Thermochemical Energy Storage System Research Articles

Sustainable and open sorption system for low‐temperature heat storage applications

In the present study, an open sorption thermochemical energy storage (TCES) system was developed and investigated experimentally for low-temperature heat storage applications using zeolites. Desorption and adsorption experiments were carried out sequentially for 15 cycles to study the energy storage and retrieval characteristics. Further, the performance characteristics were analysed to find the system's suitability for intended applications. The charging and discharging processes were carried out respectively at around 95°C and room temperature, for zeolite 13X and zeolite 4A. Zeolite 13X exhibited better average total energy storage density during the desorption and adsorption and they are respectively 129.4 and 57 kWh/m3. The average cumulative energy storage efficiency for zeolite 13X and zeolite 4A are respectively 44.1% and 24%. Similarly, the average exergy efficiency for zeolite 13X and zeolite 4A are respectively 21.5% and 11%. For the tested thermochemical materials (TCMs), the deviations in mass change due to multi-cycle test-run was small and hence suitable for long-term usage without concern about their stability. The present study has demonstrated the technical competence in utilizing the energy sources (eg, solar energy, industrial waste heat) towards low-temperature heat storage applications, viz. building's space heating and water heating.

Analysis of a novel constructal fin tree embedded thermochemical energy storage for buildings applications

Because of their potential for long-term and loss-free thermal energy storage, thermochemical materials are attractive candidates for storing solar thermal energy in buildings applications. A drawback, however, is that of poor heat transport in the thermochemical material bed during charging and discharging. This study presents a novel thermochemical energy storage system with embedded constructal fin tree structure to enhance the discharge process. The influence of the constructal fin design parameters on the energy storage density and levelized cost of storage is studied to establish design envelopes that satisfy the U.S. Department of Energy Buildings Thermal Energy Storage program requirements, which include a round-trip thermal energy storage density of more than 80 kWh/m3 and storage cost less than $15/kWh. The study reports optimum designs of the constructal fin tree enhanced thermochemical reactor bed based on minimum levelized cost of storage and maximum energy storage density for building-integrated thermal energy storage applications.

Thermochemical storage of medium-temperature heat using MgO promoted with eutectic ternary mixture LiNO3-NaNO3-KNO3

Decarbonation of MgCO3 is promising for thermochemical energy storage (TCES) at medium temperatures as it has appropriate reaction thermodynamics and low material cost. For approaching the problem of kinetic hindrance and severe reaction metastability, MgO was modified with the triple eutectic mixture LiNO3-NaNO3-KNO3 (Li0.30Na0.18K0.52NO3) to investigate the sorption/desorption properties, which were studied in detail for prospective conditions of a TCES system. The composites with various salt contents were comprehensively characterized by X-ray diffraction, N2 sorption, Scanning electron microscopy (SEM). The sorption behavior was tested at various salt contents, temperatures (290–360 °C) and CO2 pressures (50–100 kPa). The conversion of MgO to MgCO3 up to 0.65 and the CO2 uptake up to 16.2 mmol/g were found. The heat storage capacity reached 950 kJ/kg-composite and decreased down to 750 kJ/kg-composite after 20 carbonation/decarbonation cycles. The results obtained suggest an excellent performance of the material under the conditions that allow utilization of heat at T > 400 °C.

Experimental screening of salt hydrates for thermochemical energy storage for building heating application

The selection of a suitable salt hydrate for use in a thermochemical energy storage system is challenging. In this work, the most promising salts to store intermediate heat energy were selected and tested. The criteria set are; volumetric energy density of >500 kWh m−3 with a dehydration temperature of <100 °C, material cost of <3.5 USD kg−1 (<15 USD kWh−1), melting does not occur during dehydration and safety. Based on that, the salt hydrates SrCl2, MgSO4, Na3PO4, MgCl2 and SrBr2 were selected and tested experimentally. A constant temperature and humidity chamber was used to measure moisture sorption of different salts. The hydration is investigated under the conditions of 20 °C and 20, 30, 40, 60 and 80% RH, while dehydration is investigated under the conditions of 70, 100 and 140 °C using an oven. These dehydration temperatures of <100 °C are suitable for solar application whereas the dehydration temperature of 140 °C is suitable for waste heat. Furthermore, the salts are cycled over 30 times under the hydration conditions of 20 °C, 60% RH with a dehydration temperature of 100 °C. From these results, it is concluded that SrCl2 and SrBr2 are the most promising salts. This study outlines both the advantages and disadvantages of each salt and states the conditions they are most suitable for.

