Heat Storage Material Research Articles

Feasibility study of a metal hydride-based solar thermal collector system

The present study aims to assess the technical feasibility of a novel Metal Hydride-based Solar Thermal Collector (MH-STC) system. This system includes a flat-plate solar collector integrated with a metal hydride bed, a hydrogen compressor, a photovoltaic panel, a hydrogen tank, and a water storage tank. This system combines the principles of a conventional solar thermal collector with the energy storage capabilities of metal hydrides, enabling the storage of surplus thermal energy. The LaNi5 alloy was used as heat storage material. A 3D-mathematical model is established and a numerical code written in Fortran-90 is developed to simulate the dynamic behavior of the proposed solar thermal collector. It was shown that the developed 3D-model produces computational results that are consistent with experimental data. In addition, to check the accuracy of the mathematical model and numerical approach, the relative errors in the mass balance and energy balance were calculated and values of 0.054 % and 0.18 %, respectively, were obtained.The simulation results offer insights into the system's technical feasibility, revealing an overall efficiency of 90.6 %, the water temperature at the collector outlet can reach 357.3 K, and a water volume heated of 230.4 L under the considered operating conditions. Moreover, the results indicate that the proposed MH-STC system exhibits significant potential as a viable alternative for thermal storage in domestic hot water systems.

Preparation and characterization of Al-12Si/ceramic composite phase change heat storage material

Preparation and characterization of Al-12Si/ceramic composite phase change heat storage material

Microencapsulation of Zn-10 mass% Al alloy phase change material via dry synthesis method

Thermal energy storage (TES) via latent heat storage (LHS) using metal alloy phase change material (PCM) offers advantages in medium-to-high temperature operation around 400 °C and high heat storage capacity. Microencapsulation of alloys as PCMs can mitigate issues of reactivity and improve handling properties of PCM. This research presents the novel development of microencapsulated PCM (MEPCM) with a core of Zn–10 mass% Al that operates around 400 °C. The MEPCMs were synthesized using high-speed impact blending (HIB), where fine AlOOH particles mechanically coat the surface of Zn–10 mass% Al alloy microspheres, resulting in robust surface modification. Subsequent heat-oxidation treatment at 800 °C was performed to obtain stable oxide coating. The HIB treatment resulted in an AlOOH coating containing Zn nanoparticles, which the heat-oxidation process transformed into α-Al2O3 and ZnO nanoparticles. The MEPCMs exhibited heat storage densities, including latent and sensible heat (ΔT=200 °C), that were 1.9 times higher than the capacity of solar salt, which is commonly used as a sensible heat storage material. Furthermore, the MEPCMs maintained their shape and latent heat capacity after 300 and 1000 cyclic tests. These superior MEPCM characteristics hold the potential to significantly advance the development of LHS-based TES systems operating around 400 °C, with applications in energy generation and industrial processes.

Numerical modeling of discharge modes and evaluation of the major characteristics of latent heat thermal energy storage at a nuclear power plant

Under conditions of uneven power consumption schedules, construction of renewable power plants and low maneuverability of nuclear power plants (NPPs), combining NPPs with latent heat thermal energy storage systems (LHTES) can improve efficiency and maneuverability of NPPs. Combination of the LHTES with an additional low-capacity steam turbine will allow not only meeting peak electricity loads, but also increase the NPP safety by additional reservation of its own needs using this multifunctional turbine in emergency situations of complete blackouts. A scheme for combining a PCM-based thermal storage system with a two-circuit nuclear power plant is proposed, where the LHTES is charged with part of fresh steam from steam generators in the night hours of off-peak loads in the power grid and heating feed water above the nominal temperature during the peak loads. Non-stationary heat transfer between the heat storage material and feed water during the LHTES discharge was modeled using the finite volume method. The design characteristics of the LHTES as part of the NPP and the weight-size parameters of the thermal accumulator have been determined. The rational phase change material and the types of finned tubes have been determined. A solution has been proposed to ensure stable water temperature at the outlet of the PCM-based thermal accumulator during its discharge within the NPP that will significantly increase efficiency of its performance. Heat losses from the LHTES to the environment during the day have been calculated.

