Phase Change Materials Storage System Research Articles

A novel approach for solidification enhancement of phase change materials through direct contact with a boiling fluid: An experimental investigation and visualization

Due to their remarkable properties, such as high latent heat and stable temperatures during phase transitions, phase change materials (PCMs) are widely used in thermal energy storage (TES) and thermal management systems (TMSs). However, their low thermal conductivity has limited their broader application across various industries. This study experimentally explores, for the first time, the effects of injecting boiling fluid (BF) into the PCM container as a new method to enhance heat transfer during the solidification process of PCM. To this end, Paraffin wax and acetone with saturation temperature lower than paraffin’s freezing point are selected as PCM and BF, and the influence of four various parameters, namely the initial PCM temperature (75, 85, and 95 °C), the height of the PCM inside the container (15 cm, 25 cm, and 35 cm), the flow rate of the BF (0.32, 0.46, and 0.57 L/min), and the nozzle diameter (2 mm, 3 mm, and 4 mm), on the solidification behavior of PCM, temperature distribution inside the container, and heat transfer enhancement (released energy and Nusselt number) is thoroughly scrutinized. In order to visualize and further evaluate the two simultaneous phase transitions (vaporization of the BF and solidification of the PCM), a Hele-Shaw cell with a height, width, and thickness of 50, 20, and 1 cm is considered as the PCM storage system. The findings indicate that when the BF is injected into the paraffin storage, the high heat transfer coefficient of boiling superbly improves the thermal behavior of PCM, and the solidification process occurs in a much shorter time. Also, boiling of the acetone inside the container and its direct contact with paraffin leads to a significant mixing inside the container and the creation of vortices and turbulent flow in the system, which further improves the freezing phenomenon. Furthermore, it was observed that regardless of other parameters, the flow rate of BF is the most crucial parameter, and after that, the height of the paraffin and the initial temperature have the greatest impact. By employing the highest flow rate, the proposed technique is capable of freezing 0.7, 0.5, and 0.3 L of paraffin in 48, 33, and 18 s, respectively, indicating multiple times of improvement in the full solidification time compared to previous studies.

Analyzing competing effects between heat transfer area and natural convection to enhance heat transfer in latent heat storage

Phase change materials (PCMs) are effective means of storing thermal energy and to balance temporal supply-demand mismatch. To enhance heat transfer within the PCM, internal fins are often employed to increase the heat exchange area, but they usually suppress simultaneously natural convection reducing the performance of the PCM storage. To better understand these two conflicting effects and to find a better trade-off between the different heat transfer means, a comprehensive numerical study of PCM storage with different fin shapes (straight and sinusoidal wavy fins) and surface areas, but with equivalent volume fraction, was accomplished. The results show that increasing the surface area of sinusoidal fins improves only marginally the heat transfer, mainly because the flow velocity of natural convection along the normal direction of the solid interface is inhibited. The velocity normal to the solid interface was found to be the most critical factors to the overall heat transfer efficiency of the system and to the time needed to complete the phase change in the PCM container. The study clearly shows that to enhance the heat transfer in PCM, the effects from natural convection (direction and strength) play a more important role than the heat exchange surface area. To improve the thermal performance and efficiency of PCM storage systems both factors need to be combined in an optimal way.

Thermal energy storage with PCMs: A comprehensive study of horizontal shell and multi-tube systems with finned design

