Materials Selection for MgCl2.6H2O-based PCM Thermal Energy Storage System

Role of PCM addition on stratification behaviour in a thermal storage tank – An experimental study

Thermal energy storage (TES) systems using phase change materials (PCM) have been lately studied and are presented as one of the key solutions for the implementation of renewable energies. These systems take advantage of the latent heat of phase change of PCM during their melting/ solidification processes to store or release heat depending on the needs and availability. Low thermal conductivity and latent heat are the main disadvantages of organic PCM, while corrosion, subcooling and thermal stability are the prime problems that inorganic PCM present. Nanotechnology can be used to overcome these drawbacks. Nano-enhanced PCM are obtained by the dispersion of nanoparticles in the base material and thermal properties such as thermal conductivity, viscosity and specific heat capacity, within others, can be enhanced. This paper presents a review of the patents regarding the obtaining of nano-enhanced materials for thermal energy storage (TES) in order to realize the development nanotechnologies have gained in the TES field. Patents regarding the synthesis methods to obtain nano-enhanced phase materials (NEPCM) and TES systems using NEPCM have been found and are presented in the paper. The few existing number of patents found is a clear indicator of the recent and thus low development nanotechnology has in the TES field so far. Nevertheless, the results obtained with the reviewed inventions already show the big potential that nanotechnology has in TES and denote a more than probable expansion of its use in the next years.

The overall objective was to develop innovative heat transfer devices and methodologies for novel thermal energy storage systems for concentrating solar power generation involving phase change materials (PCMs). Specific objectives included embedding thermosyphons and/or heat pipes (TS/HPs) within appropriate phase change materials to significantly reduce thermal resistances within the thermal energy storage system of a large-scale concentrating solar power plant and, in turn, improve performance of the plant. Experimental, system level and detailed comprehensive modeling approaches were taken to investigate the effect of adding TS/HPs on the performance of latent heat thermal energy storage (LHTES) systems.

Fe-26.38Si-9.35B eutectic alloy is proposed as a phase change material (PCM) as it exhibits high latent heat, high thermal conductivity, moderate melting point, and low cost. For successful implementation of it in the latent heat thermal energy storage (LHTES) systems, we investigate the use of graphite as a refractory material that withstands long-term melting/solidification in contact with the Fe-26.38Si-9.35B alloy. The PCM has been thermally cycled up to 1–4 times below and above its melting point at the temperature interval of 20 °C or 100 °C. It is observed that this eutectic alloy shows good thermal stability over a small temperature range of 1057–1257 °C. Some SiC and B4C solid precipitation will be formed at the top of the alloy. However, it does not seem to increase with time. The graphite crucible as a refractory material will produce a protective layer of SiC and B4C that will hinder the interaction between the PCM and the crucible. The small volume change during solidification will not break the graphite crucible during cycling. The chemical wear or dissolution of the crucible is negligible. It demonstrates the viability of Fe-26.38Si-9.35B alloy as a heat storage material in this type of container.

The current society is experiencing serious problems in terms of energy and environmental pollution. Environmentally friendly and renewable sources such as phase change materials have been employed as a reliable and effective source of energy storage. Phase change materials (PCMs) are known to absorb or release sizeable amount of energy during melting and solidification process. PCMs have been employed in both thermal protection and energy storage systems, more in active as well as passive cooling applications. However, PCMs are associated with low thermal conductivity, which hinders the process of heat rate exchange during the melting/solidification cycles. To improve the thermal conductivity of PCMs, various conductive fillers have been incorporated to such systems. Thermal cycle test is done to verify the stability of PCMs in thermal energy storage systems. This review emphasizes on the morphology, preparation methods and thermal cycle of various types of PCMs in the presence of conductive filler. Furthermore, the bibliometric analysis based on key research areas, top ten leading countries, and citations by country on phase change materials for energy storage research are reported in this review paper. The bibliometric analysis shows the dominance of the People’s Republic of China on PCMs for energy storage research.

Concerns about environmental issues and energy consumption have increased the need for efficient renewable energy utilization, with thermal energy storage (TES) systems playing a key role. TES systems using phase change materials (PCMs), which are able to store energy within narrow temperature ranges, show significant potential. One promising approach involves the use of phase change material emulsions, where PCMs are dispersed in heat transfer fluid and stabilized by emulsifying agents. Recently, Pickering emulsions, stabilized by solid particles, have gained interest for their enhanced long-term and thermal stability. This study focuses on oil in-oil Pickering emulsions, using paraffin as the PCM and polyethylene glycol (PEG400) as the continuous phase, stabilized by solid silica nanoparticles. The thermal-mechanical properties of emulsions with different PCM concentrations were analyzed for energy storage applications. Key words. Thermal energy storing, Phase change materials, Pickering emulsions.

