Utilization Of Thermal Energy Research Articles

Efficient-thermal conductivity, storage and application of bionic tree-ring composite phase change materials based on freeze casting

Thermal energy storage, management, and utilization with phase change materials have received increasing attention in industrial fields such as photo-thermal-electric conversion and integrated circuit cooling. However, the inherent low thermal conductivity and melting leakage are long-term bottlenecks that prevent their widespread commercial application. Herein, a novel composite phase change material (CPCM) with high-thermal conductivity and stability based on bionic porous SiC skeleton is proposed, which is oriented by optimized freeze casting to design vertical tree-ring porous structure for fast photo-thermal conversion and storage. The results demonstrate the novel bionic SiC skeleton can regulate the porosity (50%–70%) by changing the slurry solid content, which also exhibits good anisotropic thermal conductivity. SiC/paraffin CPCM's mass and latent enthalpy of attenuated merely by 0.87% and 1.5% after 200 repeated heat storage/exhaustion cycles, confirming its excellent longevity and stability. The high-temperature SiC/NaCl-MgCl2-KCl CPCM has a thermal conductivity of 12.54 W‧m−1‧K−1, an effective thermal-storage density per production cost of 74.5 kJ‧CNY-1, and a high photo-thermal storage efficiency of 91.8%. Finally, a variable-power chip dissipation experimental system was built to verify the thermal performance of the CPCM module in the paper. It could dissipate heat rapidly and maintain a lower temperature. This work provides a promising strategy for photo-thermal utilization and thermal management of electronic devices.

Simplicity is the ultimate sophistication: One-step forming for thermosensitive solid–solid phase change thermal energy harvesting, storage, and utilization

In light of the growing recognition of low-carbon initiatives, renewable energy is gradually assuming a dominant role within the energy framework. Phase change materials can enhance the efficiency of renewable energy utilization by energy peak shaving and time shifting. However, leakage and inherent rigidity signify that a significant amount of energy input is required for scale-up applications of phase change materials to enhance shape stability and processability during industrial installation. In conventional enhancement strategies, high-quality encapsulation means more intricate processes and higher energy consumption. Here we propose a simplified thermally-initiated encapsulation and molding strategy, which involves grafting the phase change materials onto thermosetting polymer backbones by covalently integrated, to construct self-supported phase change materials with complex three-dimensional geometry. The encapsulation process is macroscopically manifested as a transformation from solid-liquid to solid–solid phase change. Therefore, by imposing restrictions on liquid materials, any ultra-high-precision complex structure can be molded, and mechanical properties are imparted through curing to achieve shape stability, ultimately enables the integration of phase change material encapsulation and casting. The complete process requires no curing agents or organic solvents, and no pollution emissions, making it highly maneuverable and environmentally friendly. Furthermore, we demonstrate the universal high value applications of new materials in different fields. In the ancient thermotherapy experiment, the sample exhibited sustained heat release for 8 min. In the advanced chip cooling simulation, the chip exhibits superior heat dissipation performance, as evidenced by its operating temperature being 50 °C lower than that of natural cooling within 20 min. It confirms the remarkable potential of phase change materials constructed through this approach for thermal energy applications.

Binary nitrate molten salt magnetic microcapsules modified with Fe3O4-functionalized carbon nanotubes for accelerating thermal energy storage

Molten salts are important media for heat transfer and thermal energy storage in concentrated solar power (CSP) system, but it has drawbacks such as poor thermal conductivity and corrosive properties. This study increases the thermal energy utilization rate and expand the range of applications for phase change materials by developing a multifunctional magnetic microcapsule phase change material composed of SiO2@Solar Salt microcapsule and Fe3O4-functionalized carbon nanotubes (CNTs-Fe3O4). The microcapsules have regular spherical core-shell structure and relatively small size, which improves the disadvantage of corrosiveness of molten salt and prolongs their working life. The microcapsule not only shows a good latent heat-storage capability with satisfactory phase-change enthalpies of over 88.6 J/g under an encapsulation efficiency of over 61.6 %, but also exhibits high temperature stability and cycling stability. The encapsulation of SiO2 and introduction of the CNTs-Fe3O4 high thermal conductivity enhancement phase increased the thermal conductivity of the microcapsules by approximately 53.4 % compared with pure nitrate. The microcapsules also possess superparamagnetic characteristics and photothermal conversion characteristics, both of which may be used as an additional method to improve the thermal storage efficiency. As a result, this novel material provides a promising solution for energy collecting, conversion, and storage.

