Heat Storage Medium Research Articles

Comparative Thermal Performance Analysis of Circular and Triangular Embossed Trapezium Solar Cooker with and without Heat Storage Medium

Comparative Thermal Performance Analysis of Circular and Triangular Embossed Trapezium Solar Cooker with and without Heat Storage Medium

Comparative study on conventional and phase change material (PCM) based solar desalination still using low-pressure water as a heat storage medium.

Over the years, solar desalination is a renewable energy-driven method to produce freshwater from saline/ brackish water. Since solar radiation is available only in the daytime, many studies have been undertaken to store solar energy using phase change material (PCM). The aim of this study is to compare the two solar stills (still I as a conventional solar still and still II as a PCM-integrated solar still). In still II, using low-pressure water as thermal energy storage, PCM in a copper tube with a 1 liter capacity has been additionally installed than still I. Five trials have been conducted to compare the performance and yield between stills I and II, with various factors during the experiment. Remarkably, three distinct vacuum pressures - 712mmHg (for trials 1, 2, and 3), - 690mmHg (for trial 4), and -660mmHg (for trial 5) were used for the investigation to compare the performance of PCM-based solar still with conventional solar still among five trials. Finally, at a vacuum of -712mmHg and 175ml of water poured inside the low-pressure system, the distillate yield obtained from still II is 9.375% higher than the yield of still I.

Evaluation and optimisation of hybrid sensible-latent heat thermal energy storage unit with natural stones to enhance heat transfer

Latent heat thermal energy storage improves the utilization efficiency of renewable energy. Phase change materials (PCMs) commonly suffer from low thermal conductivity and many heat transfer enhancement methods have been developed. However, conventional methods need additional material preparation and processing, which increases the cost and makes them less environmentally friendly. In the current study, natural stones are used to enhance the heat transfer of the PCM in a shell-and-tube unit, forming a hybrid sensible-latent heat storage configuration. Namely, stones, which are widely accessible, low-cost and environmentally friendly, not only act as sensible heat storage media but as the thermal enhancer of the PCM. Results indicate that the energy storage rate of cases with 25 mm-sized stones increased by 8.3%–92.6%. The case with a filling height of 72.8 mm is superior owing to the high energy storage rate and large total stored energy. The stone size rarely influences the total stored energy that increases almost linearly with the void fraction, while it affects the energy storage rate significantly. Cases with 20 mm and 40 mm-sized stones generally have a higher storage rate. Finally, the mechanism is analysed.

Solid state sensible heat storage technology for industrial applications – A review

Cost effective methods of storing heat can be an enabling technology to promote utilization of solar thermal and heat recovery systems for industrial applications. The technology can reduce the use of conventional heat sources like coal and gas by offering a competent option of producing industrial process heat. Solid state sensible thermal energy storage (TES) systems have emerged as a viable method of heat storage especially with the prospect of using natural stones as heat storage media which are cheap, locally available, and harmless to the environmental. This study reviews research work on solid state sensible heat storage systems focusing on the solid materials being used for heat storage applications. Also, the review covers numerical and experimental investigations that have been done to evaluate different design parameters and thermal performance of solid-state TES systems. In addition, the environmental impact of adopting this heat storage technology is also discussed. The study has revealed that, there are areas that still need further research, and these include, experimental characterization of thermal properties of natural solid materials with potential for heat storage purposes, investigations on improving thermal performance as well as durability of solid-state sensible TES systems.

