Thermal Energy Storage Method Research Articles

Numerical study on the thermal performance of high-temperature latent heat packed-bed with a rectangular heat storage unit

As one of the most effective methods of thermal energy storage, packed-bed (PB) systems using phase change material (PCM) as heat storage media have been vigorously developed. To obtain the thermal performance of brick structure heat storage unit (HSU) in high-temperature latent heat PB, a 3-D PBsystem based on Navier-Stokes equations for heat transfer fluid, phase change model for PCM, and surface-to-surface (S2S) radiation model is established. The idea of changing the geometric structure of the brick HSU is proposed to improve the thermal performance of PB system. The influence of three-dimensional size of carbonate-based composite PCM with brick structure on the thermal performance of high-temperature PB is studied systematically. The numerical analyses show that the influence of three-dimensional size of brick-type HSU in different directions on the thermal performance of the PB system is independent. And the system has a higher energy efficiency (66.5%) and lower heat loss when the width and height of HSU are around 25 mm. The research results can guide the optimization of high-temperature composite PCM PB system.

Al2O3 Nanopartiküllü ve Nanopartikülsüz Parafinin Erime Davranışları Üzerine Sayısal Bir Çalışma

One of the most effective methods of thermal energy storage is the use of Phase Change Materials (PCM). Paraffin, which is among the organic PCMs, is frequently used in thermal storage applications due to its easy accessibility and high heat storage capacity. However, it significantly limits the thermal charge / discharge (melting / solidification) rate of systems caused by their low thermal conductivity. There are many methods applied to enhance the thermal conductivity of paraffin. In this research, the melting processes of pure paraffin (Rubitherm RT50) and paraffin containing 10% Al2O3 nanoparticle in a rectangular melting area were numerically investigated. For comparison, the effect of increasing the wall temperature of the rectangular area to 65 ° C, 70 ° C and 75 ° C on the total melting time was investigated for both pure paraffin (melting temperature 50 ° C) and paraffin with nanoparticle additives. In this study, in which the Computational Fluid Dynamics (CFD) approach was used, ANSYS Fluent software was used to perform numerical analysis. Consequently it was determined that the use of Al2O3 nanoparticles improved the rate of paraffin heat transfer.

Enhanced heat transfer in a PCM shell-and-tube thermal energy storage system

The dominant technology among latent heat thermal energy storage methods relies on solid–liquid phase change. Since the primary disadvantage of phase change materials is low thermal conductivity, heat transfer enhancement techniques are required for these types of systems. In this paper, we propose a new double-tube latent heat thermal energy storage units. The melting time and exergy efficiency are compared for eight different design solutions. 3D simulations of the phase change material melting process were performed using the enthalpy-porosity model, Boussinesq approximation, and select temperature-dependent phase change material properties. This study shows that the proposed latent heat thermal energy storage unit (M06) significantly reduces PCM melting time compared with vertical (76%), horizontal (66%), and helical-coiled (53%) systems. The helical-coiled unit with spiral fins (M05) has the highest exergy efficiency (0.77) at the end of melting time. The M05, M06 and M08 units have the highest exergy efficiency at times t = 1200 s and t = 3307 s, which is essential for climates with time constraints on latent heat thermal energy storage. • Proposition of a new helical-coiled tube enhanced with spiral fins and conical shell. • 60% PCM melting time reduction, compared with horizontal LHTES unit. • The helical-coiled unit with spiral fins has the highest exergy efficiency (0.77). • Analysis of the effect of fins and conical shell design on melting process.

An experimental investigation on melting and solidification behavior of phase change material in cylindrical latent heat storage units with minichannel

The latent heat storage using phase change materials (PCM) has relative advantages compared to other thermal energy storage methods, according to numerous studies in the literature. The design of the heat exchanger are very important for performances of latent heat storage systems. Although there are studies using PCM in different design heat exchangers in recent years, they are quite limited. In this study, a design different from the literature has been used to create an alternative to latent energy storage (LHS) systems by passing different diameter minichannel through a cylindrical enclosure. The thermal effect of the PCM on both the charge and discharge process have been studied at different inlet temperatures of the HTF. Moreover, different flow rates of HTF and different minichannel diameters have been studied only for the charge process. According to the experimental results, as the inlet temperature has been raised from 60°C to 65°C, 70°C, 75°C, 80°C, start of the melting time has decreased by 51.22%,62.99%, 64.46%, 73.28%, respectively. As the minichannel diameter has been decreased from 1.9mm to 1.5mm and from 1.5mm to 1.21mm, the liquid fraction has decreased by 10.6 and 50.5%, respectively, for 75°C HTF inlet temperature conditions. Additionally, the results has showed that the effect of HTF flow rate on thermal energy storage (TES) can be negligible. It was concluded that the optimal shell-tube radius ratio could be up to about 25 in the LHTES systems studied. It is a very important result for engineering systems using PCM for energy storage in heat exchangers.

