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Phase Change Materials (PCM) may be excellent thermal insulation due to their poor conductivity and high heat capacity. Researchers are adding PCM to windows. This integration modifies internal surface temperatures and delays peak temperatures to improve indoor thermal comfort. This work investigates experimentally and numerically the impact of the different filling materials in four Triple Glazed Windows (TGW) configurations in an Iraqi environment: the first window filled two cavities with air (standard); the second window has one cavity filled with a PCM and the other with air; the third window has blinders with various tilt angles in one cavity and PCM in the other cavity; and in the fourth window, both cavities are filled with PCM. Numerically utilizing Computational Fluid Dynamics to evaluate the thermal performance of TGW. In August, when the solar radiation was at its maximum (623 W/m2), the results showed that the peak interior surface temperature dropped by 4.51, 13.28 and 11.53 % in the TGW configurations (PCM-air), (blinder-PCM), and (PCM-PCM), compared to the standard TGW. The fourth window increased the time lag by 2 h, effectively shifting the load and in the third window, the best tilt angle blinder is 45°

To improve building energy efficiency and address thermal storage challenges during periods without a heat source, such as cloudy weather or night-time, a range of solutions is required. Innovative technologies and sustainable practices are essential for combating climate change and reducing carbon emissions. This study primarily focuses on Thermal Energy Storage (TES) systems, specifically those using Phase Change Materials (PCMs), to increase energy efficiency for Transpired Solar Collectors used in buildings applications. During the last 30 years Transpired Solar Collectors (TSC) have been extensively investigated. However, a primary concern still exists regarding thermal storage when the heat source is unavailable, such as during periods of cloudy weather or at night. Thus, a Thermal Energy Storage (TES) system coupled with the TSC is a potential solution. In this study we are investigating using numerical simulation the arrangement of encapsulation for TES, integrating phase change materials (PCM) in spherical elements when compared with plate encapsulation elements. The model reproduces a part of a real scale thermal energy storage inserted in a Double Skin TSC. The model consists of a Plexiglas duct in which four different arrangements for the spherical encapsulated PCM were studied. For each of the arrangements the heat transfer between the TES elements and the air passing through the collector was analyzed. The primary finding of the study indicates that the hexagonal arrangement offers better passive airflow control, thus enhancing the heat transfer up to 12.3% compared to the rectangular arrangements [ABSTRACT FROM AUTHOR]

In order to mitigate the global energy problem and address environmental issues, it is becoming more important to include renewable energy sources, such as photovoltaic (PV) panels. However, the working temperature of PV panels has a major influence on their efficiency, which may result in a decrease in energy conversion efficiency and hasten deterioration. Phase change materials (PCMs) and heatsinks have been the focus of current research to improve the thermal performance of PV panels. Using PCMs and heatsinks, this work gives a thorough numerical and analytical examination targeted at improving the thermal efficiency of PV panels. The proposed study uses a multiphysics method to examine the performance of different PCM-based cooling systems in combination with conventional heatsinks by integrating heat transfer, fluid dynamics, and phase change phenomena. In order to do the numerical simulations, a complex mathematical model must be created and include important factors such as the surrounding temperature, solar radiation, panel material qualities, and PCM characteristics. The study investigates the transient behavior of the PCM during the charging and discharging processes, maximizing its heat storage and release capabilities. This is done by using verified computational techniques. The result of changing the thickness of the fin helps to understand the process of transferring thermal energy from the solar panel and passing it to the phase change material. The thickness of 1 mm was the surface temperature of 46.95 degrees Celsius, while the thickness of 2 mm was the temperature of the surface of the plate at 45.734 degrees Celsius. At a thickness of 3 mm, temperatures went down to 44.665 degrees Celsius. The benefit of reducing the temperatures on the surface of a solar panel is to obtain high efficiency and generate the largest possible capacity. A power voltage diagram with varying fin thickness shows that the value of the capacity increases with the increase in the thickness. The basic principle for comparison and understanding of the case is to increase the electrical efficiency, which is the basis for understanding the improvement in temperature. [ABSTRACT FROM AUTHOR]

As far as thermal insulation is concerned, phase change materials (PCM) have a very good potential to be excellent insulation materials due to their thermal properties like low thermal conductivity and high latent heat. The researchers started to incorporate the walls and windows with PCM to reduce the internal surface temperature and indoor temperature of the room. This paper focuses on double and triple-glazed windows’ thermal performance, different filling insulation materials, ventilation windows, and thermochromic glazing. In addition, a detailed discussion on the effect of changing the thickness and the thermal characteristics of the PCM and its influence on the internal surface temperature, temperature time lag, and other parameters such as total energy transmitted and indoor temperature. Previous studies have shown that including PCM in triple-glazed windows decreases the temperature of the inner surface by 2.7°C and 5.5°C compared to double-glazed windows with PCM and triple-glazed windows. Utilizing ventilation during summer nights saves 46% on cooling energy. By using two different PCM melting temperatures, the maximum interior and surface temperatures are reduced by 6°C. The integrated PCM blind system prevented the room occupants from being exposed to direct sunlight. Finally, additional recommendations were made based on the identified research needs.

A new concept of dynamic phase change material (PCM) wall structure in building envelope is proposed to enhance the passive solar energy utilization, in which PCM wall position could be exchanged with insulation layer. The thermal performance of phase change materials in buildings is related to many factors. To ensure that the novel dynamic PCM wall structure could reach its full potential, the thermal performance of the structure was numerically simulated and optimized based on different climatic conditions, room sizes and the position of PCM layer in the wall. The results indicated that the suitable PCM was different when using the novel dynamic PCM wall in different climates. Among the four cities of Harbin, Tianjin, Jinan and Guangzhou, northern cities, like Tianjin, were more suitable for using PCM A16 than southern cities. In terms of room size design, when the volume of the room remained identical, the room size design formed a certain correlation with the indoor temperature. In addition, results showed that the location of the novel PCM wall system in the wall would cause a great difference in indoor temperature, which was related to heat dissipation at different locations. [ABSTRACT FROM AUTHOR]

Phase-change materials have various applications across industries from thermal energy storage through automotive battery temperature management systems to thermal stabilisation. Many of these applications are shell and tube structures with different shell shapes. However, it is not yet known how the shape of the shell affects the melting, solidification times, and heat transport processes in such structures. To fill this research gap, seventeen shell shapes/orientations were compared using a simulation study. The well-known and validated enthalpy porosity algorithm implemented in the Fluent 2021R2 software was used. The numerical calculations were preceded by the measurement of thermal conductivity, phase change enthalpy, and specific heat during melting and solidification of the phase-change material. The shortest melting time was achieved for a semi-circular shell shape in the downward position, which was 44% shorter than the reference circular case. The shortest solidification times were recorded for an isosceles trapezium in an upward orientation relative to the reference circular case. Therefore, it is possible to significantly reduce the melting time in shell-and-tube systems as a result of the appropriate selection of the shell shape. [ABSTRACT FROM AUTHOR]

