Thermal Storage Devices Research Articles

SIMULATION OF FLOW AND HEAT EXCHANGE IN A HEAT ACCUMULATOR TANK

The article deals with the research of thermal energy storage tanks. It is proposed to use a «thermal core» to minimize the effects of thermal stratification and high thermal inertia. The thermal core consists of a binary tube placed along the central axis of the tank, filled with a paraffin mixture with a melting point of 45 to 65oC and a density of 0,880 to 0,915g/cm3 at 15oC. In the study the Fluent software package was used to model the temperature distribution in the tank under free convection conditions, the data was then converted to the Transient Thermal module of the ANSYS software package for further calculations of the unsteady temperature distribution in the thermal core. The study showed that a 1400-liter thermal energy storage device, heated for 1 hour by a heat-transfer fluid at 115oC, cools down to 50oC in 4 hours. The research also revealed the need to improve the tank design based on the analysis of the hydrodynamic structure of the flow in the tank, as evidenced by the trajectory distribution of free convective flows. The authors concluded that the use of a heat core, regardless of the type of paraffin used to form it, helps to reduce temperature stratification by height in the tank and that the type of paraffin used has no significant effect on the overall cooling of the tank. However, using ceresin as a core filler results in a slightly higher average tank temperature. Based on the results of the study, the time of complete cooling of the tank was determined by the non-uniform temperature field of all elements of the tank.

Experimental investigations on nano-Fe2O3/ beeswax phase change materials for thermal energy storage applications

The efficacy of solar thermal energy storage mechanisms that use Nanoparticle distributed Beeswax Phase Change Material (PCM)is the presentsubject ofstudy. To acquire a stronger insight intothe thermal behaviourof this PCM made from beeswax, a series of experiments have been carried out. These investigations were aimed at understanding how the presence of Fe2O3 nanoparticles inPCM altered both thermal properties. Fe2O3 particles were distributed at varied concentrations, comprising 1%, 2%, 3%, and 4%, to increase the heat transfer of the beeswax based PCM. The findings of these trials suggested that the addition of Fe2O3 Nanoparticles to the composite material increased its melting rates. This higher melting rate is attributable to the enhanced heat conductivity of composite material by 1.2%, 5.2%, 7.2%, and 8.8%, by the introduction of 1%, 2%, 3%, and 4% Fe2O3 nanoparticles. This rise in thermal conductivity is followed by a reduction in the material's heat capacity. The composite material comprised of Beeswax and Fe2O3 exhibited a lowermelting temperature over the pure phase material, according to further measurements. The implications of these results for thedevelopment of more efficient and effective solar thermal energy storage devices are significant, which encourages their use in space heating, water heating and battery cooling applications.

Melting process of a phase change material using single and double elliptic charger applied in thermal storage for building application: A numerical study on effect of position and aspect ratio

Nowadays phase change materials are considered as very useful and innovative working medium that can be used in different engineering systems for various purposes, including the thermal stabilization regime in building elements, cooling of electronic systems, development of thermal energy storage devices and other fields. The present research deals with numerical analysis of phase change material melting behavior in a closed adiabatic cavity under an influence of one or two elliptical local heaters that can be considered as local charges for the working material. Using the finite element technique, the governing partial differential equations formulated using primitive variables and enthalpy-porosity formulation have been solved numerically. The computational results have been validated utilizing published experimental and numerical data. Influence of the local heaters position and its shape on evolution of melting process has been studied. It has been revealed that in the case of vertically oblong one elliptical heater the melting rate is the maximum, while for the case of circular charger one can find a minimum melting rate. It has been ascertained that more intensive melting occurs when the charger is placed near the bottom wall (Sv = 0.2) and for this case the non-dimensional charging time for MF = 1 is about 2. While for other cases less intensive meting can be found. Moreover, in the case of elongated chargers for vertical axis (Ar = 0.1) and for horizontal axis (Ar = 10) the melting occurs intensively, namely the non-dimensional charging time for MF = 1 is about 1.5, while the maximum values (at about 24) of the average Nusselt number during the melting process are for Ar = 0.5 and Ar = 1.0. The highest values of the average Nusselt number (at about 12) are related to the minimum melting time (at about 1.1) that can be found for cases 6 and 9 when two chargers are placed in central part or along the bottom line.