Study on the Influence of Phase Change Process on the Desorption Characteristics of Gas-Containing Anthracite in Phase Change Heat Storage Materials

Study on the Influence of Phase Change Process on the Desorption Characteristics of Gas-Containing Anthracite in Phase Change Heat Storage Materials

Thermo-economic assessments on building heating by a sewage source heat pump coupled with heat storage system

To enhance the economic feasibility of building heating systems, phase change heat storage materials are often utilized to utilize renewable energy and address system peak loads. This article presents an innovative method of integrating a sewage source heat pump with a heat storage device. Upon an industrial building in Xilinhot as a case study, numerical models for the heat accumulator coupled with the energy consumption of buildings are established, taking into account dynamic hourly loads and meteorological conditions. Through a comprehensive analysis, the thermophysical properties of the heat accumulator as well as the economic implications of the multi-energy complementary heating system are investigated. Results demonstrate that the complete melting time for a 95 % filling rate is significantly reduced, 87.11 % shorter than that of pure phase change material, achieving the highest heat storage efficiency. Furthermore, the phase change storage device with a 75 % filling rate had the shortest investment payback period, requiring only 6 years. These findings have significant implications for guiding green renovation projects in building heating systems.

Study and Investigation of Heat Storage Materials for Solar Cooker

Study and Investigation of Heat Storage Materials for Solar Cooker

Experimental Analysis of Scheffler Reflector-Based Solar Cooking System: An Application of Sensible and Latent Heat Storage Materials

Solar cooker with different collector like evacuated tubes collector, parabolic trough collector, flat plate collector, and Scheffler reflector collector etc are generally used for the cooking food with SHSMs or PCMs. Present research article, Scheffler reflector with combined heat storage material (one SHSM and one PCM) for late-evening cooking has been experimentally investigated. One material is placed within the inner pot of a solar cooker, while another material is placed outer pot of the solar cooker. Six combinations are formed from various SHSMs (sand, pebbles, and iron pieces) and PCM (acetamide). During the daytime, the solar cooker absorbed and stored heat from the sun, which was transferred to the cooking pot through the heat storage units. The heat required for evening cooking (Rice) has been transferred by the thermal storage system which is kept inside an insulator box. After the experiment, it was observed that food was successfully cooked in pairs of sand-acetamide, acetamide-sand, and acetamide-pebbles and partially cooked in pairs of pebbles-acetamide, iron pieces-acetamide, and acetamide-iron pieces. The water activity test is to be conducted to check the cooking quality of food, and as per the result received from the test, the range of cooking and partially cooking is differentiated between 0.928 and 0.936 and 0.948 and 0.955, respectively. The cooked food’s temperature was determined to be between 60 and 63 oC at 20:00 h. The system’s total cost and payback duration were calculated for the economic analysis resulting in 50750 INR and 9.70 years, respectively.

Experimental evaluation on the power characteristic of direct-photovoltaic charging for thermal storage equipment

Thermal storage is an essential equipment for storing excessive heat, especially for water heating systems. The present work proposes a preliminary study to maximize the operation of thermal storage using photovoltaics as the primary source for charging the heat storage material. The assessment indicates the concept is feasible, where the output power from photovoltaics can be directly converted to heat using a heating element. The power ratio is considerably high (up to 38.6%), resulting in the maximum temperature of the heat absorber material (water) increasing to 43.2 °C. The final assessment using suitable phase transition material shows that steady phase behavior is essential to maximizing the temperature profile of the material. It is achieved using stabilized-hexadecanoic acid, which shows a transient phase transition at a temperature of 54.2 °C, reducing the possibility of heat loss with an average temperature rate of 0.54 °C/min in the discharge stage. This finding proves the proposed concept is applicable, while further improvement can be done to adjust the suitable power output from photovoltaic and storage tank arrangement for the actual system. Despite that, the result is expected to accelerate the utilization of photovoltaics as reliable solar renewable technology.

Large‐scale synthesis of nano‐ZIF‐90 from zinc chloride application orientation heat storage materials

AbstractThe paper presents the results of the first research on the synthesis of nano‐ZIF‐90 from zinc chloride. More specifically, the paper also introduces the results of large‐scale pure nano‐ZIF‐90 synthesis with a high specific surface, uniform cubic crystals, and good thermal strength. ZIF‐90 is synthesized from zinc chloride‐containing medium capillaries, which have both a weak acid center and a strong base center. The post‐synthetic ZIF‐90 was also evaluated for heat storage based on its ability to adsorb water, methanol, and ethanol. XRD, FTIR, SEM, TEM, N2 adsorption and desorption methods, TG mass thermal analysis, and NH3‐TPD/CO2‐TPD were used to study the ZIF‐90 crystallization process with modifications of precursors, solvents, additives, and reaction conditions. From this, a large‐scale synthesis of nano‐ZIF‐90 from high‐efficiency zinc chloride has been derived. DSC measurements are used to evaluate the enthalpy adsorption of water, methanol, and ethanol on ZIF‐90.