To create a highly efficient photovoltaic-thermal (PV-T) system and maximise the energy and exergy efficiency, this study aims to propose an innovative configuration of a PV-T system comprising wavy tubes with twisted-tape inserts. Following the validation of a numerical model, a parametric study has been conducted to assess the geometrical effects of twisted tape and wavy tubes, as well as the coolant fluid type and velocity, on the overall performance of a PV-T system, located in Shiraz, Iran. It is found that employing twisted tape improves the energy and exergy efficiency by approx. 6.3%. The best configuration yields 12.4% and 16.8% increase in energy and exergy efficiency compared to conventional PV systems. This is achieved at 15% volumetric concentration of microencapsulated phase change material slurry. The monthly variation of global horizontal irradiance in Shiraz highly affected the energy and exergy efficiency of PV-T, with July and October exhibiting the most efficient months, corresponding to 90% and 11.3%, respectively. [ABSTRACT FROM AUTHOR]

The rapid increase in computing power has facilitated the use of computational fluid dynamics (CFD) as an attractive tool for simulating solar systems. As a result, researchers have conducted numerous experimental and numerical studies on solar technologies, with an increasing emphasis on the utilization of CFD for simulation purposes. Hence, this article is intended to be the first of a two-part assessment of recent improvements in the use of ANSYS-Fluent CFD simulation in solar systems. In this part, the article aims to provide a comprehensive overview of CFD simulations, using ANSYS-Fluent, for different solar systems without concentrators, including solar thermal systems, hybrid photovoltaic/thermal (PV/T) systems, and photovoltaic/phase change material (PV/PCM) systems, while the concentrating solar systems are covered in the second part. Further, this review study includes informative data about the simulations, including the considered assumptions, models, and solution methods that were used with different cooling fluids, PCM materials, absorber designs, and innovative system designs. The present assessment also highlights the results and some remarks that show different important additional information such as the applied radiation and melting/solidification models. Besides, validation techniques and errors between the experimental work and simulations are introduced. In general, the ANSYS-Fluent CFD results were validated and it was possible to optimize many design parameters with minimal effort and expense. Recent research indicated that nanofluids could be a better alternative to conventional fluids to improve the thermal functionality of flat plate and hybrid PV/T systems. Effective cooling mechanisms could reduce PV panel temperature by 15–20%. Besides, integrating PCM with PV systems could enhance efficiency by 33–46% on summer days. Incorporating different nanomaterials and using fined PV/PCM configurations, the PV/PCM system demonstrated improved cost-effectiveness, while a foam layer outside the PCM could extend PV thermal management time by 55%. Many other conclusions about the commonly used physical models, solution methods, and assumptions dealing with different systems are highlighted inside. The article also identifies additional research proposals and challenges that must be addressed to advance the study of this topic. [ABSTRACT FROM AUTHOR]

A computational fluid dynamics (CFD) model based on the mass, momentum, and energy conservation equations is used to simulate the industrial-scale hydrogen storage in activated carbon (AC: AX-21) bottle surrounded by a layer of metal foam (MF)-phase change material (PCM: RT 22 HC) latent thermal unit. The aim is to boost the recuperation (storage) of the heat liberated from the H₂'s exothermic (adsorption). Following the model's validation, several numerical simulations were performed to evaluate the impact of various physical features of the MF (copper), at variable porosity (ε = 0.80–1.0), on heat transfer in the hole reactor. Independently of the MF porosity, the AC-bed temperature suddenly increased (from 295 K), reaching a maximum (at about 500 s) and decreased afterward. The temperature's intensity was dependent on the probe's position in the AC-bed (i.e. several positions were studied). The H 2 concentration in the AC-bed may reach 25 mmol/g. The PCM-based unit received the discharged heat from the AC-bed slowly, but with PCM incorporation in MF, the heat was quickly recovered (stored). Thanks to the MF-induced PCM's increased thermal conductivity, the heat flux, the heat transfer coefficient, and the melting rate of the PCM were all accelerated (during the charging phase) several times by decreasing the MF porosity (increasing MF mass) from 1 (pure PCM) to 0.8. The temperature and the melting contours throughout the absorption process (up 10,000 s) supported all these findings. It is obvious from the results of the current study that improving the reactor geometry and the solid bed's thermal conductivity (thermal performance) is necessary for an effective hydrogen storage system. • Numerical H 2 storage in large-scale activated carbon (AC)-MF-PCM reactor was done. •Mass and heat transfer were analyzed in the various regions of the AC-MF-PCM reactor. •The MF-PCM system participates in the AC-charging through absorbing the reaction heat. •MFs considerably increases the melting rate of the pure paraffin (PCM). •Lower MF porosity accelerates the heat transfer and the PCM melting rate. [ABSTRACT FROM AUTHOR]

Energy storage may shift and reduce peak power demand throughout the year. The ventilation system can be improved by incorporating phase change materials in heat exchangers as thermal energy storage. Optimizing and developing the air to a PCM heat exchanger is crucial. Using ANSYS (FLUENT 19.2), the numerical 2D model is used to optimize the heat transfer performance between airflow and PCM slabs. As latent heat thermal energy storage, nine rectangular slabs filled with PCM-RT25 were proposed. The PCM panels are 10 mm thick, and there is a 20-mm air channel between them. The PCM is encapsulated in 3-mm steel, and the shell is insulated with 10-mm wood. The length of the heat exchanger is 1 m, and its width is 0.6 m. The CFD model has been used to investigate the liquid fraction in PCM panels, as well as outlet air temperature and pressure drop through air channels. The findings revealed that air channel height, PCM panel height, melting temperature of PCM, and the heat exchanger's length-to-width ratio significantly impact melting and solidification rate through charging and discharging PCM. The proposed APHX takes 4 and 3.25 h to melt and solidify, respectively. The result of using RT25 + RT21 in succession is the same as using RT21 for melting, with a 1-h reduction in solidification time. [ABSTRACT FROM AUTHOR]