Mechanical Booster Pump-Assisted Thermochemical Mode for Low-Grade Heat Storage and Upgrading: A Thermodynamic Study

To assure stable and dependable functioning of the thermochemical energy storage (TCES) system under unstable low-grade heat temperatures, three mechanical booster pump-assisted TCES (MBP-assisted TCES) modes operating with SrBr2·H2O/H2O, LiOH/H2O, and CaCl2·H2O/H2O are proposed for the application of heat storage and upgrading. The operating modes are the MBP-assisted charging mode (A mode), MBP-assisted discharging mode (B mode), and MBP-assisted charging and discharging mode (C mode). A thermodynamic model is established to evaluate the influences of condensing temperature, compression ratio, MBP isentropic efficiency, and reaction advancement on the heat source temperature and system performance from both energy and exergy perspectives. The results indicate that compared with the other two modes, the B mode is more effective in reducing the heat source temperature and achieving better system performance. Compared to the conventional TCES mode, the proposed modes can operate at lower heat source temperatures that can be minimized by up to 21∼25°C by employing the B mode with a compression ratio of 3.0 at the condensing temperature of 24°C. The B mode with SrBr2·H2O/H2O exhibits the highest energy and exergy efficiencies that the coefficients of performance based on total energy input and electric power consumed (COPtotal and COPelec), and exergy efficiency varies in the range of 0.53∼0.59, 7.4∼19.6, and 0.78∼0.95, respectively. In contrast, CaCl2·H2O/H2O shows the lowest system performance, but a higher heat output temperature can be required. In addition, to maintain the MBP discharge temperature below 180°C, there is a maximum permitted compression ratio that varies depending on the operating modes, operating conditions, and working pairs. The findings of this research can be used as theoretical references and suggestions for selecting MBP-assisted TCES modes, operating conditions, and working pairs for low-grade heat storage and upgrading.

Steam-enhanced calcium-looping performance of limestone for thermochemical energy storage: The role of particle size

Steam injection has been proposed to attenuate the decay of CaO reactivity during calcium looping (CaL) under operating conditions compatible with carbon capture and storage. However, it is yet unknown whether the perceived advantages granted by steam hold under the distinct operating conditions required for the integration of the CaL process as a thermochemical energy storage system in Concentrating Solar Power Plants (CaL-CSP). Here, we study the influence of steam in conditions compatible with a CaL-CSP scheme and assess its impact when injected only during one stage; either calcination or carbonation, and also when it is present throughout the entire loop. The results presented here demonstrate that steam boosts the CaO multicycle performance in a CO2 closed loop to attain residual conversion values similar to those achieved at moderate temperatures under inert gas. Moreover, it is found that the enhancement in multicycle activity is more pronounced for larger particles.

Effects of eutectic alkali chloride salts on the carbonation reaction of CaO-based composites for potential application to a thermochemical energy storage system

The reversible reaction of a CaO-CaCO3-based thermochemical energy storage (TCES) system is a suitable option for enhancing the efficiency of CSP system’s energy storage due to its high working temperature and promising energy storage capacity. However, the CaO-based composite often suffers a reduction of reversibility during multicycle reactions, which steeply reduces the energy storage performance of the system. The carbonation is limited to the near-surface of CaO particles because the produced CaCO3 layer passivates the inner CaO from further reaction. In this study, we focused on adding eutectic alkali chloride salt (ECS) to CaO-based composites to enhance the carbonation reaction. The effects of the ECS additives were investigated in terms of carbonation temperature and melting point of the salts, and the resulting carbonation behaviors are discussed. For that, four kinds of ECS, which have different melting point, were added to CaO-based composites. It was observed that the temperature needed to induce the majority of the carbonation conversion was lowered when the ECS melting point was low. The predominant progress of carbonation conversion was followed by the production of molten ECS. The result indicates that molten ECS dissolves the CaO from a Ca–O grid, and provides an additional pathway for diffusion of free CaO ion pairs to CO2 adsorbed on the particle surface. Multicycle performances of ECS-added CaO-based composites were promoted compared to the CaO and CaO/MgO.