Due to its unique qualities and advantages, phase change materials (PCMs) are crucial for thermal energy storage in various applications. The poor conductivity of PCMs is known to cause delayed charging and discharging rates. So, various techniques were proposed by the researchers to improve the thermal performance of PCM systems. To address this challenge, a comprehensive numerical research was presented on a horizontally oriented finned shell-and-tube type of PCM storage. The investigation was divided into four parts: (i) effects of the quantity and arrangement of heat transfer fluid (HTF) tubes; (ii) effects of the quantity and arrangement of fins; (iii) effects of the length of fins; and (iv) effects of various configurations of the finned shell-and-tube PCM storage. The outcomes depicted that due to buoyancy impact and horizontal location, the upper portion of the PCM storage melted more quickly than the lower portion. Also, it was found that, concerning the effect of the HTF arrangement (lacking fins) on the PCM melting process, with a 67.1 % improvement factor over a base model without fins, a double vertical array of HTF tubes produced the quickest melting time. Moreover, regarding evaluating the impact of the fins arrangement (one HTF tube), with a 39 % improvement factor, the diamond arrangement of fins was shown to be the best configuration for speeding up melting. For the complete melting process (LF = 1), the most significant improvement factor of 53.2 was noted for a fin length of 5.1 mm. Finally, the obtained numerical outcomes depicted that the complete melting time (at LF = 1) was reduced by 69.14 % in the model with a double vertical array of HTF tubes and a double vertical arrangement of fins, making it the ideal layout for the finned shell-and-tube PCM storage system.

An experimental study on heat power stored by thermal dissipation in electronic components using thermosyphon integrated hybrid nanocomposite phase change material

This study investigates the heat power stored by the thermal dissipation of electronic components using a thermosyphon integrated hybrid nanocomposite phase change material storage system. The study examines various thermal performances including the percentage of thermal dissipation, thermal resistance and heat transfer coefficient using benzene, deionized water, methanol and methyl acetate as heat transfer fluids, with an intended heat input of 50 – 120 W. The 0.5 wt% copper-titania hybrid nanocomposite particles are dispersed with phase change material (methyl cinnamate) and chosen as hybrid nanocomposite phase change material. The assessment of charging and retrieving characteristics of stored hybrid nanocomposite phase change material has been done by the impact of heat transfer fluids flowing through the copper tube at the different heat inputs. The result findings show that methyl acetate has the maximum percentage of thermal dissipation, low thermal resistance and high heat transfer coefficient of about 99.2 %, 0.311 K/W and 242.36 W/(m2.K) respectively at 120 W. The obtained results are attributed to the low boiling point and enthalpy of vapourization of methyl acetate. The highest heat power stored by hybrid nanocomposite phase change material is discovered as 6.5 W during melting by the impact of vapourized methyl acetate at maximum heat input owing to the higher mass flow rate and lesser time to attain steady state temperature of hybrid nanocomposite phase change material. Also, the developed system promotes thermal management in electronic components along with a minimum power saving of about 5–6 %.

Genetic algorithm optimization for double pipe heat exchanger PCM storage system during charging and discharging processes

Nowadays, world faces an energy crisis and residential buildings in developed countries account for 20–40% of the world's total energy demand. Therefore, reducing energy consumption in this sector is crucial for sustainable energy systems. Using phase change materials (PCMs) in energy systems is one of the most reasonable solutions. This study investigates PCMs in a dual-pipe latent heat exchanger system for thermal energy storage. The outer pipe of the exchanger contains the salt hydrate TH29 PCM, while the inner pipe carries water. The system is charged using hot water at 70°C and discharged with cold water at 8°C. An adiabatic time interval is introduced to optimize the charging and discharging operations during which the pump power is cut off and the water flow is stopped. The stored energy and exergy destruction during one hour of system operation is investigated by varying the adiabatic time interval. The Genetic algorithm is implemented to maximize the stored energy or minimize the destruced exsergy in the heat exchanger. The algorithm starts with 20 initial samples and 50 number of samples per iteration. The results show that the stored energy is a function of adiabatic time and maximizes to 25,312 J with an adiabatic time interval of 2150 s (out of 1 hour). Furthermore, the exergy destruction is minimized by an adiabatic time interval of 2249 s.