Among the various techniques for enhancing the storage and consumption of energy in a thermal energy storage system, the establishment of thermal stratification in a hot-water container is an effective technology. The current study aims to assess the performance of the thermal stratification for hot-water containers using (ANSYS Fluent) R.1.0, 2022, through the study of the impact of different numbers of paraffin-filled containers, namely 3, 5, and 7, that are equivalent to 5, 7, and 9 kg of paraffin, respectively. To validate the present numericalmodel, a comparison between the current study results and the experimental findings from the literature was conducted, and the results demonstrated that there was a good approval between these results. The results of this study depict that the profile temperature at the outlet of the container indicates an enhancement in the Richardson number and stratification number by 37.9% and 45.8%, respectively, when the charging process is finished. Furthermore, increasing the number of paraffin-filled containers from 5 to 9 results in a 29.9% improvement in charging efficiency, resulting in an improvement in storage efficiency. Finally, the results have proven that the 3D CFD approach is a highly beneficial tool to assess the effect of PCM mass on stratification performance in a hot-water container. [ABSTRACT FROM AUTHOR]

Thermal solar collector considers one of the main devices employed to transform solar energy into thermal energy and can be classified into three main types named Evacuated tube collector (ETC), flat plate collector (FPC), and compound parabolic collector (CPC) collector. In this study, where it was taken to evacuated tube solar collectors three different geometries of the inner pipe diameter were proposed and combined with type of phase change materials (PCM) to evaluate their performance using PCM. And mass flow rate 0.5 L\min, A validated computational fluid dynamic (CFD) model was used in this examination. The data indicates that the highest outlet water temperature was observed at 45 °C from 1:00 pm to 2:00 pm for case-1 with a smooth pipe, whereas for case-2 with two lobes and case-3 with four lobes, the maximum temperatures were 41 °C and 40 °C. respectively, The results showed that case-1 with Paraffin wax has the best efficiency among the proposed cases. Where it was recorded maximum outlet water temperature was about 45 °C. [ABSTRACT FROM AUTHOR]

The techniques for releasing thermal energy accumulated in periods of high availability to meet the demand in periods of low energy supply contribute to the continuity of the cycles involved in thermodynamic processes. In this context, phase change materials are capable of absorbing and releasing large amounts of energy in relatively short periods of time and under specific operating conditions. However, phase change materials have low thermal conductivity and need to be coupled with high-thermal-conductivity materials so that the heat flux can be intensified and the energy absorption and release times can be controlled. This work aims to numerically study the solidification process of a phase change material inserted into a triplex tube heat exchanger with finned copper walls to intensify the thermal exchange between the phase change material and the cooling heat transfer fluid, water, that will receive the energy accumulated in the material. This work proposes the 3D numerical modeling of the triplex tube heat exchanger with finned walls and meets the need for numerical models that allow for the analysis of the full geometry of the latent heat thermal energy storage system and the thermal and fluid dynamic phenomena that are influenced by this geometry. Results of the temperature, liquid fractions and velocity fields during phase transformations are presented, analyzed and validated with experimental data, presenting average errors of below 5%. The total material discharge time was approximately 168 min, necessary for the complete solidification of the phase change material, with water injected into the triplex tube heat exchanger at a flow rate of 8.3 L/min and a temperature of 68 °C. The solidification process occurred more slowly in the same direction as the length of the triplex tube heat exchanger, and from 80% of the material in the solid state, the difference between the solidification time for z = 0 and z = 480 mm was 30 min. The fluid dynamic conditions developed in the latent heat thermal energy storage system promoted a maximum negative heat flux of −6423 w/m2 to the annular internal surface and −742 w/m2 to the annular external surface, representing a heat removal process nine times less intense on the external surface. The total energy released to the cooling heat transfer fluid was 239.56 kJ/kg. [ABSTRACT FROM AUTHOR]

Nanostructured phase change materials (NePCM) are phase change materials that contain different types and sizes of colloidal I removed the word sizes particles. Many investigations in the literature assess those type of phase change materials to investigate their thermal performance. However, there is a discrepancy between the experimental observations and numerical results of the melting process of the NePCM because most numerical models do not count for the mass transfer of the particles. In the current work, we will investigate the melting process of NePCM that consists of copper nanoparticles suspended in water for the geometry of a square cavity, heated from the two sides, cooled from one side, and the remaining side is thermally insulated. Our numerical model will account for the mass transfer of the particles using a one-fluid mixture and the enthalpy porosity model for accounting for the phase change process. We found that adding the particles will lead to the deceleration of the melting process, as described by the experiments, because of the reduction of the convection intensity. We found that for NePCM suspension containing 10% of nanoparticles by mass, the deceleration of melting will be about 2.2% compared to pure water. Most of the particles are convected away by the flow cells toward the bottom side of the cavity, especially near the isolated right side of the cavity. Our findings indicate that incorporating mass transport of particles leads to a significantly improved prediction of the melting behavior of the NePCM. [ABSTRACT FROM AUTHOR]

The objective of this paper is to examine the thermal performance of a LHTES system comprised of a single tube, by means of a Computational Fluid Dynamics (CFD) computer code. Two different types of fins, straight and annular, were considered to enhance the heat conduction between the tube and the RT42 Phase Change Material (PCM). The dimensions of the fins were elected so that the total area of the fins to be almost equal, in both configurations. The RT42 PCM is a paraffin wax with medium to high thermal energy storage and chemically inert. Whereas possible, temperature dependent thermal properties, provided by the producer, used for the definition of the material model. Between the finless tube and the one with straight fins, the melting time reduction was approximately 56.7% and between the finless and the annular tube, the PCM melt time was reduced by 61.5%. Heat conduction was the driving heat transfer mechanism during the first seconds of the PCM melting process. On the other hand, natural convection was the lead heat transfer method as the liquid PCM was able to move due to density and temperature differences. The investigation of the liquid PCM travel revealed that in the finless model and the one with the straight fins the PCM movement was parallel to the axial direction whereas in the model with the annular fins the velocity of the PCM was parallel to the radial direction. [ABSTRACT FROM AUTHOR]

Thermal energy storage technologies are a crucial aspect of a sustainable energy supply system, with latent heat thermal energy storage tanks being among the best thermal energy storage systems. The use of phase change materials (PCMs) is a suitable way to enhance the energy efficiency of the system and fill the gap between demand and supply. The objective of this work is to conduct a numerical and experimental investigation of the thermal storage tank capacity of different types of PCMs, such as wax, salt hydrate, and salt hydrate mixtures. An experimental investigation was conducted to determine the melting and super cooling temperature, which indicates the temperature gap for all the PCMs that were used in this study. A numerical model was developed to investigate the proposed heating system to determine the maximum heat storage capacity. Streamlines of the melting PCM, melting fraction, and temperature distribution were presented. According to experimental results showed that wax is the most stable PCM. The numerical stage showed that the thermal response of sample C (8:2 of used Ca(NO3)2·4H2O:Mg(NO3)2·6H2O) was comparatively better than that of the other samples (i.e., samples A and B) in terms of thermal capacity storage PCM. In sum, the samples/composite PCMs are favorable for thermal energy storage system utilization.

