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• The charging performance of a thermal energy storage device is studied. • The device has a maximum charging rate at 1.3 kJ/s. • The charging thermal efficiency can reach 87%. • The charging exergy efficiency can reach 70%. • The optimal charging depth was obtained. Thermal energy storage is essential whenever there is a mismatch between the supply and consumption of energy. When the air conditioning system is applied in transport, a great challenge occurred due to frequent fluctuations of cooling load which causes comfort degradation and even healthy concern. In this study, we evaluate charging performance including charging time, transient charging rate, overall energetic and exegetic efficiency of the designed device under different operating conditions. Evolutions of PCM temperature with processing time both in the axial and radial directions are also investigated. What's more, the dynamic exergy efficiency is studied for the first time to assess the optimal charging depth and charging time. The experimental results show that the charging time can be reduced by 49% and 28% by dropping the charging temperature from 15 to 11 °C and increasing the inlet air velocity from 0.70 to 1.20 m/s. The designed energy storage device has flexible charging rates with the maximum value of 1.3 kJ/s, high thermal efficiencies at 87% and overall exergy efficiencies up to 70%. Both the drop of the inlet air temperature and the rise of the inlet air velocity contribute to the energy efficiency. The analysis of dynamic exergy efficiency shows that the maximum exergy efficiency can reach around 90% with the optimal charging time varying from 10 to 52 min. The corresponding optimal charging depth varies between 46% and 58% under the studied conditions. These findings could provide guidelines for the design and optimization of PCM energy storage device specifically when it is used in the transport field. [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]

Due to the poor thermal conductivity of the Phase Change Materials (PCMs), heat transfer performance of Latent Thermal Energy Storage (LTES) systems is usually unsatisfactory. In this work, a detailed numerical study is carried out to analyze the impact of fin geometry (including fin-length, fin-ratio and the angle between neighbor fins) and outer tube conductivity on PCM melting process; the influence of the natural convection in the horizontal sleeve-tube unit within the longitudinal fins is further examined. Results shows that small fin-ratio can reduce melting time, but not remarkably; the angle between neighbor fins has little impact on melting process, however, there is an optimization of the angle between neighbor fins to reduce melting time in the full-scale unit. The outer tube conductivity has great impact on melting process whether considering the natural convection or not. [ABSTRACT FROM AUTHOR]

Highlights: [•] A concentric-dispersion model is established for packed bed storage with PCM. [•] Effects of PCM diameter, inlet velocity and tank height on thermal behavior is investigated. [•] Particle diameter has significant influence on the charge efficiency. [•] A higher thermal storage tank is beneficial for higher charge efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] An exact solution of a latent heat storage unit (LHSU) consisting of several flat slabs was obtained. [•] The working fluid (HTF) circulating by forced convection between the slabs charges and discharges the storage unit. [•] The charging/discharging process is investigated for various HTF working conditions and different design parameters. [ABSTRACT FROM AUTHOR]

Abstract: Experimental study was performed to investigate the effect of copper coating on the thermal performance of encapsulated phase change material/carbon foam composite (hybrid foam). Two types of carbon foam materials were used namely, pristine and copper-coated carbon foams. Both foams were infiltrated with paraffin wax. The temperature distribution within hybrid foam was monitored experimentally using constant heat load setup. Copper-coated carbon foam shows excellent results compared to the pristine foam. Within the coating foam; the time required to reach the melting temperature was shorter and the heat transferred faster. Further, copper coating process enhanced the overall thermal conductivity of the composite by a factor of 1.67 compared to the pristine foam. [Copyright &y& Elsevier]

• Phase change materials and beam splitting nanofluids were studied in a PV/T system. • A detailed optical and thermal model was developed for this novel solar collector. • The proposed system showed an 14.9% improvement in total exergetic efficiency. • Placing phase change materials below the nanofluid achieved the best performance. • An outlet temperature above 100 °C and a PV temperature below 50 °C were achieved. Spectral splitting concentrated photovoltaic/thermal systems aim to utilize the full spectrum of solar radiation by thermally decoupling the photovoltaic cells from the thermal components. Liquid absorptive filters are a type of spectral splitters which (ideally) transmit only the solar spectrum that can be most efficiently converted to electricity in the photovoltaic cell, while absorbing the rest for a thermal application to achieve a much higher total solar utilization. In this paper we attempt to advance this field by investigating the potential of employing a phase change material and a nanofluid to achieve a concentrated photovoltaic/thermal system with high energetic and exergetic efficiency. The optical properties of nanofluid and phase change material in solid and liquid states were simulated based upon data from the literature. Two different phase change materials, RT25 (paraffin) and S27 (hydrated salt , Ca C l 2.6 H 2 O) and an Ag/water nanofluid were employed as the spectral filter components, with water as a coolant. After validating the model with available data from the literature, the effect of time, glass type, phase change material type, nanofluid position, and mass flow rate were analyzed with respect to the outlet temperature and the resultant energetic and exergetic efficiencies were calculated and compared against conventional concentrated photovoltaic/thermal and nanofluid-based spectral splitting concentrated photovoltaic/thermal systems. The results revealed that by employing the combination of the phase change material and the nanofluid it was possible to reduce the photovoltaic operation temperature (by up to 30%), increase the outlet temperature (by up to 54%), and obtain a relative improvement over previous systems in terms of the total exergetic efficiency (by up to 14.9%). The S27 leads to better performance than the RT25 due to the difference in their optical properties, which shows the importance of selecting the appropriate phase change material. By locating the phase change material below the nanofluid (instead of above it), the total energy and exergy efficiencies were increased by over 11 and 7%, respectively. The concentration ratio and the liquid filter's mass flow rate were found to have the most significant impact on the performance of the spectral splitting photovoltaic/thermal system. Overall, this study is significant because it develops a new pathway towards harvesting the full spectrum of incident solar energy. [ABSTRACT FROM AUTHOR]

