It has been always a daunting task to develop thermal systems with a wide range of thermochemical properties and high stability. It presents a significant challenge, especially when aiming to utilize ...them for heat storage and transfer applications. In this regard, the thermal characteristics and thermal stability behaviour of molten salt mixture as a heat transfer fluid (HTF) at high temperatures were explored. A novel ternary eutectic salt mixture (base mixture) made of cuprous chloride (CuCl), potassium chloride (KCl) and sodium chloride (NaCl) was investigated as HTF for thermal energy storage (TES) system with a range up to 653 °C in a concentrated solar power (CSP) plant. To extend the temperature span and stability, the effect of an additive was investigated. Different compositions were studied in detail concerning the properties and stability regarding the additive. The molten salt with 7 % CaCl2 additive improved thermal stability and operating temperature from 653 °C to 700 °C. The transport characteristics and thermal stability of the eutectic mixture with and without the additive were measured by high-temperature thermal analyzers. The results indicated that the melting temperature decreased and the average specific heat capacity considerably increased with the addition of CaCl2 additive compared to the ternary chloride base mixture. As the temperature increased, the eutectic salt mixture exhibited a reduction in viscosity and density. The viscosity and density of the salt mixture with and without the additive were almost uniform at 700 °C. The average thermal conductivity of the ternary salt mixture with and without additives was 0.72 W/(m°C) which is much more than that of Solar and Hitec salts. In a 100 h experiment of long-period isothermal stability, the eutectic salt mixture showed less than 4 % weight loss at 700 °C. It was defined as the highest operating temperature at which the eutectic salt mixture remained stable. The stability and recyclability of the salt mixture were confirmed through the short-period stability test. The effect of the CaCl2 additive on thermal stability of base salt mixture was analyzed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) techniques. According to the results, this novel eutectic salt mixture had outstanding thermal stability up to 700 °C and could be employed as a viable TES material in CSP plants.
•CuCl–KCl–NaCl eutectic mixture with a low melting point (144 °C) and high thermal stability (658 °C) was investigated.•Addition of 7 % CaCl2 reduced the melting point to 138.3 °C and improved thermal stability to 700 °C.•The proposed salt mixture has an excellent operating temperature range of 200–700 °C.•The long and short period thermal stability exhibited excellent stability and recyclability up to 700 °C.
•Advancement in solar thermal technologies and industrial process heating system.•Design and integration of solar heat in the industrial process.•Prospects of solar process heating systems in ...industries.
Energy is the essential need for the development, modernization and economic growth of any nation in the industrial sector. About 32–35% of the total energy of the world is used in the industrial sector. Solar thermal energy application is an initiative towards the sustainable and zero-carbon energy future. Solar thermal collectors are recognized as promising alternatives for fossil fuels in the industrial sector for process heat due to energy security, economic feasibility and environmental benefits. This work is an extensive compilation and review of the recent literature concerning research works carried out to solar thermal collectors and its industrial applications, global advancements in solar thermal technologies, collectors and the solar thermal energy storage system with a focus on the sun tracking system, thermal performance, and modeling techniques. In this review paper, current industrial process-heat systems are classified based on solar collector technologies and heat demand temperatures for the identification of typical applications for solar process heat. These classifications are pertinent to every country within the same industry type along with similar weather and economic conditions. Moreover, future prospects to integrate solar heat in the heat supply level of an industrial company in Pakistan is outlined for a sustainable energy system. It is found that solar thermal technologies can be used for a variety of industrial applications for sustainable energy system in industries and these should be used for industrial applications which are more compatible to be integrated.
•Performance of GD-NeLHTSU is analyzed by using Al2O3 nano-embedded TES.•Specific moisture extraction rates are 1.37 and 1.20 kg/kWh, with and without nanoparticles.•Average exergy efficiencies of GD ...were 3.45% and 2.74% with and without nanoparticles.•Energy payback time is between 2.34 and 2.92 years.•Mean annual CO2 emission is between 33.04 and 34.28 kg/year.
