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• The thermo-economic feasibility of the SPT station was investigated. • The influence of the location on the thermo-economics of the SPT station is evaluated. • The SPT station's thermo-economics are optimized. • An SM of 2.8 and a TES of 8 h were the best configurations for the STP station. Egypt is a sunbelt nation with plenty of solar resources and significant wasteland areas, particularly in its southern and western regions. Concentrating solar power technologies are tried-and-true renewable energy systems that use solar radiation to produce electricity in nearby nations. These technologies have the potential to reduce costs in the future. Comprehensive techno-economic research has not been conducted to assess the potential for the solar power tower technique in Egypt; instead, solar photovoltaic and parabolic trough systems are given the majority of the attention. The major goal of this article is to persuade the Egyptian government to pursue solar power tower technology and meet the accompanying difficulties. Using system advisor model software, six distinct locations were used to simulate a 100 MW plant for solar power tower technology. Based on a thorough technical solar power tower site evaluation research, these zones were examined. To achieve the lowest levelized cost of electricity (LCOE), thermal energy storage and solar field size optimization are carried out. The Benban location, with outputs of 521,228.8 MWh and 0.1130 $/kWh, respectively, has the greatest produced energy and the lowest levelized cost of electricity, according to the findings. The ideal design for the solar power tower plant was shown by the results to be a solar multiple of 2.8 with a thermal energy storage of 8 h. The solar power tower plant's lowest levelized cost of electricity might then be reduced, in accordance with the optimum configurations, to 0.1057 $/kWh. [ABSTRACT FROM AUTHOR]

Salt-hydrate based thermochemical energy storage is currently a momentous technique utilized for long-term energy storage due to the reversible gas-solid reaction under low-temperature. Among available salt candidates, LiOH·H 2 O is a promising thermochemical material owing to its high heat storage density of 1400 kJ/kg and low charging temperature. The expanded graphite (EG) is selected as a host matrix owing to its excellent thermal conductivity and abundant microstructure, which can promote the heat and mass transfer. This work focuses on the thermochemical performances of the form-stable LiOH·H 2 O/EG composite sorbents. Five samples were being synthesized with EG contents of 0, 5, 8, 12 and 15 wt%. These porous sorbents are characterized to understand the microstructure and thermophysical properties. Considering the comprehensive effect of thermal conductivity and storage density, as well as the adsorption kinetics, the 8 wt% EG-doped sample is the most favourable sorbent, which possesses the thermal conductivity of 6.92 W/(m K) and energy density of 1120 kJ/kg. The cyclability results also reveal the energy capacity of this composite maintains ∼90% of the original after ten consecutive heat charging (dehydration) and discharging (hydration), suggesting good stability. Additionally, the active energy of 2.58 × 109 s−1 and pre-exponential factor of 59.5 kJ/mol for the sorbent is derived. Finally, the thermal power of 123 W and thermal efficiency of 83.6% are achieved for the storage unit in simulation. All these results further confirmed the feasibility of the developed composite sorbent in low-grade heat storage. Image 1 • The TCMs based on LiOH·H 2 O with EG doping are developed. • The 8 wt% EG doped composite shows superior sorption property. • Over 90% of the original storage density is maintained after 10 cycles. • The active energy of 2.58×109 s−1 and pre-exponential factor of 59.5 kJ/mol are derived. • The thermal efficiency for heat charging is 83.6%. [ABSTRACT FROM AUTHOR]

Electronic devices are commonly used for exploiting and extracting shale oil in deep downhole environments. However, high−temperature−and−pressure downhole environments jeopardize the safe operation of electronic components due to their severe thermal conditions. In the present study, an active thermal−insulation system is proposed, which consists of a spiral annular cooling plate (ACP), a thermal storage container with phase−change material (PCM) and an aerogel mat (AM). The effect of the ACP's structure, layout and working−medium flowrate on the heat−protection performance were experimentally measured; temperature−control capability and system−operating time were used as the criteria. The results show that the AM layer is necessary and that the inner−ACP case displays better thermal−protection performance. Next, a dimensionless temperature−control factor (TCF) was proposed to evaluate the trade−off between temperature control and the system's operating time. Note that the TCF of the spiral ACP can be improved by 1.62 times compared to the spiral−ACP case. Since the lower flowrate allows better TCF and longer operating times, intermittent control of the flowrate with a 1−minute startup and 2−minute stopping time at 200 mL/min can further extend the system's operating time to 5 h, and the TCF is 3.3 times higher than with a constant flowrate of vm = 200 mL/min. [ABSTRACT FROM AUTHOR]

The current research examines how increasing the thickness of the phase change material (PCM) layer impacts the thermal and economic behavior of the hybrid sensible-latent heat storage reservoir utilized in solar power plants in order to prevent temperature fluctuations at the end of discharge cycles. On the basis of two-phase dispersion-concentric equations, a detailed transient numerical analysis is developed. The mathematical model equations are computed using the MATLAB program, and the present numerical findings are validated. Numerical investigations are used to compare the proposed storage system to the sensible heat storage (SHS) system in the context of cost and efficiency. The impact of various performance evaluation indexes, including axial temperature allocation, thermocline layer degradation, charging time, discharging time, and overall efficiency, are investigated. The results showed that the (35% PCM-30% SHS-35% PCM) configuration possesses the most considerable thermocline thickness of 7.94 m at the charge period of 360 min, while the SHS case has 3.2 m thermocline thickness at the charge period of 420 min. Due to its optimized efficiency, reduced thermocline area, and comparatively low cost, the (15% PCM-70% SHS-15% PCM) configuration demonstrates a more viable choice among the considered cases. • The thermal performance of a hybrid sensible-latent heat storage tank is analyzed. • A numerical model is used for the thermo-economic evaluation. • Thermo-economic evaluation of increasing the thickness of the PCM layer. • The (15% PCM-70% SHS-15% PCM) configuration demonstrates a more viable choice. [ABSTRACT FROM AUTHOR]