• This article contains the experimental investigations of different cooling methods used for photovoltaic (PV) panels. • Phase change material (PCM), thermoelectric (TE) and aluminum fins were chosen as the cooling methods. • PV with fin system produced the highest power generation of 47.88 W while PV with PCM and TEM produced the lowest is 44.26 W. This article contains the experimental investigations of different cooling methods used for photovoltaic (PV) panels. Phase change material (PCM), thermoelectric (TE) and aluminum fins were chosen as the cooling methods. The CaCl 2 ·6H 2 O is chosen as one of the PCM which is widely used in the cooling of PVs and the other is the PCM with melting temperature above the surface temperature of the PV panel. By using TE material in different numbers (6, 8 and 12) and aluminum fins in different layouts, surface temperatures and output powers of PV panels were compared. It is observed that the PCM which is not chosen appropriately has insulation feature in the PV panel and enhances the temperature of the panel and decreases the output power. When the most successful cooling methods were tested under the same environmental conditions, PV with fin system produced the highest power generation of 47.88 W while PV with PCM and TEM produced the lowest power generation of 44.26 W. [ABSTRACT FROM AUTHOR]

• An integrated system is proposed to produce power, cooling, and freshwater. • Novel Thermal Energy Storage (TES) is suggested using phase change material (PCM). • Using high temperature PCM for TES, continuous operation of system is feasible. • The overall energy and exergy efficiencies are 40.52% and 14.40%, respectively. • The LCoE of the plant follows the downward trend of concentrated solar plants. In this article, three different modes of a novel integrated system would be evaluated by the application of high temperature Thermal Energy Storage (TES) to produce electricity, cooling, and freshwater. Freshwater is produced using the reverse osmosis (RO) desalination unit while Absorption Refrigeration Cycle (ARC) provides cooling. In this system, a high temperature Phase Change Material (PCM) is utilized to make the system working continuously even at nights. The output heat of gas turbine (GT) is also recovered utilizing the Organic Rankine Cycle (ORC). According to exergoeconomic analysis, the efficiencies, exergy destructions and product cost rates are computed. The multi-objective optimization has also been performed considering six different ORC working fluids and the changes in the direct normal irradiation of a city in Iran. In the trigeneration condition, the optimum values of the GT's compressor pressure ratio and ORC's turbine inlet pressure were obtained 9.06 and 3300 kPa, respectively. The exergy efficiency of the suggested system at the optimal condition is computed to be 14.40%, while that of energy is 40.52% with the total product cost rate of 30.524 $/GJ. The produced cooling capacity of the absorption system is also 1.62 MW whereas the output amount of freshwater and electricity for the users are about 5209.5 m3/day and 2.42 MW, respectively. The Levelized Cost of Electricity (LCoE) is also calculated to be 0.2341 $/kWh, which shows promising economic performance. [ABSTRACT FROM AUTHOR]

• A new model is developed to predict PV/PCM performance with a minimal time cost. • The model results are in good agreement with experimental and CFD counterparts. • A seasonally optimum inclination angle of PV/PCM is allocated for a real condition. • PCM thickness is investigated during days of successive melting and solidification. A novel simplified one-dimensional mathematical model is proposed to predict the temperature of the PV (T pv) that is in contact with the PCM, with nearly the same accuracy of CFD modeling yet reducing the computational time by two or three orders of magnitude. The new approach, "1D Enhanced Conduction Model (ECM)", novelty is based on estimating the equivalent thermal conductivity that enhanced by the convection currents within the PCM during melting and solidification processes, and under the various angle of inclination for a PV panel. In addition, a CFD model for simulating the performance of PV/PCM is also developed. The two models are validated with experimental published data and exhibited good agreements. Comparisons have been performed between both models at different inclination angles (from 0° to 90°) and aspect ratios of two, four and eight. The maximum deviations between the two models in calculating the average T pv , during the high-intensity period of melting (10:00 to 15:00), and for all angles of inclination are 0.74% and 1.78% for lowest and highest aspect ratio respectively, and practically no deviation during solidification. Employing this fast model, optimized seasonal inclination angles of PV/PTM for maximizing the electrical yield were obtained for Alexandria, Egypt under real ambient and solar energy conditions. Furthermore, the effects of various PCM thicknesses during successive days of the simulation were investigated. [ABSTRACT FROM AUTHOR]