A two-dimensional time-dependent computational analysis was carried out to examine the effects of inclined plate on melting time of Phase Change Material (PCM) filled square block on the bottom wall of a channel. Solution of the governing equations are performed by using finite volume method. The RT25HC material is chosen as PCM. The study is done for different parameters of inclination angle of the plate and Reynolds number. It is observed that the inclined plate can be used to control of melting time of PCM in a block as well as flow field and temperature distribution in the channel. Using of acceleration angle as θ = 110° accelerates the melting time of PCM inside the block. Thus, mass fraction rate increases 4 times with application of inclined thin plate. [ABSTRACT FROM AUTHOR]

The most significant drawback of latent heat thermal energy storage systems is the low thermal conductivity of phase-change materials (PCMs), which significantly slows thermal energy transfer rates. The objective of this research is to introduce the helical-coiled shell-and-tube unit with spiral fins as an energy and exergy efficient, and melting and solidification time reduction design for the PCM-based TES applications. The new design is a combination of the advantages of horizontal and vertical systems by offering helical-coiled shell-and-tube, proper shell-to-tube dimension ratio and the addition of spiral fins in a single configuration. Numerical experiments are conducted to compare PCM melting and solidification times, energy and exergy efficiency during charging, discharging for nine thermal energy storage designs. The results show that the proposed latent heat thermal energy storage unit, significantly reduces PCM melting and solidification times when compared to vertical (60% reduction in melting time; 26% reduction in solidification time) and horizontal (44% reduction in melting time; 21% reduction in solidification time) shell geometries, and achieves the highest overall exergy efficiency, the lowest solidification time, and low melting time. All units with conical shell geometries significantly reduce PCM melting time, while greatly extending total PCM solidification time. [ABSTRACT FROM AUTHOR]

Changes in the energy sector, associated with the move away from fossil fuels, pose a challenge for appropriate thermal energy management in residential buildings. The important element to deal with the variability of renewable energy in thermal systems is latent heat thermal energy storage. Due to the low thermal conductivity of phase change materials, a number of techniques are proposed to enhance the heat transfer process. In this research, the global sensitivity of fin geometrical parameters on the melting and solidification times and energy efficiency of these processes was investigated. The computational model of the phase change was developed using the finite volume method with the enthalpy-porosity model and Boussinesq approximation. Numerical simulations were carried out according to the design of experiments technique. The multi-dimensional response surface was developed, and the multi-objective optimisation was done. The research shows that the melting process is most influenced by the position of the top fin (α angle) and the solidification process by the position of the bottom fin (γ angle). The angle of the tree fin (β) has a different effect on both processes, with the energy efficiency decreasing during melting and increasing during solidification. Maximum values for the energy efficiencies of melting ( η m = 0.973 ) and solidification ( η s = 0.988 ) were obtained for α = 18. 2 ° , β = 89. 0 ° , L = 10.7 mm and γ = 21. 0 ° . [ABSTRACT FROM AUTHOR]

Three-dimensional computational analysis has been performed to investigate the melting time of the phase change material (PCM) in a sinusoidal pipe inserted into another pipe. The other pipe is filled with PCM and the system is heated from the inner sinusoidal pipe at different temperatures. The main aim of the study is to control the melting time. The finite volume method (FVM) is used to solve time-dependent governing equations. Four different cases are chosen for the sinusoidal wall to see the effects of geometry on melting. After the analysis, it is observed that melting time can be controlled via an adjustment of the geometrical parameter, namely a passive technique, without spending extra energy. [ABSTRACT FROM AUTHOR]

The aim of this paper is to provide an implicit transient numerical formulation of novel minichannel-coupled passive thermal arrangement to cool down unidentical IC chips on substrate board. In the proposed design, PCM is integrated in the minichannel which is kept at the periphery of IC chips. Through means of direct conduction from substrate board, phase change material absorbs latent heat and allows it to change its phase from solid to liquid by providing effective thermal cooling performance in system. A comparative study is developed between without PCM, with minichannel-coupled PCM and optimized single minichannel near the heat source. Results show that between paraffin wax, N-Eicosane and ATP 78 PCM, N-Eicosane can provide effective cooling performance. With the N-Eicosane temperature in the system controlled from 53.234∘C of the generic model to 51.520∘C and a significant 1.74∘C of temperature drop compared with the generic model, an additional 0.5∘C of temperature reduction occurs as compared with the case of paraffin wax PCM and 1.35∘C when compared with ATP 78 PCM. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) have a key role in reducing the greenhouse gas emissions contributed by the transportation sector. Lithium-ion (Li-ion) battery which is composed of different cells is the major component in EV, that serves as the power source due to its superior performance. Battery thermal management systems (BTMS) are essential to improve the life and performance and to reduce the risk of fire hazards. In the present study, a single Li-ion cell with Phase Change Material (PCM) and fins is numerically modeled. The finite volume-based simulation is used to predict the heat transfer and flow characteristics of the systems at various operating conditions. Three different unconventional honeycomb-shaped finned PCM systems including baseline model are simulated and compared against the case of PCM without fins and simple honeycomb fin. Cell maximum temperature, temperature difference, and PCM liquid fraction are selected as the parameters for the performance comparison among the different finned configurations. A reduction of 2.77% in maximum cell temperature is obtained in a simple honeycomb structure compared to no fin design at 5C discharge conditions. It is also concluded that the three advanced honeycomb structure shows similar thermal performance but shows better performance than simple honeycomb structure. It is found that 1-Tetradecanol and n-Eicosane PCMs reduce the maximum cell temperature by 13.36 K and 11.81 K, respectively, compared to RT-35 PCM at 5C discharge. The results show that the proposed BTMS exhibits maximum performance at 309.15 K ambient temperature with copper fins and 1-Tetradecanol as PCM. • Numerical model of Lithium–Ion cell equipped with honeycomb finned PCM structure. • PCM with honeycomb finned structures show 2.77% reduction in maximum cell temperature at 5C, enhancing thermal management. • Metallic honeycomb fins ensure uniform temperature distribution, preventing hotspots and thermal stratification. • Ambient temperature just below the solidus temperature of PCM ensure the optimal thermal comfort to the cell. • Copper honeycomb fins and 1-Tetradecanol PCM is selected as the best system combination for BTMS. [ABSTRACT FROM AUTHOR]