Heat transformation performance of salt hydrate-based thermochemical energy storage sorbent during hydration

Given that the outstanding benefits of high energy storage density (ESD) and long-term energy storage ability with ignorable heat losses, thermochemical energy storage (TCES) in salt hydrates is a promising way to bridge the gap between supply and demand sides for renewables in residential heating. In this article, the hydration process (for heat discharge) of the sorbent composed of binary lithium-based salt hydrate and expanded graphite (LiOC@EG) in an individual thermal energy storage (TES) module is numerically investigated. For the airflow of 0.2 m/s and 20℃ with 80% relative humidity (RH), the bed temperature and outlet temperature dramatically rise with 30 min, and the maximum values are around 46 ℃ and 52 ℃, respectively. With hydration reaction advancement, the water vapour concentration increases in the bed due to the slowdown of adsorption kinetics. The temperature gradient and hydration reaction difference alone radial direction in the TES unit is almost negligible, and the time required to basically complete the hydration process (α > 95%) is ∼6.5 h, indicating the thermochemical sorbent coupled with the TCES unit is appropriate for home heating supply. The results of this study may provide reference and prediction on heat and mass migration behaviours of TCES system.

Combined enhancement of thermal and chemical performance of closed thermochemical energy storage system by optimized tree-like heat exchanger structures

The full exploitation of thermochemical energy storage potential is still hampered by several technical limitations, such as the poor heat and mass transfer in the reactive beds. This paper addresses the need of enhancement of heat and mass transfer in solid-gas reactive beds by proposing, investigating and optimizing the use of branched fins made of high conducting material. Two reactor configurations in closed-system operation are examined, and the optimal fin designs are derived by means of surrogate models based on high-fidelity finite elements predictions. The results indicate the use of optimized branched fins to increase the amount of discharged energy up to +9.1% compared to literature benchmarks. However, in the instance of reactive beds where transfer of heat and mass mainly occur along the same predominant direction, fins bifurcations might also hamper the transfer of reactants, leading to diminished thermal performance particularly during the latest stages of the energy discharge process. As a consequence, the optimal number of bifurcations is smaller for reactors that require to operate for longer discharge time. Conversely, such trend is not present in the instance of reactive beds where transfer heat and mass mainly occur along district and mutually orthogonal directions. In this case the typical heat transfer maximization design guidelines can be adopted, indicating a negligible influence of mass transfer on the optimal fins architecture.

Flow characteristics simulation of spiral coil reactor used in the thermochemical energy storage system

According to environmental and energy issues, renewable energy has been vigorously promoted. Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously. Heat storage is a considerable solution for this problem and thermochemical energy storage is the most promising way because of its great energy density and stability. However, this technology is not mature enough to be applied to the industry. The reactor is an important component in the thermochemical energy storage system where the charging and discharging process happens. In this paper, a spiral coil is proposed and used as a reactor in the thermochemical energy storage system. The advantages of the spiral coil include simple structure, small volume, and so on. To investigate the flow characteristics, the simulation was carried out based on energy-minimization multi-scale model (EMMS) and Eulerian two-phase model. CaCO 3 particles were chosen as the reactants. Particle distribution was shown in the results. The gas initial velocity was set to 2 m·s −1 , 3 m·s −1 , and 4 m·s −1 . When the particles flowed in the coil, gravity, centrifugal force and drag force influenced their flow. With the Reynold numbers increasing, centrifugal and drag force got larger. Accumulation phenomenon existed in the coil and results showed with the gas velocity increasing, accumulation moved from the bottom to the outer wall of the coil. Besides, the accumulation phenomenon was stabilized when φ > 720°. Also due to the centrifugal force, a secondary flow formed, which means solid particles moved from the inside wall to the outside wall. This secondary flow could promote turbulence and mixing of particles and gas. In addition, when the particle volume fraction is reduced from 0.2 to 0.1, the accumulation at the bottom of the coil decreases, and the unevenness of the velocity distribution becomes larger.