A novel multi-level predictive management strategy to optimize phase-change energy storage and building-integrated renewable technologies operation under dynamic tariffs

In the evolving energy sector, where buildings are recognized as dynamic components of energy networks and smart grids, the implementation of new regulations and guidelines is crucial to optimize the interaction between buildings and the grid. The imperative to reduce building energy consumption facilitates the promotion of new technologies that rely on renewable energy generation and innovative materials. As technology has progressed, the multitude of energy vectors involved has made controlling energy systems increasingly challenging. This poses a barrier to the widespread adoption and implementation of cutting-edge technologies. In this framework, this paper explores an energy-efficient solution using an integrated photovoltaic/thermal collector and an active phase-change material storage system. The study optimizes the integration of technologies through a resistance capacitance model, assessing the impact on thermal comfort, energy savings and costs. A novel cascade methodology, combining particle swarm optimization search with model predictive control, is designed to select the optimal mode of operation for the proposed technologies. The economic feasibility of the proposed system is analyzed across different tariff structures, whereas the interaction with the grid is evaluated using energy flexibility key performance indicators. The energy and economic performance, as well as the flexibility of the system are assessed through a proof-of-concept conducted in an office building scenario. The results demonstrate an increase in energy efficiency, with savings ranging from 9% to 28% compared to a suitable baseline scenario, and a significant energy shift from on-peak to off-peak periods, potentially accounting for up to 46% of the total building load. This energy flexibility enables the grid to receive reduced demand during morning hours.

Advances in Indoor Cooking Using Solar Energy with Phase Change Material Storage Systems

One of the key areas of the UN’s sustainable development goals is growing affordable and clean energy. Utilizing solar energy that is now accessible will significantly lessen the demand for fossil fuels. Around the world, cooking is a crucial activity for homes and uses a lot of non-renewable energy. Uncontrolled firewood usage results in deforestation, whereas using biomass-related fuels in inefficient stoves can result in smoke emanating from the kitchen and associated health issues. The benefits of solar cooking include reducing smoke-related problems and saving on fossil fuels and firewood. Applying thermal storage systems in cooking helps households have all-day cooking. This review article presents the research and development of a solar cooking system that transfers solar energy into the kitchen and integrates with the thermal energy storage system, finding the factors affecting indoor solar cooking performance. Adding portable cooking utensils helps in improved solar indoor cooking. Multiple phase change materials arranged in cascaded to store thermal energy helps in quick heat transfer rate, thus enabling better and faster cooking. A novel indoor solar cooker with an innovative arrangement of evacuated tube-based compound concentrating parabolic (CPC) collectors with a cascaded latent heat thermal energy storage system is proposed and needs to be tested under actual meteorological conditions.

Effect of phase-change materials in the performance of a solar air heater

This work presents an experimental analysis of a double-channel solar air heater (SAH) with and without phase-change material (PCM) as thermal energy storage system (TES). Two identical prototypes were designed and constructed, and one of them was modified to house macro- encapsulated PCM in the absorber plate. Both collectors were evaluated in an experimental setup instrumented for hot air temperature and velocity, solar radiation, temperature probes in the glass cover, absorber plate, PCM storage system, and a weather station to record the environmental conditions. To evaluate the performance of the SAH under sudden variations of solar radiation, three different case studies were considered with varying conditions of weather: clear sky and high radiation, partially cloudy, and clear sky with a substantial drop in solar radiation at noon. The maximum outlet temperatures reached by the SAH with PCM were 82 °C, 62 °C, and 79.5 °C for the three cases, respectively. The outlet temperature of the SAH without PCM was consistently 10 °C lower compared to the collector with PCM. The PCM maintained the heating during day irradiation transients and extended it after dusk, without any decrease in the thermal efficiency. Further studies of modeling and design optimization appear very pertinent.

