Search

The key technology for the continuous supply of electricity from solar power plants is a thermal energy storage (TES) approach. The selection of the best storage system and the correct thermal storage material remains a significant challenge in solar power research and development. The thermocline TES system is a cost-effective choice for storing latent and sensible heat by comparing it to the liquid storage substance in a two-tank TES system. The study is performed to assess the thermal characteristics of thermocline tank structure by using a hybrid sensible latent heat storage system. The dispersion-concentric simulation studies were first examined using the MATLAB code, and afterward, the current findings of the research were verified. The major goal of this study is to look into and assess the effect of changing the sensible storage material layer of a hybrid sensible, latent heat storage system on the TES tank's thermal performance. The findings reveal that employing a sensible heat storage material with a high specific heat capacity, such as slag pebble, permits the TES tank to charge for the most extended duration feasible and discharge more stored energy with greater efficiency. The recovered energy of hybrid slag pebble phase change materials (HSPPCMs) configuration is 142.6 MWh, which is more significant than all other configurations examined. The HSPPCMs arrangement demonstrates the maximum capacity ratio and the utilization ratio of 82.39 % and 80.91 %. [ABSTRACT FROM AUTHOR]

One of the most common solutions currently available to meet future energy needs in the world is concentrated solar power (CSP) plants combined with thermocline thermal energy storage (TES) tank subsystems. The air rock thermocline TES tank asserts to be an effective and inexpensive TES subsystem for CSP plants. In this study, a discrete element method (DEM) combined with a numerical model of computational fluid dynamics (CFD) was adopted to investigate the thermal performance of a scale model of an air rock thermocline TES tank. The study is carried out to optimize TES thermocline tank's thermal behavior by changing the heat transfer fluid (HTF) inlet velocity. The DEM–CFD coupled model is validated against analytical and experimental data. The results show that the use of the distributor reduced the influence of the wall effect by distributing the HTF in a regular way as the fluid passes through it, especially at high inlet velocity. Moreover, the results show that each TES tank subsystem has a critical velocity at which the tank operates most efficiently. Furthermore, the results demonstrated that the maximum value of the overall cycle efficiency was equal to 70.15% at 10 m/s, while the minimum value was equal to 42.5% at 2 m/s. The highest capacity and utilization ratio are 81.31 and 72.81% at 16 m/s, while the lowest capacity and utilization ratio are 52.01 and 44.75% at 2 m/s. The pumping energy needed to overwhelm the pressure drop rises when the HTF inlet velocity increases. This study can provide an effective reference for the efficient operation regulation and optimal design of the thermocline tank. [ABSTRACT FROM AUTHOR]

A thermal energy storage (TES) approach is the primary technology for ensuring the continuous supply of electricity from solar power plants. In solar power research and development, selecting the best storage device and the right thermal storage content remains a major challenge. As compared to the liquid storage substance in a two-tank TES system, the thermocline TES system is a more cost-effective alternative for storing sensible heat. Centred on the concept of using a thermocline tank in concentrated solar power plants, the current study utilizes a range of solid storage materials as filling materials, with air acting as the heat transfer fluid. The major contribution of this research is to directly compare the thermo-economic efficiency potential of four storage materials (Quartzite, BOF-slag, Magnetite, and River rock) used in the thermocline storage tank in order to meet some design criteria of a CSP plant without the need for parametric studies. The thermo-economic performance of an air rock thermocline TES tank was investigated using a discrete element system combined with a numerical approach of computational fluid dynamics. The Quartzite presents the highest overall efficiency of 70 %, followed by the River rock with 61 %, and BOF-Slag equals 54 %, while Magnetite is the least in a row with 52 % overall efficacy. Based on thermal-economic performance evaluation, the results showed that the storage capacity of the Quartzite is greater by 37.5 %, 51.2 %, 21.2 % than BOF-Slag, River rock, and Magnetite. [ABSTRACT FROM AUTHOR]