Perovskite Solar Cell (PSC) have recently emerged as exciting new candidates of Photovatics (PVs) for solar-to-electrical energy conversion. Nevertheless, one huge obstacle to its commercialization is how to improve its tolerance to operation at elevated temperatures. To address this issue, Composite Phase Change Material (CPCM) incorporated with a porous skeleton structure is proposed to integrate with PVs. In this structure, an important theoretical problem is that the temperature dependence of PV and the temperature control behavior of CPCMs interact with each other (bidirectional relationship). In this work, a pore-scale lattice Boltzmann phase change model is established to describe the dynamic thermal behavior of CPCMs and explore the roles of the bidirectional relationship between PVs and CPCMs, the change of power conversion efficiency influenced by temperature variation and glass transmissivity is discussed by comparing the overall liquid fraction of CPCMs, and the average temperature and power conversion efficiency of PVs. Furthermore, the situation of time-varying solar irradiation is discussed to mimic real application conditions. Results indicate that the neglecting temperature dependency of PVs leads to underestimation of PV surface temperatures and overestimation of power conversion efficiencies, while glass transmissivity provides reverse effects. These phenomena not only happen in constant solar irradiation but also in varying solar irradiation, calling for increasing attention to designing PV/CPCMs for varying heat flux conditions. The findings of this work establish a comprehensive manner toward integrated design of CPCMs for PV thermal control. • The roles of the bidirectional relationship between PVs and CPCMs are discussed. • Neglecting temperature dependency endows an overestimation of PV efficiency. • The highest temperature is underestimated if simplifying the variable heat flux to constant heat flux. • The temperature dependency of a PV has a slight influence on phase change. [ABSTRACT FROM AUTHOR]

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. • Salt hydrate-based sorption technology is the potential for heat storage. • The composite thermochemical materials need to be further developed. • The optimisation includes three levels: material, reactor, and system. • Mechanism, model, and performance control strategy need to be further studied. • Challenges and prospects of this technology are identified. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rip saw fin design (case 9) was considered to be the best because it has thin fins and has higher heat transfer coefficient. [•] Due to higher surface area density the heat transfer coefficient and Nusselt number obtained for case 7 is lower than other fin types. [•] The values of the average Nusselt number obtained for all the cases vary in small order of magnitude. [•] The maximum Nusselt number was obtained for the ripsaw fin design (case 9). [ABSTRACT FROM AUTHOR]

[Display omitted] • Binary lithium-based salt hydrates hierarchical inclusion in the matrix. • Temperature lift is over 20℃ accompanied by high energy density. • Energy capacity decreases with the discharging temperature. • Over 95% of the original energy capacity is maintained after 20 cycles. Considering the eminent 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 potential technology to bridge the gap between supply and demand for renewables in domestic heating. The development of thermochemical material is currently the primary concern. In this work, the composite sorbents consisting of expanded graphite (EG) and varying mass ratios of LiOH and LiCl are synthesised and characterised, and the thermochemical behaviours such as sorption kinetics and sorption isotherms are also investigated. The results suggest the salts are uniformly dispersed in the EG matrix in the form of hierarchical micro-nano scale particles, and the salt contents of samples are over 60 wt%, which in favour of the enhancements of vapour sorption property and ESD. By regulating the mass ratio of LiOH and LiCl, the composite sorbents (LiOC@EG) can achieve thermal upgrade with different temperature requirements, i.e., 35–45℃ for space heating and 45–55℃ for domestic hot water (DHW) production, accompanied by high volumetric ESD (over 200 kWh/m3) benefiting from the reaction enthalpy. Besides that, the effects of regenerative temperature and vapour pressure on the water uptake and ESD of the sorbent are revealed. The cyclability results indicate that more than 95% and 96% of the original ESDs are retained after 20 dehydration-hydration cycles for the samples of LiO2C1@EG and LiO3C1@EG, suggesting good stability of the composites. The developed composite sorbents provide new insights into the fields of long-term energy storage and heat upgrade with high energy density. [ABSTRACT FROM AUTHOR]

The present study aims to improve the thermo-chemical conversion behaviours, including reactive transport processes and output performances of an open thermochemical energy storage (TCES) unit. The local thermal non-equilibrium (LTNE) model and the effect of non-uniform porosity are adopted and considered to better elucidate the conversion processes. Cascading the reaction sub-units filled with different thermochemical materials (TCMs), i.e., zeolite, salt hydrate-based composite sorbent, and pure salt of SrBr 2 ·6H 2 O, to form an integrated storage bed ameliorates the output performance. The numerical results indicate that the maximum temperature difference ranging from 3.5 to 4.9 °C between heat transfer fluid and solid reactants exists during desorption, and the realistic non-uniform porosity facilitates the reactant conversion near the wall compared to the uniform porosity assumption. The cascaded scheme promotes the charging and discharging processes compared to the cases filled with sole TCM, the time required for charging this 10.8 kWh storage model is 16 h. Increasing the charging temperature from 100 °C to 145 °C, the charging time reduced to 6.5 h, saving 59.4%. Boosting the inlet velocity of airflow also accelerates the charging rate. The cascaded storage unit significantly stabilises the output temperature during discharging, warming up the airflow from 20 °C to 35 °C for 24 h with a tiny temperature fluctuation. Airflow with higher relative humidity facilitates hydration but shortens the stable period. Overall power and thermal efficiency of the "thermal accumulator" in charging are 598 W and 92.8%, 164 W and 92.4% in discharging, with a total COP of 0.71. The satisfying performances suggest that the cascaded TCES unit may provide a strategy and reference in the design and promotion of the low-grade energy storage system. [Display omitted] • Local thermal non-equilibrium model is adopted. • Inhomogeneous porosity is considered. • Cascaded heat storage materials stabilise output temperature. • Numerical system storage capacity and COP are 10.8 kWh and 0.71. [ABSTRACT FROM AUTHOR]

Due to the characteristics of high energy storage efficiency, large energy storage capacity and constant phase change temperature, organic phase change materials have been widely used in the field of thermal energy storage. However, organic phase change materials present a lower thermal conductivity which emerges as a critical limitation to the energy storage efficiency of latent heat thermal energy storage systems. To improve the thermal properties, the superior composite phase change materials of graphene aerogel impregnated paraffin wax were prepared in present study. Hydrothermal reaction method was used to prepare aerogel. Optimal conditions for aerogel preparation were identified as 140 °C/2.5 h/90%/(1:100) (140 °C is the hydrothermal working temperature of the reactor, 2.5 h indicates a treatment time, 90% is the solution occupying the reactor volume and 1:100 is the graphene oxide (GO)/water ratio in the solution). Furthermore, the addition of ethylenediamine and graphene nanoplatelets accelerated the reaction process, which required a hydrothermal treatment time by 50%. For the composite phase change material PW-GO/GNP-3 with a GO/GNP mass fraction of 4.4%, the thermal conductivity was 209.7% of that for the pure PW and the energy storage efficiency was still maintained at 91.60%. Meanwhile, the composite phase change material exhibits a leakage ratio of lower than 3.8%. In addition, based on the prepared composite phase change material samples, the phase change characteristics of phase change material in single cavity and three-cavities have also been examined. The synchronous phase change in three-cavities has been obtained by arranging the phase change material with low melting temperature in the cavity with low temperature, which requires the shortest melting time. [ABSTRACT FROM AUTHOR]