Optimizing the shape of PCM container to enhance the melting process

Abstract The shape of container influences natural convection inside a latent heat storage with a phase change material (PCM). Often, the geometrical design of a PCM container is based on empirical observations. To enhance convection and melting of the PCM, authors propose here new design guidelines for an improved container. Using the so-called Co-factor method as the optimized basis, which is defined as the vector product of the velocity and temperature gradient, the new design method strives to raise the velocity of natural convection in liquid PCM, increase the amount of PCM in the direction of the convective flow, and reduce the amount of PCM far from the heating surface. Following these guidelines and Co-factor, an optimized PCM container with an elongated and curved shape is proposed and compared with a rectangular container. Numerical simulations indicated that the total melting time of the PCM in the optimized container could be reduced by more than 20% compared with the rectangular one. The higher natural convection velocity and the better use of it to melt the PCM in the optimized container space attributed to the better performance than that in rectangular container. The results can be used to design more effective PCM storage systems.

Efficient storage and recovery of waste heat by phase change material embedded within additively manufactured grid heat exchangers

The low thermal conductivity of organic phase change materials (PCMs) hinders their usage for energy storage purposes. We demonstrate a compact PCM-based thermal battery that employs three-dimensional (3D) printed metal surfaces for a robust thermal energy storage and recovery. The thermal battery could be utilized to store excess heat from various sources. The concept includes organic paraffin and fatty acid PCMs embedded within aluminum silicon alloy grid heat exchangers (GHE) produced via additive manufacturing. The heat exchangers consist of two parts: (i) a planar part with embedded water channels and (ii) a surface extrusion grid outside the planar part embedded in the PCM storage system. Three different grid designs are investigated and compared with a simple planar heat exchanger (PHE) without grid extension. The charging and discharging processes of the thermal battery were analyzed experimentally. The laboratory scale experiments reveal that the 3D printed grid surfaces of GHE significantly reduce the charging and discharging time from more than 240 min to less than 20 min. In contrast to PHE, the GHE may increase thermal power by a factor of ∼20 from 35 W to 670 W. Furthermore, the grid structure positively restrains the natural convection flow of the PCM melt, increasing conduction in the highly conductive grid structure and resulting in high charging-discharging power of the thermal battery. The swift charging and discharging with high power and energy density make the compact grid thermal battery a promising solution for thermal energy management.

The graphite foam/erythritol composites with ultrahigh thermal conductivity for medium temperature applications

The mesophase pitch derived graphite foams with low bulk density (L-GF) and high bulk density (H-GF) were spontaneously infiltrated by erythritol to prepare graphite foam/erythritol (GF/erythritol) phase change materials (PCMs) with ultrahigh thermal conductivity for medium temperature thermal energy storage applications. Results of thermophysical properties indicated that thermal diffusivity of the GF/erythritol PCMs can be enhanced by 66 and 117 times as compared with that of pristine erythritol in solid (0.36 mm2/s). This enhancement resulting from three-dimensional ordered network of graphite foam can significantly reduce the charging and discharging time of the PCM storage system. Although H-GF as a matrix can obtain a higher thermal conductivity (68.71 W/(m·K)) than L-GF (40.52 W/(m·K)), the smaller porosity cannot allow more erythritol to be absorbed, and its melting enthalpy (178.4 J/g) is lower than L-GF (266.6 J/g). In addition, the enhancement of thermal conductivity and the increase of interfacial surface area caused by graphite foam structure strongly suppresses the supercooling of erythritol, which can be reduced from 86.0 °C to 53.2 °C. The obtained results demonstrated that the GF/erythritol PCM as a stable PCM is a promising material for medium temperature thermal energy storage applications.

PCM-Based Energy Storage System with High Power Output Using Open Porous Aluminum Foams

Thermal comfort (heating, ventilation and air conditioning, HVAC) and the energy consumption involved with it can put a strain on the driving range of fully electric vehicles (FEV), especially in certain times of the year as midsummer or winter. In order to reduce the energy consumption of HVAC, improved thermal management and adapted means of energy storage are needed. One part of the solution can be the use of phase change materials (PCM) for storing waste heat. For the specific application, however, a high loading/unloading power rate is required, which is challenging as the PCMs exhibit low heat conductivities. In the presented work, a storage demonstrator system was investigated which is part of an HVAC system of a specific fully electric vehicle. The profile of requirements of the system (power, stored capacity and allowed volume) make a new design of the storage necessary. Two demonstrator units, in which the PCM was combined with aluminum foam, were manufactured and their power output in dependency on the fluid flow of the coolant system was compared. An adapted squeeze casting process with polymer placeholders was used for the production of the aluminium foam. This process results in foams with a specific pore structure and allows the in-situ integration of the heat transfer fluid (HTF) pipes. Both newly developed PCM storage systems satisfy the HVAC system requirements.