Maintaining the temperature of the photovoltaic (PV) panel within the described standard helps in achieving higher power conversion efficiency. To regulate the PV temperature, phase change material (PCM)-based cooling techniques have been proposed in several literature. However, most of the studies utilize organic PCMs whose low thermal conductivity confines their potential. Thus, in the proposed work, the rear side of the 20 Wp PV panel is coated with hydrated salt-based PCM and is integrated with an aluminum sheet (PV-PCM-Al) to increase the thermal conductivity of the system. The effect of the PV-PCM-Al panel in enhancing the PV efficiency is realized by comparing it with a standard uncooled PV panel. This concept was experimented under direct sunlight for about a week in Chennai, the southern part of India. To perceive the performance enhancement, thermal images were taken for both the cooled and uncooled PV panels. In addition, open-circuit voltage, short-circuit current, and power output were measured. The experimentation is also backed up by numerical simulations to understand the heat transfer characteristic features of the designed integrated PCM and aluminum cooling system. The experimentation results highlight that a maximum increase of about 7.67% in the PV efficiency was obtained using a cooled PV panel when compared to an uncooled PV panel. A maximum increase of 7.34% in the open-circuit voltage and a maximum drop of 4.6 °C in the PV temperature were obtained. [ABSTRACT FROM AUTHOR]

Heat exchangers, devices for the transfer of heat between two or more working fluids, are extensively used in cooling applications and heating applications. Heat exchangers in buildings are typically components of space-conditioning systems, as well as of water-heating applications. Heat exchangers are also sometimes used in applications that require storage and release of energy at specific times. Phase change materials (PCMs) enhance these heat-exchange processes, given their ability to melt and solidify at a fixed range of temperatures, absorbing or releasing significant amounts of latent heat. Five different configurations of PCM–air heat exchangers for thermal control in buildings are analyzed in this work. The heat exchangers were fitted with PCM encapsulated in plastic and composite pouches of various shapes, and packaged in stackable panel layers. Three-dimensional computational fluid dynamics (CFD) modeling of coupled incompressible fluid and conjugate heat transfer were performed on the designs. The phase change process was numerically modelled using the apparent heat capacity method. Steady-state CFD simulations provided quantification of pressure drop as a function of air flow velocity. Transient simulation results describe the thermal evolution of PCM in the pouches, helping to determine the best performing configuration with respect to total thermal charging time. [ABSTRACT FROM AUTHOR]

The design of passive cooling systems is part of the energy‐efficient building since population growth and indoor requirements in various dwellings are paramount. As a part of passive designs, modifying the conventional roof with phase change materials (PCM) is one of the techniques to control the abnormal changes of the inner surface temperature of the roof. In this aspect, a numerical investigation has been carried out by incorporating the PCM encapsulated pipes in the RCC (reinforced concrete), and a comprehensive analysis has been carried out. Three different shapes are chosen, namely circular, oval, and rectangular oval, to encapsulate the PCM. Diurnal outside changes are considered to envisage the inner surface temperature of the roof. Validation of the literature's experimental results is done before developing a numerical model for the current study. The effect of encapsulated shape on PCM's average temperature, liquid fraction and energy storage has been studied. The inner surface temperature is reduced drastically with the roof consisting of elliptical encapsulated PCM than other designs such as circular and rectangular oval encapsulated PCM. Moreover, the performance of PCM is sensitive to encapsulated shape and location within the system. [ABSTRACT FROM AUTHOR]

PV/T is designed to convert solar radiation into electricity energy; however, as the temperature rises, their efficiency decreases. This study evaluates experimentally and numerically the performance of PV/T systems. Two cooling methods were used: air jets for enhanced heat transfer and phase change material (PCM) as an energy storage source. Four cases were compared: case A (with PCM and jet), case B (with PCM, without jet), case C (without PCM, with jet), and case D (no cooling). The results were validated by experimental measurements under a solar simulator and the comparison between the experimental and numerical results is satisfactory. The findings show that case A (with PCM and jet) reduced the PV temperature by 21 °C and improved the electrical efficiency by 7.2 % compared with case D (no cooling). The highest electric and thermal efficiency of the PV/T system reached were 12.94 % and 79.1 % respectively at higher air flow rates in case A (with PCM and jet). The novelty of present study is the combination of jet impingement and phase change material, which can provide high electric and thermal efficiencies and allows 2 h' work after sunset. [ABSTRACT FROM AUTHOR]

• Analysis of single and double pass solar air heater-phase change material. • Evaluation based of PCM thickness to length ratio. • Improved outlet temperature during non-sunshine hours. • Improvement in useful energy during discharging period. • System's maximum efficiency of 63.34% achieved during PCM discharging. This paper presents a two-dimensional transient model for a solar air heater with phase change material (SAH-PCM), focusing on the thickness-to-length ratio (t/L) of the PCM container. Verified through experiments, the model considers single (SP) and double pass (DP) flow configurations, assessing liquid fraction, dead length, outlet temperature, energy, exergy, and system efficiency during PCM charging and discharging. Increasing the t/L ratio improves peak liquid fraction, reduces dead length, and delays PCM discharge in both configurations, enhancing system energy and exergy efficiencies. In a SP flow system, optimizing t/L at 0.042 yields a peak liquid fraction of 0.928, a 92.28% dead length reduction, and a 2 h and 22 min delay for PCM discharge (base-case t/L ratio: 0.0182), achieving a highest discharging efficiency of 39.1%. For a DP flow system, the optimized t/L ratio of 0.058 results in a peak liquid fraction of 0.976 and a 1 hour and 34 min delay for PCM discharge, attaining the highest discharging efficiency of 63.34%. Moreover, an improvement in the energy payback time (EPBT) is observed for both SP and DP flow as the t/L is increased. For the DP flow, a minimum EPBT of 0.68 years (energy basis) and 6.55 years (exergy basis) is observed at a t/L ratio of 0.058. In terms of energy cost, SP flow reaches a minimum of Rs. 20.824 Rs/kWh at a t/L ratio of 0.042. For DP flow, the minimum energy cost is 13.033 Rs/kWh at a t/L ratio of 0.058, representing a noTable 37.42% improvement compared to SP flow. These findings underscore the critical role of optimizing system parameters, specifically the t/L ratio, for enhanced energy and exergy performance, and economic viability of SAH-PCM. [ABSTRACT FROM AUTHOR]

In this study, the development and testing of a hybrid thermal energy storage (TES) including phase change material (PCM) macro-capsules inside a vertical sensible tank is presented. The storage was specifically developed for delivering hot water on board of ships. Accordingly, a commercial PCM was selected and tested. Subsequently, the hybrid TES was designed and tested under mimicked boundary conditions at lab scale, showing the possibility of increasing the volumetric energy storage density up to 30% compared to the sensible configuration. On this basis, two numerical models were developed: a detailed one, implemented in a Fluent environment, aiming at investigating the main parameters affecting the heat transfer efficiency inside the TES and a second one, implemented in an ESP-r environment to simulate the TES as a component to be implemented inside a more complex system, thus helping its accurate design and operation through a reliable modelling phase. Both models were satisfactorily validated against the experimental results, thus being made available for future investigations and design optimization. [ABSTRACT FROM AUTHOR]