Charging and discharging analysis of thermal energy using magnesium nickel hydride based thermochemical energy storage system

A concentrated solar power plant integrated with thermal energy storage system helps to operate the plant during non-sunshine hours. This helps to increase the power generation capacity and improve the dispatchability of the power plant. Thermal energy systems are classified into sensible, latent, and thermochemical energy storage systems. Thermochemical energy storage with high energy storage density is one of the potential energy storage techniques available. The metal hydride-based thermal energy storage system has high energy storage density, better chemical reversibility, long cyclic, and high temperature stability. A dual bed metal hydride system uses high and low-temperature metal hydrides. High temperature metal hydride is used as energy storage media, while low-temperature metal hydride is used as hydrogen storage media. In this article, a detailed discussion on the energy sorption (absorption and desorption) analysis of a metal hydride suitable for high temperature in a dual bed metal hydride-based thermal energy storage system is performed. A 3-D model of Magnesium Nickel alloy in cylindrical geometry with radially distributed axial tubes is developed in COMSOL Multiphysics 5.5. The energy absorption and desorption analysis of metal hydride with variation in the number of heat transfer fluid tubes and different aspect ratio geometry are performed in detail. Study on variation of the number of heat transfer fluid tubes includes identifying the requirement of the adequate number of heat transfer fluid tubes to supply/remove heat to/from metal hydride during energy absorption/desorption. Variation of aspect ratios on the heat energy sorption characteristics and heat transfer phenomenon is studied in detail for both energy absorption and desorption cycle. The adequate number of heat transfer fluid tubes for the aspect ratio 0.5, 1, and 2 are found as is 32, 48, and 72, respectively. The stored and released energy for absorption and desorption study for the aspect ratio 0.5, 1, and 2 are 274.83 kJ, 255.44 kJ, and 240.27 kJ and 250.11 kJ, 234.43 kJ, and 224.10 kJ, respectively. The energy storage efficiency of the metal hydride bed for aspect ratios 0.5, 1, and 2 is 91%, 91.77%, and 93.27% respectively, while the overall system efficiency of the metal hydride bed for aspect ratios 0.5, 1, and 2 is 70.46%, 71.23%, and 72.39% respectively. The outcomes of this study helps to design the metal hydride based thermochemical energy storage system for process heating and power generation.

Compression-assisted decomposition thermochemical sorption energy storage system for deep engine exhaust waste heat recovery

In the context of the stringent automobile emission legislations, this paper proposes a novel compression-assisted decomposition thermochemical sorption energy storage system for recovering engine exhaust waste heat, which is utilized to produce cooling capacity for a refrigerated vehicle. In this system, the desorption pressure of sorbent can be flexibly adjusted by changing the suction pressure of compressor embedded between the sorption bed and condenser, which ensures the stable operation of system even at relatively low exhaust temperatures. Simultaneously, the decomposition reaction increases suction pressure of compressor, so the coefficient of performance (COP) is thus greatly improved. Furthermore, the sorption bed can output cooling capacity for refrigerated compartment when the vehicle is parked. Currently, vehicle emission standards generally adopt World Harmonized Stationary Cycle test, and 13 engine operating points are selected. At an operating point 3 (a low engine load), i.e. 55% speed and 25% torque, the COP of the novel system at an evaporating temperature of −25 °C and a condensing temperature of 45 °C is 1.65, 1.5 times higher than that of conventional one. The weighted average COP under 13 operating points is still up to 1.48. Eventually, the novel system promotes the realization of low-carbon and low-cost refrigerated transportation.

Effect of Steam Injection during Carbonation on the Multicyclic Performance of Limestone (CaCO3) under Different Calcium Looping Conditions: A Comparative Study

This study explores the effect of steam addition during carbonation on the multicyclic performance of limestone under calcium looping conditions compatible with (i) CO2 capture from postcombustion gases (CCS) and with (ii) thermochemical energy storage (TCES). Steam injection has been proposed to improve the CO2 uptake capacity of CaO-based sorbents when the calcination and carbonation loops are carried out in CCS conditions: at moderate carbonation temperatures (∼650 °C) under low CO2 concentration (typically ∼15% at atmospheric pressure). However, the recent proposal of calcium-looping as a TCES system for integration into concentrated solar power (CSP) plants has aroused interest in higher carbonation temperatures (∼800–850 °C) in pure CO2. Here, we show that steam benefits the multicyclic behavior in the milder conditions required for CCS. However, at the more aggressive conditions required in TCES, steam essentially has a neutral net effect as the CO2 uptake promoted by the reduced CO2 partial pressure but also is offset by the substantial steam-promoted mineralization in the high temperature range. Finally, we also demonstrate that the carbonation rate depends exclusively on the partial pressure of CO2, regardless of the diluting gas employed.

