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We use Monte Carlo simulations to investigate the effect of incorporating calcium chloride salt into nanoporous carbon on the performance of an ammonia–carbon adsorption refrigeration system. Simulations of ideal carbon slit-pores with pore sizes of 1, 2, and 3 nm, each containing calcium chloride with ion densities of 0.0, 0.25, and 0.5 nm−3, were carried out at temperatures between 0 and 30 °C and ammonia pressures up to 15.0 bar. The results reveal that ideal 1 nm pores are able to achieve a good refrigeration performance using waste heat below 100 °C to drive the process, but adding salt to these pores increases the waste heat temperature required beyond 100 °C. However, ideal 2 nm pores require the addition of 0.25 nm−3 salt to achieve a similar performance, while the 3 nm pores were unable to achieve a satisfactory refrigeration performance. Considering that real nanoporous carbons usually feature a variety of specific adsorption sites and non-ideal geometries that should have a similar impact to adding salt, these results indicate that nanoporous carbons with pores in the range of 1–2 nm are likely to hold the most promise for adsorption refrigeration applications and that the addition of salt may not always be helpful. [ABSTRACT FROM AUTHOR]

Roughly, 50% of primary energy worldwide is rejected as waste heat over a wide range of temperatures. Waste heat above 573 K has the highest Carnot potential (> --> 50 %) to be converted to electricity due to higher Carnot efficiency. Thermoelectric (TE) materials have gained significant attention as potential candidates for efficient thermal energy conversion devices. Silicon nanowires (SiNWs) are promising materials for TE devices due to their unique electrical and thermal properties. In this study, we report the successful fabrication of high-quality double-sided SiNW arrays using advanced techniques. We engineered the double-sided structure to increase the surface area and the number of TE junctions, enhancing TE energy conversion efficiency. We also employed non-agglomeration wire tip engineering to ensure uniformity of the SiNWs and designed effective Ohmic contacts to improve overall TE efficiency. Additionally, we post-doped the double-sided SiNW arrays to achieve high electrical conductivity. Our results showed a significant improvement in the TE performance of the SiNW array devices, with a maximum figure-of-merit (ZT) value of 0.24 at 700 K, fabricated from the single SiNW with ZT of 0.71 at 700 K in our previous work [Yang et al., Nat. Commun. 12(1), 3926(2021)]. [ABSTRACT FROM AUTHOR]

A novel methanol steam reforming system is proposed to enhance the utilization efficiency of waste heat in hydrogen production from methanol. The system is integrated with a monoethanolamine carbon capture system and a two-stage compression heat pump system. In this integrated system, the high-temperature products of the methanol steam reforming system exchange heat with the feedstock and undergo gas-liquid separation. The low-temperature gas produced is pre-compressed and utilized for heating the feedstock. Furthermore, a two-stage heat pump uses the low-temperature lean solution from the carbon capture system as a heat source for feedstock heating. The analysis is conducted based on a hydrogen production capacity of 200 kg/h, revealing an enhanced energy and exergy efficiency of 5.4% and 3.5%, respectively, compared to the reference system. Additionally, waste heat utilization efficiency increases from 62.1% to 92.0%. The cost of hydrogen production is reduced from 3.089 $/kg to 2.054 $/kg, which is very close to the cost of hydrogen production without carbon capture. The exergoeconomic analysis indicates that the introduction of energy levels enhances the value of high-temperature steams, and the hydrogen production unit exergy of cost rate is elevated from 3.443 $/kWh to 4.411 $/kWh. The proposed system can readily harness low-grade waste heat and exhibits high thermodynamic efficiency, presenting a promising approach for low-energy-consumption methanol-hydrogen production. • A low-energy, low-carbon methanol-based hydrogen production system is introduced. • Waste heat utilization of the integrated system is enhanced from 62.1% to 92.0%. • The overall energy and exergy efficiencies of the system reach 86.7% and 77.3%, respectively. • Hydrogen production cost is reduced from 3.089 $/kg to 2.054 $/kg by recovering waste heat. [ABSTRACT FROM AUTHOR]