In this study, influences of integrating nanoparticles into paraffin-based latent heat thermal energy storage system on the thermal and drying behaviors of a greenhouse dryer have been analyzed. The major goal of this survey is improving the drying performance of a greenhouse dryer by employing nano-embedded latent heat storage unit. In this regard, two even-span greenhouse dryers have been produced and modified with paraffin-based and Al2O3 nano-embedded paraffin-based thermal energy storage units. Tests have been conducted at two flow rates that are 0.010 kg/s and 0.016 kg/s. According to the findings, average specific moisture extraction rates for the systems with and without nanoparticles were attained between 1.01 and 1.37 and 0.83–1.20 kg/kWh, respectively. Average exergy efficiency metrics were found as 3.45% and 2.74%, respectively in the test done at 0.016 kg/s flow rate for the greenhouse dryers with and without nanoparticles. These values were found as 3.01% and 2.40%, respectively in the test conducted at 0.010 kg/s. In addition, energy payback time, mean annual CO2 emission and net CO2 mitigation in lifetime values were obtained between 2.34 and 2.92 years, 33.04–34.28 kg/year and 8.45–9.08 tons, respectively. Results indicated the successful utilization of Al2O3 nanoparticle-embedded latent heat storage unit in a greenhouse dryer.
Intelligent design and operation optimization allow energy systems to take advantage of the flexibility that multi-generation provides. This study proposes a basic solar-driven system integrated with ...thermal energy storage for round-the-clock energy harvesting. A modified configuration is then designed incorporating innovative multi-heat recovery approaches to increase the capacity and product diversity of the basic system. The modified system is able to cover vital urban utilities such as electricity, fresh water, cooling, and hydrogen throughout the day. To overcome the time-consuming procedure of dynamic techno-economic simulation as well as the limitation of commercial engineering equation solvers for tri-objective optimization, a deep learning approach is developed to reduce the computational complexity and improve the analysis accuracy. In this regard, the trained neural networks play an intermediary role in coupling the developed code with the MATLAB optimization toolbox. A comparison between the modified and conventional configurations indicates that implementing the multi-heat recovery approach results in a 29% increase in power generation while only increasing the overall system cost by 1.97%. From an economic perspective, the Sankey diagram depicts that the storage unit with a cost rate of 12.25 $/h accounts for 6.77% of the plant's cost rate, which enables the system to operate continuously. According to the sensitivity analysis and contour plots, the number of collectors significantly affects the total cost rate and fresh water production capacity while it has no tangible effect on the exergy efficiency.
•A novel multigeneration system with thermal energy storage is designed.•A modified configuration with heat recovery is introduced to boost the capacity.•The comparative study indicates a 17.6% improvement in the power generation.•A dynamic simulation code is developed based on meteorological data.•A deep learning techno-economic optimization is applied to the system.
In this paper, the paraffin/sepiolite composites were fabricated as novel shape-stable phase change materials (SSPCMs) by vacuum impregnation for thermal energy storage. The structure-property ...relationships and comprehensive performance of sepiolite-based composite SSPCMs prepared with/without treatment of sepiolite from three mineral deposits were investigated. Compared with the natural sepiolite (SEP), the sepiolite after the purification and acidification treatment (TSEP) is a more suitable supporting carrier for paraffin wax. The prepared paraffin/TSEP composite SSPCM exhibits a significant promotion in absorption mass of paraffin and phase change latent heat. The maximum increase in latent heat of melt and crystallization is 78.32 % and 77.47 %. Simultaneously, the prepared sepiolite-based SSPCMs can reach up to 35.18 % paraffin loading. Its highest latent heat of melting and freezing is 60.12 J/g and 57.09 J/g, respectively, and the relative enthalpy efficiency is as high as 94.45 %. In addition, the sepiolite-based composite SSPCMs show good thermal stability and chemical stability according to the thermal cycling test. Moreover, it is demonstrated that sepiolite-based SSPCMs can slow down the spread of heat by absorbing heat energy and have reliable energy storage and temperature regulation performance. Therefore, the inexpensive and abundant sepiolite can be applied in phase change materials for waste heat recovery and temperature regulation.
•Paraffin/sepiolite phase change material was prepared by vacuum impregnation.•Sepiolite from three mineral deposits was utilized as support material.•The latent enthalpy of the PCM was improved by acid activation of sepiolite.•The PCM exhibits good phase transition performance and thermal stability.
•PCM microcapsules was fabricated using a novel thin film UV reactor.•UV treatment accelerates the process of microencapsulation at low temperatures.•PMMA m-PCMs demonstrated the highest ...microencapsulation efficiency, and PCM content.•Adding cross-linking agents mitigated sub-cooling and improved microencapsulation efficiency.