Experimental and computational study of melting phase-change material for energy storage in shell and tube heat exchanger

A number of models and modelling approaches for phase transitions of phase change materials (PCMs) have been proposed in recent years. However, many of these models have not been thoroughly validated with experimental data. This is in particular the case of the models for thermal hysteresis and partial phase transitions of PCMs, where the design and execution of relevant experiments is difficult. The most widely used experimental techniques for characterization of PCMs - Differential Scanning Calorimetry (DSC) and T-history method – require minimization of the temperature gradients in the test samples and thus the obtained results do not represent very well the behavior of PCMs in thermal energy storage (TES) systems (where large temperature gradients in PCMs are commonplace). An experimental set-up for the acquisition of data suitable for validation of phase change models have been proposed and assembled. The set-up can be used for the model validation in case of both the direct and inverse heat transfer problems. The set-up is based on the monitoring of the phase change front propagation in a rectangular cavity, where the positive or negative heat flux is introduced at one of the cavity walls. Such an arrangement results in (often significant) temperature gradients in a PCM. Unlike in similar experimental set-ups, where a heat transfer fluid (HTF) is used to introduce the heat flux at the wall, the Peltier cells are used in the proposed experimental set-up for this purpose. Also, most experiments reported in the literature only addressed the melting process (heating of a PCM) with the positive heat flux introduced at the wall. The Peltier cells allow for relatively quick switching between the positive and negative heat flux (heating/cooling) and as a result the thermal processes similar to real-life operation of TES systems can be investigated. The cubical cavity with 250 mm long internal edges is made of PMMA. The wall, at which the heat flux is introduced, is made of a 15 mm thick aluminum plate with embedded RTD temperature sensors for wall temperature monitoring. A heat flux sensor is installed on the side of the aluminum plate facing the PCM (the heat flux sensor covers the entire surface of the plate). An extended heat transfer surface in the form of a finned aluminum sink is installed on the Peltier cells to improve the heat transfer between the cells and the ambient environment.

The aim of the present research work is to reduce starting time of engine by utilizing the heat stored in thermal energy storage (TES) system by using different properties of phase change material (PCM) are studied by varying test conditions and based on the performance paraffin wax was selected as best suitable material for experimentation. This paper represents an experimental investigation of thermal energy storage system by light duty petrol engine. The storage system was initially design by considering size of the engine and amount of heat required, thus to reduce exhaust gases emission of engine at starting time and also improve engine performance. The experimental work concludes that reducing the start up time of engine by five minute and also improve warm up time nearly at 45% achieved with TES system.

Optimization of tube arrangement and phase change material for enhanced performance of solar air heater- A numerical analysis

Geocooling with integrated PCM thermal energy storage in a commercial building

Shell-and-tube or packed bed thermal energy storage systems integrated with a concentrated solar power: A techno-economic comparison of sensible and latent heat systems

This paper presents a numerical simulation-based study that evaluates the potential of an active phase change material (PCM) incorporated thermal energy storage (TES) system for space cooling in residential buildings. In the proposed concept, TES system is composed of stand-alone PCM storage units which are installed between the concrete ceiling slab and the ceiling finishing layer. Active control of the thermal energy storage is achieved by night cooling of a phase change material by means of cold water flowing within a capillary pipe system. Effectiveness of the system under the typical summer conditions of the Baltic States is analysed by using computational fluid dynamics (CFD) software Ansys Fluent. Results showed that installation of the active TES system has a positive effect on thermal comfort, reducing the average indoor air temperature by 6.8 °C. The outcome of this investigation would be helpful in selecting the key characteristics of the system in order to achieve the optimum performance of an active TES system for space cooling of buildings in similar climates.

An overview of recent literature on the micro- and nano-encapsulation of metallic phase-change materials (PCMs) is presented in this review to facilitate an understanding of the basic knowledge, selection criteria, and classification of commonly used PCMs for thermal energy storage (TES). Metals and alloys with high thermal conductivity can be used as PCMs for rapid heat storage in compact systems owing to their high volumetric TES density. The emerging application of metal PCMs in different fields such as solar thermal energy management, smart wearable devices with thermal comfort control, and cooling of electronic devices call for the need of micro- and nano-TES particles, which can be synthesised in different forms to satisfy specific requirements. As metals are easily oxidised, especially at the micro- and nano-level, encapsulation of metal-based PCM particles is important for sustainable use at high operating temperature in ambient conditions. Recent studies focusing on the encapsulation of metallic PCMs at the micro- and nano-level have been reviewed and classified in terms of the melting point of metal/alloy PCMs used and types of encapsulation materials, such as oxides, polymers, carbon, and metals. The current review is expected to provide an outlook on novel metal and alloy PCMs with function-directed structures and superior TES properties for a broad range of applications.

Numerical analysis for maximizing effective energy storage capacity of thermal energy storage systems by enhancing heat transfer in PCM