• A novel Coupled PCM-liquid cooling system (CPLS) for Li-ion battery pack. • Design of CPLS is optimized for the thermal performance of battery pack. • Effectiveness of CPLS is verified by the designed experiments. • Controlling strategy for the velocity and inlet temperature of coolant. • Improved cooling performance and energy-saving at different ambient temperatures. In order to improve the working performance of the lithium-ion battery pack in continuous operation under different ambient temperatures, a coupled composite phase change material and liquid cooling thermal management system is proposed. The simulation for this system under a cycle that a 3C rate discharging and then a 0.5C charging was conducted, as well as comparison tests concerning factors such as cell-to-cell spacing, cell-to-tube distance, channel number and coolant velocity. Simulation results showed that the coupled system with suitable design exhibited good thermal performance at an ambient temperature of 30 °C, which kept the maximum surface temperature and the temperature difference of the battery pack at 41.1 °C and 4 °C at the end of 3C discharge. Then, the latent heat of phase change material was also recovered by the liquid cooling during the 0.5C charge. Specially designed experiments have also been conducted to verify the effectiveness and practicability of the proposed coupled system. Based on this system, a liquid cooling strategy was proposed for controlling the velocity and inlet temperature of coolant by monitoring the temperature of the phase change material and environment. This further improved the thermal performance of the battery pack during cycling at different ambient temperatures and significantly reduced the unnecessary power consumption of liquid cooling during this process. [ABSTRACT FROM AUTHOR]

• PCM melting in a double pipe helical coiled tube LHTES was studied numerically. • Performance of coil LHTES compared with vertical and horizontal double pipe LHTES. • Pitch, HTF temperature and Re effect on PCM melting in the new LHTES were studied. • PCM melting time of the LHTES significantly shorter than straight pipe LHTES. • Pitch, Re and HTF temperature affected PCM melting and optimal pitch was 2 OD. This study proposes the use of a double-pipe helical-coiled tube as an innovative well-performing phase change material (PCM) containment design for latent heat thermal energy storage (LHTES) systems. A 3D numerical model considering the convection effects during PCM melting is built and successfully validated via experiments. To assess the new LHTES design, the melting evolution of PCM in horizontal and vertical straight double-pipe LHTES systems with the same surface area is initially simulated and compared with the new same-size LHTES system. Thereafter, the thermal performance of the double-pipe helical-coil storage has been intensively investigated under various operational conditions. Results reveal that the thermal performance of the double-pipe helical-coil LHTES during the PCM melting phase is spurious compared with that of others. The required saving in the PCM melting time is approximately 25.7% and 60% for the horizontal and vertical straight double-pipe LHTES systems, respectively. Moreover, results show that the coil pitch has a remarkably impact on the total PCM melting time in the double-pipe helical-coiled tube, however the optimum coil pitch is 2 OD. The analysis also reveals that the initial temperature and Reynolds number (Re) of heat transfer fluid (HTF) are other factors that significantly affect the PCM melting process. [ABSTRACT FROM AUTHOR]

• Design of a composite PCM to air heat exchanger for space heating. • Performance analysis of the system for 16 h discharging and 8 h changing. • A uniform output temperature of 46.9 °C for 17.4 h with 0.01 kg/s air mass flow rate. • 56% less solidification time using a composite PCM compared with PCM-only. • Compare the results of 2-D and 3-D modelling of the composite PCM to air heater. The objective of this numerical study is to develop a latent heat storage (LHS) air heater in both charging and discharging processes to find the geometrical and operating conditions for dwelling space heating. The aim of the storage heater is to provide a uniform output temperature according to the required heating load of a typical room in the required heating hours. The phase change material (PCM) is embedded in a copper porous structure to enhance the rate of heat transfer and overcome the low thermal conductivity of PCMs. The geometrical parameters is first obtained from analysing the discharging process including the height, air channel and PCM shell widths and air mass flow rate according to the discharging time as well as the output temperature of the air. Then, the charging mechanism is assessed to find the required area for the employed rectangular heating element. The results show the significant advantages of composite metal foam/PCM-air heat exchanger in comparison with the PCM-only unit on both the discharging time (56.5% reduction) and the uniformity of output temperature. The system with the height of 30 cm, PCM and air channel thickness of 15 cm and 2 cm, respectively, and a depth of 1 m, is capable to provide the desired output temperature of 47 °C for almost 17.4 h with the air mass flow rate of 0.01 kg/s. The charging analyses shows that the dimensions of the required rectangular heating element with constant temperature of 100 °C is 15 × 60 cm located at both sides of the unit. [ABSTRACT FROM AUTHOR]