Heat transfer enhancement in latent heat thermal energy storage unit using a combination of fins and rotational mechanisms

Due to the rapid growth of research in the field of thermal energy storage (TSE), optimization of these systems (especially the method of latent heat thermal energy storage (LHTES)) is significantly investigated in last couple of years. Using fins is one of the conventional ways to increase the heat transfer rate. In the present study, a numerical simulation is conducted to assess the combined effects of applying both fins and rotation. This study investigates the solidification and melting process by using the enthalpy porosity method. Solidification and melting time and heat transfer rate are two essential parameters in the operating of LHTES heat exchangers. Results show that rotational speed has a positive effect on the operating system, with a reduction in time for the solidification process of 83.21% and the increased heat transfer rate of 12.89 W. Additionally, increased rotational speed has a direct relationship to the improvement of the heat transfer ratio by 2.45 and 3.87 times in the charging and discharging process, respectively.

A systematic assessment on a solar collector integrated packed-bed single/multi-layered latent heat thermal energy storage system

Thermal energy storage (TES) methods stand out as a key technology that eliminates the supply-demand imbalance in cooling or heating systems. This paper focuses on investigating the charging performance of the solar-aided packed-bed latent heat TES system. An in-house 1D transient mathematical model is developed to simulate the latent heat TES system's heat transfer phenomena. The TES tank is integrated with a flat plate solar collector to include the variable boundary condition effects of solar energy and ambient air. The enhanced thermal conductivity approach is implemented into the mathematical model to consider the natural convection effects of the PCM's liquid phase, and the method is validated. The mathematical model of the packed bed latent heat TES tank is also validated with the experimental and numerical results from the literature. As design and working parameters, the mass flow rate of heat transfer fluid (HTF) and spherical storage material diameter are varied. Single-, double- and triple-phase change material (PCM) arrangements are also studied by varying the melting temperature of PCM along the flow direction. The time-wise variation of energetic and exergetic efficiencies of the integrated system, PCM mean temperature inside the storage tank, and the liquid fraction in flow direction are investigated. Further extensive parametric analyses are conducted for heating season months, i.e., November, December, January, and February. As a result, the best design and working conditions for the integrated latent heat TES system within the range investigated are proposed. Also, it is concluded that decreasing the capsule diameter and increasing the HTF's mass flow rate has a positive effect on system indicators.

Thermal stability evaluation of selected zeolites for sustainable thermochemical energy storage

ABSTRACT In recent times, the thermochemical energy storage (TCES) method is gaining prominence due to its high energy storage density and minimal heat losses compared to the conventional thermal energy storage (TES) methods. This paper presents the cyclability behavior of selected zeolites for the TCES applications. The zeolites were subjected to sequential desorption and adsorption processes for five times using a differential thermogravimetric analyzer (DTG-60H). To investigate their suitability for the commonly available sources of thermal energy (e.g. solar energy, industrial waste heat), the samples were heated up to 150°C. These zeolites were also tested on Brunauer–Emmet–Teller (BET) analyzer for total surface areas and pore volumes, thus to read their sorption behavior. A field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray (EDX) analyzer was used to examine the surface morphology and elemental composition of zeolite sorbents before and after the multi-cycle test run. The changes in the mass of a material during a process, either desorption or adsorption, were notably almost the same across the cycles tested, which confirms the cyclability of the materials tested. Amongst the tested materials, Zeolite-NaY and Zeolite-HY exhibited relatively better process enthalpies owing to their active water adsorption capacities. Of the six materials tested, Zeolite-NaY has offered better results and its enthalpies range from 287.5 J g−1 to 348.5 J g−1 for the desorption and from 81 J g−1 to 292.1 J g−1 for the adsorption. A mass gain was noticed for each of the tested materials as they undergo the cooling process, thus affecting water vapor adsorption capacity negatively.

