Phase Change Material Container Research Articles

Performance optimization for a novel two-stage thermoelectric generator with different PCMs embedding modes

In this study, a novel two-stage TEG with different phase change materials (PCMs) embedding modes is proposed to improve the efficiency of TEG systems. The output power and electrical energy of single-stage and two-stage TEG combined with different PCMs is firstly compared at the limit of total length of the PCM containers. Furthermore, the effect of different PCMs embedding modes, including arranged at the heat source side, between two TEGs and heat sink side, on the performance of two-stage TEG system was discussed. Finally, the amount of different PCMs arranged at different locations was optimized. The results showed that although application of high temperature PCM on the heat source side can alleviate the effect of heat source fluctuations to provide more stabilized output power, the total electrical energy is seriously reduced in the two-stage TEG system. Compared with the single-stage TEG system, the two-stage TEG system provides a much higher output power and electrical energy, in which the harvested total electrical energy of the optimum two-stage TEG system is increased by 44.8% with a conversion efficiency of 6.9%. These results are of great significance to the design of advanced TEG system for waste heat recovery.

A numerical examination on the use of phase change materials to improve the sun-tracking photovoltaic panels' performance

The power generation of a photovoltaic (PV) panel is inherently affected by the amount of solar radiation striking the panel and the PV temperature. Tracking PV panels reach higher temperature than fixed panels due to more received radiation. Phase change materials (PCMs) are widely used as a passive method for cooling fixed PV panels. The melting dynamics of the PCM is very different during tracking compared to previous research carried out on fixed panels due to the changing orientation. A tracking PV-PCM system is numerically modeled in this research, and the temperature distribution and convection in the PCM are analyzed. The numerical results are presented as temperature-time curves for several different positions inside the PCM container, liquid fraction and streamlines in melted PCM, and isothermal curves. The temperature variation shows that the temperature of solid PCM increases rapidly in the initial time, reaching the melting temperature. The PCM changes from the solid phase to the liquid phase at a constant temperature. After complete melting, the PCM temperature increases over time. The PCM temperature changes were compared at two different distances from the photovoltaic panel. The streamlines show that the PCM starts to melt near the heated wall at the container's top corner. The melted PCM expands toward the down of the container due to vortex circulation created in the molten material. It is observed that the increase in PV panel temperature between 1.5 and 7 h is only 5.3 K, showing that using PCM is an effective method for absorbing heat from the PV panels during melting. Results show that the temperature of PV panel with PCM is on average 6.9 K lower than that without PCM.

Thermal energy storage via waste heat from finned heater by using different phase change materials in a closed space

In this study, a numerical analysis of the melting of phase change materials (PCMs), is analyzed in a closed space, which is heated from the bottom wall. The heater has a set of fins with constant geometry, placed on the bottom heated wall. The closed space has also two rectangular-shaped containers (placed horizontally), which are attached to the vertical walls at different dimensions and locations. Each of the containers has different types of PCMs, which receive waste heat from the fins. The performance analysis of the combined system is carried out by solving governing equations using the finite volume technique was used to solve the transport equations. The thermal performance of the composite system is assessed for the wide range of geometrical parameters such as length ratios of the fins (Lp), height ratios (c/H), and flow control parameters such as Grashof numbers (Gr). The result showed that the inclusion of PCM containers can effectively utilize the waste heat and can modulate the thermal transport process significantly. The position and size of the fins significantly alter the convective process inside the enclosure. The flow structure shows asymmetric features due to the obstruction by the fins attached to the vertical walls. Too much closure position of the PCM-filled longer fins to the fins assembly leads to the multi-cellular vortices like ‘Bénard cell’ due to the strong temperature gradient between the two sets of fins. For the long fins, too much closure position reduces the total melting time. The usage of PCM 2 is always beneficial for faster acclimation energy due to fast melting for any length and position of the fins. Different phase change materials and their melting behaviors are studied first time in this work to get cooling effect of a finned heating system, which is the main originality and the work. Such a concept could be adopted as thermal energy storage (TES) system, which can benefit the reduction in energy losses.