In the present study, the phase change material (PCM) layer thickness of the top and bottom PCMs change gradually with constant the middle PCM layer thickness for the three-layers thermocline thermal energy storage (TES) tank. It has been studied using spherical capsules packed with three types of PCMs with different thermophysical properties. A transient two-phase dispersion-concentric (D-C) model is used to calculate the process of phase change inside pellets to identify the temperature allocation. The method of heat transfer among molten salt and PCMs capsules is extensively discussed, with multiple numerical results shown. The results show that the thickness of the PCM layer has a high impact on the thermal performance of the TES tank. As the layer thickness of the top PCM increases, the time required to discharge the thermocline TES tank increases. The (80 % high phase change material (HPCM) -10 % intermediate phase change material (IPCM) - 10 % low phase change material (LPCM)) configuration has 14.6 %, 27.2 %, and 46.8 % higher overall efficiency than (33.3 % HPCM - 33.3 % IPCM -33.3 % LPCM) configuration, (70 % HPCM - 10 % IPCM - 20 % LPCM) configuration, and (10 % HPCM -10 % IPCM - 80 % LPCM) configuration. In contrast, the (80 % HPCM - 10 % IPCM - 10 % LPCM) configuration shows the highest capacity and utilization ratio. [ABSTRACT FROM AUTHOR]

Solar tower power (STP) plants integrated with thermal energy storage (TES) subsystems are expected to be a potential solution to meet the world's future energy needs. Air rock bed TES subsystem emphasizes to be efficient and cheap storage for STP plants. In the present study, the discrete element method (DEM) coupled with the computational fluid dynamics (CFD) model are adopted to study the fluid flow and heat transfer process of an air rock thermocline TES tank. The study is carried out to investigate the thermal behaviour of the TES thermocline tank by changing the Reynolds number. The results show that the temperature difference between both the heat transfer fluid (HTF) and the spheres for charging cycle decreases with increasing of the Reynolds number, but also the total rate of heat transfer increases. The results illustrated that the difference in temperature between the HTF and the spheres for discharging cycle decreases with increase in the Reynolds number and this difference in temperature is less during the discharging cycle than the charging cycle. In addition, the Re = 1,200 case exhibit the optimized behaviour as it possesses the higher matching in temperature distributions of spheres with the temperature profiles of HTF. The Re = 400 shows reduced charging/discharging performance as the low rate of heat transfer between spheres and HTF. [ABSTRACT FROM AUTHOR]

The current paper investigates the cycle cut-off criterion on the thermal performance of the three-layers thermocline thermal energy storage (TES) tank system which is used in concentrating solar power (CSP) plants. The one dimensional transient dispersion-concentric (D-C) scheme is applied to calculate the phase change inside each capsule. Using MATLAB software, the numerical model equations have been figured out. Five different scenarios have been created to investigate the cycle cut-off criterion on the thermal performance of the TES tank. The results indicate that there are two important aspects to assess system performance which are the temperature distribution during the charging/discharging cycles and the time required to achieve equilibrium conditions. These aspects directly affect the overall power and external efficiency of the storage system and play a key role in understanding the system start up properties and provide insight into storage availability when designing the power cycle for CSP applications. It was also noted that the cycle times and the time required to achieve periodic conditions are very sensitive not only to the storage temperature difference but also to the cutting temperature difference. The difference in the duration of the charge cycle and the corresponding discharge cycle can be attributed to the consideration of a similar cut-off standard. [ABSTRACT FROM AUTHOR]