Effect of orientation on thermal performance of a latent heat storage system equipped with annular fins – An experimental and numerical investigation

Because of high energy storage density, latent heat storage is preferred over other thermal energy storage methods. The most common configuration of latent heat storage unit is shell and tube configuration, the performance of which greatly depends on its orientation. The influence of orientation may get altered when fins are provided for heat transfer enhancement. Hence, the current work is intended to examine the performance of a shell and tube latent heat storage unit in which annular fins are attached to the tube. Both experimental and numerical investigations are carried out to get a thorough insight into the melting behavior. The experiments are conducted at 0°, 30°, 60° and 90° inclinations (0° corresponds to vertical configuration); both energy and exergy analyses are carried out. The findings revealed that the melting rate is nearly same at all the inclinations during the initial stages. Later with the progression of time, the melting rate is decreased and the decrement is more for horizontal configuration. 85.63% more time is required for complete melting at 90° inclination (horizontal) in comparison with the 0° inclination. This is because of the suppression of convective transport in the bottom half for the case of horizontal orientation. Higher energy efficiency is obtained for horizontal orientation, whereas vertical orientation exhibited higher exergy efficiency. Energy stored, average Nusselt number and effectiveness of the latent heat storage system are also higher for 0° inclination.

Heat storage process analysis in a heat exchanger containing phase change materials

• One of the most effective methods of thermal energy storage is the use of phase change materials (PCMs). • The highest thermal energy storage in these materials occurs during the phase change process. Accurate analysis of the PCMs behavior will result in the optimal use of these materials. • The performance of a shell and tube heat exchanger containing PCMs is analyzed using the modeling results of PCMs. • The effect of PCMs type, HTF temperature, heat exchanger outer diameter, and fins number are analyzed. The need for energy storage has increased due to increased energy consumption and unbalanced consumption curves. The energy storage improves the availability and efficiency of energy resources. One of the most effective methods of thermal energy storage is the use of phase change materials (PCMs). PCMs are organic or inorganic compounds capable of absorbing and storing latent heat within themselves. The highest thermal energy storage in these materials occurs during the phase change process. Accurate analysis of the PCMs behavior will result in the optimal use of these materials. In this paper, the performance of a shell and tube heat exchanger containing PCMs is analyzed using the modeling results of PCMs. The Crank-Nicolson numerical solution in MATLAB software is used to solve the heat transfer equations with governing boundary conditions. After confirming the validation of the proposed method, the effect of PCMs type, the heat transfer fluid (HTF) temperature, the heat exchanger outer diameter and fins number on the heat exchanger performance is analyzed. The results showed that, the use of materials with more latent heat leads to store more thermal energy in the lower temperature ranges. Also, as the HTF temperature increases, the temperature difference between the HTF and the PCM increases and therefore, the amount of stored energy and the speed of energy storage will increase. It is also shown that, by increasing the number of fins and the use of six fins instead of four fins, the amount of equilibrium temperature and stored thermal energy will increase.

Application of Integrated Cold Thermal Energy Storage for Improving the Performance of Vapor-Compression Refrigerators

New options of the design of a vapor-compressor refrigerator with cold thermal energy storage are proposed. A comparative analysis of the performance of the considered systems is carried out. Results on the effectiveness of using various methods of cold thermal energy storage in the vapor-compression refrigerator circuit have been obtained. Recommendations regarding the field of application of these systems and the volume of cold thermal energy storages are given.

A heuristic modeling of solar-assisted earth’s geothermal power production capacity

Geothermal energy is in nascent stage in India. Extracting energy from earth’s interior and converting it into power are a general practice in countries like Kenya, New Zealand, Tanzania, Mexico, Iceland, etc. India has low enthalpy subsurface regime. Power generation from earth’s internal heat is limited in India. The present study deals with a heuristic modeling technique where solar energy is hybridized with geothermal energy. To enhance enthalpy and in turn elevate power generation concentrated solar trough (CST) device is utilized. Thermodynamic models are prepared for CST-geothermal setup. CST is hybridized with geothermal energy both in series and parallel modes. The study also suggests thermal energy storage methods for uninterrupted power supply in night. The cost of the hybrid plant is 25–50% lesser compared to photovoltaic plants. The economic analysis of the proposed plant is evaluated based on energy and exergy models.