Preparation and thermophysical properties of a novel metallic microencapsulated phase change material/eutectic salt/ceramic composite

The development of thermal storage material is crucial for the utilization of thermal energy. At present, eutectic salt/ceramic composite has been widely studied as latent heat storage material, however, its thermal conductivity is low and its latent heat per unit volume is still not ideal, despite its high latent heat per unit mass. Herein, a metallic microcapsule with high thermal conductivity and latent heat per unit volume is introduced to improve the above properties. Using MgO as the support material, metallic microcapsule (Sn@Void@SiO2) and eutectic salt (LiNO3-NaCl) with almost the same temperature range as phase change material, metallic microcapsule/eutectic salt/ceramic composite was prepared by cold-pressure sintering method. The result shows that the best performance of metallic microcapsule/eutectic salt/ceramic composite was achieved with the addition of 30 wt% Sn@Void@SiO2 instead of MgO, the latent heat per unit volume and per unit mass of the composite are 237.1 J/cm3 and 117.9 J/g, which are improved by 56.72 % and 15.48 % respectively. And the thermal conductivity of the composite was improved by 63.79 %, from 0.58 W/(m·K) to 0.95 W/(m·K). Further, the addition of a small amount of Sn to metallic microcapsule/eutectic salt/ceramic composite can not only increase its latent heat but also improve its thermal conductivity as Sn fills the pores inside the composite after melting. The result showed that the thermal conductivity of the composite was increased by 155.17 % than that of eutectic salt/ceramic composite when Sn was added at 5 wt%. Finally, thermal cycle results showed that composites have high thermal reliability and proved high thermal cycling stability of metallic microcapsule prepared by “double-layer coating, sacrificial inner layer” method.

Numerical Investigation of the Inner Profiles in Ironmaking Blast Furnace: Effect of the Ratio of Belly Diameter to Effective Height

The elaborate and appropriate design of blast furnace (BF) inner profile is indispensable. In practice, in this work, dumpiness, quantified by the ratio of belly diameter to effective height (RD–H), primarily determines the inner profile and significantly affects the BF performance. However, the effects of RD–H on BF operation are not investigated thoroughly, and an optimal range of RD–H is not yet proposed. In this work, a numerical study on this topic is presented to recommend an RD–H range for BF designers. This is achieved by using a recently developed 3D multi‐fluid BF process model based on a 380 m3 industrial BF. In the results, it is shown that both too slender and too dumpy BFs do not favor BF production. Excessively slender BF leads to a dramatic increase in gas pressure drop; however, the saving of coke or the improvement of productivity is insignificant. In contrast, excessively dumpy BF leads to a dramatic increase in coke rate and a significant decrease in productivity. Under the current conditions, the recommended dumpiness exists in the value of RD–H at around 0.35, where a low coke rate, low gas pressure drop, high productivity, and high thermal energy utilization are all ensured.

Design and Optimization Strategies for Flexible Quasi-Solid-State Thermo-Electrochemical Cells.

Currently, efficient utilization of low-grade thermal energy is a great challenge. Thermoelectricity is an extremely promising method of generating electrical energy from temperature differences. As a green energy conversion technology, thermo-electrochemical cells (TECs) have attracted much attention in recent years for their ability to convert thermal energy directly into electricity with high thermal power. Within TECs, anions and cations gain and lose electrons, respectively, at the electrodes, using the potential difference between the hot and cold terminals of the electrodes by redox couples. Additionally, the anions and cations therein are constantly circulating and mobile via concentration diffusion and thermal diffusion, providing an uninterrupted supply of power to the exterior. This review article focuses mainly on the operation of TECs and recent advances in redox couples, electrolytes, and electrodes. The outlook for optimization strategies regarding TECs is also outlined in this paper.