Featured Application: Different simplified and low-computational-cost models for phase-change CFD simulation were compared with experimental data for geometries where convective flows could be negligible. The melting process of lauric acid in a square container heated from the top surface was numerically studied from an experimental case. Knowledge of this process is of special interest for computationally efficient modeling systems, such as PCM-enhanced photovoltaic panels in horizontal positions or energy storage using PCM embedded on flat surfaces. In these systems, the geometric arrangement of the PCM hinders the fluid-phase movements through natural convection, which slows the melting process and can cause overheating in the fluid phase. Using Ansys Fluent Software, three different approaches and two simulation methods, enthalpy-porosity and effective heat capacity, were developed for the numerical study. The results were compared with experimental measurements in a successful evaluation of the accuracy of computational fluid dynamics simulations. It could be observed that the effective heat capacity method presented significant advantages over the enthalpy-porosity method, since similar accuracy results were obtained, and a lower computational cost was required. [ABSTRACT FROM AUTHOR]

Improvement of stirring performance is one of the primary objectives in solid–liquid mixing processes, such as the preparation of phase change materials (PCMs) for energy saving in refrigeration and heat pump systems. In this paper, three novel impellers are proposed: pitched-blade punched turbine (PBPT), bionic cut blade turbine (BCBT) and bionic cut punched blade turbine (BCPBT). An experimental test was conducted to validate the stirring system model based on the Eulerian–Eulerian method with the kinetic theory of granular flow. Then the performance of the novel impellers was predicted, studied, and compared. The outcomes indicate that a novel impeller, specifically BCPBT, can effectively suspend particles and dramatically reduce power consumption. A better solid–liquid suspension quality was obtained with an aperture diameter of 8 mm and aperture ratio of 13%. Within the range of impeller speeds and liquid viscosity studied in this this paper, higher impeller speeds and more viscous liquids are more conducive to particle dispersion. One of the most important contributions of this work lies in the design of novel impellers, an extent of energy conservation to 17% and efficient mixing was achieved. These results have reference significance for improving the energy efficiency of temperature regulation systems. [ABSTRACT FROM AUTHOR]

• Anew design of smart window integrated photovoltaic, phase change materials, and vacuum glazing is proposed. • Five distinct window designs are numerically investigated. • The design combined the air gap, glass photovoltaic, PCM and vacuum glass layers decreases the total heat gain 91.5 % compared with the basic case. • The PCM (RT35HC) with a thickness of 50 mm decreases the heat gain by 73 % and maintain the inner surface temperature lower than 25 °C. Nowadays, new generations of building envelope need to manage the energy exchange between outdoor and indoor environment responsively and save the building energy. A significant amount of solar heat gain in buildings comes through the windows. The transparent envelope also must answer to visual requirements allowing for external vision but guarantying comfort conditions. In this framework, this article aims to test numerically the thermal performance of a new design of multifunctional glazed window combining the most recent technologies used in building envelopes. Five distinct window designs combing phase change material (PCM), vacuum glazing (VG), photovoltaic (PV), and air cavity were numerically tested for hot weather conditions. The proposed window designs slide inside the wall of the building. A comprehensive transient Multiphysics model coupling the thermo-electric model of the PV, melting and solidification model of the PCM, and the heat transfer mechanisms in the vacuum and air gaps are developed. The model is step by step validated with data in the literature. Various PCM types and PCM thickness are investigated. Among the five investigated window designs, the result showed that the window, including the air gap with PV, PCM cavity, and VG, is the optimal design for the indoor air's thermal isolation. Simultaneously, the PCM with a melting point of 35 ˚C and thickness of 50 mm is the best performance material in a hot arid region in summer at Cairo. The proposed multifunction window generated maximum electrical power intensity of 162 W/m2 at received solar radiation of 1000 W/m2. [ABSTRACT FROM AUTHOR]

The temperature of battery modules in electric vehicles must be controlled adequately to remain within a specified range for optimum performance. In this research work, thermal management of battery modules with PCM was investigated experimentally and computationally. The Li-Ion battery pack cooled with a PCM for removing heat generated during the battery charging and discharging cycles. Computations and experiments were carried out to estimate the heat transfer, solidification and melting characteristics of the PCM used in the thermal management of a Li-Ion cell module. Four PCM (GR44, RT50, OM35, and paraffin wax) with different melting temperature were used for the study. Battery operating temperature and melting point are the key parameters for selection of PCM. Experiments have been carried out only for OM35 and paraffin wax, because OM35 melting point is within the battery operating temperature and paraffin wax for considering harshest condition. The OM35 melting temperature range is below 35 °C which is accordance with a desire to keep battery temperature below that temperature. Based on experimental and simulation results, it was found that OM35 is keeping battery temperature range minimal, which was the ideal for Li-Ion battery thermal management. [ABSTRACT FROM AUTHOR]

The electrical efficiency of photovoltaic (PV) modules can be improved through the cooling of the PV. Among the passive cooling strategy, one of the most promising concerns the use of phase change materials (PCMs) to decrease the operative temperature of a PV panel. This paper investigates the performances of a conventional PV panel in which two organic PCMs are added (PV-PCM) to reduce the temperature rise of PV cells and consequently to increase the electrical performances. With this aim, unsteady numerical simulations have been carried with Ansys Fluent software using a two-dimensional simplified geometry for the PV modules with the PCM is incorporated (PV-PCM), as well as for the benchmark PV module. The numerical simulations have allowed evaluating the PV cell temperatures, the power production, as well the PCM thermal behavior. As regards this latter aspect the dynamic analysis has evidenced the need to extend the time of simulation at least for two days in such way to take into account of the degree of solidification achieved during the night by the PCM materials. PCM with low melting temperature cannot complete solidifying during the night and so the heat stored during the day will be lesser than the theoretical one. The results of this study pointed out that the PV-PCM units allow achieving higher performances in comparison with a conventional PV module, especially during the hottest months. An increase in the peak power of 10% and of 3.5% of the energy produced all year round is attained. [ABSTRACT FROM AUTHOR]