Effect of tubular-typed charcoal height variations on efficiency in passive interfacial solar desalination

Passive solar desalination is a process of reducing the salt content of salt water to produce fresh water by utilizing solar heat. In recent years, interfacial heating has been proposed as an alternative to evaporation by creating localized heat on the water surface. Charcoal is an absorbent, heat storage, and wettability material, so the evaporation process not only occurs on the surface of seawater but also on the surface of the charcoal, which results from this wettability. The height of the charcoal indicates the distance the steam travels to reach the glass surface for the condensation process, thereby speeding up evaporation. The experiment was carried out in 4 single-slope-type basins using tubes filled with charcoal as high as 30, 40, and 50 mm for 8 hours in the sun. The results showed that adding heat-absorbing material to the basin was able to accelerate seawater to reach its boiling point so that it could evaporate. The temperature and humidity in each basin also have a similar changing trend where temperature is strongly influenced by solar radiation. The use of charcoal can also increase the rate of convection and evaporation heat transfer in the basin, as well as the maximum efficiency in basin 4 with an efficiency value of 56.40%, basin 2 at 53.17%, basin 3 at 51.62%, and basin 1 44.17%. Efficiency is obtained from the desalination efficiency equation, namely the ratio of the latent heat of vaporization to the solar energy entering the system

Unlocking the power of LiOH: Key to next-generation ultra-compact thermal energy storage systems

This study explores the potential of untapped lithium hydroxide (LiOH) as a phase change material for thermal energy storage. By overcoming the challenges associated with the liquid LiOH leakage, we successfully thermal-cycled LiOH in a laboratory scale experimentation, and observed its stability (>500 thermal cycles), without chemical decomposition. This step has never been performed to date. Its solid-to-liquid reversible transitions temperatures and related solidification/melting enthalpies values have been verified. Then, the first experimental characterization of LiOH's thermal properties shows unexpected values for its heat capacity, thermal conductivity and diffusivity, in contradiction with the few ones available in literature. This opens avenues for LiOH's applications for the storage of sensible and latent heat, as shown through the increased cycle efficiency potential of a thermal energy storage system if based on its energy storage capacity; up to six times more volumetric energy density compared to traditional Solar Salt-based systems used in the solar tower plant (4.5 GJ/m3 vs. 0.76 GJ/m3 over 1000 thermal cycles). Additionally, we observed a softening phenomenon that occurs inconsistently during heating, but which may account for its excellent melting properties and the interplay with other raw chemicals. This new insight contributes certainly to the underlying mechanisms in the synthesis of another promising heat storage material in development: the peritectic compound Li4Br(OH)3. This pioneering work suggests LiOH as a promising ultra-compact thermal energy storage material for filling the intermediary gap from current to next-generation solar power plants, although its large-scale application requires further investigation to achieve economic viability.

Charge/discharge Profiling of Organic Latent Heat Material Embedded in Polymer Matrix for Heat Energy System

The operational aspect of a latent thermal energy storage (LTES) system is highly dependent on the performance of its latent heat storage material (LHSM). In this work, performance evaluation of the LHSM is conducted using low-density polyethylene (LDPE) and linear LDPE. As an initial assessment, three different organic LHSMs are used for the evaluation. The thermal assessment indicates that the heat of fusion for the LHSM varies between 142.45 J/g and 198.8 J/g. Thermal decomposition demonstrates that the LHSM is suitable for operating a thermal power system under 100 °C. The addition of polymer clearly influences the charge/discharge rate for each LHSM. For example, it has a positive influence on paraffin wax, which increases the charge rate up to 54.4 %. A positive outcome is also observed for palmitic acid, which has the highest charge rate at around 4.4 °C/min. Interestingly, the charge/discharge rate for stearic acid is decreased by the presence of a polymer. It implies that the melting/solidification rate can be decreased, which may be advantageous for passive thermal systems. In general, the addition of LDPE/LLDPE alters the performance of LHSM. It makes the polymer suitable to be taken as a stabilizer for the LHSM.

Preparation of phase change Heat storage wood with in-situ generation of thermal conductive particles to improve photothermal conversion efficiency

Wood has been developed with phase change heat storage function using balsa as a natural packaging material, and PEG was employed as a material for phase change heat storage (PCHS). Moreover, the thermal conductivity efficiency of the wood was be improved by in-situ synthesizing Fe3O4 in wood. The prepared PCHS wood was characterized by high solidification and melting enthalpies. The temperature of phase change ranged from 21.47 °C to 35.30 °C, consistent with the temperature range that makes humans comfortable in their body. The in-situ generation of Fe3O4 not only improves the PCHS wood's thermal conductivity efficiency, but also forms a 3D network structure with PCHS materials, thereby improving the dimensional stability. Comparing with original wood, PCHS wood shows good temperature regulation function, which can quickly convert light energy into internal energy and has a longer period of thermal radiation at low temperatures. The generated PCHS wood shows a promising application as indoor temperature regulating materials to promote building energy conservation.

