Phase Change Material Container Research Articles

A novel and effective passive cooling strategy for photovoltaic panel

This paper reports experimental work related to passively cooled free-standing silicon photovoltaic panels (PV) in different cooling configurations with a considered utilization of phase change materials (PCM). The PV panels (20Wp) were examined in typical Mediterranean climate conditions during several months of field monitoring. The focus of the research was to reconsider the usually conventional applied passive cooling approach for PVs in cases when the PV panel is cooled with phase-change materials (PV-PCM cooling systems). The conventional approach usually assumes one solid container filled with a PCM that is fixed into the backside surface of the PV panel to regulate the operating temperature of the PV panel. In the herein considered novel approach, instead of one PCM filled container, several smaller containers filled with PCM materials were used and experimentally tested to determine the performance benefit. The gained experimental results of the two different PV-PCM cooling configurations were compared with a referent PV panel. Based on the experimental results, it was found that the performance of the PV system (overall power yield), for the assumed measurement period, was improved for about 2.5% in the case of the concept with a full PCM container when compared to the referent PV panel. The proposed novel PV-PCM passive cooling approach, with several independent PCM containers, reached a performance improvement of 10.7%, which is considerably higher with respect to the usually applied concept with a full PCM container. The quantity of utilized PCM materials and aluminum, in several container configurations, was 47% (PCM) and 36% (aluminum) less, when compared with the passive cooling configuration with solid a PCM container. The revealed results indicated the potential of the novel proposed PV-PCM passive cooling approach regarding performance improvements and resource utilization, which would affect both economic and environmental aspects.

Nanofluid-PCM heat sink for building integrated concentrated photovoltaic with thermal energy storage and recovery capability

A new configuration of phase change material (PCM) heat sink has been developed to be combined with a building integrated concentrated photovoltaic (BICPV) system. This new proposed system includes PCM encapsulated in aluminum pack and immersed in nanofluid container to improve thermal conductivity. A comprehensive numerical model was validated and simulated to evaluate thermal and electrical performance of the proposed system for both passive and active cooling conditions. Two different configurations of nanofluid-PCM enclosures with single PCM pack or multi-smaller packs were compared with conventional BICPV-PCM system. Melting and solidification of PCM were also studied with solar concentration ratio of 5. In passive cooling, single-pack configuration regulated the silicon temperature of CPV below 78 °C with more uniform temperature distribution. Whereas the multi-packs configuration demonstrated 97% phase transition to liquid PCM which provided the highest stored thermal energy. The performance improvement would be attributed to the enhancement of thermal conductivity and natural convection of nanofluid in PCM container. Furthermore, in active cooling condition, the silicon temperature controlled under 43 °C with uniform distribution. The nanofluid flow could be solidified up to 97% and 90% of initially melted PCM after 60 min for multi-packs and single-pack configurations, respectively.

Hybrid cooling of cylindrical battery with liquid channels in phase change material

In an electric vehicle, energy storage is in the form of electrochemical batteries, which are prone to thermal runaway and capacity fading if not maintained below safe temperature limits. An efficient battery cooling system is necessary for safer usage of electric cars during their life cycle. The current work presents a novel design that allows the coupling of liquid channels to a phase change material container in cylindrical batteries. The channeling approach allows heat dissipation from the phase change material container to both circulating media and convecting air. The design also helps to operate the cooling system without the circulation of liquid media in case of low ambient conditions. The comparison of the proposed system with a noncoupled liquid channel system is also presented to underline the merits of the system. The cooling media at a supply temperature of 30°C and the flow rate of 30 mL/min is adequate during the high ambient temperature of 40°C. The coupling of liquid channels to phase channel containers resulted in lowering the battery temperature well below 41.2°C even at an extremely high ambient temperature of 40°C.

Study on thermal performance of a PCM enhanced hydronic radiant floor heating system

Radiant floor systems enhanced with Phase Change Materials (PCMs) could achieve significant energy savings while improving the thermal comfort of occupants in lightweight buildings. Effective integration of PCMs typically requires customised solutions based on a comprehensive analysis due to their complex nature. The objective of the present study is the experimental and numerical investigation of a hydronic radiant floor heating system integrated with macroencapsulated PCM. Experimental tests were carried out on a laboratory-scale by the University of Ferrara, Italy, within the H2020 European project IDEAS. A 2D model was then implemented in COMSOL Multiphysics and calibrated in steady as well as in transient state according to the experimental tests. The behaviour of the system, including temperature distribution and heat flux, were analysed under different conditions. The impact of using dry and wet sand, as well as the effect of the position of PCM – above or under heating pipes – on thermal performance, were investigated. Results showed that the use of high thermal conduction in mortar increases much faster the overall performance of the PCM integrated underfloor heating system. Furthermore, the coupling technology with PCM containers installed under piping significantly enhances the positive effect of wet sand.

