Thermal Storage Research Articles

Assessment of phase change materials for thermal energy storage in solar drying applications

Assessment of phase change materials for thermal energy storage in solar drying applications

Advances in ground heat exchangers and thermal energy storage for sustainable energy systems

Advances in ground heat exchangers and thermal energy storage for sustainable energy systems

The effect of lateral position of heating surface and angular orientation of latent heat thermal energy storage system on the melting characteristics: a numerical investigation

Purpose This study aims to address the low thermal conductivity and suboptimal performance of phase change materials (PCMs) by examining the impact of geometric adjustments on their melting rate. Design/methodology/approach A two-dimensional numerical model was created to investigate the effect of different positions and angular inclinations of the inside heating surface (IHS) on the melting rate of PCM within a latent heat thermal energy storage system. The model analysed the IHS at the centre and below the centre at various positions (10, 20, 30 and 40 mm) and inclinations (0°, 15°, 30°, 45°, 60°, 75° and 90°). Findings The 90° inclination (vertical) significantly reduced the melting time by 75% compared to the 0° inclination (horizontal). The best melting performance was recorded with the IHS positioned 20 mm below the centre. At a 30° inclination, the maximum reduction in melting time was observed with the IHS at 30 and 40 mm placements. The system demonstrated the highest energy storage capacity of 307.72 kJ/kg at a 75° inclination with the IHS positioned 10 mm laterally, and the lowest capacity of 255.02 kJ/kg at a 0° inclination with the IHS at a 30 mm lateral position. Practical implications To address the deficient part of PCM like low thermal conductivity and below level performance characteristics, a structural (geometrical) adjustment was developed to study the effect on the melting rate of PCM without any cost addition. Using the computational model, an optimised thermal energy storage system is developed that can play a pivotal role in improving the applicability of thermal energy storage systems. Originality/value This research is novel in simultaneously investigating the numerical characteristics of PCM melting behaviour with different lateral positions and angular orientations of the IHS. A unique design modification was introduced, using a 2D numerical model and simulations to explore the effects under isothermal conditions.

Enhanced comprehensive thermal performance of ternary composite phase change materials with graphite powder hybridizing expanded graphite/erythritol

ABSTRACT Sugar alcohols are considered highly promising medium-temperature phase change materials (PCMs) due to their superior overall performance. In this study, erythritol (Ery) was used as the base PCM, with expanded graphite (EG) and graphite powder (G) as additives. Ternary composite PCMs were prepared using a melt blending method, and their thermal storage properties were systematically characterized. The results showed that the two ternary composite PCMs, 1.5 wt% G/1.5 wt% EG/Ery and 4.5 wt% G/1.5 wt% EG/Ery, exhibited the best overall thermal performance, with excellent heat storage and crystallization heat release characteristics. While maintaining the same melting point, these two composite PCMs retained high melting enthalpies, specifically 325.8 kJ/kg and 316.1 kJ/kg, respectively. Their thermal conductivities reached 2.11 W/(m·K) and 2.48 W/(m·K), representing an increase of 2.0 and 2.5 times compared to Ery, with thermal effusivities improved by 45.8% and 57.0%, respectively. The crystallization enthalpy increased to 233.6 kJ/kg and 230.8 kJ/kg, with heat release ratios improved by approximately 10%. Additionally, thermal stability was significantly enhanced, with decomposition temperatures increased by 21.6°C and 15.1°C, respectively. Both PCMs maintained good cycling stability over 40 consecutive heating-cooling cycles and were more economical compared to other composite PCMs of Ery.

Reviewing experimental studies on latent thermal energy storage in cementitious composites: report of the RILEM TC 299-TES

Reviewing experimental studies on latent thermal energy storage in cementitious composites: report of the RILEM TC 299-TES

Assessment of Particle Candidates for Falling Particle Receiver Applications Through Irradiance and Thermal Cycling