Investigation of hydration/dehydration processes in a fluidized bed reactor using MgO/Mg(OH)2 thermochemical energy storage system

Thermochemical energy storage (TCES) is a promising energy storage method because of its high energy storage density and long-term storage ability. The reactor is the most critical part of the TCES system, and the fluidized bed reactor (FBR) is a novel reactor, which is not restricted by the low effective thermal conductivity of energy storage materials. However, there is little theoretical guidance about the design and operation of the FBR for a TCES system. In this study, we investigated the performance of an FBR using MgO/Mg(OH)2 as reaction materials by establishing a numerical model followed by experimental validation. The influence of operating parameters on the bed temperature was discussed based on numerical results. According to the sensitivity analysis, the reactor inner diameter, material mass, and inlet gas velocity were the main factors affecting the bed temperature. The optimal boundary surface temperature was analyzed, which influences the proportion of TCES in the total heat storage.

Numerical approach for solution of fluid and heat transfer coupled problem through porous media

The fluid and heat transfer in porous medium play vital role in many industrial applications. Fluidized bed, heat pipe, thermochemical energy storage systems are few applications related to fluid and thermal flow in porous medium. Theoretically fluid and heat transfer subject domain handle separately but in practical case coupling problem based on both domain exist. In the present paper, numerical approach for solution of fluid and heat transfer coupled problem through porous media is presented. The mathematical model is developed based on Darcy’s extension law, energy equations and constitutive relationship. The FEM solution of the problem is also compared with analytical solution to satisfy the model used.

Thermal performance analysis of the sorption heat storage system with packed bed based on a spatially resolved 2D model

For a thermochemical energy storage (TCES) system, the fluid flow, heat and mass transfer, and reaction kinetics in packed bed reactors are closely related to the packing structure, which is crucial for charging/discharging performance. This study presented a spatially resolved 2D model to investigate the effects of packing structure on the discharge process in a packed bed reactor of a TCES system. Good agreement between the numerical results of the developed 2D model and experimental measurements was observed regarding the temperature profile and breakthrough curve. The proposed model effectively bridged the gap between the pseudo-homogeneous model and the spatially resolved 3D model, which could resolve the particle-resolved physical fields with limited computational resources.The radial profiles of velocity and intra-particle water loading complied with the oscillating distribution of the radial porosity. Furthermore, when the diameter ratio increased from 5.8 to 9.67, the relative velocity increased slightly from 3.98 to 4.33 in the near-wall region, whereas the non-uniformity of the velocity in the centre region decreased. Additionally, the developed 2D model was employed to conduct a parametric study of packed beds. According to the numerical results, the packed bed had an energy density of up to 245 kWh/m3.

Efficiency Enhancement of an Ammonia-Based Solar Thermochemical Energy Storage System Implemented with Hydrogen Permeation Membrane

The ammonia-based solar thermochemical energy storage (TCES) is one of the most promising solar TCESs. However, the solar-to-electric efficiency is still not high enough for further commercialization. The efficiency is limited by the high ammonia decomposition reaction temperature, which does not only increase the exergy loss through the heat recuperation but also causes a large re-radiation loss. Nonetheless, lowering the reaction temperature would impact the conversion and the energy storage capacity. Thanks to the recent development of the membrane technology, the hydrogen permeation membrane has the potential to enhance the conversion of ammonia decomposition under the moderate operating temperature. In this paper, an ammonia-based solar thermochemical energy storage system implemented with hydrogen permeation membrane is proposed for the first time. The system model has been developed using the Aspen Plus software implemented with user-defined Fortran subroutines. The model is validated by comparing model-generated reactor temperatures and conversions profiles with data from references. With the validated model, an exergy analysis is performed to investigate the main exergy losses of the system. Furthermore, the effects of the membrane on system efficiency improvement are studied. The results show that exergy loss in the charging loop is dominant, among which the exergy losses of Heat Exchanger Eh,A, together with that of the re-radiation Er, play important roles. Compared with the conventional system, i.e., the system without the membrane, the Eh,A and Er of the proposed system are more than 30% lower because the hydrogen permeation membrane can improve ammonia conversion at a lower endothermic reaction outlet temperature. Consequently, the proposed system, presumably realized by the parabolic trough collector at ~400 °C, has a theoretical solar-to-electric efficiency of ηste, which is 4.4% higher than the conventional ammonia-based solar thermochemical energy storage system. Last but not least, the efficiency is 3.7% higher than that of a typical parabolic trough solar power plant, which verifies the thermodynamic feasibility of further commercialization.