Experimental characterization, parameter identification and numerical sensitivity analysis of a novel hybrid sensible/latent thermal energy storage prototype for industrial retrofit applications

Hybrid design combinations of sensible and latent heat thermal energy storage (TES) leverage the advantages and reduce the disadvantages of both types. Thus, the range of application of said individual storage types is extended and crucial retrofit opportunities are enabled. Such hybrid TES concept consisting of a Ruths steam storage (RSS) and a surrounding layer of storage containers filled with an eutectic mixture of sodium nitrate (NaNO3) and lithium nitrate (LiNO3) as phase change material (PCM) was for the first time realized and investigated during operation in a steel production plant.In this work, the hybrid TES prototype is characterized with the help of detailed modelling and real measurement results. Uncertain model parameters are identified via parameter optimization and the numerical models show satisfactory validation results. Additional 30% of thermal energy could be stored in the PCM containers retrofitted to the lab-scale RSS. Charging/discharging times and specific thermal power of the PCM containers were roughly measured as 8h and 12h and 560kWm−3/−802kWm−3, respectively, in the typical operation region. A sensitivity analysis of the performance indicators reveals potential but also engineering challenges for following generations of the hybrid TES concept. Compared to the achieved experimental results, charging/discharging power could be increased by up to 10 and 5 times, respectively, in the future by adequate measures to increase heat transfer between both storage types.

A novel application of the geothermal asphalt pavement: A feasible E-fuel source

In this study, a novel application of geothermal technology was proposed and evaluated as a potential sustainable clean energy source. The proposed system incorporates thermoelectric generators (TEG) to transform the extracted heat from the pavement into electricity and enclose an enhanced geothermal system into the asphalt structure, intending to cool the pavement surface and provide the thermal gradient required for energy harvesting simultaneously. The study hypothesized the amplification of the thermal gradient through geothermal pipes embedded in the asphalt layer, a phase change material container in the subgrade, and an external cooling system in direct contact with the TEGs. A comprehensive experimental study was conducted to evaluate the thermal, electrical, and structural performance of the proposed geothermo-electrical asphalt pavement system. Also, a large-scale experimental physical model was established to simulate and assess the system's performance under real-life conditions. By monitoring the system's performance over six consecutive days, the results showed that the enhanced geothermal system efficiently reduced the surface temperature of the asphalt pavement by 40% and sustained a thermal gradient of around 40 °C, which was sufficient to sustainably harvest energy through using the TEGs. The harvested energy was then successfully used to charge an attached battery. The results of this study demonstrate the feasibility and potential of using geothermal technology in asphalt pavements as a sustainable energy source. Furthermore, the proposed system not only improves the performance of the pavements in terms of structural behavior but also introduces a new way of energy harvesting, opening the door for new possibilities in the renewable energy field.

Annual Thermal Management of the Photovoltaic Module to Enhance Electrical Power and Efficiency Using Heat Batteries

Several studies state that phase change material (PCM) improves the electrical power and efficiency of the photovoltaic (PV) module. To find the suitable PCM for tropical climatic conditions, multi-PCMs are examined simultaneously with melting temperatures of 31 °C, 35 °C, 37 °C, and 42 °C. In this study, PCM containers are integrated behind the PV module with a thickness of 50 mm. The performance of the multi PV-PCMs is monitored year-round and compared with PV-noPCM. The experimental results show that the selected four PCMs performed the cooling process autonomously in all the climates, such as PCM with a melting temperature of 37 °C and 42 °C enhanced the higher cooling rate in summer, and the same PCMs failed to achieve a higher cooling rate in winter. The lowest temperature drop was noted for pre-monsoon and monsoon seasons due to the low irradiance. On the other hand, the highest temperature drop of 16.33 °C is observed for pre-summer (March) and 15.7 °C, and 17.14 °C for summer (April) as compared to PV-noPCM. The results of the present investigation highlight the requirement for choosing the proper PCM melting temperature based on optimal year-round performance. Further, it is recommended that a single PCM melting temperature for cooling the PV modules year-round in tropical climates is inappropriate, and instead, a cascaded structure with different PCM melting temperatures is recommended.

