Performance Of Storage Unit Research Articles

Partitions influence on rectangular latent heat thermal energy storage unit performance during melting and solidification

The growing use of renewable energy sources demands efficient storage solutions due to their variability. Thermal energy storage systems utilising phase change materials are emerging as viable options to address this challenge. This study evaluates the impact of various partition types on phase change duration in thermal energy storage systems. The well-known and validated enthalpy-porosity algorithm implemented in the Fluent 2021R2 software was used. The shortest melting time was observed in the case with four vertical tubes and three horizontal partitions, which was 82 % shorter than in the reference case. The highest change in specific enthalpy of phase change material (252.5 kJ/kg) during melting was also noted for this system. The shortest solidification time was observed for the case with four tubes and two diagonal partitions, which was 72 % shorter than in the reference case. The greatest increase in the specific enthalpy of phase change material (240.4 kJ/kg) during the solidification process was also observed in this system. In conclusion, due to the thermal conductivity of the partitions, the temperature distribution throughout the domain becomes more homogeonous, thus contributing to more uniform heat flux extraction and supply throughout the process.

Thermal performance augmentation of honeycomb metal matrix embedded phase change material in shell-tube latent heat storage unit

Due to the global warming challenge, there is a transition from the utilization of fossil fuels to harvesting new and renewable energy sources globally. Solar energy, being the infinite source with easy accessibility, leads the race among other allied sources. However intermittent nature of it demands an efficient thermal energy storage system. In the present experimental study, an innovative heat transfer augmentation technique i.e. aluminium honeycomb grill and fine mesh embedded in PCM is demonstrated. Both visualization of PCM melt fraction and capture of temperature contour complemented each other to identify the honeycomb version (HC-LHSU) as substantially better (43 % improvement in charge period) than the base model (BM-LHSU). On the other side, due to fine pores (porosity = 95 %), the fine meshmodel (FM-LHSU) yielded poorer results than BM-LHSU. Even the temperature gradient that exists during the charge or discharge period is gauged and recognized HC-LHSU as the best, followed by BM-LHSU and FM-LHSU. Since the onset of the phase transition zone reflects heat storage rate, the same is identified, and the charge period (sensible heat + latent heat) assessed to be 8000 s, 10000 s, and 12,000 s for HC-LHSU, BM-LHSU, and FM-LHSU, respectively. Further, an improvement in the average Nusselt number by 74 % and 67 % during the charge and discharge period respectively compared to the base model justified the honeycomb grill's role in augmenting the energy storage unit's performance.

Effect of novel fin distribution on the melting process of thermal storage units

Thermal storage units play a crucial role in storing excess energy and utilizing it when required. Enhancing the thermal performance of these units is of utmost importance for better thermal energy management. Therefore, this paper suggests introducing new fin distributions to decrease the thermal resistance of the storage unit and, thus, enhance the melting process. An octagonal tube and shell unit with nanoparticle-enhanced phase change material are suggested. Three considered fin distributions to improve the heat transfer inside the unit are straight dual-radial fins, tree-like fins, and roots-like fins. Also, since copper has high thermal conductivity, its nanoparticles are incorporated with the phase change material with different concentrations, i.e., 0, 4, and 8 vol%. The Galerkin finite element technique is employed to model the storage unit. The results show that using roots-like fins has a significant effect in reducing the phase change material melting time by 56% and 91% lower than dual-radial fins and tree-like fins, respectively. The higher nanoparticle concentration (8 vol%) can also improve the thermal storage unit performance by 28.9% compared to the pristine phase change materials. Thus, this study recommends using roots-like fins with nanoparticles in the thermal storage units to enhance thermal performance.

Performance comparison and enhancement of the thermal energy storage units under two expansion methods

To improve the performance of the basic thermal energy storage unit, two expansion methods, modular combination and linear structural expansion, are proposed and compared through numerical simulations. The impacts of the two expansion methods on the performance of the storage units are compared by investigating the thermal storage and release processes. Following the numerical study, both expansion methods can increase the heat storage capacity and airflow rates compared to a basic phase change material (PCM) storage unit linearly. However, the linear structural expansion method will increase the PCM melting time from 147 min to 367 min when the heat storage capacity of the basic unit is increased two times, which is about 2.5 times longer duration than using the modular expansion method. As for the heat release process, the results indicate that thermal release performance using linear structural expansion is lower than that of the modular combination along with a decrease in heat release efficiency of about 32.53 %. In conclusion the modular combination method is proved to be more efficient compared to the linear structural expansion method for improving the performance of the PCM storage units.