Characteristics and performance investigation of solar AES system with novel flat-plate collector-evaporator integrated unit capable of salinity wastewater thermal self-storage

Fluctuations and variations in the solar irradiation intensity, both regular and irregular, seriously damage the performance and effectiveness of conventional solar evaporation systems for salinity wastewater recovery. Furthermore, a novel flat-plate collector-evaporator integrated unit with thermal self-storage of salinity wastewater is designed and implemented in the solar air evaporating separation (AES) system. Comprehensive operating characteristics and performance investigations are conducted through the construction of the experimental system and the establishment of the multi-process coupling model. Results of experimental and simulation investigations indicate that this function of wastewater itself as heat-storage medium in the unit actually helps to counteract the reduced system performance and energy efficiency caused by fluctuations in solar irradiation, especially under overcast weathers, when average EE, GOR and ηsys of this system can still be maintained at 3.83 kg/kWh, 2.02, 59.78 %. What's more, this system supports effective 24-hour operation mode under variable environmental conditions, while maintaining superior wastewater recovery performance energy efficiency. Under variable conditions, including night time and cloudy weather, the average GOR, ηsys and ηex,sys,daily for 24-hour operation can be up to 4.49, 62.2 % and 3.95 %, while the average OPEX is only 0.0089$/kg and the OVEX for 15-year service lifetime is only 0.0142 $/kg.

Application of Copper Oxide Nanofluid and Phase Change Material on the Performance of Hybrid Photovoltaic–Thermal (PVT) System

The objective of the study is to investigate the thermal, electrical, and exergetic performance of a hybrid photovoltaic–thermal (PVT) system under the influence of copper oxide (CuO) nanofluid and phase change material (Vaseline (petroleum jelly)) as a heat storage medium. A mathematical model was developed with the help of various energy-balance equations over the layers of the hybrid system. The performance evaluation of the PVT system was performed using pure water, CuO-water nanofluid (0.2 and 0.4% weight fractions), and CuO-water nanofluid 0.4% weight fraction with Vaseline as a phase change material. The results of the overall analysis show that the performance of the PVT system is better using CuO-water nanofluid (0.4% wt. fraction) with PCM as compared to the water-cooled PVT system and CuO-water nanofluid. The results obtained from the study show indicate that the cell temperature of PVT was reduced by 4.45% using nanofluid cooling with PCM compared to a water-cooled PVT system. Moreover, the thermal, electrical, and overall efficiencies improved by 6.9%, 4.85%, and 7.24%, respectively, using 0.4% wt. fraction of CuO-water nanofluid with PCM as compared to PVT water-cooled systems. The performance of the PVT system was also investigated by changing the mass flow rate (MFR). The increase in mass flow rate (MFR) from 0.05 kg/s to 0.2 kg/s tends to enhance the electrical and overall efficiencies from 12.89% to 16.32% and 67.67% to 76.34%, respectively, using 0.4% wt. fraction of CuO-PCM as fluid.

Rapid evaluation of the particle-erosion resistance of Al2O3 ceramics, composites, and coatings using a resonant acoustic mixer

ABSTRACT The solid particle technology usage in concentrated solar power plants as direct heat absorption and storage medium necessitate well selection of the materials for the components such as transport and sluice systems, which are in direct contact with moving and falling hot particles up to 1500 ˚C. Beyond mechanical properties, chemical inertness and high-temperature stability, abrasion/erosion resistance are one of the key properties, for which, there is no easy-applicable and rapid test method exist enabling controlled lab-scale parametric studies. A novel particle impact test was established using a resonance acoustic mixer, in which ceramic particles are strongly accelerated and collide with the ceramic surface within a closed vessel. After determination of the most representative parameters such as ceramic ball size, vessel diameter, and retainment/removal of debris, selected experiments were conducted on three candidate materials aimed to be used as high-temperature transport/port systems; dense C 799 Al2O3, porous water-plasma sprayed Plascera-type Al2O3 and WHIPOX-type Al2O3/Al2O3 ceramic matrix composites with porous matrix; with and without porous protective Al2O3 coating. The distinct mass loss behaviour of candidate materials highlighted the viability of the test method and the relevance of microstructures of porous Al2O3 materials on abrasion resistance.