Thermocline thermal energy storage (TES) technology that uses the molten salt as heat transfer fluid is cheaper than a traditional two-tank structure, owing to its composite design and use of inexpensive filler materials. Nevertheless, this TES type suffers from the significant disadvantage of low capacity and utilization ratio when it is integrated with concentrating solar power plants due to moderate charge/discharge cut-off values. The primary purpose of the current research is to investigate and evaluate the impact of the change charge/discharge cut-off values on the thermal performance of six different TES tank configurations. First, the equations for the dispersion-concentric model were approached through the MATLAB program, and then the present research results are authenticated. The results show that the thermocline zones shrink when the charge cut-off value rises, and the discharge cut-off value reduces because a higher charge cut-off value and a smaller discharge cut-off value permit a longer charge/discharge time. Moreover, when the cut-off value of the charge/discharge changes simultaneously, the combined sensible-latent heat storage configuration has the highest capacity ratio, utilization ratio, recovered energy, and overall efficiency, which equals 90.55%, 83.3%, 147.2 MWh, 91.3%, respectively, at low charge cut-off value. • The thermal performance of the different thermocline tank configurations is analyzed. • The SHS configuration demonstrated the shortest charge/discharge time of 239/207 min. • At a higher charge cut-off value, the CSLHS case has the highest capacity ratio of 90.55%. • The MLPCMs-4 case has the highest recovered energy of 183.2 MWh with a lower charge cut-off value. [ABSTRACT FROM AUTHOR]

With the increasingly energy consumption and environmental degradation, the recovery of low-grade industrial waste heat and the development and utilisation of renewables have become urgent needs. At present, the recovery of waste heat is mainly at high temperature, and the recovery rate of waste heat at medium and low temperatures is low. Adsorption thermochemical energy storage (TCES) is a pivotal technology applied for long-term thermal energy storage based on the reversible gas-solid reaction at mid-to low-temperature. LiOH·H 2 O is a potential thermochemical material (TCM) candidate because of the high energy storage density (ESD). In this paper, the expanded graphite (EG) is used as supporting matrix to impregnate LiOH to further improve its heat and mass transfer. The water vapour adsorption properties such as sorption capacity and sorption isotherms of the consolidated composite sorbents with EG contents of 0, 5, 8, 12, and 15 wt% were tested. It was found that the samples with 5% and 8% wt% EG have superior sorption capacity and kinetics at various relative humidities (RHs), and the maximum water uptake substantially decreased with increasing temperature. The cyclability results showed 90% and 92% of the original ESDs are retained after 12 cycles for the samples with 8% and 15% wt% EG, suggesting good stability of composite sorbent. The ad/desorption isobars processes also proved the existence of the sorption hysteresis loop, and this phenomenon is more obvious at low pressure. The data fitting results revealed that the kinetics coefficient of the promising composite sorbent containing 8 wt% EG is 0.01671 s – 1 at 30 °C with 58% RH. Compared with the sensible or latent energy storage, the heating temperature produced from the sorbent is adjustable for different purposes. Considering the low emissions and pollution of LiOH-based heat production compared to the coal-fire system, i.e., 1262 kg pollutants are theoretically reduced for a household per year, it is a clean alternative for the residential heat supply. Image 1 • Sorption capacity of a mixture is 32% higher compared to pure salt at 58% relative humidity. • Over 90% of the original storage density is maintained after 12 cycles. • The adsorption hysteresis loop is more obvious at low pressure. • Sorption kinetics coefficient 0.01671 s – 1 at 30 °C with 58% relative humidity. • 1262 kg/y emissions of pollutants avoided for a household. [ABSTRACT FROM AUTHOR]

Thermochemical energy storage (TCES) based on hydrated salts is gaining popularity because it can provide high storage capacity at low costs. It is critical to improving heat storage efficiency and capacity due to technical challenges such as low thermal conductivity of thermochemical materials (TCMs) and poor mass transfer. The reversible reaction of strontium bromide monohydrate (SrBr 2 ·H 2 O) and water vapor forming strontium bromide hexahydrate (SrBr 2 ·6H 2 O) for TCES is used in numerical simulation, aiming to investigate the discharging performance of a double-pipe closed TCES reactor considering the influences of fin layouts (radial and longitudinal fins) by evaluating several indicators such as the reaction time and outlet temperature. The results show that the use of fins can improve the exothermic process. The discharging time of the reactor with upward L-shaped fins is reduced by 8.6% for radial fins and by 8.9% for the reactor with four longitudinal fins. The addition of fins expands the heat transfer area and makes the hydration rate of TCM around fins significantly higher than other parts. The Taguchi method is adopted to optimize the structure parameters of case 7 as it has the highest heat transfer amount of heat transfer fluid (HTF), and the optimal combination (A (fin number) = 4, B (fin extension length) = 20 mm, C (fin thickness) = 2 mm) increases the peak value of average outlet temperature by 1.47% and the heat exchange efficiency by 4.7% compared with case 7. • Hydration of SrBr 2 ·H 2 O in a closed TCES reactor is investigated in bed scale. • Adding fins increases average outlet temperature and heat transfer efficiency. • Effective heat transfer of reactor with radial fins is slightly higher than that of reactor with longitudinal fins. • The optimal structure parameter combination of the reactor is obtained by the Taguchi method. [ABSTRACT FROM AUTHOR]

Adsorption thermochemical energy storage (TCES) is currently a momentous technique utilised for long-term energy storage due to the reversible gas-solid reaction under low-temperature. A novel 3D heat storage reactor, including two shaped columnar sorbent reactive beds is proposed. The heat charging (dehydration) and discharging (hydration) processes under different operating conditions are numerically investigated. The roughly uniform temperature and conversion degree evolutions of the bed during reaction suggest a good heat and mass transferability of the porous shaped sorbent bed. For reference cases, the time required to finish the dehydration and hydration processes are 328 and 748 min; the decreased condensation temperature and increased evaporation temperature promote dehydration and hydration kinetics. The charging power and thermal efficiency increase firstly and decline later till the end of dehydration, the final values are 212 W and 91.1%; while discharging power and efficiency decrease with the advancement of conversion degree, with thermal power and thermal efficiency of 93 W and 87.5%. Moreover, the overall thermal coefficient of performance of 80.9% and exergy coefficient of performance of 27.7% are achieved; and the coefficients of performance can be further optimised at specific charging temperature and flow rate of heat transfer fluid (HTF). All these satisfying performances of this model preliminarily confirm its feasibility in TCES. • A 3D closed thermochemical energy storage model is proposed. • Pressure effect in dehydration and hydration kinetics is investigated. • The average charging power is 212 W for this reactor model. • Overall COP th and COP ex are 80.9% and 27.7%. • Specific charging temperature and flow rate of the heating medium further enhanced COP. [ABSTRACT FROM AUTHOR]