Unsteady conduction simulation during freezing of water in presence of nano-powders with different sizes

Increment in speed of solidification has been scrutinized in this work by means of dispersing nanomaterial. Altering the shape of container and loading additives can be assumed as effective ways for increasing performance of storage unit. The fraction (φ) and diameter (dp) of additives were assumed as variables. The main assumptions for mathematical models are ignoring convective terms and considering uniform concentration. The solutions of such unsteady form of equations have been derived based on finite element method combined with an adaptive grid. The longest freezing happens for pure water case and it takes 446. 45s. The middle magnitude of dp has the best performance and with dispersing such particles with a fraction of 0.04, the freezing time drops about 41.2 %. As dp increases, the period of freezing, firstly decreases about 19.96 % then it augments around 49.19 %. The needed time for the best case is 262.49s.

Simulation for performance of storage unit with analyzing water freezing in presence of nanoparticles

The influences of loading alumina with different range of diameter and concentration have been considered in this study. The single phase mixture for predicting the features of nanomaterial was incorporated and equations in unsteady form were presented. For deriving the solution of the model, Galerkin method was used incorporating implicit technique. Validation tests have been provided and reasonable accuracy has been obtained. The geometry has tree shape fins which can help to accelerate the process. Although increasing size of powder can augment the interaction of them, the freezing time increases if the size of particles increases greater than 40 nm. Adding nano-powders can decrease the required time by about 41.26 %. With the changing size of nanoparticles, firstly, freezing time decreases about 20.02 % then it increases about 49.33 %. The minimum required time for freezing is 3991.58 s and this period happens when dp = 40 nm and ϕ = 0.04.

Numerical simulation of the improvement of latent heat storage unit performance in solidification process by eccentric fractal finned tube

In order to explore the mechanism of eccentric fractal finned tube on enhancing the solidification performance of latent heat storage unit, the solidification of paraffin in latent heat storage unit of eccentric fractal finned tube was simulated by two-dimensional unsteady state. Under the consideration of natural convection, the heat transfer characteristics of eccentric rectangular fins and eccentric fractal fins are firstly studied, and then the improvement of solidification process by two local strengthening schemes with fins on the upper part and fins on the lower part is compared. Then the influence of fin angle is studied. Finally, the lower part of the secondary branch fin with an angle of 60° was selected to add a fin strengthening structure to further strengthen the paraffin solidification process in the latent heat storage of eccentric fractal fin. Concluded that compared with eccentric rectangular finned, eccentric fractal fin shorten the coagulation time by 41.2 %, upper add fin and lower add fin both local reinforcement schemes are made the whole process of solidification rate has increased, about 1000 s, the upper encryption fin make solidification rate increased by 16.7 %, the lower encryption fin make solidification rate increased by 50 %, the total solidification time of the lower fin is basically unchanged, while the structure of the upper fin reduces the total solidification time by 15.3 %. Three structures with fin angles of 45°, 60° and 90° were simulated and the total solidification time was shortened with the increase of fin angle. Compared with the original eccentric fractal fin structure, the solidification time of the final strengthened structure is reduced by 70 %.

Heat and mass transfer characteristics of charging in a metal hydride-phase change material reactor with nano oxide additives: The large scale-approach