Abstract Falling particle receiver (FPR) systems are a rapidly developing technology for concentrating solar power applications. Solid particles are used as both the heat transfer fluid and system thermal energy storage media. Through the direct irradiation of the solid particles, flux and temperature limitations of tube-bundle receivers can be overcome, leading to higher operating temperatures and energy conversion efficiencies. Candidate particles for FPR systems must be resistant to changes in optical properties during long-term exposure to high temperatures and thermal cycling in highly concentrated solar irradiance. Seven candidate particles—two previously tested particles such as CARBOBEAD HSP 40/70 and CARBOBEAD CP 40/100 and the five novel particles such as CARBOBEAD MAX HD 35, CARBOBEAD Solar HSP, CARBOBEAD Solar CP, CARBOBEAD Solar MAX HD, and WanLi Diamond Black—were tested using simulated solar flux cycling and tube furnace thermal aging. Each particle candidate was exposed for 10,000 cycles (simulating the exposure of a 30-year lifetime of a concentrated solar power plant) using a shutter to attenuate the solar simulator flux. Feedback from a pyrometer temperature measurement of the irradiated particle surface was used to control the maximum temperatures of 775 °C and 975 °C. Particle solar-weighted absorptance and emittance were measured at 2000 cycle intervals. Particle thermal degradation was also studied by heating particles to 800 °C, 900 °C, and 1000 °C for 300 h in a tube furnace purged with bottled unpurified air. Here, particle absorptance and emittance were measured at 100-h intervals. Measurements taken after irradiance cycling and thermal aging were compared to measurements taken from as-received particles. WanLi Diamond Black particles had the highest initial value for solar-weighted absorptance, 96%, but degraded up to 4% in irradiance cycling and 6% in thermal aging. CARBOBEAD HSP 40/70 particles currently in use in the prototype FPR at the National Solar Thermal Test Facility had an initial value of 95% solar absorptance with up to a 1% drop after irradiance cycling and 4% drop after 1000 °C thermal aging.

Nanofluids in Thermal Energy Storage Systems: A Comprehensive Review

Nanofluids, which consist of nanosized particles dispersed in a base fluid, represent a promising solution to improve the performance of thermal energy storage systems. This review offers a comprehensive overview of nanofluids and their applications in thermal energy storage systems, discussing their thermal properties, heat transfer mechanisms, synthesis techniques, and application in latent heat storage systems. Various types of nanofluids are examined, including metal oxide, carbon-based, and metallic nanofluids, highlighting their effects on thermal conductivity, latent heat and the phase change temperature. A review of experimental and numerical studies showcases the performance of thermal energy storage systems incorporating nanofluids and the factors influencing their thermophysical characteristics and energy storage capacity. Finally, the key findings of current research are summarized, as well as the challenges and the potential future directions in nanofluid-based thermal energy storage systems research, emphasizing the need to optimize nanoparticle concentration and long-term durability.

Solar Stirling for Renewable Energy Multigeneration Systems

This study explores the feasibility and potential of integrating dish–Stirling systems (DSSs) into multigeneration energy systems, focusing on their ability to produce both thermal and electrical energy. By leveraging the concentrated solar power capabilities of DSSs, this research examines their performance relative to alternative solutions such as photovoltaic (PV) systems and solar heating. A 25 kW Stirling Energy Systems (SES) DSS served as the basis for the analysis. Simulations were performed for local 2022 weather conditions in Germany. The study employed a detailed modeling approach using the NREL System Advisor Model (SAM) to quantify the energy outputs and evaluate the system efficiencies. The results indicate that the DSS achieved an electrical efficiency of 25% and a combined efficiency of 78% when accounting for the maximum thermal energy generated. Seasonal analysis highlights the adaptability to fluctuating energy demands, with advantages in winter heating applications. Comparative evaluations revealed DSSs as a viable cogeneration alternative to standalone PV systems and solar heaters, offering reduced environmental impacts and enhanced energy efficiency. Future work will address real-world operational conditions, including thermal storage and multigeneration integration, positioning the DSS as a sustainable solution for renewable energy generation.