Salt hydrate based thermochemical heat storage (TCHS) is currently a pivotal technique used for long-term energy storage due to its reversible gas-solid reaction at middle-to-low temperature. MgSO 4 is a promising salt candidate owing to its theoretically ultrahigh energy storage density (ESD). However, its poor heat and mass transfer performance severely restricts its large-scale application. Composite salts consist of MgSO 4 and other promising salt are prepared to improve the thermochemical performance such as the adsorption kinetics. Simultaneous thermal analysis (STA) is used to screen several other potential salt candidates by comparing the ESD. SrCl 2 shows the highest ESD and is selected to mix with MgSO 4. X-ray diffraction confirms that the composite salt hydrate is successfully prepared, and the chemical composition is measured by X-ray fluorescence spectrometry. The STA results show that the mixture with an appropriate composition proportion can enhance ESD at mid-low temperatures. The mixture with 20 wt% MgSO 4 possesses the best adsorption kinetics even under the most unfavorable condition. Vapor adsorption isobars for dehydrated SrCl 2 , MgSO 4 , and their mixtures are measured between 30 °C and 90 °C, which is conducive to understand the chemisorption mechanism. Additionally, cyclability test results show that the aforementioned mixture has better cycle stability than do pure salts. Specifically, the heat storage capacity of the mixture stays above 75% of the original after 20 consecutive heat charging (dehydration) and discharging (hydration) cycles. All these results indicate that the composite salt has good potential for use in long-term TCHS at mid-low temperatures. Image 1 • Salt mixtures composed of MgSO 4 and SrCl 2 are developed. • Composite salt of 20 M wt% increases the volumetric ESD to 595 kWh m-3 under 150 °C. • Adsorption kinetic and capacity are enhanced. • 75% of the original ESD is maintained after 20 cycles. [ABSTRACT FROM AUTHOR]

• Methane steam reforming reaction was investigated by numerical simulation. • The reaction performance of grille-sphere composite packed bed is higher. • The conversion of methane is increased by 2.72% with the introduction of grille. • The temperature of tube wall is decreased by 50 K with the introduction of grille. • The pressure drop is closely related to the packing structure. Packed bed reactors have been widely used in chemical reaction engineering. A kind of grille-sphere composite packed bed has been proposed to decrease the pressure drop and increase the radial heat transfer performance. In the present paper, both the homogeneous model and the solid particle method are used to study methane steam reforming reactions in a grille-sphere composite packed bed. Firstly, the homogeneous model is adopted to compare the overall chemical reaction performance between the randomly packed bed and the grille-sphere composite packed bed. In the homogeneous model, the packed bed is considered as a porous media and the kinetic reaction rates are incorporated into Fluent software with user-defined functions. Secondly, an optimization is conducted by using the solid particle method for packing structure in the single channel of the grille-sphere composite packed bed with sub-channel to particle diameter ratios between 1.00 and 2.00. In the solid particle method, both fluid and solid domains are included. User-defined scalars are used to represent species inside catalytic particles and the chemical reactions are modeled with user-defined functions. It is found that when compared with the randomly packed bed, the conversion rate of methane in the grille-sphere composite packed bed is increased from 9.58% to 12.30% and the temperature of the tube wall is lowered by 50 K, indicating a longer tube life. Moreover, in the grille-sphere composite packed bed, with the proper selection of sub-channel to particle diameter ratio and the packing form, the pressure drop is greatly reduced and the heat of the chemical reaction is improved. When sub-channel to particle diameter ratio is less than 1.71, the main stream is not disturbed by particles, which results in lower pressure drop and higher overall thermal storage performance. [ABSTRACT FROM AUTHOR]

Abstract Phase change materials used in thermal energy storage systems are critical for energy utilization. Organic phase change materials have received considerable attention both for applications and research due to their favorable properties, such as large latent heat, low cost, stability, nontoxicity, and corrosion resistance. Because of the inherently low thermal conductivity, there has been a lot of research on various combinations of organic phase change materials with high conductivity materials. Carbon nanotubes, graphene and porous carbon have excellent properties, such as ultrahigh surface area and high thermal conductivity, which have become the preferred materials for thermal properties enhancement. Benefit from the varied dimensional spaces for retaining materials, these carbon-based materials can act as excellent confinement for phase change materials to form shape stabilized, phase change tunable, and thermally enhanced phase change composites. In this paper, a review about recent advancement and challenges for organic phase change materials confined in different types of carbon-based materials is presented, associated with some relevant theories trying to understand the mechanism of heat transfer and phase change in micro/nano confinement. Some promising applications in thermal management and energy conversion that have great potential for more explorations are also introduced. Highlights • Carbon-based materials are suitable for infiltrating organic phase change materials. • The thermal properties of organic phase change materials can be improved effectively. • The challenges and perspectives of organic phase change materials are proposed. [ABSTRACT FROM AUTHOR]

CO 2 hydrate is a potential cold thermal energy storage material with latent heat of 500 kJ/kg, however, the dissociation principle of CO 2 hydrate is different from that of solid-liquid phase change materials and therefore, exploring the dissociation mechanism of CO 2 hydrate is of great significance for efficient cold storage. In this paper, a new lattice Boltzmann model is proposed, considering dissociation kinetics, two phase flow, heat transfer, latent heat, surface reaction, thermal buoyancy and variable parameter depended with temperature. The necessity of the temperature consideration related with latent heat and buoyancy is clarified. For the combined effect of depressurization decomposition and thermal decomposition of CO 2 hydrate dissociation, depressurization decomposition diminishes as time increases and initial pressure increases and thermal decomposition enhances as hot wall temperature increases. The fully dissociated Fo is 0.544, 0.514, 0.604, 0.628, showing a first decreasing and then increasing trend while initial pressure increases from 0 to 0.002, 0.004, 0.006 lu. As hot wall temperature increases from 8, 10, 12–14 °C, the fully dissociated Fo is 0.566, 0.544, 0.473 and 0.419 respectively. This new lattice Boltzmann model is of significance in providing guidance for the future cold thermal energy storage system application by using CO 2 hydrate. • A lattice Boltzmann model with thermal buoyancy consideration is developed for the dissociation process of CO 2 hydrate. • The dissociation tendency of CO 2 hydrate is revealed when coupling depressurization and thermal decomposition. • Increasing initial environmental pressure reduces the dissociation rate, but prolongs the fully dissociated time. • Increasing hot wall temperature apparently accelerates the heat transfer and dissociation performance. [ABSTRACT FROM AUTHOR]