• The thermo-economic feasibility of the SPT station was investigated. • The influence of the location on the thermo-economics of the SPT station is evaluated. • The SPT station's thermo-economics are optimized. • An SM of 2.8 and a TES of 8 h were the best configurations for the STP station. Egypt is a sunbelt nation with plenty of solar resources and significant wasteland areas, particularly in its southern and western regions. Concentrating solar power technologies are tried-and-true renewable energy systems that use solar radiation to produce electricity in nearby nations. These technologies have the potential to reduce costs in the future. Comprehensive techno-economic research has not been conducted to assess the potential for the solar power tower technique in Egypt; instead, solar photovoltaic and parabolic trough systems are given the majority of the attention. The major goal of this article is to persuade the Egyptian government to pursue solar power tower technology and meet the accompanying difficulties. Using system advisor model software, six distinct locations were used to simulate a 100 MW plant for solar power tower technology. Based on a thorough technical solar power tower site evaluation research, these zones were examined. To achieve the lowest levelized cost of electricity (LCOE), thermal energy storage and solar field size optimization are carried out. The Benban location, with outputs of 521,228.8 MWh and 0.1130 $/kWh, respectively, has the greatest produced energy and the lowest levelized cost of electricity, according to the findings. The ideal design for the solar power tower plant was shown by the results to be a solar multiple of 2.8 with a thermal energy storage of 8 h. The solar power tower plant's lowest levelized cost of electricity might then be reduced, in accordance with the optimum configurations, to 0.1057 $/kWh. [ABSTRACT FROM AUTHOR]

The current research examines how increasing the thickness of the phase change material (PCM) layer impacts the thermal and economic behavior of the hybrid sensible-latent heat storage reservoir utilized in solar power plants in order to prevent temperature fluctuations at the end of discharge cycles. On the basis of two-phase dispersion-concentric equations, a detailed transient numerical analysis is developed. The mathematical model equations are computed using the MATLAB program, and the present numerical findings are validated. Numerical investigations are used to compare the proposed storage system to the sensible heat storage (SHS) system in the context of cost and efficiency. The impact of various performance evaluation indexes, including axial temperature allocation, thermocline layer degradation, charging time, discharging time, and overall efficiency, are investigated. The results showed that the (35% PCM-30% SHS-35% PCM) configuration possesses the most considerable thermocline thickness of 7.94 m at the charge period of 360 min, while the SHS case has 3.2 m thermocline thickness at the charge period of 420 min. Due to its optimized efficiency, reduced thermocline area, and comparatively low cost, the (15% PCM-70% SHS-15% PCM) configuration demonstrates a more viable choice among the considered cases. • The thermal performance of a hybrid sensible-latent heat storage tank is analyzed. • A numerical model is used for the thermo-economic evaluation. • Thermo-economic evaluation of increasing the thickness of the PCM layer. • The (15% PCM-70% SHS-15% PCM) configuration demonstrates a more viable choice. [ABSTRACT FROM AUTHOR]

Thermocline thermal energy storage (TES) technology that uses the molten salt as heat transfer fluid is cheaper than a traditional two-tank structure, owing to its composite design and use of inexpensive filler materials. Nevertheless, this TES type suffers from the significant disadvantage of low capacity and utilization ratio when it is integrated with concentrating solar power plants due to moderate charge/discharge cut-off values. The primary purpose of the current research is to investigate and evaluate the impact of the change charge/discharge cut-off values on the thermal performance of six different TES tank configurations. First, the equations for the dispersion-concentric model were approached through the MATLAB program, and then the present research results are authenticated. The results show that the thermocline zones shrink when the charge cut-off value rises, and the discharge cut-off value reduces because a higher charge cut-off value and a smaller discharge cut-off value permit a longer charge/discharge time. Moreover, when the cut-off value of the charge/discharge changes simultaneously, the combined sensible-latent heat storage configuration has the highest capacity ratio, utilization ratio, recovered energy, and overall efficiency, which equals 90.55%, 83.3%, 147.2 MWh, 91.3%, respectively, at low charge cut-off value. • The thermal performance of the different thermocline tank configurations is analyzed. • The SHS configuration demonstrated the shortest charge/discharge time of 239/207 min. • At a higher charge cut-off value, the CSLHS case has the highest capacity ratio of 90.55%. • The MLPCMs-4 case has the highest recovered energy of 183.2 MWh with a lower charge cut-off value. [ABSTRACT FROM AUTHOR]