Latent thermal energy storage technologies and applications: A review

Abstract The achievement of European climate energy objectives which are contained in the European Union's (EU) “20–20–20″ targets and in the European Commission's (EC) Energy Roadmap 2050 is possible, among other things, through the use of energy storage technologies. The use of thermal energy storage (TES) in the energy system allows to conserving energy, increase the overall efficiency of the systems by eliminating differences between supply and demand for energy. The article presents different methods of thermal energy storage including sensible heat storage, latent heat storage and thermochemical energy storage, focusing mainly on phase change materials (PCMs) as a form of suitable solution for energy utilisation to fill the gap between demand and supply to improve the energy efficiency of a system. PCMs allow the storage of latent thermal energy during phase change at almost stable temperature. The article presents a classification of PCMs according to their chemical nature as organic, inorganic and eutectic and by the phase transition with their advantages and disadvantages. In addition, different methods of improving the effectiveness of the PCM materials such as employing cascaded latent heat thermal energy storage system, encapsulation of PCMs and shape-stabilisation are presented in the paper. Furthermore, the use of PCM materials in buildings, power generation, food industry and automotive applications are presented and the modelling tools for analysing the functionality of PCMs materials are compared and classified.

Thermal energy storage

Thermal energy storage (TES) is an advanced energy technology that is attracting increasing interest for thermal applications such as space and water heating, cooling, and air conditioning. TES systems have enormous potential to facilitate more effective use of thermal equipment and large-scale energy substitutions that are economic. TES appears to be the most appropriate method for correcting the mismatch that sometimes occurs between the supply and demand of energy. It is therefore a very attractive technology for meeting society’s needs and desires for more efficient and environmentally benign energy use. In this study, thermal energy storage systems, energy storage, and methods, hydrogen for energy storage, and technologies are reviewed.

Experimental study of MgO/Mg(OH)2 thermochemical heat storage with direct heat transfer mode

Thermochemical heat storage uses a reversible chemical reaction to store thermal energy. This thermal energy storage method has high energy density and allows long-term thermal energy storage. MgO/Mg(OH)2 is a promising reversible reaction for thermochemical heat storage systems. The performance of this reversible reaction inside a reactor plays a key role in its practical applications. The direct type heat transfer reactor is a novel design compared with an indirect powder bed reactor. It allows the gaseous heat transfer fluid to flow through the powder in order to break the heat transfer limitation from the heat exchanger between the MgO/Mg(OH)2 powder and the heat transfer fluid. In this study, we evaluated the performance of a direct type MgO/Mg(OH)2 reactor under various operating conditions. Parametric analyses indicated that the heat output is limited by the reaction rate rather than the heat transfer efficiency. Results also showed the best bed thickness in order to achieve the highest temperature output. Material characterization indicated that the MgO/Mg(OH)2 particles did not agglomerate with each other after 15 heat charging and discharging cycles.

Renewable Energy: Volume 2: Mechanical and Thermal Energy Storage Methods

The present book reviews the possible methods of storing energy in the form of mechanical or thermal energy. The methods for mechanical energy storage that are reviewed include those that make use of gravitational potential energy, such as pumped hydroelectric energy storage and the potential energy associated with solid masses. The storage of energy by compressing air and the storage of energy as rotational energy in a flywheel are also described. The applications of these methods include grid storage and grid stabilization, as well as energy storage for transportation. There are three basic categories of thermal storage are (1) sensible heat of materials, (2) the latent heat of phase transitions and (3) the heat associated with chemical reactions. Sensible heat storage is discussed in terms of its application to residential heating, community-based heat storage, solar ponds, and thermal storage for grid-integrated energy systems. Latent heat storage may be used for both heating and cooling purposes and examples utilizing the solid-liquid transition of water and the liquid-gas transition of air are described. The basics of energy storage utilizing thermochemical reactions are presented.

Phase Changing Material Usage to Increase the Efficiency of Photovoltaic Panels

Energy based on renewable energy sources continues to meet the increasing need of growing population. In renewable energy production, not only energy production but also efficient using is crucial. In recent years, photovoltaic panels, which are increasingly used and highly important, have warmed on the surface due to the radiation energy emitted by the sun, and this warmth reduces the efficiency of the panel. In this study, it is aimed to reduce this efficiency loss by using phase changing material with latent heat which is one of the thermal energy storage methods. One of the two solar panels placed parallel to the ground was filled with phase changing material. With this, it is aimed to cool photovoltaic panel by using calcium chloride hexahydrate phase changing material; and radiations air temperature, current, voltage, power, surface temperature, efficiency graphs were obtained. As a result of simultaneous measurements, the increase in yield was 2.95%.