• Thermal performance of multilayered PCM(s) thermocline TES tank is analyzed. • A numerical model is used for the thermal evaluation of thermocline configurations. • A parametric study of PCM melting temperature and heat of fusion is performed. • Results indicated the optimal values of melting temperature and latent heat for MLSPCM(s). The current paper presents two parametric studies (inverse Stefan number and dimensionless temperature difference) to optimize the values of latent heat and melting temperature of multilayered phase change materials (MLPCM(s)) in thermocline tank for concentrating solar power (CSP) plants. Spherical capsules filled with PCM(s) of different thermo-physical properties are used to fill the bed region, and the molten salt is used as heat transfer fluid (HTF). The numerical model that has been developed uses the Dispersion-Concentric (D-C) equations. By using MATLAB, the governing equations are solved and validated against the experimental results. The results show that in the optimal configuration of the case (B), the values of InvSte number and dimensionless temperature (θ m) are equal to 1.2 and 0.8 for the top PCM layer, respectively; 0.75 and 0.55 for the middle PCM layer, respectively; and 0.65 and 0.3 for the bottom PCM layer, respectively. Moreover, it is also found that to obtain the best design and distribution of temperature for a thermocline tank consisting of three layers of PCM, the top PCM layer should melts by Δ T = 55.4 °C below the HTF charging inlet temperature, the PCM layer at the bottom should solidifies by Δ T = 83.1 °C above HTF discharging inlet temperature. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage (LTES) has been recommended to complicated aerospace systems due to the excellent ability of storing thermal energy in recent years. Metal foam, as an effective additive to enhance the effective thermal conductive coefficient of phase change materials, has been wildly used in the LTES system. In support of the future space exploration, solid–liquid phase change within metal foam under different gravitational accelerations and corresponding heat transfer characteristics are investigated in this work to enhance understanding of heat transfer capability in reduced gravity conditions. A pore-scale lattice Boltzmann method with the double distribution functions is developed to study the solid–liquid phase change problems with the natural convection heat transfer in metal foam. Here, microstructure of metal foam is experimentally obtained by the use of X-ray computed tomography. Two numerical validation cases are performed, one for fluid–solid conjugate heat transfer problem, and the other for melting process in a square cavity without the porous media. The presented lattice Boltzmann results are in good agreement with previous analytical and numerical results. Based on the analysis of temperature and velocity fields during melting within metal foam, it is found that the clockwise circulation, caused by the temperature gradient, leads to the inhomogeneous distribution of liquid–solid interface along vertical direction. What’s more, gravity effects on the temperature and velocity fields together with the average Nusselt number and liquid fraction coefficient are investigated. Results show that with the decrease of gravitational accelerations from 1 g to 0 g , the maximum vertical velocity reduces and the thickness of velocity boundary layer thickens accordingly, and results in the pronounced reduction of average Nusselt number and melting rate. The natural convection appears to be even more tenuous as gravitational acceleration decreases, leading to the dominant heat transfer mechanism transited from convection to conduction, and finally alleviating the phase change process. The liquid fraction under 0 g , 0.01 g and 0.1 g conditions are 54.6%, 58.9% and 67.9% respectively of that under 1 g conditions at Fo  = 0.06. In addition, porosity effects on phase change heat transfer characteristics are discussed by comparing the liquid fraction with porosity of 0.9, 0.94 and 1. It is found that metal foam with lower porosity shows higher effective thermal conductivity and outstanding heat transfer performance, while the restriction on natural convection should not be neglected, especially for melting region which is dominated by natural convection. [ABSTRACT FROM AUTHOR]

Because of the low charging temperature, salt hydrate-based adsorption thermochemical energy storage (TCES) is currently a significant technology that promises long-term energy storage. A corrugated-shaped heat storage unit (HSU) in which embedding porous metal bracket is proposed in this work to enhance heat transfer between the thermochemical material (TCM) wrapped inside and the heat fluid transfer (HTF) in the external corrugated channel. The thermo-chemical conversion behaviours, including reactive transport processes during dehydration (charging) and hydration (discharging), as well as the influence of parameters, are comprehensively investigated. The numerical results indicate that increasing the HTF temperature facilitates the charging process while the discharging can be promoted by decreasing reaction bed temperature. The time required to complete charging and discharging for the reference cases is 2990 s and 5700 s. For both charging and discharging powers of reactive bed, the values dramatically surge in a short time and then gradually decrease, with the maximum powers of 2638 W and 1866 W, respectively. Boosting evaporation temperature (water vapour pressure) accelerates hydration while the effect of condensation temperature on dehydration is insignificant. The reaction period can be further shortened by heightening the thermal conductivity of TCM, and the porosity also has a distinct influence on the reaction. Compared to the storage unit of a straight external channel without a metal bracket inside, this heat storage module saves 34% and 23% in charging and discharging times. The results of this work provide insights into the prediction and improvement of thermochemical conversion behaviours. • A corrugated heat storage unit with porous metal support is proposed for heat storage. • Parametric studies for energy charging and discharging are performed. • Higher temperature facilitates dehydration while lower temperature promotes hydration. • The maximum thermal power is 2638 W when the charging temperature is 110 °C. • Energy charging and discharging times are saved by 34% and 23%. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) have been considered suitable energy materials to address the mismatch between energy demand and supply to improve the utilization efficiency of the latent heat thermal energy storage (LHTES) system. However, the relatively low thermal conductivity of PCMs leads to an undesirable thermal response rate of the LHTES system. Among the common methods to improve the heat transfer performance of PCMs, the employment of metal foam (MF) has attracted growing attention as an effective strategy. Plenty of studies have investigated thoroughly the vital parameters of MF impacting the phase change process, while a corresponding discussion of the situations and limitations of the known technologies is still lacking. In this review, a total of 476 literature derived since 2000 are visualized based on scientometric analysis to exhibit the attractive spotlights and new trends. The impact factors on the heat transfer performance of PCMs embedded with MF (PCMs/MF) are presented in-depth. Besides, the developments of hybrid heat transfer enhancement techniques based on the MF are overviewed comprehensively. Combined with the thermal characteristics of typical applications, systematic information on PCMs/MF in these applications is summarized, and the suitability of these technologies is discussed. Finally, ongoing challenges of PCMs/MF are identified, and developmental tendencies and opportunities for further research work to address them are discussed. This review provides helpful information to facilitate the development of innovative and feasible PCMs/MF in the LHTES system and encourage and attract researchers and scholars to get some advancement in their future work. • Scientometric analysis is used to exhibit attractive spotlights and new trends. • Impact factors on heat transfer enhancement of PCMs/MF are presented. • Effects of hybrid enhancement techniques based on MF are overviewed. • Systematic information on PCMs/MF in typical applications is summarized. • Challenges and prospects of PCMs/MF are identified. [ABSTRACT FROM AUTHOR]