Integrating metal hydride (MH) for hydrogen storage with phase change materials (PCMs) received increasing attention today to ensure effective thermal management in MH-storage reactors and reduce the operating cost of the process. This study revealed the first coupling approach (at large scale) of hydrogen storage in LaNi5 alloys with heat recovery by using a PCM loaded with nanoparticles (i.e. the MH-nano-PCM system) in a cylindrical MH-tank reactor (diameter: 1 m) equipped with four tubes of nano-PCM. Mass and heat transfer phenomena were computationally analyzed in the diverse regions of the reactor. The temporal temperature profiles (average and contours), the MH-hydrogenation efficiency, the velocity contours and PCM-liquid fraction were established in the presence (at 5% v/v) and absence of four types of nano-oxides (Al2O3, MgO, SnO2 and SiO2). Significant results were obtained. The nano-PCM system efficiently recuperates the heat lost from the exothermal absorption reaction; however, a slight reduction in the latent energy storage unit's performance is obtained compared to pure paraffin, probably due to the thermo-transfer resistant created by the nano-particles agglomeration during the melting cycle. The PCM-tube position plays a crucial role in the PCM melting rate, where the tube located above the H2-charging pipe melts more quickly than the other tubes.

Thermal efficiency analysis of the phase change material (PCM) microcapsules

The aim of the present study is to evaluate the thermal behavior of cylindrical modules in a thermal energy storage unit as a combined sensible and latent heat. A thermal energy storage unit is designed, fabricated, and connected to a cold and hot water supply at constant temperatures to monitor the performance of the storage unit. The thermal energy storage unit contains the cylindrical microcapsules containing paraffin waxes as a phase change material which is located inside an insulating cylinder storage tank. Water is used as a heat transfer fluid to transfer heat from a hot water reservoir to the thermal energy storage unit during the phase change material charging process and also during the discharging process water receives heat from the thermal energy storage unit. Charge tests are carried out at the constant temperature. Moreover, the effect of different inlet flow on storage unit performance is investigated. Data were analyzed using Design Expert software and regression analysis which indicated that the increase of charge inlet temperature and charge inlet flow leads to the increase of heat power, thermal performance of thermal energy storage unit, and output variables. In comparison to the heat storage system without phase change material, microcapsules phase change material can improve the heat power of the heat storage system. Also, based on the optimization process, the maximum thermal performance of 96.4% and the maximum heat power level of 1.7 kW can be achieved in the optimized condition of the charging inlet temperature of 75 °C, charging inlet flow of 1.8−4 m3/s, and discharging inlet temperature of 35 °C.

TES-PD: A Fast and Reliable Numerical Model to Predict the Performance of Thermal Reservoir for Electricity Energy Storage Units

The spread of renewable resources, such as wind and solar, is one of the main drivers to move from a fossil-based to a renewable-based power generation system. However, wind and solar production are difficult to predict; hence, to avoid a mismatch between electricity supply and demand, there is a need for energy storage units. To this end, new storage concepts have been proposed, and one of the most promising is to store electricity in the form of heat in a Thermal Energy Storage reservoir. However, in Thermal Energy Storage based systems, the critical component is the storage tank and, in particular, its mathematical model as this plays a crucial role in the storage unit performance estimation. Although the literature presents three modelling approaches, each of them differs in the considered parameters and in the method of modelling the fluid and the solid properties. Therefore, there is a need to clarify the model differences and the parameter influences on plant performance as well as to develop a more complete model. For this purpose, the present work first aim is to compare the models available in the literature to identify their strengths and weaknesses. Then, considering that the models’ comparison showed the importance of adopting temperature-dependent fluid and storage material properties to better predict the system performance, the authors developed a new and more detailed model, named TES-PD, which works with time and space variable fluid and solid properties. In addition, the authors included the tank heat losses and the solid effective thermal conductivity to improve the model accuracy. Based on the comparisons between the TES-PD model and the ones available in the literature, the proposal can better predict the first cycle charging time, as it avoids a 4% underestimation. This model also avoids overestimation of the delivery time, delivered energy, mean generated power and plant round-trip efficiency. Therefore, the results underline that a differential and time-accurate model, like the TES-PD, even if one-dimensional, allows a fast and effective prediction of the performance of both the tank and the storage plant. This is essential information for the preliminary design of innovative large-scale storage units operating with thermal storage.