Experimental investigation of salinity gradient solar pond with nano-based phase change materials

ABSTRACT Heat energy storage is pivotal in modern times. However, the technology to efficiently stored heat energy is still in the research stage. Heat energy storage is possible through phase change material, exothermic chemical reactions, and solar ponds. The latter uses a natural phenomenon that relies on solar Energy and convective heat transfer. Solar ponds can store more heat energy throughout the day than other processes and meet higher energy demands. The working principle of a typical solar pond can be adopted to develop a compact setup that can store sufficient heat energy to meet the heat energy demand of a small family. Salinity gradient solar ponds are used for heat storage to meet the demand of rural and urban communities in arid and semiarid zones around the globe. Often the solar ponds are constructed on the ground by storing a large volume of salt water. The performance of the solar pond is affected by the intensity of solar radiation. In this study, a compact solar pond is constructed using aluminum plates and a glass cover. Sea water was used to store solar radiation in this experiment. The experiment was carried out in South India during the winter season when the intensity of solar radiation was minimum. The study aims to determine the performance of the solar pond and its thermal properties under low sunshine. Heat storage mediums comprising paraffin wax and additives of nanoparticles of graphene and carbon nanotubes were used to enhance the heat storage capacity of the solar pond. It was found that compared to the simple salinity gradient solar pond, the heat storage medium with carbon nanotube nanoparticles increased the maximum temperature attained by 26.5%. The carbon nano tubes infused phase change material increased the heat transfer, heat transfer coefficient, and the heat stored in the saline water by 244%, 713%, and 83.3%, respectively. It is concluded that the carbon nano tubes and phase change material augmented the performance of the solar pond even while the intensity of solar radiation was low.

Thermal Energy Storage Capacity of Composite Solid Desiccant Used In Sun Drying Applications Using Paraffin Wax

Abstract: Systems for storing thermal energy have become more important in solar thermal applications in order to supply the energy during overcast and gloomy hours. The capacity of a solid desiccant made up of 60% bentonite, 10% calcium chloride, 20% vermiculite, and 10% cement on a dry weight basis paired with a latent heat storage medium made of paraffin wax is examined in this study. Solid desiccant and paraffin have volume percentages of 90: 10, 80: 20, and 70: 30, respectively. The hollow cylindrical solid desiccant mould is filled with paraffin wax, which has a latent heat of fusion of 253 kJ/kg and a melting point of approximately 61.6 degrees Celsius. An experiment is conducted at air mass flow rate of 0.01, 0.02, and 0.03 kg/m2s with temperatures of 40, 50 and 60OC. The heat storage and retrieval capacity of 80% solid desiccant with 20% paraffin wax at 50oC and 0.02kg/m2s show the better results which are suitable for solar drying.

Performance investigation of a modified single-basin solar distiller by augmenting thermoelectric cooler as an external condenser

Harvesting freshwater from saline and seawater using solar energy has proven a significant impact in recent times. The present study aims to investigate the performance of the solar desalination system by incorporating glass reflectors, heat storage media, and a thermoelectric cooling system with a single-basin-type distiller. Accordingly, the objective of the study is to improve the performance of the solar distiller in terms of freshwater production and efficiency compared to a conventional setup. Moreover, the designed unit was tested under the environment of the Western part of India (Mehsana-23.5880° N, 72.3693° E) for 19days in the months of May and June 2022. The maximum daily productivity observed during the day was 2.5l at an average solar radiation of 1200 W/m2, which was 1.23 times higher than its conventional counterpart. Similarly, the energy efficiency showed a maximum improvement of 23.73%. At the middle of the day, i.e., maximum performance condition, the exergy efficiency was doubled with current modifications. Solar radiation and ambient temperature were found to be the most critical parameters that influence performance. Modifications also increase the % off sunshine hour productivity compared to sunshine hour from ~ 10 to 11% to ~ 20.8 to 24%, respectively. The cost of water distillation for the proposed solar still was found as 0.037 $/l/m2,s and the payback period was estimated as 2.27years. The overall results indicate the positive influence of the modifications; hence, this type of setup is feasible for implementation on the field in harsh and coastal line areas. However, modified single-basin solar still needs extended field study to realize the full potential of the modifications.