Towards a More Efficient Design of High Temperature Concentrating Solar Power Plant With Cascaded Thermal Energy Storage

This work proposes a novel concentrating solar power (CSP) plant configuration aiming at a high operation temperature of 1000°C. The thermal energy storage system (TES) would be the focus of this research by modifying it and proposing four configurations to enhance the overall efficiency of high-temperature solar power towers. The objective is to identify the most thermodynamically efficient designs by analyzing the literature on the different components and comparing them to a reference base case of a conventional 100 MWe solar power tower plant (2-tank molten salt TES) operating at 565°C. The proposition consists of a Brayton/Rankine combined cycle with a double cascade TES. In the proposed cascade TES, the primary unit consists of a high-temperature air/ceramic packed-bed thermocline operating at 1000°C, while the secondary unit is a single molten salt tank used as sensible heat. The secondary TES is used as a heat sink during charge, improving efficiency and reducing the size of the air/ceramic-packed bed by extracting the thermocline out of the tank. Excess energy stored in the secondary TES is utilized for preheating during discharge. The methodology incorporates evaluating various combinations of solar block, TES, and power block integration. Combinations are selected from a comprehensive literature review. The study focuses on night-time operations. Further analysis of the cost-benefit of the designs would be required to compare the overall energy production and furthermore the LCOE.

Experimental Operation of a Prototype 750C Advanced Chloride Molten Salt Bellows Valve

To achieve DOE 2030 SunShot targets that reduce the cost of liquid-based solar by an additional 40% to 70% beyond 2018 costs, a more reliable, highly manufacturable flow valve, capable of achieving operational temperatures of >700°C is required [1]. This paper investigates the development of an innovative high-temperature chloride molten salt valve, with operation up to 750°C. This valve is intended to be employed within Gen 3 CSP liquid-based thermal energy storage (TES) systems as well as Gen 4 modular salt reactor (MSR) technologies. This work details the general design and flow testing of a bellows-seal flow control valve (FCV). This design includes an integrated closed-loop thermal control system to ensure robust design for freeze-thaw cycles. The self-contained thermal management STM system, is unique in the salt valve industry since it is an integrated solution to provide a consistent, repeatable alternative to typical heat tracing. Additionally, the design includes the employment of a novel heat pipe valve stem to facilitate enhanced passive thermal management into the valve assembly. This valve stem heat pipe is designed to facilitate natural circulation within the bonnet to ensure robust operation, during both nominal and transient thermal operation. The valve body and trim will be designed using SS316H, consistent with Flowserve Corporation’s existing product base and is code qualified but will utilize clad material for materials corrosion, manufacturing cost reduction and compatibility to ensure design flexibility. A test campaign was performed in this investigation utilizing a novel 750°C ternary chloride (20%NaCl/40%MgCl2/40%KCl by mol. wt. %) molten salt flow loop. A discussion about the design and installation of the valves within this test bed is provided for this investigation. Valve test results from this study assessed Cv curves as well as multiple actuator cycles, under varying thermodynamic and operational mode conditions, which would be characteristic within a commercial molten salt facility. The results indicate nominal operation for the baseline design, though improved performance and reliability is expected with the full designed FCV.

Perspective on phase change composites in high-efficiency solar-thermal energy storage

To clarify future research directions, this study first analyzes the heat transfer process of solar-thermal conversion and then reviews solar-thermal phase change composites for high-efficiency harnessing solar energy. The focus is on enhancing heat absorption and conduction while aiming to suppress reflection, radiation, and convection. Most advancements have concentrated on improving absorption and thermal conductivity, while reducing the aforementioned unfavorable processes remains less explored. In the current research, the best results show that the solar-thermal conversion efficiency has approached the theoretical limit (100%), and a typical thermal conductivity has reached 33.5 W/(m·K). However, further enhancement of the absorption and conduction remains a challenge, highlighting the need for structural modifications and grafting. Other factors hindering conversion efficiency have received limited attention and warrant further in-depth investigation, with the potential to reduce reliance on fossil fuels and contribute to environmental sustainability.

Numerical Investigation of Dual Metal Hydride Bed Based Thermochemical Energy Storage System

