Sorption Thermal Energy Storage Systems with Embedded Membranes for Improved Power Density (original) (raw)
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A Review on Open Sorption Thermal Energy Storage System Using MgCl 2 .6H 2 O
– In most recent couple of decades, Thermal Energy Storage (TES) has turned into the topic of most extreme significance in many engineering applications and has been demonstrated as the subject of great interest of research work. Sorption systems (adsorption or absorption) are reliant on a chemical processes and subsequently are also named as chemical heat storage. The Chemical Thermal Energy Storage (CTES) incorporates sorption and thermochemical systems. In sorption energy storage, heat is stored by dissociation reaction and is recovered in chemically reverse reaction. Sorption TES has high storage densities than other types of TES, in this way permitting huge amount of thermal energy to be stored by utilizing small amount of storage substances. Energy storage dependent on chemical reaction is especially reasonable for long term and short term storage applications, e.g., solar heat storage, daily waste heat storage, etc. Amid the storage duration, since the process includes no heat losses, storage is typically completed at surrounding temperatures. This paper reviews only the open sorption TES utilizing MgCl 2 .6H 2 O salt hydrate with an interest in comparing different heat storage materials, latest advancements in materials, their characterization, their limitations and conceivable changes for their applications. INTRODUCTION The sharp rise in requirement for energy, the ascent in the cost of fuel connected with the ever increased consumption of non renewable fossil fuels, and the constant increase in CO 2 discharges all require the improvement of more energy efficient procedures and a move from non-renewable energy sources to renewable energy sources.[1] In this sense, thermal energy storage and change (TESC) can improve the thermal energy effectiveness of a process by reusing the waste heat from industrial processes, solar power or different sources. Sensible, Latent and Thermochemical (sorption and chemical) heat storage methods are the main types of thermal energy storage strategies.[2][3] This paper concentrates just on sorption chemical heat energy storage. Sorption thermal energy storage is expressed as storage of heat energy for heating and cooling applications amid the prescribed time period. It is renewable energy system which serves to upscale the efficiency of existing system and making the energy accessible as when required. Sorption system is to be designed for a specific storage duration, temperature necessities, available space, storage capacity and heat losses.[4] Chemical sorption TES systems operates on reversible chemical reactions i.e. Thermochemical TES These are more efficient, compact, possesses higher energy storage densities and can be used for long and short term storage. It is based on chemically reverse reaction as: C + Heat ↔ A + B. where, C is the heat storage material which is stable chemical mixture of A and B. By providing heat to C, the substance A and the substance B are separated and are stored separately. The reaction happens in reverse order when A and B are united together and the substance C is regenerated thus releasing useful heat from TES system. The system capacity is calculated by the value of heat liberated during regeneration of C. As mentioned in above reaction, the substance A will be among the ammoniate, hydroxide, hydrate, chloride, etc. and B can be water, NH 3 , hydrogen, etc. C is usually a solid or liquid (no restriction on phases) but A and B can be of any
Energy, 2011
Adsorption refrigeration and heat pump systems have been considered as important means for the efficient use of low-grade thermal energy of 60e150 C. Sorption systems are merely thermodynamic systems based on heat exchangers, and therefore a good design to optimize heat and mass transfer with reaction or sorption processes is very important, for which the notable technique is the use of expanded graphite to improve both heat and mass transfer in the chemisorption beds. Studies have also shown the need to enhance the heat transfer in adsorption bed by matching with the efficient heat transfer of thermal fluids. Heat pipes and good thermal loop design coupled with adsorption beds could yield higher thermal performance of a sorption system. A novel design with passive evaporation, known as rising film evaporation coupled with a gravity heat pipe was introduced for high cooling output. It has also been shown that the performance of traditional heat and mass recovery in the sorption systems is limited, and novel arrangement of thermal fluid and refrigerant may improve the performance of sorption systems. Based upon the above researches, various sorption systems have been developed, and high performances have been reached.