Kinetic investigation and numerical simulation of reactor with prepared diatomite/CaCO3 for high-temperature thermal energy storage application

Calcium looping (CaL) thermochemical energy storage (TCES) gradually appears in high temperature concentrating solar power (CSP) plants. However, the CSP-Cal integrated system has encountered challenges related to the high temperature stability of calcium-based materials and reactor design. Firstly, the wet ball milling-impregnation method was used to experimentally prepare the diatomite calcium-based thermal storage materials, and a natural diatomite skeleton matrix was obtained. A modified diatomite/CaCO3 composite thermochemical energy storage material was synthesized. The material can keep maintaining an effective conversion rate of up to 85 % by repeating charging and discharging heat storage processes for 20 times. At the same time, the 3-dimensional diffusion model was applied to investigate the reaction kinetics during the heat storage process. Secondly, numerical studies were carried out to simulate the decarbonization process of the packed bed reactor used in CSP, illustrating the complex coupling mechanism of the multiple physical processes. The results reveal that increasing the temperature and velocity of heat transfer fluid (HTF) can accelerate the heat storage process and changing porosity can modify the reaction pattern. Finally, in order to enhance the heat transfer and flow rate of HTF inside the reactor, spiral metal porous channels of large permeability with high thermal conductivity are embedded in the reactor, which promotes CO2 emission and reduces the completion time during a decarbonization reaction. This study not only proposes a novel approach to prepare the calcium-based heat storage materials but optimizes the energy storage performance of packed bed reactors.

Thermochemical cooling for high-power chip using sodium acetate trihydrate/expanded graphite: A new strategy and model

This study uses thermochemical heat storage (TCHS) material comprising of sodium acetate trihydrate/expanded graphite (SAT/EG) to cool the high-power devices in enclosed space. Due to its extraordinary energy storage density of 785 J/g, SAT/EG effectively reduces the weight/volume of the cooling system. Comparing to using phase change materials, the dummy chip temperature can be maintained less than 160 °C for 18.7 % longer in time. Moreover, a novel thermogravimetric-thermochemical storage (TGTS) model is developed to describe the thermal management process of TCHS. New govern equation adopts the weightloss curve measured by thermogravimetric analysis and directly translates it as a process indicator of the decomposition, thereby omitting the need for correlations of conventional models developed from mechanism functions. As a result, the TGTS model exhibits notable advantages in terms of its simplicity, low programming difficulty, time-efficient preprocessing, and maintains the same level of result accuracy as conventional models (with an average error of 5.19 %). The model can theoretically guide the optimization of the thermal management system by achieving a balance between the decomposition enthalpy and thermal conductivity of SAT/EG under different cooling requirements.

Development and thermal property analysis of biobased binary composite heat storage materials

Natural aliphatic dibasic acids are a type of bio-based material that shows promising potential as green phase change thermal storage materials due to their favorable thermophysical properties. However, these materials have been found to have issues with subcooling, low thermal conductivity, and poor temperature matching. In this study, three aliphatic dibasic acids, namely adipic acid (AA), sebacic acid (SA), and azelaic acid (ZA), were selected for further investigation. Three biobased eutectic systems, AA-SA (melting point: 118.3 °C), ZA-SA (melting point: 96.2 °C), and AA-ZA (melting point: 98.4 °C), were then prepared based on the calculation of Schrader's equation and experimental screening. The eutectic systems were thoroughly characterized, revealing thermal conductivities ranging from 0.4 to 0.5 W·m−1·K−1, with all systems exhibiting a subcooling of around 20 °C. Based on the principle of optimal overall performance, the AA-SA system was selected for modification. By incorporating Expanded graphite (EG) as a highly thermally conductive additive and nucleating agent, the AA-SA/EG composite phase change material (CPCM) was successfully prepared. This modification effectively reduced the supercooling degree of the bio-based phase change materials (PCM) and significantly improved its thermal conductivity by a factor of four. The resulting AA-SA/EG CPCM demonstrated excellent temperature suitability and has the potential to contribute to the application of bio-based phase change materials in waste heat recovery and solar energy systems. This study provides valuable insights into the development and optimization of bio-based phase change materials, contributing to the sustainable utilization of renewable resources for thermal energy storage applications.