Thermochemical energy storage system is known for good thermal stability and high energy storage density. Metal hydride based thermochemical energy storage systems are reported to store thermal energy at higher temperatures. In this analysis, NaMgH2F and Mg2NiH4 are used as high temperature and low-temperature metal hydrides. One kg of NaMgH2F is used as thermal energy storage media, while Mg2NiH4 is used as hydrogen storage media. The analysis includes the study of energy charging and discharging characteristics with heat transfer phenomenon in metal hydride with variation in thermal conductivity of high temperature metal hydride bed. With the increase in thermal conductivity of high temperature metal hydride bed, the heat transfer between heat transfer fluid and metal hydride bed during the energy charging and discharging process has improved. A marginal increase in thermal energy stored and discharged in/from the metal hydride bed system has been observed with an increase in the thermal conductivity of the metal hydride bed. Thermal energy stored in the MH beds for thermal conductivity of 0.5 W/m K, 0.75 W/m K, and 1 W/mK, are 270.88 kJ, 273.39 kJ, and 274.96 kJ, respectively. The energy desorbed from the system for thermal conductivity 0.5 W/mK, 0.75 W/mK, and 1 W/mK are observed as 251.25 kJ, 258.22 kJ, and 260.57 kJ, respectively. The three cases of thermal conductivity have reported an energy storage efficiency of 92.75%, 94.45%, and 94.77%, respectively.

Bamboo–PCM: Comparative Analysis of Phase Change Material-Impregnated Dendrocalamus giganteus Culm Behavior Exposed to Thermal Variation in Wind Tunnel Assay

The construction industry’s pursuit of eco-friendly materials has sparked interest in bamboo, a renewable resource with exceptional physical and mechanical properties. This study analyzed the integration of Dendrocalamus giganteus bamboo with phase change materials (PCMs) to enhance thermal energy storage in building applications, aiming to improve temperature regulation and reduce energy consumption for climate control. The study compared the performance of bamboo impregnated with an industrial PCM or coconut oil, used in conjunction with a polyurethane resin (PU) coating treatment, assessing their thermal regulation performance against traditional building materials such as ceramic tiles, fiber cement, and metal sheets. From an anatomical perspective, the pores within bamboo culms offered ample space for PCM storage, resulting in a substantial heat storage capacity. Thermal behavior tests conducted in a wind tunnel revealed that the impregnated bamboo samples effectively mitigate temperature fluctuations by aligning them with the PCM’s phase change temperature. Additionally, it was observed that air flow velocity had an impact on this phenomenon. The study concluded that bamboo culms impregnated with PCM hold promise for temperature regulation in construction applications, with variations in airflow exerting an impact on the outcomes obtained.

Enhancing Energy Efficiency in Mediterranean Large-Scale Buildings: A Study on Mobilized Thermal-Energy-Storage Systems

This study investigates the use of Mobilized Thermal Energy Storage (MTES) systems to enhance energy efficiency in large-scale Mediterranean buildings, focusing on a university campus in Tripoli, Lebanon. The research question addresses whether MTES can effectively utilize waste heat from a power plant to meet heating, cooling, and water heating needs. We hypothesize that MTES, using Erythritol as the phase change material (PCM) and Therminol55 as the heat transfer fluid (HTF), will improve energy efficiency and reduce costs compared to conventional systems. The methodology involves simulating the MTES system’s performance, including charge, self-discharge, and discharge phases, using Simulink-MATLAB. Key findings reveal that increasing the HTF flow reduces the charging time by 29% and enhances the efficiency by 8%, while larger project scales decrease heat costs. Economic analysis shows a payback period (PBP) of 2 years 11 months for heating only and 2 years 1 month for heating and cooling, with annual maintenance costs considered at 5%. These results demonstrate MTES as a sustainable and cost-effective solution for thermal energy storage, with potential applications in the energy sector.

A novel photovoltaic thermal and thermoelectric converter air collector integrated with solar dryer having thermal energy storage - An experimental approach

A novel photovoltaic thermal and thermoelectric converter air collector integrated with solar dryer having thermal energy storage - An experimental approach

Multi‐Objective Optimization of a Spherical Thermal Storage Tank Using a Student Psychology‐Based Approach

ABSTRACTEnergy storage technologies often store heat, with water as a preferred medium due to its availability and low cost. However, maintaining water in a liquid state at high temperatures requires large pressure vessels, posing significant design challenges. Balancing thermal storage capacity with pressure constraints is essential. This paper explores the dynamics of thermal storage water tanks, aiming to optimize their design using a multi‐criteria approach. An equilibrium thermodynamic model was developed to evaluate the impact of geometric structure and operating parameters. The results show that optimizing a single variable is insufficient to minimize pressure swing, reduce heat loss, and maximize storage capacity. To address these trade‐offs, a multi‐objective student psychology‐based optimization (SPBO) algorithm was employed for three‐objective optimization, outperforming particle swarm optimization (PSO) in convergence. The technique for order preference by similarity to ideal solution (TOPSIS) method was applied to the Pareto frontier, yielding ideal solutions using both data‐driven and manually weighted approaches. Compared with the initial design, the data‐driven weighted (entropy‐weighted and coefficient of variation methods) optimal designs improved all objectives, reducing pressure swing by 12.8% and 19.8%, respectively. A manually weighted approach reduced pressure swing by up to 86.7%, albeit with a decrease in thermal storage capacity.