Phase-change materials (PCMs) have shown great promise for energy management in buildings and gained attention in the field of sustainable and energy-efficient construction. However, to fully utilize PCMs, their proper containment is vital. In this study, a photo-induced polymerization process using a new thin film UV reactor at room temperature for PCM microencapsulation in polymer shells of different acrylate-based monomers was investigated. Four different acrylate-based monomers were investigated: namely, methyl methacrylate (MMA), ethyl acrylate (EAA), butyl acrylate (BAA), and tert-butyl acrylate (TBMA). Commercial Rubitherm’s RT21 PCM (Tpeak,melting ∼ 21 °C and ΔH = 123 kJ/kg) and Irgacure® 819 as a photosensitive initiator were used. When MMA or EAA were used, scanning electron microscopy (SEM) images revealed smooth surfaces of PCM microcapsules (m-PCMs) with a hemispherical shape. While m-PCMs with rough surfaces, buckles, and dimples were found when BAA and TBMA were applied. The results showed that the highest levels of microencapsulation efficiency, yield, and PCM content were observed for MMA and EAA samples. The TBMA sample shows low values of microencapsulation efficiency and yield (about 29.1 and 53.4 %, respectively). Furthermore, results showed that adding cross-linking agents to the recipe has had multiple favourable effects. It has mitigated sub-cooling, increased PCM content, improved microencapsulation efficiency, and boosted the overall yield of PCM. In conclusion, the current work will contribute to the development of a microencapsulation technology of PCMs that overcomes the shortcomings of long time and high temperature needed in the present traditional microencapsulation procedure.
In this work, novel bentonite-based and form-stable composite phase change materials (Bb-FSPCMs) were produced for LHTES in buildings by impregnation of CA, PEG600, DD and HD with bentonite clay. The ...microstructures of the compatibility of the Bb-FSPCMs were by using SEM and FT-IR techniques. The DSC results indicated that the produced Bb-FSPCMs composites had suitable phase change temperature of 4–30°C and good latent heat capacity between 38 and 74J/g. The TG results demonstrated that all of the fabricated Bb-FSPCMs had good thermal resistance. The Bb-FSPCMs maintained their LHTES properties even after 1000 heating–cooling cycling. The total heating times of the prepared Bb-FSPCMs were reduced noticeably due to their enhanced thermal conductivity after EG (5wt%) addition. Display omitted
•Bb-FSPCMs were produced by impregnation of CA, PEG600, DD and HD with bentonite.•DSC analysis indicated that Bb-FSPCMs had melting temperature in range of 4–30°C.•DSC analysis also showed that Bb-FSPCMs had latent heat between 38 and 74J/g.•The TG analysis demonstrated that Bb-FSPCMs had good thermal resistance.•Thermal conductivity of Bb-FSPCMs were enhanced noticeably with EG (5wt%) addition.
In this work, for latent heat thermal energy storage (LHTES) applications in buildings, bentonite-based form-stable composite phase change materials (Bb-FSPCMs) were produced by impregnation of capric acid (CA), polyethylene glycol (PEG600), dodecanol (DD) and heptadecane (HD) into bentonite clay. The morphological characterization results obtained by scanning electron microscopy (SEM) showed that the bentonite acted as good structural barrier for the organic PCMs homogenously dispersed onto its surface and interlayers. The chemical investigations made by using fourier transform infrared (FT-IR) technique revealed that the attractions between the components of the composites was physical in nature and thus the PCMs were hold by capillary forces. The results of differential scanning calorimetry (DSC) analysis indicated that the prepared Bb-FSPCMs composites including 40wt% CA, 43wt% PEG600, 32wt% DD and 18wt% HD, respectively had suitable phase change temperature of 4–30°C and good latent heat capacity between 38 and 74J/g, respectively for solar space heating and cooling applications of buildings envelopes depending on climatic conditions. The results of thermogravimetric (TG) analysis demonstrated that all of the fabricated Bb-FSPCMs had good thermal resistance. The Bb-FSPCMs maintained their LHTES properties even after 1000 heating–cooling cycling. Furthermore, the total heating times of the prepared Bb-FSPCMs were reduced noticeably due to their enhanced thermal conductivity by addition of expanded graphite (EG) in the mass fraction of 5wt%.