Techno-economic analysis of multi-tower solar particle power plants

Solar tower systems using solid particles as heat transfer and storage medium promise to achieve, in combination with advanced power cycles, lower levelized cost of electricity (LCOE) than state-of-the-art concepts. In this study the cost potential of a multi-tower solar power plant with centrifugal particle receiver is evaluated. Most of the underlying assumptions were chosen in accordance with those specified within the US-DoE Gen3 project “G3P3”. For the power block a high-efficiency supercritical CO2 system with 100MWe was assumed. The solar subsystem is built from 12 identical solar tower modules, each with heliostat field, tower, receiver and storage. The nominal thermal power of each module is 41MWth.Since the cost assumptions for the tower and the heat exchanger (HX) are still relatively uncertain, different correlations were used representing optimistic and conservative cases. For the particle receiver two outlet temperature levels were investigated, namely 800 °C and 1000 °C.The results of the techno-economic analysis indicate a strong impact of the cost assumptions for the primary heat exchanger and the tower. With 800 °C as particle outlet temperature, the estimated LCOE range from $56.18/MWh (optimistic values for tower and HX cost) to $67.30/MWh (conservative values for tower and HX cost).Increasing the particle outlet temperature to 1000 °C results in a significant reduction of LCOE (about 12% for the optimistic cases, down to $50.46/MWh). The reason for this is the significant reduction of heat exchanger area, particle inventory and particle mass flow, resulting from the larger temperature difference in the particle system. However, operating the system at such elevated particle temperatures will require some modifications to the components that are not fully reflected in the used cost correlations yet. Nevertheless, the results propose further investigation of this option. All in all the results indicate a clear potential to achieve the SunShot goal of less than $60/MWh.

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

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

Analysis of energy storage materials for developments in solar cookers.

Solar energy is accessible freely and can be utilized for many household and industrial applications. The consumption of solar energy for cooking applications has found significant success. Various innovations have been employed in facilitating cooking during off-sunshine hours. Thermal energy storage helps in overcoming the fluctuations in the supply of energy required for cooking during different time periods of the day. This study focuses on the different types of thermal energy storage mediums that are currently utilized in solar cooking. Primarily, oils and pebbles are most commonly used as sensible heat storage (SHS) while organic phase change materials (PCMs) are used as latent heat thermal energy storage materials (LHTES). The properties and performances of various SHS and latent heat storage (LHS) mediums have been compared for their suitable utilization. SHS materials are cost-effective but have lower thermal gradient compared to LHTES materials. The energy storage capability of LHTES is high while degradation with the increasing number of charging and discharging cycles is also considerable. The melting point should be close to the utilization temperature for being used as LHTES as thermal diffusivity of the materials greatly influences the performance of solar cookers. The cooking time is lower for solar cooking systems equipped with energy storage compared to non-equipped cooking systems. It is recognized that the use of energy storage has been proved as a huge advantage to solar cooking systems, however, the design, and heat transfer characteristics of the cooking vessel along with the storage material type and volume must be optimized in order to make this technology more influential.

Numerical and experimental investigation on the melting heat transfer of nanographene-enhanced phase change material composites for thermal energy storage applications