Performance of Loaded Thermal Storage Unit with a Commercial Phase Change Materials based on Energy and Exergy Analysis

This work presents an energy/exergy analysis to investige performance of thermal storage unit which loaded with a commercial phase change material (Plus ICE H190). The influence of fluid parameters on the energy/exergy effectiveness was examined. The temporal changes of the energy and exergy rate and performace of the storage unit are obtained in the results. Latent heat principle is considered an efficient method to gain a higher effectiveness of system from an energy and exergy aspects. The fluid mass flow rate during charging and discharging periods were 2.50 kg/min and 1.26 kg/min, respectively. The results showed a significant increase of thermal resistance on the thermal storage unit performance. Fluid and phase change material show significant temperature difference on the rate of energy/exergy quantites and the time of melting or soldification. Ther results indicated that the average rate of energy and exergy were 1.3 kW and 0.54 kW, respectively. Wheras, energy and exergy average rate during discarging periods were 1.1 kW and 0.31 kW, respectively. Also, the global rate during the experimetal periods were about 84% and 54%, respectively.Article History: Received July 6th 2017; Received in revised form September 15th 2017; Accepted 25th Sept 2017; Available onlineHow to Cite This Article: Olimat, A.N., Awad, A.S., Al-Gathain, F.M., and Shaban, N.A.. (2017) Performance of Loaded Thermal Storage Unit With A Commercial Phase Change Materials Based on Energy and Exergy Analysis. International Journal of Renewable Energy Development, 6(3),283-290.https://doi.org/10.14710/ijred.6.3.283-290

Performance of Loaded Thermal Storage Unit with a Commercial Phase Change Materials based on Energy and Exergy Analysis

This work presents an energy/exergy analysis to investige performance of thermal storage unit which loaded with a commercial phase change material (Plus ICE H190). The influence of fluid parameters on the energy/exergy effectiveness was examined. The temporal changes of the energy and exergy rate and performace of the storage unit are obtained in the results. Latent heat principle is considered an efficient method to gain a higher effectiveness of system from an energy and exergy aspects. The fluid mass flow rate during charging and discharging periods were 2.50 kg/min and 1.26 kg/min, respectively. The results showed a significant increase of thermal resistance on the thermal storage unit performance. Fluid and phase change material show significant temperature difference on the rate of energy/exergy quantites and the time of melting or soldification. Ther results indicated that the average rate of energy and exergy were 1.3 kW and 0.54 kW, respectively. Wheras, energy and exergy average rate during discarging periods were 1.1 kW and 0.31 kW, respectively. Also, the global rate during the experimetal periods were about 84% and 54%, respectively.

Analysis and design of a drain water heat recovery storage unit based on PCM plates

This paper is focused on the detailed analysis of a PCM plate heat storage unit with a particular configuration, looking for the maximum contact area with the fluid (water) and the minimum volume to be used in a real household application. In that sense, a numerical study of the thermal and fluid dynamic behaviour of the water flow and the PCM melting-solidification processes, together with the thermal behaviour of the solid elements of the unit, has been carried out. On the other hand, an experimental set-up has been designed and built to validate the numerical model and characterise the performance of the heat storage unit. The purpose of the numerical and experimental study is to present a series of results to describe the heat storage unit performance in function of the time. Thus, after a preliminary design study three different cases have been simulated and tested. A 7.2%of discrepancy between numerical results and experimental data has been evaluated for the heat transfer. The PCM heat storage unit designed is capable to store approx. 75%of the thermal energy from the previous process wasted water heat, and recover part of it to supply around 50%of the thermal energy required to heat up the next process.

Experimental study on the thermal performance of a new type of thermal energy storage based on flat micro-heat pipe array

The thermal performance of an air-based phase change storage unit is analyzed and discussed in this study. The thermal energy storage uses flat micro-heat pipe array (FMHPA) as the core heat transfer component and lauric acid as phase change material (PCM). An experimental system is devised to test the heat storage–release property of the storage unit under different inlet temperatures and flow rates of the heat transfer medium. The performance of the storage unit and the melting/solidification curves of the phase change material are obtained based on extensive experimental data. Experimental results indicate that the flat micro-heat pipe array exhibits excellent temperature uniformity in the heat storage–release process, and the performance of the storage unit is efficient and steady.