• Branch-structured fins are designed for high temperature environment. • Thermal behaviors of modules under different ambient temperatures are compared. • How PCT influences the performance of PCM is investigated under high temperature. Battery modules with phase change material (PCM) cooling inevitably suffer from heat-storage saturation and poor secondary-heat dissipation, especially in high-temperature environments or hot regions. To optimize thermal management, this study firstly explores the thermal behaviors of PCMs with different phase change temperatures (PCTs) in a high-temperature environment. The experimental results show that a PCM with a PCT of 46 °C offers the best cooling effect at a high ambient temperature of 40 °C in this study. For example, the maximum temperature of a cell without PCM reaches 53.3 °C, whereas that of the cell with PCMs having PCTs 40, 46, and 55 °C, are 59.2, 51.6, and 57.5 °C, respectively, during the dynamic cycling process. Nevertheless, the application of above PCM is still unsatisfying because the maximum temperature of the battery in the PCM module exhibits obvious increasing trend with cycles in 40 °C environment. On this basis, several novel fins with multiple heat-flow channels (of V, Y and X shapes) are designed and introduced into the PCM module to enhance the secondary heat dissipation capability. These fins with innovative branch structures deliver excellent performance in alleviating the battery temperature than the traditional rectangular fins, which can be attributed to the ability of the branch structures to increase the heat transfer area by adding heat transfer channels. The results of this work show that the X-shape delivers the best performance in a high-temperature environment of 40 °C by maintaining the maximum temperature of the cell below 47 °C. [ABSTRACT FROM AUTHOR]

• Integration of phase change material and cooling water is developed for concentrated photovoltaic cooling. • The proposed system enhances thermal regulation, efficiency and net output power at low water flow rate. • 60% reduction in the cell temperature and 224% enhancement of the system efficiency are obtained. • Using nanofluid enhances output power by 2.5% and decreases the phase change material melting time by 12%. An integration of passive and active cooling systems for thermal regulation of concentrated photovoltaic (CPV) solar system has been developed and modeled. A heat storage battery of phase change material (PCM) is combined with a closed loop water cooling system in the developed design. A two dimensional model has been developed for the simulation of the CPV layers with the integrated cooling system. Results have been investigated to evaluate the thermal and electrical performances of the system components and the entire system. Further investigations have been conducted to study the effects of different arrangements of the PCM plates in the water tank on the system performances. Enhancing the system performance by using nanofluid as heat transfer fluid (HTF) was also evaluated. Results showed that the proposed system achieves 60% reduction in the CPV average temperature compared to the conventional direct PCM-PV and water-cooling individual systems. At 10 concentration ratio (CR) and 0.01 m/s HTF velocity, the cell temperature does not exceed 78 °C. Moreover, the PCM maximum temperature is kept below the degradation temperature limit. The effect of the PCM plates' arrangements in the water tank on the system performance is negligible. Using nanofluid as HTF enhancer increases the CPV efficiency by 2.7% and reduces the PV maximum temperature and the PCM melting time by 4 °C and 12%, respectively. [ABSTRACT FROM AUTHOR]

• 7 kg of PCM is inserted inside a finned tube heat exchanger (HX). • Characterization of impacts of HX presence on airflow and product temperature. • Detailed description of PCM charging and discharging processes. • PCM attenuates the temperature rise (from 2 °C to 1 °C) during 2 h compressor stop. • This solution increases display cabinet flexibility for energy management purposes. Display cabinets are widely used in supermarkets and represent an important part of their energy consumption. Adding PCM to a refrigerated display cabinet can increase its compressor cutoff time as the cold energy accumulated by PCM can replace the refrigeration system during a certain period of time. This technology can be considered as a solution to increase the electricity flexibility in order to match the demand and the production of a supply network, to manage energy flows on the grid and to boost the use of intermittent renewable energy sources. The present study is focused on the performance of the display cabinet with integrated phase change material (PCM). The PCM is selected according to the temperature range of the application. To enhance the heat transfer and facilitate the PCM melting and freezing, PCM is inserted in a heat exchanger. The experimental results show an important potential of PCM to maintain the air and product temperature when the compressor is off (up to 2 h). [ABSTRACT FROM AUTHOR]