The development of phase change materials (PCMs) is hampered by issues like leakage, poor thermal conductivity, and poor light absorption. In this study, we innovatively combined modified melamine foam (MF) and graphene nanoparticle (GNP) to address these defects of PCMs in the solar-thermal energy system. The MF was modified to endow the solar-thermal energy conversion ability and superhydrophobic interface characteristics due to the polypyrrole (PPy) by the in-situ polymerization and the polymerized octadecylsiloxane (PODS) layer coating on the sponge skeleton. The composite PCMs consisting of the modified MF, paraffin wax (PW), and GNP were fabricated and exhibited good leakproof ability, high thermal conductivity, and excellent solar-thermal energy conversion capability. Results showed that due to the effects of the PPy and the PODS on the sponge skeleton structure, MF@PPy-PODS/PW composite PCMs showed a decrease in the mass loss ratio to less than 0.34% and an increase in the thermal conductivity of 0.33 W/m·K and the solar-thermal storage efficiency of 75.68%. Besides, adding GNP with higher concentrations impacted positively on the thermal conductivity and the solar-thermal energy conversion ability but negatively on the phase change enthalpies. MF@PPy-PODS/GNP3/PW composite PCMs increased the thermal conductivity to 0.59 W/m·K and the solar-thermal storage efficiency to 79.36% while decreasing the phase change enthalpy to 130.61 J/g. Furthermore, a thermoelectric conversion system driven by solar energy was developed to show the potential of composite PCMs for cleaner energy production. The open-circuit voltages of the MF@PPy-PODS/GNP3/PW composite PCMs achieved 0.78 and 0.91 V at 2 and 4 Sun, respectively. The open-circuit voltages remained for a period of time and slowly dropped without the simulated solar light irradiation. This study provided a potential strategy for the optimal performance of composite PCMs and their application in solar thermal systems. • PCMs composited with modified melamine foam and graphene nanoparticle were prepared. • Composite PCMs showed good leakproof ability and high thermal conductivity. • Solar-thermal storage efficiency of composite PCMs achieved 79.36%. • Open-circuit voltage in solar-driven thermoelectric conversion system was improved. [ABSTRACT FROM AUTHOR]

• Increasing nanoparticle concentration and ultrasonic power improves TES rate but decreases TES efficiency. • Enhancement mechanism of combined effects between nanoparticle and ultrasonic field is analyzed. • Initiating ultrasonic at latent process offers a higher TES efficiency. • Priority relationship between TES rate and TES efficiency needs to be considered. To further improve the performance of thermal energy storage (TES) system with phase change materials (PCMs), this paper proposed a novel method, i.e. combining the additions of TiO 2 nanoparticles, metal foam and the provision of ultrasonic field, investigated its synergetic effects in enhancing conduction and convection heat transfer. The thermal characteristics, including the TES time distributions and the energy consumption of the TES system, were discussed to evaluate the combined effects of TiO 2 nanoparticles and ultrasonic field on the TES rate and TES efficiency. The results showed that the latent TES time reduction index reached 46.50%, when the TiO 2 nanoparticles concentration was 5.0 wt% and the ultrasonic power was 100 W, while the TES efficiency dropped to 10.66%. Increasing TiO 2 nanoparticles concentration and ultrasonic power positively improved the TES rate due to conduction heat transfer enhanced by nanoparticles and convection heat transfer enhanced by the acoustic streaming effect and the cavitation effect of the ultrasonic field, but which negatively reduced the TES efficiency mainly due to the energy consumption of the ultrasonic field. Therefore, the effects of the ultrasonic field introduced at four action stages on the TES rate and TES efficiency were compared, and it confirmed that introducing ultrasonic field at the latent TES stage was better than that in the sensible TES stage. Additionally, the proposed novel combined method needed to consider the priority relationship between TES rate and TES efficiency for designing the TES system, favoring the potentials for further advances in TES applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reaction kinetics of as-synthesised thermochemical sorbents are established. • Composite's dehydration activation energy drops by 13%. • Novel building envelope achieves space heating and air purification. • Clean air delivery rate of 41.8 m3/h is achieved for the proposed model. • Total efficiency including heating and air purification of 81% is obtained. In this paper, the dehydration (heat charge) and hydration (discharge) reaction kinetics of thermochemical sorbents synthesised in previous work by the author is established by using the isothermal method, with the aim of understanding their thermochemical conversion behaviour and developing reaction models for numerical simulations. The effects of temperature, reaction advancement, and vapour pressure are fully considered and employed in a thermochemical energy storage model. The derived dehydration reaction activation energies of the LiOH/LiCl@ expanded graphite (LiO2C1@EG and LiO3C1@EG) sorbents are 54.7 and 52.2 kJ/mol, respectively, which are lower than that of pure LiOH·H 2 O. To achieve the dual-function of space heating and air purification in an efficient manner, a novel solar building envelope combining thermochemical energy storage and photocatalysis is proposed and studied numerically based on the established reaction kinetics. Fresh air can be produced during solar harvesting. The porous wall, which is made of a composite sorbent, absorbs thermal energy to heat air near the wall and thus creates a chimney effect in the channel for continuous space heating. During discharge, the desorbed heat storage wall adsorbs the moist air and the hydration reaction enthalpy can be used again for air heating. The total efficiency including the equivalent formaldehyde degradation efficiency and the thermal efficiency is around 81% when the solar radiation is 600 W/m2. Results indicate that this passive building envelope can achieve a higher heat harvesting and utilisation efficiency in a more compact space compared to previous studies. Moreover, the influence of radiation intensity on air purification and thermal performance is investigated. The present work provides new insights and promotes the integration of passive solar building envelopes and thermochemical energy storage. [ABSTRACT FROM AUTHOR]

The growth of global energy demand during the 21st century, combined with the necessity to master greenhouse gas emissions, has led to the introduction of a new and universal energy carrier: hydrogen. The Department of Energy (DOE) proposed using a bayonet-type heat exchanger as a silicon carbide integrated decomposer (SID) to produce the sulfuric acid decomposition product sulfur dioxide, which can be used for hydrogen production within a sulfur–iodine thermochemical cycle. A two-dimensional computational model of SID having a boiler, superheater and decomposer was developed using GAMBIT and fluid. The thermal and chemical reaction analyses were carried out in FLUENT. The main purpose of this study is to obtain the decomposition percentage of sulfur trioxide for the integrated unit. Sulfuric acid (H2SO4), sulfur trioxide (SO3), sulfur dioxide (SO2), oxygen (O2), and water vapor (H2O) are the working fluids used in the model. Concentrated sulfuric acid liquid of 40 mol% was pumped into the inlet of the boiler and the mass fraction of concentrated sulfuric acid vapor obtained was then fed into the superheater to obtain sulfur trioxide. The decomposer region, which houses the pellets, placed on the top of the bayonet heat exchanger acts as the porous medium. As the decomposition takes place, the mass fraction of SO3is reduced and mass fractions of SO2and O2are increased. The percentage of SO3obtained from the integrated decomposer was compared with the experimental results obtained from Sandia National Laboratories (SNL). Further, effects of various pressures, flow rates, and acid concentrations on the decomposition percentage of sulfur trioxide were studied. [ABSTRACT FROM PUBLISHER]