Design and Validation of a State-Dependent Riccati Equation Filter for State of Charge Estimation in a Latent Thermal Storage Device

Abstract Latent thermal energy storage (TES) devices could enable advances in many thermal management applications, including peak load shifting for reducing energy demand and cost of HVAC or providing supplemental heat rejection in transient thermal management systems. However, real-time feedback control of such devices is currently limited by the absence of suitable state of charge estimation techniques, given the nonlinearities associated with phase change dynamics. In this paper, we design and experimentally validate a state-dependent Riccati equation (SDRE) filter for state of charge estimation in a phase change material (PCM)-based TES device integrated into a single-phase thermal-fluid loop. The advantage of the SDRE filter is that it does not require linearization of the nonlinear finite volume model; instead, it uses a linear parameter-varying system model which can be quickly derived using graph-based methods. We leverage graph-based methods to prove that the system model is uniformly detectable, guaranteeing that the state estimates are bounded. Using measurements from five thermocouples embedded in the PCM of the TES and two thermocouples measuring the fluid temperature at the inlet and outlet of the device, the state estimator uses a reduced-order finite volume model to determine the temperature distribution inside the PCM and in turn, the state of charge of the device. We demonstrate the state estimator in simulation and on experimental data collected from a thermal management system testbed to show that the state estimation error converges near zero and remains bounded.

Economic operation of networked flexi-renewable energy hubs with thermal and hydrogen storage systems based on the market clearing price model

This paper presents the energy management of flexi-renewable energy hubs in electric and thermal networks based on the market clearing price model and participation of hubs in the energy market. Renewable sources include wind sources and bio-waste units, where the latter simultaneously plays a role in electrical and thermal energy generation. Hydrogen and thermal storage are used as a source of flexibility in the hub. The proposed scheme has a two-level formulation. Its upper level considers the participation of hubs in the energy market. It maximizes the expected profit of energy hubs by observing the operational constraints of power sources and storage devices (in the form of a hub) and the hub's flexibility limitation. The lower-level problem presents the market clearing price model. In this problem, the expected operation cost of the generation units in the electric and thermal networks is minimized subject to satisfying the constraints of the optimal power flow of the mentioned networks. The Karush-Kuhn-Tucker method provides a single-level formulation of the scheme. Also, stochastic optimization is adopted to model the uncertainties of load and renewable power to examine the flexibility of energy hubs accurately. Finally, by evaluating the numerical results obtained from different study cases, the scheme can improve the operating conditions of energy networks and obtain optimal flexibility and economic conditions for energy hubs. The hydrogen storage device next to the thermal storage device can achieve 100% flexibility conditions for the hubs. Storage devices can enhance the economic status of renewable hubs by about 9.2%. The energy management of flexi-renewable hubs improves energy networks' operational and economic status by 21–24% and 8.8% compared to power flow studies.

Optimization of integrated energy systems considering seasonal thermal energy storage

Integrated energy system are an effective way to achieve sustainable energy development and build a low-carbon society. However, the combination of different units needs further investigation to determine the optimum configuration and operating strategy. To address the problem of large differences in user loads and renewable energy sources between seasons, a regionally integrated energy system, including the seasonal thermal energy storage system, is established. The seasonal thermal energy storage system is coupled with heat pumps and solar collectors. We optimize the planning and scheduling of each device in the integrated energy system on a planning horizon of one year. The results show that the integrated energy system with a ground source heat pump and seasonal thermal energy storage device can effectively reduce the cost of the operation planning by 9.1 %. The cost of purchased energy and carbon emissions have also been reduced by 23.4 % and 12.6 %, respectively. In addition, the study also found that the available area of solar radiation in a region influences the optimal configuration of the system.

Optimal design and thermal performance study of a two-stage latent heat thermal energy storage technology for heating systems

Power-to-heat coupled with latent heat thermal energy storage can improve the economy and flexibility of heating systems and also is one of the key technologies used for promoting the balance between power grid supply and demand. However, the existing latent heat thermal energy storage heating systems are primarily based on a single-stage device filled with a single phase change material. Their exergy and energy utilization efficiencies are limited. Moreover, it is difficult to apply the existing multistage devices filled with cascaded phase change materials to building heating because of their small capacity. Therefore, in this study, a novel two-stage latent heat thermal energy storage device was developed. First, a numerical simulation method was used to optimize the cascade mode and select phase change material. Second, experiments were conducted to determine how the flow rate, inlet temperature, and number of stages of the devices affected the thermodynamic performance. Finally, heating effects were investigated. Compared with the single-stage device, the total heat storage and release of the two-stage device increased by up to 53.0% and 66.3%, respectively. The most noteworthy finding was that the thermal performance of the device was significantly improved by increasing the flow rate of the heat transfer fluid only when the flow regime changed from laminar flow to critical flow or from critical flow to turbulent flow. In addition, the two-stage device can support a 3.0-kW heat demand for 7.2 h. This study provides theoretical guidance for engineering applications of cascaded latent heat thermal energy storage heating systems.