In this study, the efficacy of incorporating phase change material (PCM) into the building walls on the annual heat transfer reduction is examined. First, heat transfer from the base wall (without PCM) was numerically calculated monthly throughout the year. Then, PCM was incorporated into the wall and its heat transfer was calculated. It was found that using PCM in all months is beneficial and the maximum heat transfer reduction is 16.7% and occurs in June. Based on the results, the lower the thermal conductivity, the greater the PCM's ability to reduce heat transfer. Installation of PCMs such as Enerciel 22, C16–C18, Paraffin C 18 and Capric acid (with thermal conductivity of about 0.15 W m−1 K−1) inside the wall reduces heat transfer between the indoor and outdoor space by up to 15% throughout the year. Incorporating PCM of Enerciel 22 in the warm months of the year (June, July, August and September) reduces heat transfer to the room by 15.36%, while, in the colder months of the year, the heat transfer from the interior is reduced by 14.82%. Finally, throughout the year, the heat transfer between the interior and the outdoor is reduced by 14.87% due to the using PCM of Enerciel 22. [ABSTRACT FROM AUTHOR]

Liquid hydrogen has been identified as a promising propellant for long-duration space missions, benefiting from its high specific impulse when paired with liquid oxygen. A full procedural computational fluid dynamic model was proposed for the jetting, mixing, throttling, and venting processes of thermodynamic venting systems (TVS) for the purpose of minimizing liquid hydrogen boil-off on orbit. In addition to the mixing and jetting components as well as the fluid domain inside the storage tank, the external fluid circulation loop and the throttling device were also coupled into the solver in the form of user-defined code, which enabled simulation of the continuous complete thermodynamic cycles. The evaporation/condensation intensity factors for the liquid-vapor phase change were confined in a smaller range than those used in other studies through theoretical analysis. To enhance the numerical stability, the well-known Lee model for liquid-vapor phase change was modified by introducing a smoothing function. Simulations with a variety of initial temperatures, mass flow-rates and vent ratios were conducted, which revealed that the condensation of superheated vapor contributes to the depressurization processes noticeably greater than the disturbance of the temperature stratification. Depressurization efficiency was introduced for evaluating the TVS performance during the jetting process. Significant performance enhancement was observed when the temperature difference between the liquid and the ullage before jetting was enlarged. The self-pressurization period was found lasting longer time under on-orbit condition than that on the ground, which is attributable to the floating of the bulk liquid and higher uniformity of the temperature distribution after the jetting process in the absence of gravity. • A model was proposed for the full procedural simulation of TVS liquid hydrogen tank. • Lee model was modified by introducing a smoothing function to enhance stability. • Depressurization efficiency was introduced for evaluating the TVS performance. [ABSTRACT FROM AUTHOR]

The solidification dynamics of cylindrical encapsulated PCM have been analyzed under convective boundary conditions that relate to thermal energy storage systems. A three dimensional, transient CFD model has been solved for examinations. Besides the widely used conduction model of solidification, in this study, the effect of natural convection within the liquid layer has been considered in the numerical model. The effects of parameters such as the initial superheating temperature, the encapsulation size, and the heat transfer coefficient at the outer surface of the capsule have been examined in terms of solidification dynamics and extracted energy during the phase change process. It was found that while the diameter of encapsulation significantly affects the solidification and the energy extraction times, the effect of encapsulation height on the solidification and the energy extraction times are not notable. [ABSTRACT FROM AUTHOR]

The heat storage technology can improve the performance of a solar thermal utilization system effectively. This work studied the effect of phase-change materials (PCMs) on thermal stratification in a heat storage tank. A 60 l sodium acetate trihydrate heat storage tank with 331.15 K phase-change temperature was designed and fabricated. A mathematical model was built to simulate the discharge process in the water tank, and the temperature distribution during the discharge process was obtained. The computational fluid dynamics model was verified by the experimental data. Furthermore, the Ri, the fill efficiency, and the MIX number were adopted to extensively analyze the performance of a heat storage tank with different positions of PCMs with the variation of flow rates. The results indicated that the distance between the isothermal surfaces of 303.15 K and 348.15 K in PCM1, PCM2, PCM3, and PCM4 were 11.75 cm, 11.13 cm, 10.52 cm, and 9.28 cm, respectively, with 9 l/min of flow velocity when t* = 0.7, showing that the thermal stratification was improved as the position of the PCMs got closer to the inlet. The PCMs' half-life (the liquefaction rate reached 50%) was prolonged as the inlet flow rates increased. As the flow rate increased from 1 l/min to 5 l/min, the half-life of PCM4 delayed from a dimensionless time of 0.5 to a dimensionless time of 0.9. Moreover, when the flow velocity was 9 L/min, the liquefaction rate of PCM4 remained at 1. The calculated values of fill efficiency and Richardson number were higher than the experimental data slightly, while the MIX number was smaller than the experimental results. The experimental and calculated values of root mean square error (RMSE) increased with the increasing inlet flow velocity and the lowering of the positions of the PCMs. [ABSTRACT FROM AUTHOR]

• Three-dimensional CFD simulation fosters improved storage design. • Efficiency is properly studied using characterization results in simulation. • Thermal energy is effectively stored using two different phase change materials. • Nano-Al 2 O 3 addition into the materials improves charging and discharging efficiency. • Such storage with enhanced operating efficiency fits into smart heating networks. Two sequentially integrated LHTES devices based on paraffin waxes (PW), PW-L and PW-H with different phase change temperature ranges are numerically studied using Comsol Multiphysics for efficient thermal energy storage (TES). Thermal properties of the PWs are characterized and aluminum oxide nanoparticles (nano-Al 2 O 3) are dispersed into the PWs to improve their heat transfer ability. According to the laser flash apparatus results, when the nano-Al 2 O 3 composes 4 wt% of the mass of the PW-L, its thermal diffusivity can be enhanced up to 40%. The same amount of the nano-Al 2 O 3 improves the thermal diffusivity of the PW-H approximately by 25%. Further characterization studies show that the incorporation of the nano-Al 2 O 3 does not significantly change the specific heat capacity, latent heat of melting and cooling of the PCMs, but improves the heat transfer efficiency of the PCMs. Measured thermal properties of the PCMs are considered as input data in the numerical simulation of operating regimes of the devices. The full charging time of the integrated LHTES devices is reduced by 57 min and 106 min when the nano-Al 2 O 3 composed 2 wt% and 4 wt% of the mass of the PCMs respectively. Likewise, the full discharging time of the integrated devices is decreased by 32 min and 74 min by the addition of the nano-Al 2 O 3. Such reductions lead to improved charging and discharging efficiency of the LHTES devices. Moreover, simulation results show that the total amount of the stored energy in the devices fairly approximates the differential scanning calorimetry (DSC) results. [ABSTRACT FROM AUTHOR]