Parametric study on the thermal performance of phase change material-assisted earth-to-air heat exchanger

As a passive technology, the earth-to-air heat exchanger (EAHE) can be used to reduce energy consumption within a building. This paper presents a novel design for an EAHE system assisted by a phase-change material (PCM). To study the thermal performance of the newly proposed PCM-assisted EAHE (PCM-EAHE) system, a transient three-dimensional model has been built in FLUENT. A range of validated numerical models is established and utilized to investigate the effects of design and operation parameters (i.e., phase-change temperature, PCM container diameter, pipe length, pipe diameter and air velocity) on the thermal performance of the system. The results indicated that the phase-change temperature should be consistent with the time-average ambient air temperature. Furthermore, the polynomial regression models for predicting the outlet air temperature with high accuracy are obtained using statistical product and service solutions (SPSS). The optimal air velocity levels for enhancing the heat transfer performance are 4.5 m/s and 6.8 m/s during the charging and discharging processes, respectively. Therefore, it is recommended to apply the PCM-EAHE system to new and existing buildings.

Efficient thermal management of the photovoltaic/phase change material system with innovative exterior metal-foam layer

This research proposes an innovative configuration for modifying the thermal management system of the photovoltaic (PV) panel, integrated with a phase-change material (PCM) with an attached exterior metal-foam layer to the rear part of the PCM container. The configuration enables faster heat dissipation from the system leading to longer thermal-management duration for the PV panel during the energy storage (PCM charging) mode. Also, it supports faster energy recovery (PCM discharging) rate by decreasing the amount of heat trapped in the melted part of the PCM during the solidification mode. The effects of the foam-layer inclusion, PCM thickness, and PV tilt angle are numerically simulated and revealed. A mathematical model that accounts for natural convection effects of the melted PCM and non-Darcy effects of the metal foam, is formulated and validated via previous experiments. The results show that inclusion of an exterior foam layer could increase the PCM melting time, and the corresponding PV thermal-management duration, by up to 32% and 55% respectively, depending on the PCM thickness and PV tilt angle. The results also show that reducing the tilt angle from 90° to 30° increases the melting time by about 18%. Thus, a superior PCM-based thermal management is achieved. Moreover, utilizing PCM of thickness in the range of 20–30 mm lengthens the melting time by up to 54%, enhancing the potential for improved thermal management of PV panels.

Performance optimization of latent heat storage by structural parameters and operating conditions using Al-based alloy as phase change material

Heat storage technology can effectively solve the intermittency and instability of solar radiation and it also plays a vital role in solar thermal power generation. In this paper, Al-based alloys as candidates for high-temperature phase change material (PCM) with different Si/Cu content ratios are prepared. Thermal properties such as melting point, latent heat, specific heat, and thermal conductivity are investigated. A numerical model of phase change heat storage unit (PCHSU) is developed to analyze the heat transfer characteristics. The structural parameters are optimized by the PCM container structure, the surface to volume ratio, and inserted inner ring fins. The operating conditions are optimized by the flow direction, the inlet temperature, and the velocity of the thermal fluid. The results show that Al-5%Si-31.5%Cu (wt. %) has strengths in latent heat, specific heat, and thermal conductivity. The PCM container with a circular structure is superior to that of hexagonal and square structures in heat storage rate and thermal uniformity. The heat storage rate of PCHSU with inner ring finned tube is 6.83% higher than that of the smooth tube, and it has the advantage of inhibiting thermal stress due to the axial temperature uniformity. The horizontal PCHSU is more helpful in stabilizing the state of thermal fluid outlet temperature. Notably, 1023 K and 10 m/s are the optimal inlet temperature and velocity of the thermal fluid. Finally, the heat storage module is analyzed based on the variation of solar radiation intensity. These conclusions provide guidance for the design and optimization of PCHSU for heat storage systems.

Performance analysis of a PCM integrated domestic solar water heater by numerical simulations

The present work attempts to analyse the performance of a non-pressurised domestic solar water heater (DSWH) integrated with phase change material (PCM) during the two modes of operation, namely the charging and discharging modes. PCM's melting and the solidifying rate has been identified as the primary criterion influencing the heater's performance under standard test conditions. A co-axially placed cylindrical PCM container is modelled along with the evacuated tube collector (ETC) type water heater. A transient, three-dimensional numerical solver assuming constant solar insolation is used to study the phase change characteristics assisted by natural convective effects within the DSWH. The solver discretises the conservative equations using the finite volume method (FVM). Average solar insolation of 800 W/m2 has been fixed on the upper semi-cylindrical surface of ETC tubes and 35% of it as the reflected radiation falling on the ETC tubes' bottom surface. During charging, the melt fraction plot indicates that seven hours of charging is insufficient for the PCM to completely melt primarily due to the reduced heat conductivity of the PCM. Therefore, the extended period of discharge at the specified temperature expected by incorporating PCM is limited by the fraction of material remaining as solid.