Stochastic optimization – based economic design for a hybrid sustainable system of wind turbine, combined heat, and power generation, and electric and thermal storages considering uncertainty: A case study of Espoo, Finland

This work-study deals with the economic planning of an island sustainable system that consists of a wind turbine, battery, combined heat and power system, and thermal storage to meet electrical and thermal loads at the same time. The approach attempts to find minimum capital cost, repair and maintenance cost, and operating cost, as well as minimize the pollution of these elements. It is also constrained by the operation-planning model of the mentioned resources and storage, provided that a wind turbine and combined heat and power system have priority in electrical load supply, a combined system of heat and power has priority in thermal load supply, and batteries and storage devices have the task of filling the gap between supply and demand profiles. Uncertainty parameters of the scheme include electrical and thermal load and power output of the wind system. The scheme adopts the unscented transformation method to provide proper modeling of the mentioned uncertainties. Moreover, the essence of the problem is integer nonlinear programming, which uses the combined gray wolf optimization and honey bee mating optimization algorithm to achieve the desired solution. Simultaneous supply of electrical and thermal loads, modeling of uncertainties, and adoption of a combined solver in the proposed scheme are among the contributions. Finally, by implementing this scheme on data from the city of Espoo, Finland, the numerical results indicate a reduction of 10%–11% in the planning cost of the proposed scheme compared to a design that only supplies electricity.

Structure and Operation Optimization of a Form-Stable Carbonate/Ceramic-Based Electric Thermal Storage Device for Space Heating

The escalating demand for heating and the widespread use of CO2-emitting fossil fuels during cold seasons have imposed significant pressure on our natural resources. As a promising alternative to coal-fired boilers, electrical thermal storage devices (ETSDs) for space heating are gaining popularity. However, designing ETSDs for space heating involves significant challenges, which involve their storage rate and operational stability. In contrast to the research of directly developing mid-temperature ETSDs to manage heat release during long heating hours, this study proposed a new ETSD that uses K2CO3–Na2CO3 for high-temperature storage to match the off-peak hours and thereby gain potential economic benefits. This study used experimental and simulation methods to investigate the ETSD’s temperature distribution. An operational strategy was also proposed to achieve more efficient temperature distribution and higher economic benefits. The ETSD with two steel plates and two insulation layers with a power rating of 1.6 kW was found to be the optimum structure, due to its improved heat storage rate (2.1 °C/min), uniform temperature, and material heat resistance (<750 °C). An energy analysis, economic analysis, and a 7-day cycling operation performance of the device were then conducted by comparing the proposed ETSD with a traditional electric heater. The results revealed that the proposed ETSD released 53.4% of the stored energy in the room, and stored 48.6% of it during valley electric time. The total cost of the proposed ETSD was consistently lower than the traditional electric heater in the second heating season (by the 213th day). The efficiency of its valley heat storage for users was 37.2%. Overall, this study provides valuable insights into the development and practical applications of ETSD systems for space heating.

Effect of novel concentric annular fins on the melting and solidification process of stearic acid in thermal energy storage devices

The latent heat thermal energy storage device provides an alternative solution to the problem of imbalance between energy supply and demand. To enhance heat transfer, a series of latent heat thermal energy storage devices with novel concentric annular fins are proposed, as the design accelerates the melting and solidification processes of stearic acid. Based on the finite volume method, the enthalpy-porosity approach is employed to numerical simulation the charging/discharging process. Effects of the number and arrangement of concentric annular fins on the liquid fraction, melting and solidification front, melting uniformity, temperature uniformity, velocity uniformity and total melting and solidification time during melting and solidification are studied. Results showed that the melting and solidification rate increases with increasing fin number. The total melting and solidification times were reduced by 72.83% and 86.39%, respectively, for the case with 9 concentric annular fins compared to the bare tube. Both melting performance and temperature uniformity were improved. Further, the effect of fin arrangement on the melting and solidification performance was investigated with the same total volume of fins. Results revealed that the heat transfer performance of progressively shorter fin structures < uniformly distributed fins < progressively longer fins < performance of non-uniformly distributed fin arrangement. The non-uniform fin arrangement reduces the total melting and solidification time of stearic acid by 85.46% and 90.11%, respectively, compared to bare tube. This work provides new insights into the understandings of the transient phase change process and the strategies for guiding the design for thermal energy storage devices using annular fins.