Evaluation of Calcium Looping Cycle as a Time-flexible CO2 Capture and Thermo-Chemical Energy Storage System

Currently, the time flexibility of energy conversion systems is an issue of great operational importance considering the high integration of time-irregular renewable energy sources (e.g., solar, wind) which put an additional pressure on the conventional fossil-based systems. In addition, the reduction of fossil CO2 emissions from various energy-intensive industrial sectors needs to be addressed considering the issues of global warming and climate change. This paper evaluates the innovative Calcium Looping (CaL) cycle both as an energy-efficient post-combustion CO2 capture option and as a time-flexible thermo-chemical energy storage system. As illustrative energy conversion system to which the calcium looping cycle will be applied, a natural gas-based combined cycle power plant was considered. The net power output was about 400 - 500 MW with a 90 % CO2 capture rate. Corresponded non-decarbonized case was also considered to calculate the CO2 capture penalty. In-depth modelling, simulation and thermal integration evaluations were done to cover the following relevant operational elements: characterization of decarbonized combined cycle power plants with CaL cycle with / without solid sorbent storage; mass and energy integration issues; detailed techno-economic and environmental calculations of main performance indicators; flexible part load operation of the power plant to take advantages of CaL thermo-chemical energy storage characteristics etc. As the results show, the flexible time-operation of the decarbonized power plant integrated with CaL cycle using sorbent storage option improves the overall performances e.g., capital cost reduction up to 10 %, lower electricity production cost up to 5 % etc.

Discharging behavior of a shell-and-tube based thermochemical reactor for thermal energy storage: Modeling and experimental validation

Thermochemical energy storage (TCES) has attracted significant attention in recent years due to some unique features of the technology such as very high energy density and negligible heat loss during storage. The TCES, however, is still at its early stage of development currently at a technology readiness level of 1–3. Major technical challenges of the TCES include materials stability, charge/discharge kinetics and limited temperature lift. Here we firstly studied the application of shell-and-tube thermochemical reactor with silica gels as heat storage material in open TCES system by experimental method. And then validated model (the maximum root mean square percentage error of 13.62% between the modeling and experiments) of single tube reactor containing 0.29 kg silica-gel was established to numerically investigate the discharging behavior of the thermochemical reactor under different operating conditions and flow directions of air and water. The numerical simulation results showed inverse heat transfer occurred for a counter-flow of air-water. The problem could be solved by changing the counter-flow of air and water to the parallel-flow. Thus, the water outlet maximum temperature limit was broken through. The total heat uptake increased by at least 24.14% when water flow rate was less than 0.36 kg/h and 11.93% when air flow rate was more than 1.07 kg/h, respectively. By increasing the inlet temperature of air and water from 23 °C to 38 °C, the maximum temperature lift could be significantly increased by 79.94% for air and 80.81% for water, respectively. Meanwhile, the total heat uptake increased by 107.44%. For a completely charging and discharging process, the discharging rate of parallel-flow was faster than that of counter-flow.

Salt hydrate–based gas-solid thermochemical energy storage: Current progress, challenges, and perspectives

Due to the prominent advantages of high energy density and long-term energy conservation ability, salt hydrate-based gas-solid thermochemical energy storage (TCES) is a promising technology for effectively employing low-grade energy such as industrial waste heat and minimising fossil fuel-based sources depletion. As an innovative thermal energy storage technology that has drawn great attention from scholars in recent years, it still remains in the stage of a laboratory-scale investigation. This study establishes a reasonable classification of salt hydrates-based TCES systems, discusses the properties and performance regulation strategies of materials, types of reactors, applications, heat and mass transfer process, reaction mechanisms, and also provides critical comments and outlooks on this adsorption TCES technology. It is comprehensively elaborated and evaluated in the following steps.(i) The development of various thermochemical materials (TCMs), including pure salts, mixtures of salt hydrates, and composite TCMs of salt/matrix, is summarised and assessed in detail from the perspectives of thermochemical performances such as ESD and cyclability.(ii) The progress of the conceptual design of the reactor and prototype used for vapour/salt gas-solid reaction are presented and analysed.(iii) The existing theoretical models ranging from the views of microcosmic molecular dynamics to macrocosmic reaction kinetics are discussed.(iv) Additionally, the existing challenges regarding salt hydrate-based TCES technology are identified, and the prospects are also provided.This review enables researchers to timely grasp the latest advancements and thus may provide some rewarding insights for future investigations of salt hydrate-based gas-solid TCES and facilitate scholars to achieve better improvements.