The synthesis of transparent thermoelectric materials, particularly at low processing temperature possesses a good promise for future power generation by renovating waste heat into electrical energy. The fabrication of invisible thermoelectric module is hindered by limited choices of appropriate p-type transparent thermoelectric materials so far. The present study deals with the growth and characterization of optically transparent p-type copper iodide (γ-CuI) thin films. Thermal annealing (maximum up to 200 °C) was performed to tune the electrical and optoelectronic properties for nurturing the thermoelectric performance. Annealing induced microstructural modifications instigated the preferential crystal growth by regulating the surface morphology. Low thermal conductivity is credited to strong phonon scattering leading to improved thermoelectric performance. Consequently, we attain a record Seebeck coefficient of ∼270 μV/K and power factor of ∼20 μW/(m·K2) that is almost two-order of magnitude higher as compared to conventional p-type transparent TE materials, indicating the potential of transparent γ-CuI thin films regarding its practical applicability in transparent thermoelectric devices. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials have attracted significant attention because they can be used to directly harvest waste heat into electricity. Organic TE materials like poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) have advantages including high mechanical flexibility, low cost, and low intrinsic thermal conductivity. However, their TE properties are notably inferior to their inorganic counterparts. Here, PEDOT:PSS films with very high thermoelectric properties through the sequential treatments with H2SO4, water, and ethanol solution of tetrakis(dimethylamino)ethylene (TDAE) are reported for the first time. The PEDOT:PSS films can exhibit a Seebeck coefficient of 58.2 µV K−1 and electrical conductivity of 1552 S cm−1, and the corresponding power factor is 526 µW m−1 K−2. The water treatment prior to the TDAE solution treatment is crucial for the high TE properties of PEDOT:PSS films. Without the water treatment, the control PEDOT:PSS films exhibit a Seebeck coefficient of only 32.4 µV K−1 and electrical conductivity of 1124 S cm−1, and the corresponding power factor is only 118 µW m−1 K−2. The effect of the water treatment on the Seebeck coefficient is attributed to the swelling of PEDOT:PSS films, which facilitates the penetration of TDAE from solution into the polymer films and thus the reduction of PEDOT:PSS. [ABSTRACT FROM AUTHOR]

In response to the issues of poor economic efficiency and high CO2 emissions in the urea-to-ammonia technology of thermal power plants, this paper innovatively proposes a new ammonia production process for thermal power plants. This process utilizes the waste heat of thermal power plant boilers and conducts urea pyrolysis through two-stage heating to prepare ammonia and cyanuric acid. From this, the prepared ammonia can be used in the denitrification process of thermal power plants, and the prepared cyanuric acid can bring additional benefits to thermal power plants. The optimal process scheme was determined through orthogonal experiments of urea pyrolysis. And with the help of Aspen Plus software, a whole-process modeling analysis of urea pyrolysis experiments was carried out to investigate the influences of the melting temperature, melting time, reaction temperature, and reaction time on the process. The results show that when the melting temperature was 160 °C, the melting time was 45 min, the reaction temperature was 240 °C, and the reaction time is 20 min, which was the best scheme, 18.45% ammonia and 52.35% cyanuric acid could be obtained. Through the combined analysis of the Aspen Plus simulation and urea pyrolysis experiments, it was found that the melting temperature should be controlled within 160–167 °C, the melting time should be controlled within 40–45 min, the reaction temperature should be controlled within 240–245 °C, and the reaction time should be controlled within 15–20 min. Compared with the existing urea-to-ammonia process, this process has the advantages of nearly zero emissions and good economic benefits, thus providing reliable research data support for future industrialization. [ABSTRACT FROM AUTHOR]

This review explores the state‐of‐the‐art of thermoelectric materials, covering different crystalline structures and material families (e.g., chalcogenides, Zintl phases, skutterudites, clathrates, oxides, half‐Heusler, organic–inorganic composites, metal–organic frameworks, and silicides). It examines their corresponding thermoelectric properties while considering the synthesis methods employed, paying significant attention to those that particularly follow sustainable routes. Additionally, the work addresses current challenges in the field, such as enhancing stability at high temperatures and reducing manufacturing costs. The understanding gained in this field opens avenues for designing more efficient and sustainable devices to convert waste heat into electrical energy, thereby advancing cleaner technologies. [ABSTRACT FROM AUTHOR]

Printing technologies have the potential to reduce the manufacturing costs of many electronic devices significantly. Here, a scalable manufacturing route for high‐performance fully printed thermoelectric generators (TEGs) as a cost‐effective solution for energy harvesting is demonstrated. This work presents a facile one‐pot synthesis method to develop a high‐performance Ag2Se‐based n‐type paste, which is used to fabricate a fully printed origami TEG by employing the Ag2Se‐based material for the n‐type legs and a previously reported Bi‐Sb‐Te‐based paste for the p‐type legs. The n‐type film exhibits a power factor of 13.5 µW cm−1 K−2 and a maximum figure‐of‐merit (ZT) of ≈ 0.92. Furthermore, printable carbon paste is introduced as an effective interface between the thermoelectric and electrode materials, which reduces the contact resistances in the thermoelectric device. The origami folded TEG exhibits an open‐circuit voltage (VOC) of 284 mV, a power output of 370.88 µW, and an exceptionally high power density (pmax) of 10.72 Wm−2 at a temperature difference (∆T) of 80.7 K, considering that the TEG fabrication does not involve any pressure treatment and vacuum sintering. These results underscore the scalability of the presented manufacturing process and the capability of printed origami TEGs for powering the Internet of Things (IoT) with low‐grade waste heat. [ABSTRACT FROM AUTHOR]