Phase change materials (PCMs) low thermal conductivity limit the performance of latent heat thermal energy storage systems. To enhance the thermal conductivity of the heat storage medium, highly conductive additives could be added to the base PCM. Hence, the present work aims to perform numerical and experimental investigations on the melting heat transfer of the PCM (OM 65) loaded with highly conductive graphene nanoparticles (GNPs) at weight fractions of 1%, 2%, and 3%. Based on the aforementioned weight fractions of graphene nanoparticles in the PCM, the nanographene-enhanced PCM (NPCM) composites are named NPCM 1, NPCM 2, and NPCM 3 respectively. The temperature-dependant thermal conductivity and dynamic viscosity were measured. A transient heat transfer during the melting of the PCM and NPCMs in a two-dimensional rectangular domain heated from the bottom-up configuration was considered for the numerical study. The base temperature was maintained at a constant temperature (Th = 70 °C), and the remaining walls are adiabatic. The transient variation of liquid fraction and temperature were presented. The PCM and NPCMs are experimentally studied using the proposed three-dimensional rectangular test section with twenty-four thermocouples and a temperature logger. Compared to the base PCM, the reduction in melting time from the numerical and experimental study was 37.5% and 36.5% for NPCM 3. It was evident that adding GNPs to PCM enhances its thermal conductivity. However, the higher concentration of GNPs could drastically increase the NPCMs viscosity, as well as cause agglomeration and sedimentation of GNPs during melting. Therefore, adding a maximum of 3wt% GNPs into the PCM was recommended.

KARAKTERISTIK PENYIMPAN KALOR LATEN PADA PARABOLIC MIRROR DISH

Storing heat in the form of latent heat is a good method, because it is able to store a large amount of heat energy with a small volume of storage media. The use of paraffin as a heat storage medium has many advantages, including thermal stability, non-toxicity, no degradation, and high latent heat storage capacity. This study uses a parabolic mirror dish as a collector of solar thermal energy, equipped with a hinged holder that can be adjusted so that it points to the sun's position from morning to evening, the collected energy is stored in thermal storage using paraffin as a storage medium. The research was conducted from 09.00 WIB to 24.00 WIB, the research location was on the Ronggolawe College of Technology campus. The results showed that the highest temperature obtained in paraffin as a heat storage was 112 oC, while the duration of storing until 24.00 WIB was still able to maintain the temperature at 36 oC.

Research on dimensionless structure size of coil heat exchanger in heat discharging process of molten salt single tank heat storage system

• Optimum dimensionless size of coil heat exchanger was studied by simulation. • The optimal size of heat exchanger appears under the combined action of vortex and molten salt flow rate. • When the dimensionless pitch L/d =4, the heat exchanger has the best heat discharging performance. • When the dimensionless pitch is the best, the optimal dimensionless diameter is 0.25. There has been an increasing attention on single-tank thermal energy storage, attracted by the low cost, high efficiency and compactness in the operation. However, the most researches on single-tank thermal energy storage focused on the way of heat discharging and the arrangement of heat exchangers. Few studies on the dimensionless size of heat exchanger, which is important for the design of single-tank thermal energy storage, were carried out. In order to obtain higher heat exchange efficiency and design criteria of coil heat exchanger, the optimal dimensionless size of heat exchanger is studied by numerical simulation. The results show that both the dimensionless pitch and the dimensionless pipe diameter of the coil heat exchanger have a great influence on the heat discharging performance when the air is used as the heating medium and the molten salt is used as the heat storage medium. With the change of dimensionless pitch, the heat discharging performance and the flow field of molten salt are affected. When the dimensionless pitch L / d = 4, the heat discharging power and heat release are the highest. At this time, the temperature and flow field of molten salt are evenly distributed, and no temperature stratification and vortex are formed. When the dimensionless pipe diameter is changed on the premise of the optimal dimensionless pitch, the heat discharging power increases first and then decreases with the increase of dimensionless pipe diameter. When the dimensionless pipe diameter d / a =0.25, the molten salt flow rate in the single tank is relatively large and no vortex hindering heat transfer, and the heat discharging performance is the best. Therefore, under the joint action of molten salt velocity and vortex, the optimal dimensionless pitch and pipe diameter appear. The research results provide a theoretical basis and an example for the design of single tank energy storage system.