Performance analysis of hydrogen supply using curtailed power from a solar-wind-storage power system

A solar-wind system including solar and wind power plants, electric and thermal storage devices, and hydrogen supply devices is constructed to discuss the feasibility of combined power and hydrogen supply. On the premise that over 90% of the power demand is economically met, the installed capacities of hydrogen supply devices are optimized under different conditions to obtain the highest reliability and lowest cost of hydrogen supply. The stable and typical seasonal fluctuating load demands of power and hydrogen are considered. The influences of hydrogen production technology on system energy utilization is analyzed. Results show that when the loss of hydrogen supply probability (LHSP) is required to be 0.1, 0.05 or even 0, the hydrogen supply cost is as low as 7.49 $/kg, 10.76 $/kg and 17.33 $/kg. The fluctuating power and hydrogen supply curves with better coincidence with weather distribution, higher power supply reliability requirement and less hydrogen demand are conducive to achieve lower hydrogen supply cost under the same reliability. When LHSP is required to be 0.1, the hydrogen production technology can recover 12.6%–26.1% of curtailed photovoltaic and wind power with the loss of power supply probability (LPSP) of 0.1, and 10.6%–21.3% of curtailed power with LPSP of 0.05.

Assessment of potential renewable energy alternatives for a typical greenhouse aquaponics in Himalayan Region of Nepal

Greenhouse aquaponics (GA) can serve as a sustainable food production method, potentially improving food and nutrition security in resource-constrained and hostile climatic zones such as Nepal's Himalayan region. Energy concerns, however, are one of the major barriers to GA adoption in this region. There is a lack of comprehensive energy demand analysis for GA operations. Therefore, in this study, an energy model for GA based on a quasi-static energy balancing technique was developed to estimate energy demand for the Himalayan region. The study was conducted in 19 districts with varied GA dimensions, and a linear-model was fitted to predict yearly energy consumption. Thereafter, relations to estimate the capacity of PV systems for supplying the required energy were devised. Eventually, this study proposes potential energy management strategies to reduce dependency on a single energy source, reduce energy loss, and enhance resilience to energy concerns. Findings suggest, heating the GA is a major energy concern, accounting up to 85% of the overall energy requirement. Thermal evaluation reveals that conduction and convection losses are the most significant, contributing up to 29.5% of total energy consumption. Moreover, this study testifies the effectiveness of thermal energy storage devices in achieving significant energy savings. The proposed energy management strategies can serve as a decision-making tool for optimizing the design and operation of GA. Furthermore, this research serves as a blueprint for addressing aquaponics related energy challenges worldwide, especially in areas with similar climatic conditions, such as the Hindu Kush Himalaya (HKH) region.

Experimental and Numerical Optimization Study on Performance of Phase-Change Thermal Energy Storage System

Promoting the use of solar energy resources has always involved the challenges of instability and supply–demand mismatch. The key to solving these issues is to efficiently store and utilize solar energy resources using high-performance heat storage devices. This study designed a high-performance shell-and-tube phase-change thermal storage device and established a numerical model using ANSYS software to summarize the device’s dynamic melting law. To verify the accuracy of the numerical simulation, a performance testing platform for the phase-change thermal storage device was built to investigate the impact of various factors, such as the inlet water temperature, inlet water flow rate, type of heat storage, and initial temperature of the device, and to reveal the change law of the device’s performance. The results show that the inlet water temperature has the most significant impact on the device’s heat storage and release performance. When the device’s heat storage or release is used for heating, changing the inlet water flow rate has a weak and limited effect on the device’s performance. However, when the device’s heat release is used to provide domestic hot water, increasing the make-up water temperature and reducing the inlet water flow rate can significantly improve the device’s effective heat release. Furthermore, based on the experimental validation of the model’s correctness, this study further simulated and studied the impact of different factors on the device’s heat storage process to optimize its structural design and provide technical references for the device’s actual operation and installation. The results show that the placement of fins has a negligible effect on the performance of the heat storage device while reducing the fin spacing and increasing the fin thickness can significantly improve the melting efficiency of the phase-change material (PCM). Additionally, the heat storage characteristics of the device are significantly better in the vertical installation mode than in the horizontal installation mode. This study provides theoretical guidance and technical references for the design and use of phase-change thermal storage devices.