Effect of Phase Change Material Storage on the Dynamic Performance of a Direct Vapor Generation Solar Organic Rankine Cycle System

Solar energy is a potential source for a thermal power generation system. A direct vapor generation solar organic Rankine cycle system using phase change material storage was analyzed in the present study. The overall system consisted of an arrangement of evacuated flat plate collectors, a phase-change-material-based thermal storage tank, a turbine, a water-cooled condenser, and an organic fluid pump. The MATLAB programming environment was used to develop the thermodynamic model of the whole system. The thermal storage tank was modeled using the finite difference method and the results were validated against experimental work carried out in the past. The hourly weather data of Karachi, Pakistan, was used to carry out the dynamic simulation of the system on a weekly, monthly, and annual basis. The impact of phase change material storage on the enhancement of the overall system performance during the charging and discharging modes was also evaluated. The annual organic Rankine cycle efficiency, system efficiency, and net power output were observed to be 12.16%, 9.38%, and 26.8 kW, respectively. The spring and autumn seasons showed better performance of the phase change material storage system compared to the summer and winter seasons. The rise in working fluid temperature, the fall in phase change material temperature, and the amount of heat stored by the thermal storage were found to be at a maximum in September, while their values became a minimum in February.

Application of an active PCM storage system into a building for heating/cooling load reduction

Incorporation of phase change materials (PCMs) into buildings has recently attracted widespread attention as they can bridge the mismatch between energy supply and demand through their large energy storage capacity. This paper presents the use of an active PCM storage system in buildings and evaluates its energy performance over the different seasons. To this end, two experimental huts, each equipped with solar and electric heaters in winter or an air conditioning unit in summer, were used to investigate the concept. Also, one of the huts was provided with PCM storage units, and the results obtained were compared with those collected from the reference hut. A CompactRIO, data acquisition system, powered by LabVIEW real-time software, was used to transfer data for analysis, processing, and communicating with the host computer. In this research, the active PCM storage units could store solar energy in cold seasons or free night cooling in warm seasons for later use and hence reduce the heating/cooling load requirements. An accumulative heating energy savings of 40% in May and 10.3% in June/July 2019, were achieved. The use of PCM for space cooling also led to an accumulative energy-saving of 30% in March/April and 10% in January.

Influence of cascaded graphite foams on thermal performance of high temperature phase change material storage systems

In this study, a numerical analysis is used to compare the effects of uniform and cascaded graphite foams on the charge–discharge cycle performance of thermal energy storage systems where a phase change material (PCM) with a phase change temperature of 855 K is used as the storage media. Firstly, for a constant PCM mass, the insertion of single graphite foams with respective porosities of 80%, 85%, 90% & 95% in the storage tank resulted to an exponential increase in the charge–discharge time. It was therefore concluded that a graphite foam with a porosity higher than 90% is less beneficial because the gradient of the porosity versus charge–discharge time graph becomes steeper. Secondly, for a constant PCM mass, graphite foams of porosity 80%, 85% and 90% were combined to obtain a cascaded porosity structure. The three foam structures were cascaded in such a way that the average porosity was either 85% or 89%. Overall, results obtained for cascaded porosity structures showed that combinations having a low porosity graphite foam near the cooling/heating wall performed better than their counterparts having a higher porosity foam near the heating/cooling wall. Particularly, the best combination at an average porosity of 85% and 89% accelerated the charge–discharge time by 5% and 4%, respectively, as compared to their respective single graphite foam cases.