EXPERIMENTAL STUDY ON HEAT STORAGE AND RELEASE OF EG/Li2CO3-Na2CO3 HIGH-TEMPERATURE PHASE-CHANGE HEAT STORAGE UNIT

In this paper, a shell-and-tube high-temperature phase-change heat storage unit used in solar high-temperature phase-change heat storage systems was designed and manufactured by using 5:95 expanded graphite EG/Li&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3&lt;/sub&gt;-Na&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3&lt;/sub&gt; as heat storage medium. The temperature distribution, heat exchange efficiency, and energy efficiency of the heat storage unit were studied by testing the heat storage and heat release processes. It was found that a thermostatic platform appeared in the lateral temperature distribution, and a distinct layered distribution appeared in the longitudinal temperature distribution. When the heating power of the heat storage unit is 640 W, the exothermic air flow rate is 400 L/min, and the phase change material was completely melted, the total heat storage and latent heat of the phase change material are 12,321 kJ and 4466 kJ, respectively. The proportion of the latent heat was 0.36, heat storage efficiency and heat release efficiency are 0.57 and 0.47, respectively. In addition, it was also found from the experiment that the greater the heating power, the higher the heat storage efficiency of the heat storage unit, and the greater the heat release air flow, the higher the heat release efficiency.

Investigation and optimization of design parameters for the thermal performance of a flat-plate solar air heater with sensible heat storage medium

Investigation and optimization of design parameters for the thermal performance of a flat-plate solar air heater with sensible heat storage medium

Performance analysis of solid heat accumulator used in tower solar thermal power generation system

In recent years, solar energy, wind energy and other new energy sources have been highly praised, especially solar energy, which is considered as one of the cleanest renewable new energy sources, and solar thermal power stations have been built in many countries. Tower solar photothermal power generation is a heat absorber that reflects sunlight to the top of the tower through heliostat field. Molten salt absorbs heat through the heat absorber, heats water supply and promotes thermal power generation. However, solar energy is intermittent and unstable, so the tower solar thermal power station is equipped with heat storage molten salt tank. Solid heat storage technology has the advantages of cheap heat storage medium, no harm to the environment, strong reliability and operability of the system, and can provide cost-effective heat storage solutions for industrial process heat energy and power generation. In this paper, the molten salt tank is replaced by a solid heat accumulator. After the molten salt absorbs heat during the day, part of it heats the heat accumulator through the unit tube in the heat accumulator to store the heat in the heat accumulator, and the other part heats the water to promote the steam power cycle. At night, the heat accumulator heats the molten salt to release heat, which continues to promote the steam power cycle. In this paper, CFD software will be used to numerically simulate the change of temperature characteristics inside the solid regenerator with the time of heat storage and release, and draw the temperature nephogram and change curve.

Performance improvement and investigation of radiation heat transfer of chloride salt as high-temperature heat storage medium

• Synthesis of carbon doped molten salt composites by reaction method. • High absorptivity material combined with translucent molten salt. • Research on radiation heat transfer based on Finite Element Method (FEM). • Molten salts exhibit good thermal conductivity and radiative properties. The development of solar phase change thermal storage technology is significant for the efficient use of energy. In this study, molten chloride salt was used as a high-temperature phase change thermal storage material to improve the heat transfer performance of the chloride salt by reacting citric acid with sodium chlorite to generate a flaky carbon morphology in the molten salt. The results indicated that the carbon generated by the reaction was uniformly distributed in the molten salt matrix, and the modified molten salt obtained a high latent heat of phase change with a maximum latent heat of phase change of 227.3 J·g –1 , which was 13.7% higher than that of the undoped molten salt, and the maximum thermal conductivity could reach 2.313 W·m –1 ·K –1 , which effectively improved the applicability range. In addition, the combination of ANSYS simulations and the constructed temperature measurement platform showed that the radiation heat transfer effectively improved the temperature distribution of the molten salt in the high-temperature stage. This study may promote the research of the heat transfer behavior of molten salt at high temperature and play an important role in concentrated solar power generation.