Abstract: Solar thermal energy storage is important to the daily extended operation and cost reduction of a concentrated solar thermal power plant. To provide industrial engineers with an effective tool for sizing a thermocline heat storage tank, this paper used dimensionless heat transfer governing equations for fluid and solid filler material and studied all scenarios of energy charge and discharge processes. It has been found that what can be provided through the analysis is a series of well-configured general charts bearing curves of energy storage effectiveness against four dimensionless parameters grouped up from the storage tank dimensions, properties of the fluid and filler material, and operational conditions (such as mass flow rate of fluid and energy charge and discharge periods). As the curves in the charts are generalized, they are applicable to general thermocline heat storage systems. Engineers can conveniently look up the charts to design and calibrate the dimensions of thermocline solar thermal storage tanks and operational conditions, without doing complicated modeling and computations. It is of great significance that the generalized charts will serve as tools for thermal energy storage system design and calibration in energy industry. [Copyright &y& Elsevier]

Packed beds with methane steam reforming reaction (MSR) can be used as thermochemical storage devices. The packing configuration can have a significant effect on the flow distribution which will further influence the heat/mass transfer, dispersion and reaction characteristics. In the present paper, the hydraulic, dispersion, heat/mass transfer and the MSR reaction properties are investigated in packed beds with the simple-cubic (SC) packing, the body-centered cubic (BCC) packing and face-centered cubic (FCC) packing forms. ANSYS FLUENT integrated with user defined scalars (UDS) and user defined functions (UDF) are used to perform the simulations. Results show that firstly, the residence time distribution (RTD) can be used to evaluate the dispersion property in packed beds where a narrower RTD curve reflects a more uniform velocity distribution with less dispersion. Secondly it is found that, regions with backflow are not beneficial for heat/mass transfer and chemical reactions from two aspects. One is that the heat transfer between the main fluid and the particle surfaces is weak and low temperature of the particles will reduce the reaction rates. The other is that the poor species transport will prevent the reactant to flow into the reaction region and the products cannot be taken away by the main flow timely, which will have a negative effect on the reaction. Thirdly, it is revealed that, the dimensionless variation of the residence time distribution (DVRTD) can reflect the heat/mass transfer and reaction performances, where a smaller DVRTD corresponds to better heat/mass transfer and higher reaction rates. [ABSTRACT FROM AUTHOR]

Clean energy storage is of vital importance for cleaner production and environmental protection. This present study focuses on the promotion of clean energy storage efficiency in the widely used shell and tube latent heat thermal energy storage unit. The enhancing effects of fin inside the tube on the charging time and energy storage rate are studied. Numerical investigations are performed through the enthalpy based lattice Boltzmann method couple with curved boundary. Three kinds of configurations for one-fin and two-fin are investigated. Results indicated that fin position can effectively impact the enhancing effects. For one-fin, the maximum difference of the enhanced ratio for different fin positions is 15.17% when R a = 107, while it is 7.52% for two-fin. The optimal fin position varies with different Ra , but with appropriate approximation, it can be concluded that one-fin on the bottom and two-fin on the vertical direction are the optimal fin position for one-fin and two-fin cases. In addition, one long fin shows better enhancing effects than two short fins. Under the same fin length, the average enhanced ratio for one long fin is 41.82%, while it is only 27.03% for two short fins. These results can provide guidance for the fin configuration in the shell and tube latent heat thermal energy storage unit to achieve higher energy storage efficiency. Since this unit is widely used in various clean energy storage systems, the results would also be beneficial for various industrial applications of clean energy storage and utilization. • The characteristics of energy storage process with fins inside tube are obtained. • The different enhancing effects caused by fin position can be as high as 15.17%. • One-fin on bottom and two-fin on vertical direction are the optimal fin position. • The average enhanced ratio for one long fin is 14.79% higher than two short fins. • The charging efficiency can be enhanced by 40% with proper fin configuration. [ABSTRACT FROM AUTHOR]

• Melting of composite PCMs with void cavities is characterized by lattice Boltzmann model. • Void cavities can suppress thermal energy performance of composite PCMs. • Melting process is hindered with increasing volume fraction of void cavity. • Difference between near-wall and randomly distributed void cavities is identified. Composite Phase Change Materials (PCMs) incorporated with metal foams are promising candidates for thermal management for space exploration. However, void cavities are generated as a result of the volume change of PCM during the melting process, introducing a resistance to heat transfer due to the low thermal conductivity of the void. In this work, the effects of void cavity distribution on the conduction-dominated melting of composite PCMs under microgravity conditions are studied by a two-dimensional pore-scale lattice Boltzmann method, in which a microstructural description of the metal foam is experimentally characterized with the help of X-ray micro-Computed Tomography. Two typical distribution patterns of void cavities are analsed and computed performance is compared (1) a near-wall void cavity, and (2) randomly distributed void cavities. The evolutions of temperature distributions and melting interfaces are compared, and the average liquid fraction and energy stored per width are deduced to describe the energy storage performance. Moreover, the influence of the volume fraction of void cavities is investigated by comparing temperature distributions and energy storage performances of composite PCMs with four different volume fractions of void cavities (0%, 3.7%, 7.6%, 15.2%). After introducing void cavities, the energy stored per width is reduced by 5.7%, 12.3% and 20.2% for randomly distributed void cavities when volume fraction of void cavities is 3.7%, 7.6%, and 15.2%, respectively, and reduced by 42.2%, 64.1% and 79.7% for the near-wall void cavity, respectively. This work initiates the study of the effects of void cavity distribution on composite PCMs, which will stimulate work on structural optimization of thermal management systems. [ABSTRACT FROM AUTHOR]

• Heat transfer of gallium in three-dimensional spaces is examined by experiment. • A piece of solid gallium is deposited at the end of melting due to weaken convection heat transfer. • Overall and most of melting time of gallium heat sink are reduced by 55.5% and 56.0% respectively. Phase change thermal storage technology has received considerable attention in the thermal management of electronic devices. Unfortunately, the efficiency using paraffin is too low to meet the heat dissipation requirements of high power devices. In this work, gallium is selected as the phase change material, and the melting mechanism of gallium heat sink in spatial distributions is examined by experiment. Results show that the heat transfer efficiency of regions in the Y -cross section near the heating surface and in the X -cross section near the upper surface of the gallium heat sink are better than other regions. The average effective thermal conductivity of the gallium heat sink reaches 71.97 W/(m·K). The natural convection promotes the overall melting rate, but it results in the inefficient heat transfer in the middle melting stage and worse heat transfer in the later melting stage. Compared with the copper foam/paraffin composite heat sink in the same size, the overall and most of melting time of the gallium heat sink is reduced by 55.5% and 56.0%, respectively. At the same thermal storage capacity, the volume and weight of the gallium heat sink are reduced by 67% and 18%, respectively, compared with the copper foam/paraffin composite heat sink. [ABSTRACT FROM AUTHOR]