Phase Change Material (Pcm)-Based Solar Air Heating System For Residential Space Heating In Winter

This study presents the analysis of phase change material (PCM)-based solar air heating system to achieve comfort conditions in a living space during winter season. The technical feasibility of PCM-based solar air heating system has been demonstrated, thus reducing the risks due to indoor air pollution caused by the use of fossil fuel or biomass combustion devices. The most sensitive parameters affecting the performance of storage unit are the melting point of storage material, mass of PCM, and airflow rate. The simulation results considering various flow rates and melting temperature of PCM indicate that, when melting temperature of PCM is equal to the comfort temperature of all the winter months, the storage unit performance is maximized for all the months during winter season. A new parameter, heating capacity of the PCM, has been introduced to illustrate the performance of the PCM storage.

Utilization of Latent Heat Storage Unit for Comfort Ventilation of Buildings in Hot and Dry Climates

In hot and dry climatic conditions of South Asia, summer night temperatures are low, and phase change material (PCM) based heat storage technique could be used as heat sink to reduce ambient air temperature during hot day times, as an alternate of current ventilation techniques for the building sector. This can help in reducing electricity consumption and consequently reducing green house gas emissions. This study presents the analysis of PCM storage unit using cooler night temperatures for charging of storage material and later acting as a heat sink for hot ambient air during day time in hot and dry climatic conditions. The influence of air flow rates and melting point of PCM on the availability of comfort temperatures at storage unit outlet has been studied. The results clearly indicate the feasibility of PCM storage unit as a heat sink to keep ambient air within comfort limits during the hot day time in summer season. When the PCM melting temperature is equal to the comfort temperature of the hottest summer month, the storage unit performance is maximized for all the months during the summer season.

Thermal performance of packed bed thermal energy storage units using multiple granular phase change composites

The present article reports on the utilization of multiple granular phase change composites (GPCC) with different ranges of phase change temperatures in a packed bed thermal energy storage system. Small particle diameter of GPCC allows simple mixing of two or three ranges of GPCCs in a packed bed for enhancement of storage unit performance. Experiments have been carried out to characterize the phase changing characteristics of two GPCCs chosen for this purpose. Packed bed column experiments have been carried out to provide basic understanding of the heat transfer process in the composite bed consisting of a mixture of GPCCs at different values of mixing ratio. A mathematical model has been developed for the analysis of charging and discharging process dynamics. Once validated, the model has been used to perform a parametric study to investigate the overall bed performance at different values of mixing ratio and Reynolds number. An optimization of the value of mixing ratio has been obtained based on the overall charging and discharging times as well as the exergy efficiency. It has been demonstrated that, as compared to the use of single GPCC, careful choice of the mixing ratio of GPCCs in a composite bed can result in a significant enhancement of the overall storage unit performance. As compared to the use of multiple sequential layers of GPCCs, using units composed of a mixture of GPCCs with an optimized mixing ratio results in a remarkable improvement of the unit performance without limitations on the charging and discharging directions during practical applications.

Study on performance of a packed bed latent heat thermal energy storage unit integrated with solar water heating system

In thermal systems such as solar thermal and waste heat recovery systems, the available energy supply does not usually coincide in time with the process demand. Hence some form of thermal energy storage (TES) is necessary for the most effective utilization of the energy source. This study deals with the experimental evaluation of thermal performance of a packed bed latent heat TES unit integrated with solar flat plate collector. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the solar collector to the storage tank also acts as sensible heat storage material. Charging experiments were carried out at varying inlet fluid temperatures to examine the effects of porosity and HTF flow rate on the storage unit performance. The performance parameters such as instantaneous heat stored, cumulative heat stored, charging rate and system efficiency are studied. Discharging experiments were carried out by both continuous and batchwise processes to recover the stored heat, and the results are presented.

Comparison of measured and predicted performance of heat storage unit packed with spheres of a local material

The present paper presents a comparison between the measured and predicted performance of a sensible heat storage unit. The storage unit is packed with spheres manufactured from a powder of certain type of Egyptiain clay (trade name “tafla”) produced at Abu-Siebera, Aswan. A special experimental set up was designed to predict the performance of the storage unit. The temperature distribution of the solid spheres was measured at different mass flow rates and at different time intervals. A comparison was made between these measured values and the corresponding values obtained using a numerical model based on finite difference techniques. The results showed a reasonable agreement between the measured and predicted temperature distribution. Finally, the pressure drop through the storage unit was measured and compared with the corresponding pressure drop calculated using two different empirical formulae.