To reduce the heat loss from the PCM Trombe wall and increase its thermal efficiency, an innovative dynamic Trombe wall incorporating a PCM layer on one face and an insulation layer on the opposite face is proposed. During the charging period of the PCM, the face containing the PCM is exposed to solar irradiation, while the face containing the insulation is exposed to the conditioned air. During the discharging period, the two faces exchange position. A large-scale model of a building unit with such a wall is constructed and tested. The model is analyzed using three-dimensional computational fluid dynamics (CFD), with generally good agreement between the two sets of results. Subsequently, CFD models of three building units are analyzed, one having the proposed dynamic wall, the other an analogous static wall, and the last one identical to the static wall but without PCM. Throughout the PCM discharging period, the temperatures of all the surfaces and the air in the conditioned space in the unit with the proposed wall are found to be consistently higher than those in the companion units. Based on energy conservation analysis, compared with the static wall, with and without PCM, the energy saving efficiency of the proposed wall is higher 25.3% and 17.5%, respectively. Similarly, its thermal efficiency is higher 79.8% and 35.4%, respectively. To achieve even higher thermal efficiency, it is shown that the thermal resistance of the glazing in the envelope, and the envelope as a whole, need to be increased by using materials with low density and heat capacity. [Display omitted] • An innovative solar dynamic Trombe wall with PCM and insulation layers is proposed. • A large-scale model with the novel envelope is built and tested for the first time. • A 3D CFD model is developed and validated by the test results. • New wall is 25%/17% more energy efficient than the static wall without/with PCM. • New wall is 79%/35% more thermally efficient than the static wall without/with PCM. [ABSTRACT FROM AUTHOR]

Twin roll casting is a process used to produce thin strips of metals by continuously pouring melt on to rotating rolls. In order to make the process more productive and economical, high roll speed is recommended. The numerical simulation of high-speed twin roll casting is performed by analyzing fluid flow, heat transfer, and solidification behavior of Al-Cu hypo-eutectic alloy. The flow field, temperature, liquid fraction distribution, and cooling rate are analyzed by solving governing transport equations of continuity, momentum, energy, and turbulence. The low-Re Turbulence model is used to capture turbulence effects in the process and enthalpy-porosity technique used to account for the rise in viscosity due to phase change. The effect of melt pool height and roll velocity on average cooling rate along the strip surface is investigated. It is found that the increase in melt pool height and roll speed increases the average cooling rate along strip surface due to rise in heat transfer up to certain roll velocity but beyond that process fails due to breakout. The average cooling rate of process affects the microstructure and properties of strips. It is found that higher cooling rates result in a decrement of secondary dendrite arm spacing (SDAS) of 1mm thin strip along strip surface results in the fine and homogeneous microstructure. [ABSTRACT FROM AUTHOR]

• The presence of PCMs reduces temperature fluctuations and heat transfer to the room. • Performing sensitivity analysis for HTR based on variation in properties. • Thermal conductivity of PCM plays most significant role in selecting the appropriate PCM. • For equal thermal conductivity, closer melting point to room temperature is preferred. • When PCM is closer to the exterior, a larger portion of it melts, HTR is greater. Passive latent heat thermal energy storage approach incorporating phase change materials (PCM) is a brilliant technique to tackle high energy consumption issue in buildings. This paper investigated the thermal performance of the conventional walls of buildings in Isfahan, Iran with the inclusion of thirteen different phase change materials. The studied base wall was composed of plaster (2 cm), clay brick (15 cm), and cement (3 cm). The effect of PCM position inside the wall on the heat transfer was assessed in two scenarios, namely: close to the interior and close to exterior. The nonlinear governing equations were solved using the finite volume method. The results show that the performance of PCM-based wall is strongly influenced by the thermal conductivity, phase-change enthalpy and melting temperature of PCM. A PCM can more efficiently reduce the heat transfer to the interior space in case it has a lower thermal conductivity, has a higher latent heat of phase-change, and its phase-change temperature is closer to the room temperature. Moreover, the thermal conductivity has priority over other PCM thermophysical properties. The lower PCM thermal conductivity leads to transfer the lower amount of heat to the interior space. A two-fold increase in the thickness of the PCM leads to less than a twofold reduction in the heat transfer. Among the studied PCMs, the heat transfer reduction by Enerciel 22 was within the range 15.6–47.6%, while this range was 2–7.8% for CaC l 2. 6 H 2 O. [ABSTRACT FROM AUTHOR]

• TEG power output was relatively small due to small temperature difference. • The PV/TEG/PCM system achieved 9.5% power output more than other systems. • 50 mm thick PCM layer achieved the best performance for the PV/TEG/PCM system. Solar photovoltaic (PV) cells especially crystal silicon cells have witnessed a soaring installed capacity during past years. Research efforts have been made to increase the PV conversion efficiency and one direction is towards the cooling of PV systems since a higher PV temperature impairs its conversion efficiency. Phase change materials (PCM) capable of storing large amounts of latent heat are found to be effective on cooling PV cells while thermoelectric generators (TEG) which are solid waste heat converters can be used for converting the heat from PV into electricity. Therefore, this research investigates the concept of an integrated thermoelectric PCM system to enhance the PV efficiency. Theoretical investigations found that the TEGs had small power output due to small temperature difference under natural convection conditions. However, PCM was effective on hampering PV temperature increase during heat storage process. This research developed a numerical model for thermal simulations of the integrated system and has been validated by experimental results. The effect of various PCM thicknesses, conductivities and phase change temperatures were evaluated. The simulation results stressed the importance of high PCM conductivity for a thick PCM layer to reduce its insulation effect on the TEG and PV layers. Finally, the best thermal performance for the PV/TEG/PCM system was achieved with a 50 mm thick PCM layer with thermal conductivity of 5 W/m K and a phase change temperature of 40–45 °C. Further optimisation and experimental evaluation are however being recommended towards the establishment of the full technical and scientific boundaries. [ABSTRACT FROM AUTHOR]

In this paper, the effects of pure water, SiO2/water nanofluid, and a phase-change material (PCM) as coolants on the performance of a photovoltaic thermal (PVT) system are numerically investigated. The simulations are performed on two modules of PVT with PCM (PVT/PCM module) and without (PVT module). Parameters including PV surface temperature, thermal, and electrical efficiencies of the systems are studied and compared with each other. Moreover, the results of nanofluid as a working fluid is compared with those obtained using pure water. The results show that in the water-based PVT/PCM, the average PV cell temperature is decreased by 16 °C compared to that of the PVT system. This results in an increase of 8% in the electrical efficiency and 25% in the thermal efficiency. In addition, using nanofluid (SiO2 with 1 and 3 mass% mass fraction) as a coolant in the PVT/PCM system increases the thermal efficiency by 3.51% and 10.40%, for 1 and 3 mass%, respectively, compared to that of the PVT/PCM with pure water as a coolant. This study shows that increasing the melting temperature of the phase-change material leads to an increase in the thermal efficiency of the PVT/PCM system. [ABSTRACT FROM AUTHOR]