously studied, mostly towards their applicability and advantages. From assessing these previous studies, it is clear that there is an urgent need to develop a thermo-mechanical modelling of such a composite, subject of the extensive research program currently carried out by the authors. The layout of the present paper is illustrated in Fig. 1. Each of the parallel topics is subsequently dealt with.
Section snippets
Energy storage
Energy Storage (ES) is the storage of some kind of energy that can be drawn upon at a later time and usefully re-applied in a given operation. It has the potential of increasing the effective use of energy equipment and is normally applied to balance the possible mismatch between the supply of, and demand for energy [1]. The imperativeness of ES results from the need of having the energy production decoupled from its supply and distribution, and to support the intermittent nature of producing
Structural analysis and characterization
Several studies of isolated metal foam structures have been undertaken over the past years. Efforts have been made to determine the proper modelling of aluminium alloys. However, there are no studies attempting to develop a model specifically to a copper foam structure. The present review presents a few interesting approaches to the micro-structural characterization of metal foams and porous materials in general, which provide starting points for further investigations related to copper foam
Conclusions and further research
The aim of this review was to critically examine the current state of art in order to delineate the required further development of a high temperature model of metal foam embedded with PCM. The parameters involved in the process of loading and releasing of thermal energy have to be investigated and adjustments to improve the material’s heat flux behaviour have to be determined.
This paper is leading to focus on the study of one major thermal storage parameter: the rate of loading and releasing
Acknowledgements
This work is supported by the Centre for the Innovation in Energy (UAI, Chile), FONDECYT Chile (project number:1120490), UK Engineering and Physical Science Research Council (EPSRC grant number: EP/F061439/1), by the National Natural Science Foundation of China (Grant Nos: 51176110 and 51071184). The authors gratefully acknowledge support and advices from Dr. C.Y. Zhao of the School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China, and from Mr Y. Tuan of School of
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