Multi-stage distributionally robust optimization for hybrid energy storage in regional integrated energy system considering robustness and nonanticipativity

Hybrid energy storage system (HESS) has advantages in coping with the uncertainty of renewable energy and improving the stability of regional integrated energy systems (RIES). Few of the current HESS uncertainty scheduling methods consider both robustness and nonanticipativity, which may result in scheduling strategies that are not feasible in practice. Therefore, this research constructs a HESS (containing electric, thermal, hydrogen and natural gas storage devices) and forms a hybrid energy storage operator (IHESO) with an independent market position based on the HESS to provide energy services. Subsequently, a novel multi-stage distributionally robust optimization (MSDRO) method is established to maximize HESS revenue. Robustness and nonanticipativity can be satisfied in the uncertainty scheduling process of this method. After that, the stochastic dual dynamic integer programming (SDDiP) algorithm is introduced to solve multi-stage nested problems of complex systems. Finally, simulations are conducted in the actual system of three seasons and five scenarios. The conclusions are as follows: 1) The scheduling strategy provided by the MSDRO model and SDDiP algorithm can ensure effective operation based on satisfying robustness and nonanticipativity. 2) Compared with MSO, TSDRO and MSRO, the method proposed can improve the HESS economy and stability, increase renewable energy consumption and reduce carbon emissions.

Research on load circuit of medium frequency electromagnetic heat storage device

In order to improve the working efficiency of the electromagnetic heat storage device under high current and high frequency, the electromagnetic field finite element method is used to analyze and calculate the load circuit to make it in a suitable working state. Firstly, the circuit model of the energy storage device is built by using the field-circuit coupling method and the coil inductance is calculated. Secondly, the harmonic capacitor is analyzed and calculated, so that the load circuit works in a weak inductive state. On this basis, the variation law of loss on the inductor core and the distribution of water temperature rise flowing through the core at a certain water velocity are analyzed. A 50 kW prototype was built using the method proposed in this paper, and the experimental results show that the electro-thermal conversion efficiency of the electromagnetic thermal energy storage device reaches 93.39 %. The feasibility of the design method is proved by experiment and simulation, which has important guiding significance for the research and design of electromagnetic thermal energy storage device.

Performance study and heating simulation on novel latent heat thermal energy storage device suit for air source heat pump

Latent heat thermal energy storage (LHTES) technology can solve the problem of limited performance improvement of air source heat pump (ASHP) systems due to the time mismatch between building energy demand and operational efficiency in low temperatures. Therefore, this paper proposes a LHTES device suitable for the ASHP system. Firstly, the internal structure is obtained by ANSYS numerical simulation. Furthermore, experiments are carried out to verify the heat storage and release performance of the proposed device under different inlet water temperatures and flow rates. Finally, the operational effects of the ASHP-LHTES combined heating system are analyzed by TRNSYS. The design results show that a liquid phase ratio of 97.24 % is achieved with a pipe diameter of 16 mm, tube pitch of 70 mm, and 1/2 horizontal tube fins. Experiment results exhibit that the proposed device performs excellently under optimal conditions, with 89.7 % effective heat storage efficiency and 92.5 % available heat release efficiency. TRNSYS results indicate that the annual operating cost of the combined heating system saves 32.9 % compared with the single ASHP heating system, although the power consumption increases by 24.4 %. This study can provide theoretical support for the application of low-temperature LHTES devices in the ASHP system.