A novel concept to improve the flexibility of steam power plants using an electric feedwater heater

The concepts of operational flexibility enhancement for steam turbine power plants described in the trade literature focus on thermal energy accumulation and utilization. In this paper a new concept of flexibility improvement is presented for steam turbine power plants, using an electric heater to preheat the feedwater for the boiler. The proposed method does not require extensive alterations in the power plant process systems, and no large thermal energy storage is necessary. It is important to note that this solution is only applicable if the boiler and its control system have the capability to work under this reduced load condition. By using electric feedwater heating it is possible to reduce the power transferred to the grid and keep the plant in operation at low loads. Thanks to the developed model of a 200 MW reference power plant using the Ebsilon Professional 15 software, the authors carried out simulation tests, based on which it has been proven that it is possible to reduce the minimum load for grid production from 92 MW to 78 MW. Although the efficiency of the electricity production decreased, the cost analysis has shown that the proposed modifications are reasonable, thanks to the improved cooperation of the 200 MW power plant with the grid. The NPV in the analysed system was PLN 35 million, and the sensitivity analysis showed that the profitability will increase with the increased number of necessary shutdowns of power plants without modifications. This is particularly important considering the development of renewable energy sources and the random and stochastic nature of their electricity generation.

Dual-encapsulated phase change composites with hierarchical MXene-graphene monoliths in graphene foam for high-efficiency thermal management and electromagnetic interference shielding

Multifunctional phase change materials (PCMs) simultaneously combining high-efficiency thermal management and electromagnetic interference (EMI) shielding performance are urgently desirable yet highly challenging for miniaturized and integrated electronics. Herein, an innovative polyethylene glycol (PEG) composite is developed based on a dual-encapsulation design of vertically aligned MXene-graphene monoliths in graphene foam (MGGF hybrid aerogel). The MXene-graphene monoliths are first incorporated with reticulated graphene foam via unidirectional freezing to construct a hybridized semi-interpenetrated framework, followed by thermal annealing and encapsulating molten PEG, synchronously forming orientational-interlinked thermal pathways in PCM matrix. Impressively, the resultant MGGF/PEG composite achieves a high through-plane thermal conductivity of 11.39 W m−1 K−1 and excellent EMI shielding effectiveness of ∼56.6 dB, as well as desirable latent heat density up to 160.3 J g−1, leakage-proof ability, and superior thermal reliability. Additionally, the MGGF/PEG-based device is demonstrated for thermal energy management toward versatile demands in electronics cooling and solar-thermoelectric conversion. This work sheds new light on designing multifunctional composite PCMs and raises tremendous application prospects for electronic thermal management and solar energy utilization.

Efficient solar thermal energy utilization and storage based on phase change materials stabilized by MOF@CuO composites

Solar thermal conversion technology employing phase change composites is an available strategy for solar thermal energy utilization and storage. In this work, a novel metal-organic framework (MOF)-based phase change composites were successfully constructed through vacuum impregnation method. The stearic acid (SA) was served as phase change materials, and the SA-modified MOF (HS) with CuO derived from MOF (HS@CuO composites) was assembled to be support materials, which composed the SA/HS@CuO phase change composites. HS@CuO composites could well prevent the SA leakage over phase change point and endowed the phase change composites outstanding form stability (SA loading rate: 71.8 %) and thermal storage ability (ΔHm: 158.24 J/g). Furthermore, the SA/HS@CuO possessed greatly strengthened thermal conductivity (improved by 3.8 times over SA) and extraordinary solar thermal conversion performance (η: 95.9 %). These results powerfully suggest that the innovative phase change composites own promising potentials in not only solar energy utilization and development but also thermal storage and management fields.

Enhanced compression heat recovery of coupling thermochemical conversion to trigenerative compressed air energy storage system: Systematic sensitivity analysis and multi-objective optimization