The Environmental Potential of Phase Change Materials in Building Applications. A Multiple Case Investigation Based on Life Cycle Assessment and Building Simulation

New materials and technologies have become the main drivers for reducing energy demand in the building sector in recent years. Energy efficiency can be reached by utilization of materials with thermal storage potential; among them, phase change materials (PCMs) seem to be promising. If they are used in combination with solar collectors in heating applications or with water chillers or in chilled ceilings in cooling applications, PCMs can provide ecological benefits through energy savings during the building’s operational phase. However, their environmental value should be analyzed by taking into account their whole lifecycle. The purpose of this paper is the assessment of PCMs at the material level as well as at higher levels, namely the component and building levels. Life cycle assessment analyses are based on information from PCM manufacturers and building energy simulations. With the newly developed software “Storage LCA Tool” (Version 1.0, University of Stuttgart, IABP, Stuttgart, Germany), PCM storage systems can be compared with traditional systems that do not entail energy storage. Their benefits can be evaluated in order to support decision-making on energy concepts for buildings. The collection of several case studies shows that PCM energy concepts are not always advantageous. However, with conclusive concepts, suitable storage dimensioning and ecologically favorable PCMs, systems can be realized that have a lower environmental impact over the entire life cycle compared to traditional systems.

Thermo-economic analysis of a solar-driven multi-stage desalination unit equipped with a phase change material storage system to provide heating and fresh water for a residential complex

• A new multi-stage desalination using solar energy for production of fresh water and heat was investigated. • A PCM thermal energy storage system was included for continuous operation. • TRNSYS, HYSYS, and MATLAB software were employed to simulate the integrated structure. • Exergy and economic analyses for the entire integrated structure were carried out. • Overall exergy efficiency of the cycle was determined as 62.79%. In this paper, a novel integrated structure for the production of fresh water and heat for residential complexes in Yazd is introduced and analyzed. The proposed process consisted of flat plate solar collectors, the thermal energy storage system (TES) with phase change material (PCM), and a multi-stage desalination unit. These sub-units were used to provide the required thermal energy, energy storage, and desalinating unconventional waters, respectively. To do so, HYSYS and MATLAB software were employed to simulate the integrated structure. The proposed process produced 4500 kg/h hot water at 64.26 °C and 379.6 kg/h fresh water at 25.35 °C. Effect of the different process parameters such as mass flow rate (MFR) of the inlet water into the solar collectors and number of collectors on the collector efficiency and solar fraction as well as the amount of solar and boilers energy accumulated during the year were broadly assessed and discussed. Comprehensive exergy analysis of the whole system was scrutinized to evaluate the efficiency of the system and to find out the exact location of the exergy losses and ultimately to provide practical solutions to reduce the losses. Solar collectors had the highest exergy destruction rate, which accounts for 344.05 kW. The effect of the cost of product on the period of return and the net annual benefit was also studied.

A review of numerical modelling of high-temperature phase change material composites for solar thermal energy storage

High-temperature phase change materials (PCMs), due to their high energy density and capability of maintaining nearly constant temperature, have been widely investigated to replace the current molten salt sensible storage system in concentrated solar thermal power plants. However, the performance of the PCM storage system is severely restricted by the low thermal conductivity and high corrosion of molten salt PCMs. Fabrication of PCM into PCM composite is a promising and effective method to improve the usability and handleability of high-temperature PCMs. The feasibility of fabrication process and material characterisation has been conducted through laboratory-scale experiments. This work reviews mathematical models used to describe the heat transfer process in high-temperature PCM composites, and hence to simulate the thermal performance of the storage system. It is critical to design a high efficiency storage system via numerical modelling. In order to include the natural convection in liquid PCM, the fundamental governing equations of continuity, momentum and energy need to be applied in the numerical model, together with the heat conduction equation in the solid structure material and the heat convection equation between the PCM and structure material. This detailed model is usually applied in metal and ceramic composites where the pore size is large, and the equations are usually solved by using commercial computational fluid dynamics software. For graphite-based composites, the model can be simplified into the energy equation with thermal equilibrium between the PCM and graphite.