Optimal calculation of the operation strategy of a distributed heating system combining wind, solar and electrical energy

In this paper, a distributed combined heating system is proposed, composed of an electrically driven air source heat pump (two-stage compression type), solar collector, wind turbine heater, and thermal storage device. A multi-objective optimization mathematical model is established, aiming to minimize the operating cost and carbon dioxide emission during a certain time. The multi-objective planning problem is used to guide solutions to building heating problems in Northern China. Subsequently, for a specific example, the NSGA2 algorithm is used to solve the calculation. Based on the compromise solution of the two optimization objectives, the optimal operation strategy is determined: the amount of heat generated or stored by each device on a typical day. The optimal operating strategy is as follows. In the low heat load period (9:00-16:00), which coincides with the sunny period, the heat production of the solar collectors and the wind turbine heaters exceeds the heat load, and the storage device stores surplus heat. During peak hours (0:00-9:00, 16:00-24:00), the solar collectors are not activated because the solar irradiance is nearly zero. And at this point, the heat production by the wind turbine heaters fluctuates greatly, and the air source heat pump turns out to be the main heating equipment and the heat storage device to release heat when necessary.

Integrated heat and cold storage enabled by high-energy-density sorption thermal battery based on zeolite/MgCl2 composite sorbent

Thermal energy storage (TES) plays a critical role in renewable energy utilization, waste heat recovery, and heating/cooling applications. However, low energy density is a long-standing challenge for conventional TES systems based on sensible heat and latent heat methods, and thus impedes the widespread deployment of heat storage and cold storage. Herein, a novel high-power/energy-density sorption thermal battery (STB) is developed for realizing integrated heat and cold storage by using zeolite 13X-based composite sorbent-water working pair. The zeolite 13X is firstly treated with MgCl2 salt to improve water uptake and regulate sorption equilibrium characteristics. The results demonstrate that the energy density of zeolite 13X/MgCl2 can be improved by 15.1% when compared to zeolite 13X. The STB exhibits the distinct capability of realizing high-power/energy-density heat storage and cold storage, and the working temperature can be changed according to different demands. The average power densities for heat storage and cold storage are 279.66 W/kg and 242.95 W/kg, respectively. Meanwhile, the average energy densities for heat storage and cold storage are as high as 686.86 kJ/kg and 597.13 kJ/kg, respectively, superior to the current sensible/latent heat energy storage. The proposed zeolite/MgCl2-based sorption thermal battery offers a promising route to realize high-density heat storage and cold storage simultaneously based one thermal energy storage device.

Experimental Research on Heating Transfer Improvement of Materials that Change Phase in Tunnels in Cold Regions

In tunnel heating systems, phase change materials may minimize the consumption of conventional electric energy, which is very considerate in the field of tunnel heating in cold regions. Because of the phase change material’s poor heat conductivity, its annual growth rate heat absorption and release is slower; thus, the majority of phase change heat storage systems must improve heat transmission. In this study, a spiral metal ring is implanted in the paraffin to improve heat transmission to achieve this objective using a concentric sleeve-type paraffin heat storage device as a medium. Experiments were performed out in order to determine the effects of heating rate, hot fluid flow rate, and the use of a spiral metal ring on the heat storage and release process of a thermal storage device. In comparison to the paraffin thermal storage device, the embedding of the spiral metal ring accelerates the internal thermal performance of the composite heat storage device, resulting in a more uniform temperature distribution. When the thermal radiation heating rate is 60°C, 65°C, or 70°C during the heat storage process, the heat storage time of the composite heating storage device is reduced by 59.2 percent, 44.4 percent, and 40.7 percent, respectively. When the ambient temperature is 26°C and the heat storage device’s starting temperature is 65°C, the exothermic time is reduced by 22.6 percent.

Thermal performance of cold thermal energy storage system with fin and fin–foam structures

The heat transfer performance of most cold thermal energy storage (CTES) devices is limited by the low thermal conductivity of phase change materials (PCMs) and the increase in the thickness of PCMs. A comparative work was performed to explore the heat transfer performance of CTES systems with a fin structure (Fin-CTES) and a fin–foam structure (Fin–foam-CTES). The heat transfer performance, temperature distribution, and thermal effectiveness of Fin-CTES and Fin–foam-CTES at different inlet temperatures and volume flow rates of heat transfer fluid were investigated and compared. Results demonstrated that the overall heat transfer performance of Fin–foam-CTES is better than that of Fin-CTES. However, compared with the PCM in Fin-CTES, that in Fin–foam-CTES has a greater degree of supercooling, reaching 4.35 °C at the maximum. In the discharging (melting) process, Fin-CTES and Fin–foam-CTES have almost similar heat transfer effectiveness, in which the maximum difference is only 0.0107. That is, the enhanced heat transfer effect of the natural convection of the liquid PCM and the metal foam is basically the same during the discharging process.