The large-scale commercial application of phase change materials (PCMs) was seriously limited by the leakage, poor heat storage capacity and slow thermal response behavior. To address these issues, ...stearic acid/graphene oxide-attapulgite aerogel (SA/HGA-ATP) shape-stabilized PCMs were fabricated via hydrothermal method. The morphology, structural characteristics, thermal properties were determined and the effects of ATP percentage on the thermal properties of confined SA were studied synchronously. The nanofibers of ATP intercalated among GO sheets via grafting modification and formed fiber-bridging 3D-network. Due to the enhanced loading interspaces and suppressed volumetric shrinkage of hybrid matrix, SA/HGA-ATP exhibited excellent thermal energy storage capacity (190.9 J g−1) and ultra-high SA contents (approx. 98 wt%) without leakage. The intercalated nanofibers sheltered the oxygen-containing groups of matrices, leading to the promotion of thermal energy storage performance with increase of ATP contents. Besides, the as-prepared PCMs displayed outstanding thermal response behavior because the interconnected and fiber-bridged matrices provided continuous thermal transfer pathway. Due to the protection of matrix, the composite PCMs also exhibited superior structure stability and incomparable thermal energy storage/release reliability. Considering the outstanding thermal-physical properties and low-cost of ATP, the SA/HGA-ATP has the potential to be applied in the fields of thermal energy storage, conversion and utilization.
•Three-dimensional matrices with fiber-bridged porous structure were fabricated.•Introduction of attapulgite nanofibers is benefit for serving more loading spaces.•The constructed fiber-bridges provide continuous thermal-transfer pathway.•The mass fraction of loaded stearic acid is as high as 98% without seepage.
•The review of recent studies on CTES integration across the refrigeration sector.•Discussion on integration strategies for transport and supermarket refrigeration.•Peak shaving and reduced energy ...consumption can be achieved by CTES integration.•Experimental research is key to demonstrate the performance of PCM-CTES units.
This paper presents a thorough review on the recent developments and latest research studies on cold thermal energy storage (CTES) using phase change materials (PCM) applied to refrigeration systems. The presented study includes a classification of the different types of PCMs applied for air conditioning (AC) systems (20 °C) to low-temperature freezing of food (−60 °C). An overview of the influencing thermophysical properties of PCMs, as well as their respective characterisation methods, are presented. The current available PCMs on the market in the temperature range 10 °C to −65 °C are listed. Finally, research on CTES using PCMs in refrigeration systems are reviewed and grouped into applications for food transport and packaging, commercial refrigeration and various other refrigeration systems. The findings show that using ice/water as PCM for AC applications is the most commonly studied system, due to widespread use of these systems, expected growth in the future and low cost of using water as the PCM. Over the last ten years the published research integrating CTES in different parts of the food cold chain, using water-salt solutions and paraffin PCM in both active and passive methods, has increased. Suggestions for the integration of CTES in supermarkets and industrial applications are also emerging. The technology has received increased interest from the scientific community the last five years, due to the benefits of achieving peak shaving of the refrigeration demand, exploiting low-cost electricity hours and offering backup refrigeration in case of blackouts.
•Round trip efficiency improvement by combining the desalination and storage units.•Simultaneous generation of the power and potable water during peak demand periods.•An efficient and green ...cogeneration system for using in warm and arid climates.•Waste heat recovery from the compressors and the turbine exhaust.•Impact of the maximum to minimum pressure ratio on performance and operational time.
Compressed air energy storage is one of two existing grid-scale energy storage technologies. It can be efficiently used in dry and warm climates, where providing both electricity and potable water is indispensable. A novel integration of compressed air energy storage and multi-effect desalination system is proposed to reduce energy dissipation, exergy destruction and provide power and potable water. Compression heat in the charging period is conveyed to the desalination unit; during discharging, the remaining energy in the turbine exhaust is reassigned to the desalination unit after passing through the recuperator. Round trip efficiency is thereby improved while providing peaking power and pure water. Besides, the effect of the maximum to minimum pressure ratio of the compressed air vessel on efficiency and the operational period of the system is studied for a particular set of circumstances. Results indicate that 38 kg/s potable water is produced during charging, whereas 80 MW electricity and 62.5 kg/s distilled water are concurrently generated during peak demand periods. As a result, 69.95% round trip efficiency and 9.47 performance ratio are obtained for the proposed hybrid system.
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