Compressed air energy storage system has been considered as a promising alternative solution for stabilizing the electricity production driven by intermittent renewable energy sources. However, the inefficient utilization of thermal energy within the compressed air energy storage system hinders the efficient operation of system. Therefore, a novel trigenerative system integrated compressed air and chemical energy storage system is introduced in this study. The proposed system transforms the compression heat to the syngas in the form of chemical energy to achieve energy level upgradation during the charging process, and recuperates the thermal energy at the exit of the gas turbine to increase the inlet temperature of the compressed air for electricity enhancement during the discharging process. The residual heat during the operation process is then conducted for producing cooling and heating outputs simultaneously based on the law of energy cascade utilization. A systematic parametric analysis is carried out to investigate the effects of critical parameters on system comprehensive performance. Furthermore, the multi-objective optimization is employed to find the optimal trade-off among the thermodynamic performance, economic attractiveness and environmental friendliness of the proposed system. The parametric analysis indicates that the operating parameters of air compressor and gas turbine affect the performance indicators of thermodynamic and economic significantly. Moreover, at the best trade-off solution selected by the TOPSIS method, the system reaches 42.96 % of exergetic round trip efficiency, 105.28 $/MWh of levelized cost of energy and 206.94 kg/MWh of CO2 emission per unit energy output.

Temporal performance indicators for an integrated pilot-scale membrane distillation-concentrated solar power/photovoltaic system

Management of concentrate streams in inland applications has uncertain long-term environmental impacts. This study investigates an intensified solar-energy capture desalination system that integrates membrane distillation (MD) with a hybrid concentrated solar power (CSP)/photovoltaic (PV) collector to realize self-sustained zero-waste discharge for effective management of concentrate streams in inland and off-grid applications. The demonstration-scale CSP/PV system can produce up to 178 kWh of thermal energy and 4 kWh of electrical energy per day. The thermal and electrical energy from the CSP/PV system is directly supplied to the air gap MD (AGMD) pilot-scale system producing up to 288 L of distilled water per day. Experiments were performed on the hybrid AGMD-CSP/PV system to evaluate system performance under various operating conditions including AGMD and CSP flow rates, CSP system pre-heating, and AGMD vacuum pressure. Experimental results indicate that doubling the AGMD flow rate results in a 119% increase in thermal energy utilization and a 71% increase in distillate production. Compared to the winter months, operating the system in summer months when direct normal irradiance (DNI) is highest results in nearly double the distillate production (88 L in winter and 168 L in summer) and nearly three times the amount of thermal energy consumption (15 kWh in winter and 43 kWh in summer). Operating with vacuum resulted in a 34% increase in distillate production and allowing the thermal storage reservoir to preheat in the winter resulted in a 61% increase in distillate production. Overall, experimental results highlight the tradeoff between distillate production and thermal and electrical energy production and consumption under various environmental conditions and the potential for AGMD-CSP/PV to be a stand-alone desalination system.

Technical and economic viability of using solar thermal energy for microalgae drying

The solar thermal energy is evaluated to microalgae drying active processes as an alternative more economical and sustainable than conventional methods such as spray-dryer. A case study of microalgae production in a 10,000 m2 raceway reactor was considered where the biomass production capacity per year was calculated based on previously existing models, thus as the heat required. Different designs, configurations and operation modes of solar collectors were studied. Due to the parallel variation of biomass production and solar radiation availability throughout the year, the optimal solution was to design the solar collector for the summer season, the operation mode was optimized, thus the utilization of auxiliary energy systems and air recirculation being analysed. The final design considers the utilization of solar air collectors operating in a recirculation mode. At these conditions, it is possible to completely supply the required heat by using a 200 m2 surface collector, the operation in recirculation mode allowing to save up to 30% of the collectors’s surface required. The techno-economic analysis demonstrates that the utilization of the proposed system avoid the utilization of fossil energy, moreover the cost of the drying step reduces to 1.16 €/kg versus a cost of 2.37 €/kg for conventional spray dryers. Thus, it is demonstrated that the utilization of thermal solar energy is an opportunity to improve sustainability and economy of microalgae drying process.

Thermal performance enhancement methods of phase change materials for thermal energy storage systems – A review

Phase Change Materials (PCMs) have emerged as a promising solution for efficient thermal energy storage and utilization in various applications. This research paper presents a comprehensive overview of PCM technology, including its fundamental working principles, classification and different shapes of container used for PCM storage. The study investigates the optimal melting temperature of PCMs and explores various Thermal Energy Storage (TES) methods and their types. This paper discusses novel approaches to enhance the thermal performance of PCMs, such as incorporating high-conductivity materials, Nano-encapsulation, Composite formation, and Shape stabilization. These innovative techniques have shown great potential in enhancing efficiency of PCM-based TES systems. The information presented in this paper is an in-depth analysis of research papers published over the last five years (2019 to 2023). It is a valuable source for researchers seeking to stay current with the modern advancements in PCM technology and its applications. This research contributes to advancing sustainable and efficient thermal energy utilization by promoting a deeper understanding of PCM's capabilities and challenges.