• The effect of PCM volume fraction for three-layers TES tank is investigated. • A numerical model is used to define the temperature distribution of molten salt. • The thermal/economic performance of the three-layers thermocline tank is evaluated. • The bottom PCM layer with a higher VF has the lowest capacity cost of $38/kWh. The current paper investigates the phase change material (PCM) volume fraction (VF) effect on the thermal and economic behavior of a three-layer thermocline thermal energy storage (TES) tank system which is used in concentrating solar power (CSP) plants. The one dimensional transient dispersion-concentric (D-C) scheme is applied to calculate the phase change inside each capsule. Using MATLAB software, the numerical model equations have been figured out, and the current numerical results have been verified. Four different scenarios have been created to investigate the effect of PCM-VF on the thermal behavior and economic feasibility of the TES tank. The results described that the overall efficiency and the cost of capacity for all cases in order from the case (1) to the case (4) are 80.77%, 64.32%, 73.43%, 85.58%, and $45.37/kWh, $60.49/kWh, $46.28kWh, $38.58/kWh, respectively. Furthermore, case (4) demonstrates the storage capacity of 149 kWh/m3, which is 7.21%, 19.42%, and 15.78% higher than case (1), (2), and (3), respectively. In the comparative study, the results showed that case (4), which has higher VF for the bottom PCM layer, indicates that it is the most viable option of all the studied cases due to its best performance and relatively low cost. [ABSTRACT FROM AUTHOR]

• A three-dimensional pore-scale lattice Boltzmann model is developed for charging. • Primary natural convection and secondary convection interplays during charging. • Increasing gravitational accelerations make the melting interfaces more inclined. • The distinction between two-dimensional and three-dimensional models is identified. Latent heat thermal energy storage with metal foams has been considered as a promising candidate for thermal management in aerospace systems. Thus, there is good cause to deeply explore the heat transfer mechanisms of phase change material (PCM) melting with metal foams. In order to get close to the real situation, a three-dimensional, pore-scale lattice Boltzmann model is explored based on a three-dimensional reconstructed porous structure morphology taken from experimentally observed in this paper, to characterize the distribution of flow and temperature fields during charging of porous PCM. The gravity effects on heat transfer performance are documented by comparison of charging at different accelerates. During the charging process, nonuniform temperature distributions and inclined melting interfaces are presented at the latter stages, caused by the interplay of primary natural convection in the melting direction and secondary convection in the transverse direction. More inclined melting interfaces are observed as gravitational acceleration increases, yielding faster PCM melting in the upper region while melting in the bottom region almost terminated. This implies that natural convection gradually dominates heat transfer and leads to the temperature nonuniformity. Similar shape characteristics of melting interface are observed in two-dimensional model, while there is an apparent difference of the melting fraction, showing it gradually growing from 4.1% to 8.6% with increasing gravitational acceleration. These results indicate that secondary convection effect neglected in the two-dimensional model, leading to a significant error in the prediction of heat transfer performance. [ABSTRACT FROM AUTHOR]

Sustainable energy conversion and management processes increasingly require an integrated approach, especially in the context of addressing the climate crisis. This editorial puts forth related research frontiers based on 28 research articles of the special issue that is dedicated to the 13th Conference on Sustainable Development of Energy, Water and Environment Systems and regional series based on the 1st Latin American and 3rd South East European Conferences. Seven research frontiers are reviewed, the first three of which are (i) sustainable technologies for local energy systems, (ii) energy storage and advances in flexibility and (iii) solar energy penetration across multiple sectors. These research frontiers contain contributions based on renewable energy for wastewater treatment in islands, energy savings across urban built infrastructure, advanced district heating and cooling networks, power-to-gas and hydrogen production technologies, demand response in industrial systems, hybrid thermal energy storage, hybrid solar energy power plants, novel photovoltaic thermal technologies, and improved solar energy dispatchability. The research frontiers continue with (iv) wind, water based energy and the energy-water nexus, (v) effective valorization and upgrading of resources, (vi) combustion processes and better utilization of heat and (vii) carbon capture, storage and utilization. Significant contributions include innovative wind and hydrokinetic turbines, osmotic power technologies, synergetic solutions for water desalination, efficient catalytic pyrolysis, upgrading to reduce particle pollution, co-processing for alternative fuels, combustion characterization, electricity generation from waste heat sources, advances in heat exchangers and heat transfer, oxy-fuel combustion, post-combustion capture, and fly ash recycling for energy storage material. The research frontiers in this editorial provide ample opportunities to support societal transformations in the next decades to sustain planetary life-support systems. [ABSTRACT FROM AUTHOR]

• Multilayer sieve reactor that coupled heat and mass transfer with chemical reaction is proposed. • Effects of various operating conditions on dehydration and hydration are studied. • The optimized salt beds can achieve 11.4% time-saving in dehydration. • Thermal efficiency of charging is 85.2% and of discharging is 94.5%. • COP of exergy are 21.3% and 21.1% in charging and discharging respectively. The salt hydrate-based thermochemical heat storage (TCHS) system, based on a reversible solid-gas chemical reaction, is currently a key technique used to store heat for later discharge. Strontium bromide hexahydrate (SrBr 2 ·6H 2 O) is one of the most promising candidate materials in seasonal heat storage for residential heating due to its lower desorption temperature. This study develops and numerically investigates a novel multilayered sieve reactor that can promote dehydration and hydration reactions. This paper focuses on the interaction between the porous reactive salt beds and the vapor in an open system. The required time to totally dehydrate and hydrate the salt beds are approximately 1180 min and 940 min, respectively. The effects of various operating conditions such as input temperature, inlet velocity, and relative humidity of fluid on charging and discharging are studied, as well as the influence of thermal conductivity, permeability and kinetic factors. For instance, the reaction kinetic factor R kin = 1.0 × 10−4 is a threshold in this model. The optimized salt beds reduce dehydration time by 11.4% (130 min). High volumetric thermal powers are obtained for the multilayered sieve reactor, although the values decrease with the degree of conversion. The results indicate that the thermal efficiency η , thermal coefficient of performance (COP th), and exergy coefficient of performance (COP ex) of charging are 85.2%, 72.4%, and 21.3%, respectively, and the corresponding values for discharging are 94.5%, 71.5%, and 21.1%, respectively, for the model studied. [ABSTRACT FROM AUTHOR]