Comparative study for photovoltaic cooling using metal mesh inserted eutectic phase change material enclosure

Phase change material (PCM) is a predominant storage material that enables a higher cooling effect over sensible heat storage materials without the assistance of working fluid. In this study, novel PCM infused finned, and mesh finned containers are developed to help cooling photovoltaic (PV) in operation by reducing the PCM conduction resistance. The designed container is integrated underneath the back surface of the PV module and experimented under controlled weather conditions (indoor). Fins are attached behind the PCM container without any intermediate layer favors transferring the heat from the top to the bottom fin surface as a single unit. The main benefit of a PCM-infused fin container enhances the PCM liquid flow movement throughout the finned morphology and the heat dissipation rate increases between the finned PCM container and its surroundings. Moreover, incorporating metal mesh inside the PCM container resulting to the control of the conduction barrier and increased the heat transfer rate. It is found that metal mesh based finned PCM container shows an excellent performance enhancement between 85th and 150th minutes with a peak cooling of 2.20% and corresponding to the electrical power and energy productions of 2.01% and 2.71%, respectively compared to finned PCM container. The statistical approach on finned and mesh finned PCM containers shows that ambient temperature has a strong positive correlation with the temperature rise in photovoltaic resulting in performance degradation. Furthermore, it is recommended that the developed PCM containers are suitable for tropical climatic conditions to improve the PV power output.

Experimental investigation on electrical power and thermal energy storage performance of a solar hybrid PV/T-PCM energy conversion system

This paper presents the experimental investigation under real environmental conditions of a solar hybrid energy conversion system consisting of latent heat thermal storage (LHTS) and a PV/T panel. In this context, the heat energy from the sun was transferred to the heat transfer fluid (HTF) by means of a heat collector positioned so as not to affect the solar radiation absorption of the PV/T panel. A closed-loop liquid circulation system was developed between the heat collector and the phase change material (PCM) container to transfer the heat transferred from the sun to the PCM container. In addition, the upper surface was designed with optical material in order to increase the energy storage capacity of the PCM container. In the experimental study, a PV/T panel with a maximum electrical power generation capacity of 40 W, measuring 424 × 674 × 25 mm at a 36° azimuth and tilt angle, was used. Commercial RT55 was used as PCM, and tap water was used as HTF. The experimental study was performed between 9:09 and 18:17 on a sunny day under atmospheric conditions. The results of the paper show that a maximum of 30.56 W of electrical power can be produced from the PV/T panel at 14:00, whereas a maximum of 1.2 W of heat energy can be stored in the PCM container at 11:00. On the other hand, the total power of the solar hybrid energy conversion system reached its maximum value of 31.54 W at 12:00. In addition, the rate of energy stored in the PCM within the solar hybrid energy conversion system reached its highest value at 10:00, with 4.5%.

Implementation of T-history method to determine the thermophysical properties of the phase change materials

Phase-change materials (PCM) are an easy-to-integrate heat storage medium for buildings. In the present study, the thermophysical properties of the coconut oil (Tm = 25 °C) and commercial paraffin-based RT28HC PCM (Tm = 27–29 °C) are analysed through the T-history method. Various criteria are considered for experiments, such as heating/cooling medium, sample quantity, PCM container alignment, temperature gradient, and thermocouple placement to record PCM temperature. The experimental procedures considered standardise the T-history method and help for obtaining the appropriate cooling curve to evaluate thermophysical properties. Further, PCM melting fraction is analysed by image processing. The results show that the investigation performed in an air-cooled medium with vertical alignment of the PCM container meets the Biot number condition (Bi<0.1). The experiment with 15 g (same mass) samples yields 10% lower results than a 20 ml sample (same volume) selection due to the difference in convective length of the PCM container. RT28HC (242.004 kJ/kg) stores higher latent heat than coconut oil (71.15 kJ/kg), which is found by processing the cooling curve. Thermophysical results are validated against literature and manufacturer data. Supercooling is studied, revealing a degree of 0.1–0.7 °C in RT28HC and 2.7–3.1 °C in coconut oil. It results from poor nucleation and is reduced when the temperature gradient is less.