Catalytic Cracking Column Scheme Modernization for Efficient Utilization of Thermal Energy

Catalytic Cracking Column Scheme Modernization for Efficient Utilization of Thermal Energy

Novel Latent Heat Storage Systems Based on Liquid Metal Matrices with Suspended Phase Change Material Microparticles.

Phase change materials (PCMs) are considered useful tools for efficient thermal management and thermal energy utilization in various application fields. In this study, a colloidal PCM-in-liquid metal (LM) system is demonstrated as a novel platform composite with excellent latent heat storage capability, high thermal and electrical conductivities, and unique viscoelastic properties. In the proposed formulation, eutectic Ga-In is utilized as a high-thermal-conductivity and high-fluidity liquid matrix in which paraffinic PCM microparticles with various solid-liquid phase transition temperatures are suspended as fillers. Good compatibility between the fillers and matrix is achieved by the nanosized inorganic oxides (titania) adsorbed at the filler-matrix interface; thus, the composite is produced via simple vortex mixing without tedious pre- or post-processing. The composite shows unique trade-off effects among various properties, i.e., elastic modulus, yield stress, density, thermal conductivity, and melting or crystallization enthalpy, which can be easily controlled by varying the contents of the suspended fillers. A Joule heating device incorporating the composite exhibits improved electrothermal performance owing to the synergy between the high electrical conductivity and latent heat storage capability of the composite. The proposed platform may be exploited for the rational design and facile manufacture of high-performance form-factor-free latent heat storage systems for various potential applications such as battery thermal management and flexible heaters.

Full biomass-derived multifunctional aerogel for solar-driven interfacial evaporation

Developing high-efficient utilization of thermal energy, excellent water transport path and mechanical stablility of biochar based solar-driven interfacial evaporator (SDIE) is critical for but still challenge. Herein, a three-dimensional network of porous scaffolds aerogel is prepared by cross-linking hydrophilic plantain cellulose (PC) and biomass hollow carbon tubes (HCTs) with excellent photothermal properties. The HCTs and PC winding with each other, the water adsorption by PC and desorption by HCTs which improve water evaporation. Under 1.0 sun illumination, the optimized PC@HCTs aerogel temperature on gas-liquid interface rapidly reach to 46.7 °C and the evaporation rate is 1.86 kg m−2h−1. In addition, PC@HCTs aerogel possess excellent water evaporation under high concentration of salt solutions and salt tolerance ability. Moreover, the PC@HCTs aerogel has obvious purification effect for seawater, heavy metal ion solution, oil-water emulsion and organic dye wastewater. Importantly, the dry PC@HCTs possesses excellent hardness while hyperelasticity in water. More importantly, the PC@HCTs aerogel with green recyclability which change the growth environment of sand and plants healthier, thus take materials from nature and final regress to nature. This work has the great scientific significance to promote the actual use of biochar based solar steam evaporators.

A novel in-situ growth ZIF-67 on biological porous carbon encapsulated phase change composites with electromagnetic interference shielding and multifunctional energy conversion

With the current intricate application environment, extended versatility is critical to the future development of phase change materials (PCMs). Herein, we prepared a series of phase change composites (PCCs) with excellent electromagnetic interference shielding effectiveness (EMI SE) and versatile thermal management. Specifically, the hybridized multi-stage porous biological carbon base with magnetic and electrical conductivity was prepared as the substrate material for encapsulating paraffin wax (PW) by carbonizing in situ growth ZIF-67 on waste agricultural. The synergy between the functions of the porous biological carbon and PW makes the PCCs have high-performance EMI SE (44.81 dB) and high enthalpy value (175.88–229.52 J/g) at the identical time. In which CC-ZIF-3 @PW has outstanding effect in storing and releasing thermal energy for photo-thermal, magnetic-thermal and electric-thermal conversion. Unsurprisingly, the PCCs breaks innovative ground for energy storage and conversion materials with potential value in various fields such as electronic protection, deicing and thermal energy utilization.