Enhancing visible light absorption of form-stable CH3COONa·3H2O composite phase change material and its application in thermoelectric power generation

The utilization of Phase Change Material (PCM) for solar heat storage represents an effective solar energy storage method. Nevertheless, this promising technology encounters several obstacles, particularly PCM leakage and dissatisfied solar absorptance. This study focuses on the development of a photothermal conversion composite PCM tailored for solar energy storage and its subsequent integration into a thermoelectric power generation system. The composite PCM was synthesized using an evaporation-impregnation method, with melamine foam (MF) serving as the adsorbent material, graphene oxide (GO) as the light-absorbing component, and sodium acetate trihydrate (SAT) as the thermal storage medium. It is shown that the MF demonstrates an exceptional adsorption capacity for SAT, whose mass fraction exceeds 99 % in the final composite. The composite PCM exhibits a remarkable melting enthalpy of 251.5 J/g, comparable to that of pure SAT. The integration of GO into MF/SAT improves the solar absorptance of the composite, elevating it from 23.3 % to 81.5 %, thereby enhancing the photothermal conversion performance. To assess the practical solar energy storage potential of the prepared PCM, a thermoelectric power generation system was designed and underwent a continuous 22-hour performance test in a real outdoor enviornment. The results reveal that the system is able to maintain voltage generation for about 10 hours after the sun disappears. This proves the superior photothermal conversion and heat storage capabilities of the prepared materials. This research offers a viable approach for direct solar energy storage and conversion to electricity, advancing renewable energy technologies.

Thermal performance analysis of a double-pass solar air heater with lava rock as porous and sensible heat storage material

This study investigates the utilization of lava rock as a sensitive heat storage material in a double-pass solar air heater. Three configurations were examined: (i) Double-pass solar air heater without the lava rock, (ii) Double-pass solar air heater with a 50 % lava rock packed bed, and (iii) Double-pass solar air heater with a 100 % lava rock packed bed. The experiments were performed indoors under the solar simulator with solar irradiances ranging from 590 to 1000 W/m2 with varying mass flow rates of 0.02, 0.06, and 0.12 kg/s. Results indicate a significant improvement in thermal efficiency with the addition of lava rock. At 1000 W/m2 solar irradiance, the configurations (i), (ii), and (iii) exhibited thermal efficiencies ranging from 18.2 % to 65.02 %, 25.27 % to 72.17 %, and 26.28 % to 76.41 %, respectively. Lava rock's integration into the double-pass solar air heater significantly lowered the temperature of the absorber plate as compared to the conventional double-pass solar air heater, showcasing the thermal storage properties of the lava rock. Under solar irradiance of 1000 W/m2 and a mass flow rate of 0.06 kg/s, the temperature of the absorber plate dropped from 91.3 °C in configuration (i) to 80.0 °C in configuration (ii), a decrease of 12.56 %, and to 71.4 °C in configuration (iii), a decrease of 21.74 %, respectively. The configuration (iii), utilizing a 100 % lava rock packed bed, exhibited the most enhanced thermal performance, representing the potential of lava rock as a sensible heating storage material in double-pass solar air heaters for improved heat retention and utilization under varying solar conditions. Moreover, the use of a double-pass solar air heater with lava rock results in a consistent and even distribution of temperature throughout the heater.

Analysis of the Effects of Structural Parameters on the Thermal Performance and System Stability of Ventilation Air Methane-Fueled Reverse-Flow Oxidation Reactors

Ventilation air methane (VAM) from coal mining is a low-grade energy source that can be used in combustion systems to tackle the energy crisis. This work presents a numerical analysis of the thermal and stabilization performance of a VAM-fueled thermal reversal reactor with three fixed beds. The effects of the combustion chamber/regenerator height ratio (β), heat storage materials, and porosity on the oxidation characteristics are evaluated in detail. It is shown that the regenerator temperature tends to vary monotonically with β due to the coupling effect of the gas residence time and heat transfer intensity. The optimal β is determined to be 4/6, above which the system may destabilize. Furthermore, it is found that regardless of the methane volume fraction, the regenerator with mullite inserted has the highest temperature among the heat storage materials investigated. In contrast, the temperature gradually decreases and the system becomes unstable as SiC is adopted, signifying the importance of choosing proper thermal diffusivity. Further analysis reveals that the porosity of the heat storage materials has little effect on the system stability. Decreasing the porosity can effectively reduce the oscillation amplitude of the regenerator temperature, but it also results in greater pressure losses.