Experimental and Numerical Investigations of a Thermal Management System Using Phase-Change Materials and Forced-Air Cooling for High-Power Li-Ion Battery Packs

The thermal management system of a power battery is crucial to the safety of battery operation; however, for the phase-change material (PCM) thermal management system of a battery, the thermal cycling of phase-change material under large discharge rate conditions will lead to thermal conductivity degradation and thermal stress problems. A method of manufacturing PCM containers with metal fins to package pure phase-change material is put forward to solve the problem. The system temperature under different conditions is studied using numerical and experimental methods. A thermal resistance model is built to analyze the thermal transfer performance of PCM containers with fins. The results show that the PCM container structure can effectively control the battery temperature within the suitable temperature range under the low discharge rate, but the maximum temperature of the battery pack at the high discharge rate of 3 C will exceed the optimum operating temperature range. Adding fins can reduce the maximum temperature and improve the system temperature uniformity. By combining fins with forced-air cooling, the maximum temperature and maximum temperature difference of the battery pack at a high discharge rate can be effectively reduced.

Performance of natural wax as phase change material for intermittent solar energy storage in agricultural drying: An experimental study

Solar Air Heater (SAH) technology as a drying method for agricultural commodities is only active during the day and is highly dependent on the weather. Therefore, this study aims to investigate the effect of SAH coupled with phase change material (PCM) types of paraffin wax, soy wax, and palm wax as store energy materials to enhance the performance of conventional SAH. The PCM containers placed in the SAH are ex-bottles of milk cans which are numerous in the country due to the increase in consumption of milk by the people as an immunity enhancer during the Covid-19 pandemic. This is expected to improve the 3R (Reduce, Reuse, Recycle) strategy implemented to reduce environmental pollution. The tests conducted showed that the three types of PCM effectively improved the performance of SAH in drying agricultural commodities. The highest energy efficiency was achieved with paraffin at 30 %, 23.28 %, and 33.67 % while the highest exergy efficiency was achieved with palm wax at 20.27 %, 18.86 %, and 28.96 %, in three days respectively at different solar irradiation conditions.

Performance analysis of concentrated photovoltaic systems using thermoelectric module with phase change material

A photovoltaic (PV) module integrated with a cooling system can generate higher electrical energy in comparison to a conventional PV module that is without a cooling system. Phase change materials (PCMs) and/or thermoelectric generators (TEGs) are some of the several passive cooling methods used in enhancing the energy output of PVs. Herein, a comprehensive numerical study of highly concentrated standalone photovoltaic (CPV), CPV-PCM, CPV-TE, CPV-PCM-TE, and CPV-TE-PCM systems is conducted in COMSOL Multiphysics environment. In addition to analysing the energy output of the systems, the study explores the effect of using different PCMs as well as PCM containers with different internal configurations on the energy output of the systems. The results revealed that the energy conversion efficiencies of the CPV-PCM, CPV-TE, CPV-PCM-TE, and CPV-TE-PCM are respectively 34.8 %, 97.3 %, 106.5 %, and 111.4 % higher than that of the standalone CPV system. These results also indicated that the CPV-TE-PCM configuration is superior to the other configurations, this is due to the creation of a large temperature gradient which enhances the performance of the TEG. Moreover, it was determined that the ideal melting temperature of a PCM should be a few degrees above the ambient temperature; in this study, RT28HC PCM is found to be the most suitable PCM for cooling the systems. Finally, it was revealed that changing the fin configurations inside a PCM container has an insignificant influence on the energy efficiencies of highly concentrated PV models.

Heat storage material: a hope in solar thermal.

Solar energy is a vast renewable energy source, but uncertainty in the demand and supply of energy due to various geographical regions raises a question mark. Therefore, the present manuscript includes a review to overcome this uncertainty by utilizing various thermal energy storage systems. Phase change material is the most preferred thermal energy storage system because of its high-energy storage density. The low thermal conductivity is the critical problem in phase change material that can be overcome by integrating metallic foam, carbon fiber, and metallic fins in the phase change material container. The inclusion of metallic foam limited to 0.1-3% of the Phase change material (PCM) weight leads to a slight change in thermal conductivity but a high cost. It was also seen that the addition of carbon 0.1 to 9% of the PCM weight could improve the performance of PCM. The inclusion of a metallic fin improves the thermal conductivity with the various shapes and sizes of the fin. It is found that metallic foam composites have better performance than carbon composite and metallic fin inclusion.