A multi-period design method for the steam and power systems coupling solar thermal energy and waste heat recovery in refineries

It is imperative to reduce carbon emissions by comprehensively utilizing renewable energies and waste heat in refineries. However, the intermittent supply of solar thermal energy, the periodic changes of waste heat, and the variable demands of steam and electricity in refineries hinder optimal design and stable operation of the steam and power systems. In this work, an optimal design method for coordination of solar thermal energy and waste heat to produce steam and electricity in refineries was proposed, which features a multi-period mathematical programming model to synchronously determine the economy, the optimal capacity configuration, and the power scheduling scheme for the steam and power system. The influence of the serial and parallel structures of solar thermal energy supply, the model processing method for continuity of energy storage among different subperiods, and parametric analysis on the results were analyzed and discussed in detail. The results show that the cost of the solar thermal collectors and the energy storage system accounts for the significant proportion of the investment cost of the system. The cost of solar thermal collectors accounts for the largest proportion of the investment cost of the system, which is about 60% in the case study. The parallel structure of solar thermal energy supply can significantly reduce the total cost of the system. The coordination of solar thermal energy and waste heat recovery can jointly meet the steam demand to ensure the stability of the energy supply of the system. The comprehensive interactions and coordination between the solar steam generation systems, waste heat systems, energy storage systems, and demands are analyzed. The battery is necessary for short-time energy storage, whereas thermal energy storage should be used for either long-term or short-term energy storage. These results provide fundamental support for the optimal design of the steam and power systems in refineries by the comprehensive utilization of solar thermal energy and waste heat.

Heat transfer characteristics of triple-tube latent heat storage system placed horizontally and vertically

Phase change heat storage technology can realize the utilization of thermal energy across time and space, which is of great significance for solving the problem of mismatch between supply and demand of renewable energy and promoting the energy structure adjustment of our country. However, the low thermal conductivity of phase change materials (PCM) severely limits the application and development of PCM technology. Compared with the traditional two-tube phase change heat storage system, the three-tube latent heat storage system (TTLHSS) has the advantages of large heat transfer area and good heat transfer uniformity. However, there is a lack of comparative research on the heat storage and release performance of the triple tube phase change heat storage system placed horizontally and vertically. Based on the above, this paper studies the heat transfer characteristics of the triple tube phase change heat storage system placed horizontally and vertically, and compares the influence of the tube length on the heat storage and release performance. The coagulation/melting model and Boussinesq model of Fluent software were used to calculate the coagulation and melting process of lauric acid with the same structural parameters placed horizontally and vertically. The results show that when the tube length is 250 mm, the solidification and melting time of lauric acid in the case of horizontal placement is less than that in the case of vertical placement, decreasing by 8 % and 45.9 %, respectively. In addition, it is found that the natural convection has little influence on the axial heat transfer, so the tube length has little influence on the horizontally placed TTLHSS, which can be simplified to a two-dimensional structure for calculation. Due to the phenomenon of temperature stratification in the heat storage process in the case of vertical placement, the heat storage performance will decrease significantly with the increase of tube length, so the tube length has a certain impact on the heat storage and release performance of the triple tube phase change heat storage system placed vertically.

Thermo-dynamic and economic analysis of a novel pumped hydro-compressed air energy storage system combined with compressed air energy storage system as a spray system

The efficiency of adiabatic compressed air energy storage technology is limited by the low utilization of thermal energy in the energy storage room. Therefore, a pumped hydro-compressed air energy storage system combined with a compressed air energy storage system as a spray system is introduced in the present research and analyzed by thermodynamic and economic analysis to verify the feasibility of system. For the performance analysis of the system, the main components and the whole system are precisely analyzed from the thermodynamic point. The results show that the round-trip efficiency and total exergy efficiency of the system are 52.45% and 77.8%. The system can significantly improve the air temperature in the air storage room, reduce the pressure energy loss of the system, and increase the energy storage capacity. Moreover, achieving high system round-trip efficiency is dependent on components of the system with high efficiencies. By optimization of the system operation mode, the round-trip efficiency of the system can reach 56%.