Corrigendum to “Comprehensive analysis and optimization of combined cooling heating and power system integrated with solar thermal energy and thermal energy storage” [Energy Conv. Manag. 275 (2022) 116464

Corrigendum to “Comprehensive analysis and optimization of combined cooling heating and power system integrated with solar thermal energy and thermal energy storage” [Energy Conv. Manag. 275 (2022) 116464

Analytical and Numerical Comparison of the Two-Dimensional One-and Two-Phase Energy Storage Phenomenon in Phase Change Materials

Abstract This work investigated the thermal behavior of phase change material during the melting process in a two-dimensional (2D) plate intended for thermal energy storage. The analytical and numerical analyses were conducted for both one phase and two-phase systems. The numerical analysis was conducted using the Mathematica program, while the COMSOL Multiphysics program, which employs the finite element approach, was employed. To validate the numerical analysis answers, the Stefan-Neumann equations were solved analytically using the EES (Engineering Equation Solver) program. The present study investigated the temporal variation of heat transfer flow during the melting process of paraffin material under a constant wall temperature. A 98.9% agreement is seen between the regression analysis findings of the one-phase numerical and analytical solutions for the melting distance of paraffin from the wall in different time periods (0.8–16 h). This study examined the numerical and analytical solutions for one- and two-phase systems and found that the thermal energy storage values converged to 99.2% for two phase systems and 99.6% for one phase systems.

Improved absorption of phosphates through interface junctions and photothermal–energy–storage capability of Ca(OH)2–[Co3O4–Co3(PO4)2]

Strong absorption in the full solar spectrum is required for efficient usage of solar energy. Near-infrared (NIR) light absorption mainly depends on surface plasmon resonance and a high density of free charge carriers (FCCs). However, increasing FCC density in semiconductors is still a challenge. In this work, we demonstrated that multitudinous S-scheme interface junctions can be constructed within nanoscale Co3O4–Co3(PO4)2, leading to enhanced light absorption of phosphates over the entire solar spectrum due to the increased FCC density and charge-carrier configurations. This absorber can also boost the photothermal performance of Ca(OH)2. The photothermal dehydration conversion of Ca(OH)2 is considerably improved (13.7 times). The reversibility of the photothermal hydration–dehydration cycles of Ca(OH)2 is improved by 39 times. This composite is promising for photothermal conversion and thermal energy storage in one-step.

Experimental investigation on charging and discharging performance of finned shell and tube device containing pentaerythritol for low and medium temperature thermal energy storage

This work concerns the investigation of the charging and discharging performance of a finned shell and tube device that utilized for low and medium temperature thermal energy storage application. An experimental rig is built for evaluation in which a so-called solid–solid phase change material of pentaerythritol is used as energy storage substance and air is employed as heat transfer fluid. The PE has tested to have a melting temperature range of 185-205℃ and a latent heat of 290 kJ/kg. The study first examines the effect of fin number on the device thermal performance by considering configurations with 4, 6, 8, and 10 fins. Then the impact of fin height is evaluated where four different fin heights of 9 mm, 14 mm, 19 mm and 24 mm is investigated, and finally the influence of heat transfer fluid working condition is explored. The results indicate that the PE could be ideal PCM utilized in shell-tube typed thermal energy storage device. The enhancement of fin number and fin heigh can largely improve both the charging and discharging performance of the device. For a given air inlet pressure of 0.1 MPa, the device having fin number of 10 and fin height of 19 mm could be identified as the optimal configuration for heat transfer, and at such working conditions, the device achieves a charging efficiency of 91.49 % and a discharging efficiency of 86.4 %.