Numerical Analysis of a TEG and mPCM Enhancement System for BIPVs Using CFD

Building-integrated photovoltaics (BIPVs) are the most promising systems for net-zero energy buildings. However, there are few practical cases because of shortcomings, such as the lack of solar tracking and the rapid rise in PV surface temperature. Therefore, methods of increasing the efficiency of BIPVs have been proposed and studied. These include using phase change material (PCM) or heat fins, wavelength selection, decreasing the PV surface temperature, or using a thermoelectric generator (TEG) and convection cooling to utilize the waste heat from the PV. Many preceding studies have been conducted on TEG and convection heat dissipation methods to utilize as much waste heat as possible. Therefore, in this study, a TEG–PCM hybrid system using mPCM was proposed to improve constructability. Herein, the appropriate phase change temperature of the PCM, the heat fin spacing in the PCM container, and the TEG arrangement were analyzed through computational fluid dynamics (CFD)-based simulations. The appropriate melting temperature of the PCM, the heat fin interval, and the arrangement of the TEG for the proposed system are 25 °C, 20 mm, and 140 mm, respectively. In order to achieve optimal efficiency, it is necessary to consider an appropriate amount of heat transfer, and it has been confirmed that if there are too many thermoelectric elements, the opposite effect occurs.

Cooling enhancement of portable computers processor by a heat pipe assisted with phase change materials

Changing technologies have led to electronic components being smaller in size with higher output powers. In this study, an experimental investigation is performed on a PCM-assisted heat pipe (HP) with free and forced convection for cooling portable computers. In order to assess the applicability of the proposed design, three different configurations are studied. In the Config. 1 (Configuration 1), there is only a fan as the active cooling method; for the Config. 2, a phase change material (PCM) container is placed into the fins without using any fan; in the Config. 3, the PCM container is located close to the CPU combined with a fan cooling the far end of the heat pipe. Furthermore, the effect of the PCM melting point on the cooling is investigated using two different types of PCMs. Variations in input heat fluxes and fan voltages (fan speed) are effective parameters included in this study. The time it takes to reach critical temperature (CT) decreases with increasing input heat flux. At an input heat flux of 15 W by the addition of forced convection, the maximum temperature does not reach the CT, and by increasing the fan voltage, the steady-state temperature of the central processing unit (CPU) decreases. However, even by using forced convection, the CPU will reach CT at maximum input heat flux (45 W). PCM with a lower MP appears to optimize cooling and helps to reduce the most thermal stresses. The most important point in using PCM with forced convection is the longer time required to reach the steady-state temperature. Furthermore, image processing is performed using the function 2D CV filter in Open-CV to estimate the liquid fraction. Image processing demonstrates that at 15 W in the Config. 2, at the end of 58 min, 34.5 % of the total PCM is melted.

Intensifying the melting process of a triple-tube latent heat energy storage unit via inserting a middle plate into the phase change material container

In this paper, a novel methodology is proposed to improve the melting process of a vertical triple-tube heat storage unit via inserting a middle plate into the phase change material (PCM) container. The middle tube is filled with the PCM while water as the heat transfer fluid (HTF) is passed through the inner and outer tubes. Various scenarios are considered in this research to evaluate the efficacy of the PCM-based heat storage unit with a middle plate comprehensively. Firstly, the temperature and liquid fraction contours of the cases with no fin and uniform fins are compared with those of the cases with a middle plate. Secondly, the position of the middle plate is varied to evaluate the effects of the middle plate position on the charging process. Next, the impacts of fins number and position on the thermal performance of the PCM-based heat storage unit are evaluated in the presence of the middle plate. Finally, the effects of fins arrangement including the inline and staggered configurations on the charging process of the PCM are examined. The results show that the melting time of the PCM-based heat storage unit in the presence of a middle plate (case 4) can be decreased by 52.62 % compared to that of the no-fin case (case 1). Furthermore, the heat storage rate of case 4 increases by 109.90 % compared to that of case 1.

Comprehensive analysis of PCM container construction effects PV panels thermal management

Current research aims to identify the finest phase change material container construction and tries to close the design gap for optimum photovoltaic panel thermal management. The phase change material is used as heat sink of photovoltaic panel and heat source for thermoelectric generator. The latent heat of phase change material maximizes the power generation from thermoelectric generator. The results show that the efficiency of the photovoltaic panel was enhanced by 3% and steady for ten hours. The photovoltaic panel electrical output power was enhanced by 25% under different weather conditions. The hybrid cooling system with capsules phase change material cavity shows a significant enhancement and stability in thermal system management, photovoltaic efficiency, and system output power.