Enthalpy based mathematical modelling for thermal energy storage filled with paraffin encapsulated balls as storage material

Numerical modeling of latent heat thermal storage (LHTS) is always complex to solve because of the necessity to tediously track the moving boundary, which happens due to the continuous variation of solid–liquid interface, during the melting or freezing process of phase change materials (PCM). Moreover, when commercial grades of paraffin are employed as Phase change storage materials for thermal energy storage applications, the phase transition will not happen at a particular fixed temperature but in a narrow range. Also, such paraffin exhibits several zones of transitions such as solid–solid and solid–liquid. The enthalpy (or fixed domain) method is one of the convenient methods to model problems involving phase change (or phase change materials) with the above mentioned conditions. In this paper, the mathematical modeling by enthalpy method for a LHTS system filled with ball shaped PCM containers as storage materials and its numerical solution procedures were discussed. The numerical procedure that considers the solid to solid transition of PCM and enthalpy-temperature relationships for PCMs that exhibit unsymmetrical transition zones before and after the peak transition temperature during the solid–solid and solid–liquid transitions were introduced and analysed.

Experimental investigations of phase change material filled rectangular enclosure with inclined top and side heating mode

Abstract An experimental examinations has been conducted on an inclined top and side heating mode phase change material (PCM) filled rectangular enclosure to understand its applicability in various thermal applications like: photovoltaic (PV) thermal management systems, concentrated PV systems, building thermal management and so on. The basic objective of this research work is to experimentally analyze the melt front propagation and temperature distribution of the PCMs in rectangular enclosure with the top heating mode; which is very rarely available in the literature. Lauric acid and paraffin wax are used during an experimentations as the PCMs. The inclination angles of PCM enclosure are varied with 30°, 60° and 90° with the horizontal. Constant heat flux are applied on the heater surface using halogen lamp assembly. The heat input to the 30° and 60° inclined systems are from top side and for 90° system, the heat input is from the right side. Solid-liquid interface transition of the PCMs and its various heat transfer characteristics are explained in the present research work during the charging period. The result shows that the convection currents inside the PCM container plays the major role on PCMs heat transfer characteristics at different inclination angles. The melting rate of PCMs increases with the increase in the inclination angles; however, the heater plate temperature is observed to be smaller at high inclined systems. Heat transfer from the heater plate to the PCMs are very high during the initial period and it decreases as the time progresses.

High porosity and light weight graphene foam heat sink and phase change material container for thermal management

During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m−1 K−1, while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.

Theoretical and Experimental Modeling of Phase Change Material-Based Space Heating Using Solar Energy

Recently, renewable sources of energy, particularly, solar thermal energy, have gained significant attention for developing heating and cooling mechanisms for buildings. This work aims at developing a theoretical model for space heating based on phase change material (PCM) using solar energy in winter conditions for the Northern region of India. The system has two PCM containers placed inside the room on the two opposite walls, which receives heat from concentrating solar system during the daytime. After achieving the temperature of PCM above its melting point using the solar system, the stored heat of PCM is released to the room ambient during the nighttime when the room ambient is at lower temperature. OM-37, having melting temperature of [Formula: see text]C, has been used as a PCM for the current research work. The numerical investigation of the system shows that temperature of the room reaches to 26–[Formula: see text]C from [Formula: see text]C in 4–5[Formula: see text]h of operation and thus ensuring thermal comfort of occupants.