Alternative storage options for solar thermal systems

The efficient implementation of solar systems in buildings depends on the storage of energy yielded, as it can both increase the solar system's autonomy and make it a feasible solution for zero energy buildings, and make storage vessels more compact, reducing precious space requirements. This is of particular important in places with reduced time of sunshine, where solar systems are less effective, because of the deviation between solar radiation and the demand. The traditional storage options use water, which is practical, safe and low-cost, especially when the storage requirements are small. However, when larger storage is needed, limits concerning the use of water exist, mainly due to the need for larger installation space and the increased thermal losses. The use of phase change materials (PCM) for thermal energy storage seems an upcoming technology. The main idea is the substitution of water with PCM, which feature larger specific energy storage capacity compared to other conventional materials. In the context of the specific paper, a combined solar thermal system used for the preparation of domestic hot water (DHW) and space heating (Solar Combi System) with two different types of storage is studied, for two Greek cities. The aim is to find out which is the most efficient way of storing energy with respect to the autonomy of the system, for a solar combi system. This is being achieved by determining the comparative autonomy of PCM and water storage system for various climates. It was proven that using PCM is advantageous, as it can extend the autonomy duration of the solar system for 2 to 8 hours, depending on the season and the climatic conditions. However, it was also seen that in solar combi systems used throughout the whole year, PCM are inefficient during summer period.

Performance comparison of two eutectic solder based latent heat storage systems during discharging

Latent heat storage systems consisting of phase change materials (PCMs) offer the advantage of a large thermal energy storage density as compared to sensible heat storage systems. Most recent work has focussed on organic and inorganic PCMs which have problems of subcooling and phase segregation. Metallic PCMs are a recent innovation for medium to high temperature applications due to their high thermal conductivities, high volumetric storage capacities and their low degrees of sub-cooling during the release of latent heat. For medium temperature applications like cooking of food, very limited work has been done on metallic PCMs for energy storage. Solder based PCMs have rarely been investigated for medium temperature applications thus it is necessary to carry out an experimental study on the use of a solder as PCM candidate. No work has ever been reported using the eutectic solder (Sn63/Pb37) as a PCM. Its use is justified since it is low cost and locally manufactured solder worldwide. Another recent innovation is cascaded thermal energy storage (TES), whereby two PCMs with different melting temperatures are used in a single storage tank to improve the efficiency of energy storage. No work has also appeared in recent literature involving metallic solders in cascaded systems. In a bid to investigate the suitability of the eutectic solder as a PCM for medium temperature applications, two eutectic solder (Sn63/Pb37) based systems are experimentally evaluated during discharging cycles. The first system is a single PCM system composed of a packed bed of spherically encapsulated eutectic solder capsules. The other system is a two PCM cascaded system comprising of eutectic solder spherical capsules at the top and erythritol spherical capsules at the bottom in a storage ratio of 50 %: 50 %. Discharging experiments are carried with three different discharging flow-rates to investigate the effect of the flow-rate on the thermal performance. The three discharging flow-rates used are 4 ml/s, 6 ml/s and 8 ml/s. For both storage systems, an increase in the discharging flow-rate increases the peak discharging energy and exergy rates. For both storage systems, an increase in the discharging flow-rate increases the peak discharging energy and exergy rates. The single PCM system shows higher energy and exergy rates for most of the discharging duration compared to the cascaded system. An increase in the flow-rate increases the peak energy and exergy discharging rates for the single PCM and the cascaded PCM storage systems. The single PCM system out-performed the cascaded system during the discharging tests possibly due to the lower melting temperature and lower thermal conductivity of the bottom PCM (erythritol) in the cascaded system. However, for the higher flow-rates (6 ml/s, 8 ml/s), the cascaded system shows a slightly better or comparable performance at the start and at end of discharging.