Boosting the air conditioning unit performance using phase change material: Impact of system configuration

Boosting the energy efficiency of air conditioning (AC) systems will considerably impact on lowering domestic power consumption. Innovative methods are being developed to enhance AC performance. One promising method involves integrating phase change materials (PCM) with the AC systems. The significant PCM charging period is a primary limitation of coupling AC systems with PCM in the previous research. The current study aims to investigate the impact of coupling an AC unit with various PCM container configurations (e.g., parallel plates, staggered and aligned tubes, and elliptical tubes) on PCM charging and discharging, and AC performance. During the nighttime, the low ambient temperature is charged inside the PCMs. Then, during the daytime, the hot ambient air is cooled by passing through the cold PCM heat exchanger before passing over the unit condenser. A complete dynamic mathematical model for the proposed system is constructed and solved numerically using ANSYS software. Results indicate that applying the cylindrical arrangement lowers the solidification time of the PCM at night by approximately one-third compared to the plate arrangement. Also, raising the inflow air temperature of the air-PCM heat exchanger increases the air temperature difference through the heat exchanger and saving percentage of the AC's power and decreases the PCM's charging and discharging time. For inflow air temperatures of 318.15 K, 313.15 K, and 308.15 K, the maximum average percentage of saved power is around 25 %, 18.7 %, and 12.5 %, respectively for 2 h working and around 8.4 %, 7.2 %, and 6.3 %, respectively for 8 h working of the AC unit. Cylindrical configuration is preferable for daily use of AC systems as the charging process can be achieved through the nighttime.

Geometry effect of phase change material container on waste heat recovery enhancement

Waste heat recovery from industrial exhaust gases is a key method to reduce fuel consumption and improve system energy efficiency. Phase change materials (PCMs) are one of the major media in the waste heat storing and recovering processes. The PCM container geometry is a crucial design factor but attracts less attention for its effect on the PCM melting and heat storage operation. This study simulates the melting behaviour and heat storage performance in the PCM storage containers with the same cross area but different configurations with the rectangular shape and ones with concave folded sidewalls and protruding folded sidewalls. The geometry variation on PCM containers influences both the contact area with the hot airflow and natural convection in the melting phase of PCMs. The three-dimensional transient modelling indicates that the natural convection currents enhance the PCM melting and thermal storage rates. The PCM container design angle, α, shows a remarkable impact on the natural convection strength, PCM melting time, and energy storage rate. The protruding-shaped container with α at 133.8∘ presents the least melting time of 4,645 s, reducing 24.9% of the melting time in comparison to the rectangular chamber as the baseline with α= 90 ∘. The study can inspire the design of PCM storage geometries with efficient waste heat recovery in the industrial applications.

The Effect of Al_2 O_3 Addition on Solidification Process of Phase Change Material: A Case Study on Heating of Automobile Cabin in Cold Climate Conditions

In this paper, an experimental investigation is revealed on the solidification process of the latent heat thermal energy storage (LHTES) system, in which the heat energy emitted into the atmosphere with the exhaust gases of ICE vehicles is stored by phase change material (PCM) enhanced with nanoparticles (Al2O3). In the study using RT55 paraffin wax as the PCM, the interior heating process of a typical sedan automobile in cold climate conditions is used as the heat release medium for the LHTES system. Experimental studies carried out in real climatic conditions were repeated for pure paraffin (RT55) and five dif-ferent Al2O3 fractions (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, and 25 wt.%). Ex-periments are performed in an optical PCM container and are completed after 1200 seconds (20 minutes). The heat energy stored in the PCM container is discharged to the automobile cabin via the closed-circuit liquid circulation system by the heating radiator system in the automobile cabin. The findings showed that the solidification process is improved considerably up to 10 wt.% Al2O3 fractions compared with pure paraffin RT55, and the temperature in the cabin could be increased by approximately 29%. In addition, the Al2O3 frac-tion increased by more than 10 wt.%, which has a negative effect on the im-provement in the solidification process, but higher solidification ability and in-cabinet temperature were obtained with all Al2O3 fractions compared to pure RT55.