Recent progress in phase change materials storage containers: Geometries, design considerations and heat transfer improvement methods

• The different geometries of PCM storage containers and their design considerations are presented. • Recent advances of different heat transfer improvement techniques in PCM storage containers are reviewed. • Various designs of PCM-finned storage systems and their key design parameters are deeply discussed. • Discussions for current systems design and recommendations for future research are illustrated. The potential for phase change materials (PCMs) has a vital role in thermal energy storage (TES) applications and energy management strategies. Nevertheless, these materials suffer from their low thermal conductivity and hence heat transfer enhancement techniques should be applied to enhance their thermophysical properties. This review focuses on the geometrical configurations of PCM containers and their design considerations, aims to improve the performance of TES systems. Various methods for enhancing heat transfer of PCMs (the main challenge in container design) include microencapsulated PCMs, insertion of fins, the combination of fins and nanoparticles, the use of metal foams and graphite, and the doping of high photothermal materials are also extensively discussed as well. Moreover, this paper highlights various designs of PCM-finned storage systems and discusses deeply their key parameters to find out the suitable design for optimum melting and solidification rate of PCM. The reviewed results showed that the rectangular PCM container is the effective container for the bulk storage due to its high melting rate and storage efficiency. Moreover, the use of longitudinal finned geometry within PCM integrated triplex tube heat storage units significantly achieved better heat transfer performance compared to the other finned geometries. Additionally, the improvement of the heat transfer of PCM by the deployment of fins is more effective than the hybrid combination of fins and nanoparticles. Further optimization and experimental studies are recommended to explore new hybrid compound intensification techniques such as the triple combination of fins, expanded graphite, and heat pipes with multiple PCMs that augment the thermal performance of TES systems.

Experimental study on the influence of PCM container height on heat transfer characteristics under constant heat flux condition

Rectangular encapsulation is the most widely used packaging form of latent heat storage (LHS). The geometry of the encapsulation, especially the height, may significantly affect the melting process of a phase change material (PCM). In this study, the effect of height variation of rectangular LHS encapsulation on the melting process of PCMs under constant heat flux is experimentally studied. The effect of container height on the melting process and Nusselt number (Nu) is presented by scale analysis. With the increase in container height, the overall melting time of the PCM becomes longer, the average PCM temperature increases, and the temperature stratification in the vertical direction of the container is more remarkable. The melting time is extended by 50% and the average temperature increases above 30 °C when the height of the container is increased from 12 to 48 cm. Results show that although the height of the PCM container contributes positively to the acceleration of PCM melting in the early stage, it caused more sensible heat accumulation at the top of the container during the solid shrinking regime, which prolongs the melting time of the PCM. Therefore, when designing an LHS system, the geometry of the PCM container must be optimised.

Simulation of Triplex Tube Thermal Energy Storage System Using High Temperature Phase Change Material

To increase the capacity factor of a concentrated solar thermal power plant (CSTPP) beyond the hours of sunlight, the use of thermal energy storage systems (TES) can be a promising solution. Phase change materials (PCMs) can store latent thermal energy in the course of the melting process and release it when solar energy is not available. Generally, PCMs have low thermal conductivity. One of the most commercially promising solutions is the application of an extended heat transfer surface inside the PCM container. Moreover, the distance of the heat transfer fluid (HTF) to the core of the PCM in a TES system can affect the storage performance. Accordingly, a triplex tube heat exchanger with eight fins is considered in this paper, to investigate the impact of the different velocity of HTF and different entrance pattern in a vertical PCM container. Notably, the middle enclosure of the triplex tube is filled with PCM. Numerical analysis using an enthalpy porosity technique revealed that increasing HTF velocity reduces the charging time. Also, when the HTF enters from the bottom of the container, the storage time will diminish owing to a natural convection side-effect, but if the HTF flows downward, the amount of sensible thermal energy storage is higher than in the other cases.

Theoretical and Experimental Evaluation of a Thermoelectric Generator Using Concentration and Thermal Energy Storage

To improve the thermoelectric conversion efficiency of solar thermoelectric power, a concentration solar thermoelectric generator (CTEG) unit based on concentrating and storing energy is designed. A Fresnel lens is used to concentrate thermal energy, and a phase change material (PCM) is used to store thermal energy to increase the temperature difference between the hot and cold ends of thermoelectric (TE) sheets. The heat stored in the PCM container will help to generate continuous solar energy at night and improve the thermal power conversion efficiency of the TEGs. The energy conversion equilibrium equation is established for the CTEG unit. By numerical calculation, we conclude that the absorption rate of the coating surface is reduced by 0.1 and the maximum thermoelectric conversion efficiency is reduced by approximately 0.4%. By selecting different heights of the heat exchanger, the unit supplies 1.025 v, 0.4204 v and 0.299 v open circuit voltages on average for approximately 30, 44 and 53 minutes, respectively. Therefore, the height of the heat exchanger affects the rate of heat energy absorption and release. The reversible operation of the CTEG-PCM unit is conducive to the day and night operation of solar power generation and is more suitable to solving the self-supplying power problem for wireless temperature sensors in forests.