Preparation and assessment of paraffin/SiO2composite phase change material based on the efficacy coefficient method

Latent heat thermal energy storage by using phase change materials (PCMs) to store and release thermal energy is considered to be an efficient, environmental and promising thermal energy storage method for energy conservation. The advantages of PCMs on thermal energy storage works are in terms of keeping constant temperature during the phase change process. It is especially important for researching and developing phase-change materials (PCMs) with low operation cost, simple process, stable performance and favorable durability. In this study, paraffin/SiO2 composite phase-change materials (CPCMs) were prepared with cheap and environmental paraffin as the core material and with industrial water glass for the preparation of the nano-SiO2 as the shell material and characterized. From the technological parameters of CPCMs, select 8 items and analyze data by comprehensive assessment based on the efficacy coefficient method. It was indicated seepage circle, coating rate, phase-change enthalpy, mass loss ratio, density, thermal conductivity and temperature regulation performance are positive response. When the paraffin/water ratio was 1:4, pH is 4.5, the temperature is 35°Cand the paraffin/hydrated silica ratio is 2:1, the system efficacy coefficient of the optimum parameters is 0.8162and it’s the most significant. The method is effectively used to analyze the optimum value and could be significant in material optimization for next experiments.

Review on solar thermal energy storage technologies and their geometrical configurations

Because of the unstable and intermittent nature of solar energy availability, a thermal energy storage system is required to integrate with the collectors to store thermal energy and retrieve it whenever it is required. Thermal energy storage not only eliminates the discrepancy between energy supply and demand but also increases the performance and reliability of energy systems and plays a crucial role in energy conservation. Under this paper, different thermal energy storage methods, heat transfer enhancement techniques, storage materials, heat transfer fluids, and geometrical configurations are discussed. A comparative assessment of various thermal energy storage methods is also presented. Sensible heat storage involves storing thermal energy within the storage medium by increasing temperature without undergoing any phase transformation, whereas latent heat storage involves storing thermal energy within the material during the transition phase. Combined thermal energy storage is the novel approach to store thermal energy by combining both sensible and latent storage. Based on the literature review, it was found that most of the researchers carried out their work on sensible and latent storage systems with the different storage media and heat transfer fluids. Limited work on a combined sensible-latent heat thermal energy storage system with different storage materials and heat transfer fluids was carried out so far. Further, combined sensible and latent heat storage systems are reported to have a promising approach, as it reduces the cost and increases the energy storage with a stabilized outflow of temperature from the system. The studies discussed and presented in this paper may be helpful to carry out further research in this area.

A method and analysis of aquifer thermal energy storage (ATES) system for district heating and cooling: A case study in Finland

Aquifer thermal energy storage (ATES) systems with groundwater heat pumps (GWHP) provide a promising and effective technology to match the renewable energy supply and demand between seasons. This paper analyses the integration of an ATES and GWHP system in both district heating (DH) and district cooling (DC) networks in terms of system's efficiency, techno-economic feasibility and impact on the surrounding groundwater areas. To that end, a novel method of holistic integration of groundwater modeling is proposed and demonstrated for retrieving and analyzing data from a variety of open Finnish public data sources. A case study is presented, where the ATES integration is examined within an existing district heating network in Southern Finland. It is concluded that combining heating and cooling, with seasonally reversible ATES operation and balanced pumping volumes during summer and winter periods, had low impact on the aquifer area and is economically feasible. Finally, the study concludes that even with limited data, obtained from open public data sources, it is possible to assess the ATES integration with an acceptable accuracy.

Development of pentadecane/diatomite and pentadecane/sepiolite nanocomposites fabricated by different compounding methods for thermal energy storage

Global warming is one of the most important consequences of excess energy consumption. Phase change materials (PCMs) have prominent advantages in thermal energy storage owing to their high latent heat capacities and small temperature variations during the phase change process. However, leakage is a major problem that limits the use of PCMs. Leakage may occur in encapsulated PCMs or in composites where the PCM is attached to the surface of a supporting material or within the pores of that material. In this study, pentadecane/diatomite and pentadecane/sepiolite nanocomposites were fabricated by using unmodified and microwave-irradiated diatomite and sepiolite samples and by using different compounding processes, such as direct impregnation, vacuum impregnation, and ultrasonic-assisted impregnation methods. The microstructures and the chemical and thermal properties of the composites were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and differential scanning calorimetry. Subsequently, the thermal reliability and stability and the thermal conductivity of the PCM composites were also investigated. A melting temperature of 9.25°C and a latent heat capacity of 58.73 J/g were determined for the pentadecane/diatomite composite that was prepared with the direct impregnation method using a microwave-treated diatomite sample. The pentadecane/sepiolite composite prepared in the melting temperature range 7.98°C to 8.53°C and latent heat capacity range 41.05 to 46.02 J/g. The results of the thermal analysis indicate that fabricated diatomite-based or sepiolite-based PCM composites have good potential as thermal energy storage materials.