Performance enhancement of a photovoltaic module by passive cooling using phase change material in a finned container heat sink

The enhancement of passive cooling for a photovoltaic (PV) module in a finned container heat sink was proposed. Palm wax was chosen as a phase change material (PCM) for this research as it was much cheaper than other commercial PCMs. Initially, three different PCM containers, i.e. grooved, tubed and finned containers, were designed and investigated. It was found that the finned container exhibited the best cooling effect. Thus, the PV module temperature was much decreased, giving the highest electrical power output. Then, the passive cooling with the finned container was further analysed and compared to the module without cooling. The finned box could reduce the module temperature from 57.9 °C to 51.8 °C (a 6.1 °C temperature drop). Thus, the module efficiency was enhanced from 9.33% to 9.82%, corresponding to a 5.3% improvement. Also, the averaged performance ratio (PR) rose from 0.63 to 0.66 (4.8% enhancement). It was discovered that palm wax had potential as a PCM capable of cooling the PV module. Importantly, passive cooling of the PV module using PCM was not always beneficial, but depended on the irradiance. The results made clear that when the solar irradiance was higher than 500 W/m2, there was a great enhancement in the PV performance with cooling. However, there is no need for PV cooling if less irradiance is usually the case.

Review of latent thermal energy storage systems for solar air‐conditioning systems

Solar air-conditioning is an important approach to satisfy the high demand for cooling given the global energy situation. The application of phase-change materials (PCMs) in a thermal storage system is a way to address temporary power problems of solar air-conditioning systems. This paper reviews the selection, strengthening, and application of PCMs and containers in latent thermal storage system for solar air-conditioning systems. The optimization of PCM container geometry is summarized and analyzed. The hybrid enhancement methods for PCMs and containers, and the cost assessment of latent thermal storage system are discussed. The more effective heat transfer enhancement using PCMs was found to mainly involve micro-nano additives. Combinations of fins and nanoadditives, nanoparticles and metal foam are the main hybrid strengthening method. However, the thermal storage effect of hybrid strengthening is not necessarily better than single strengthening. At the same time, the latent thermal storage unit has less application in the field of solar air-conditioning systems, especially regarding heat recovery, because of its cost and thermal storage time. The integration of latent thermal storage units and solar air-conditioning components, economic analysis of improvement technology, and quantitative studies on hybrid improvement are potential research directions in the future.

Effect of aspect ratio and dispersed PCM balls on the charging performance of a latent heat thermal storage unit for solar thermal applications

A cylindrical latent heat thermal storage system having a phase change material, HS89, encased in spherical capsules and stacked in rows to form a packed bed phase change material containment was considered for the experimental investigation. The heat is stored at 89 °C which is very useful for many process industry applications using solar water heaters. Three different aspect ratios were considered for experimentation. The temperature profiles of the phase change material containment and the heat transfer fluid at various heights were measured and monitored continuously. These temperature values were used to determine the variation in charging efficiency, stratification number and Richardson number of the storage system which are very useful parameters to design a storage system. The results presented in this paper will be very useful to design a phase change material based thermal storage for solar thermal applications.

Thermal analysis of an inclined heat sink with finned PCM container for solar applications

This paper explores the dynamic thermal performance of Phase Change Materials (PCMs) melting in an inclined finned rectangular container with the top heating mode. Internal external fins are provided to the back surface of the PCM tank considering its applications in the large duty cycle photovoltaic thermal management systems, top heating mode heat sinks and so on. Internal-external fins attached to the back surface of PCM container are proposed for: (a) to lengthen the melting time of PCMs during charging period specifically for peak sunshine hours in the solar applications (b) to enhance PCMs solidification during the discharging period and (c) to improve the heat transfer from the molten PCM to outside after complete melting; so as to reduce heat trapped. RT 42 is used as a PCM in the present study. Unsteady numerical investigations are performed with changing PCM thicknesses, inclination angles and number of extended surfaces. The PCM layer thicknesses are varied with 20 mm, 30 mm and 40 mm for the inclination angles of 30°, 45°, 60° and 90°. PCM container configurations with 2 fins, 3 fins and 4 fins are investigated. The effect of natural convection current is also included in the present numerical simulation using Boussinesq approximations. Control volume approach is used for the estimation of melting time, temperature distribution, velocity magnitude and Nusselt number enhancement. The result shows that the melting time for all the PCM systems increases with decreases in inclination angles and addition of a number of extended surfaces. The average PCM temperature and average velocity magnitude of the PCM decreases with decreasing inclination angle. Incorporation of additional fins than three does not add any significant enhancements in the melting time, although it drastically improves the PCM heat transfer performance. During the completion phase of melting process; using extended surfaces, Nusselt number is increased by 6–9 times for 30° inclined systems and 2–3 time with other inclination angles.