European Union (EU) energy markets are changing rapidly. After the recent turmoil, a new wave of EU legislation is once again reshaping the way energy should be used in the EU, emphasizing not only the increasing importance of using renewable and local energy sources but also highlighting the importance of energy efficiency and decarbonization of high to abate sectors (including aviation and marine fuels). Heating and cooling account for about half of the total gross final energy consumption in the EU. This article explores the novel concept of using waste heat from the flexible Fischer–Tropsch (FT) process (FLEXCHX) in the existing district heating network, resulting in tri-generation: FT C5+ liquids, heat, and electricity. FLEXCHX provides operation flexibility and combines advanced biomass gasification, catalytic liquefaction, electrolysis, and waste heat recovery, allowing use of biomass residues in a more sustainable way. Our results, based on the Kaunas district heating (DH) system, show that this process could be integrated into the existing district heating network in Northern Europe and successfully compete with existing heat-only boilers and CHPs using biomass or municipal waste, resulting in more efficient use of biomass and savings accumulated up to EUR 200 million over the study period in the analysis (2020–2050), supplying up to 30% of the heat in the Kaunas DH system. Enriching the FT process with hydrogen (using electrolysis) could result in additional FLEXCHX utilization benefits by creating demand for cheap excess electricity that might otherwise be curtailed. [ABSTRACT FROM AUTHOR]

The Hewlett Packard Enterprise–Cray EX Frontier is the world's first and fastest exascale supercomputer, hosted at the Oak Ridge Leadership Computing Facility in Tennessee, United States. Frontier is a significant electricity consumer, drawing 8–30 MW; this massive energy demand produces significant waste heat, requiring extensive cooling measures. Although harnessing this waste heat for campus heating is a sustainability goal at Oak Ridge National Laboratory (ORNL), the 30 °C–38 °C waste heat temperature poses compatibility issues with standard HVAC systems. Heat pump systems, prevalent in residential settings and some industries, can efficiently upgrade low-quality heat to usable energy for buildings. Thus, heat pump technology powered by renewable electricity offers an efficient, cost-effective solution for substantial waste heat recovery. However, a major challenge is the absence of benchmark data on high-performance computing (HPC) heat generation and waste heat profiles. This paper reports power demand and waste heat measurements from an ORNL HPC data centre, aiming to guide future research on optimizing waste heat recovery in large-scale data centres, especially those of HPC calibre. [ABSTRACT FROM AUTHOR]

The rise in hydrogen production powered by renewable energy is driving the field toward the adoption of systems comprising multiple alkaline water electrolyzers. These setups present various operational modes: independent operation and multi-electrolyzer parallelization, each with distinct advantages and challenges. This study introduces an innovative configuration that incorporates a mutual lye mixer among electrolyzers, establishing a weakly coupled system that combines the advantages of two modes. This approach enables efficient heat utilization for faster hot-startup and maintains heat conservation post-lye interconnection, while preserving the option for independent operation after decoupling. A specialized thermal exchange model is developed for this topology, according to the dynamics of the lye mixer. The study further details startup procedures and proposes optimized control strategies tailored to this structural design. Waste heat from the caustic fully heats up the multiple electrolyzers connected to the lye mixing system, enabling a rapid hot start to enhance the system's ability to track renewable energy. A control strategy is established to reduce heat loss and increase startup speed, and the optimal valve openings of the diverter valve and the manifold valve are determined. Simulation results indicate a considerable enhancement in operational efficiency, marked by an 18.28% improvement in startup speed and a 6.11% reduction in startup energy consumption in multi-electrolyzer cluster systems, particularly when the systems are synchronized with photovoltaic energy sources. The findings represent a significant stride toward efficient and sustainable hydrogen production, offering a promising path for large-scale integration of renewable energy. [ABSTRACT FROM AUTHOR]

Data centers (DCs) are highly energy-intensive facilities, where about 30%–50% of the power consumed is attributable to the cooling of information technology equipment. This makes liquid cooling, especially in two-phase mode, as an alternative to air cooling for the microprocessors in servers of interest. The need to meet the increased power density of server racks in high-performance DCs, along with the push towards lower global warming potential (GWP) refrigerants due to environmental concerns, has motivated research on the selection of two-phase heat transfer fluids for cooling servers while simultaneously recovering waste heat. With this regard, a heat pump-assisted absorption chiller (HPAAC) system for recovering waste heat in DCs with an on-chip two-phase cooling loop driven by the compressor is proposed in the present paper and the low GWP hydrofluoroolefin refrigerants, including R1224yd(Z), R1233zd(E), R1234yf, R1234ze(E), R1234ze(Z), R1243zf and R1336mzz(Z), are evaluated and compared against R245fa as server coolant. For the HPAAC system, beginning with the development of energy and economic models, the performance is analyzed through both a parametric study and optimization using the coefficient of performance (COP), energy saving ratio (ESR), payback period (PBP) and net present value (NPV) as thermo-economic indicators. Using a standard vapor compression cooling system as a benchmark, the results indicate that with the evaporation temperature between 50°C and 70°C and the subcooling degree ranging from 5°C to 15°C, R1233zd(E) with moderate compressor suction pressure and pressure ratio is the best refrigerant for the HPAAC system while R1234yf performs the worst. More importantly, R1233zd(E) is also superior to R245fa based on thermo-economic performance, especially under work conditions with relatively lower evaporation temperature as well as subcooling degree. Under the given working conditions, the overall COP, ESR, NPV, and PBP of R1233zd(E) HPAAC with optimum subcooling degree range from 4.99 to 11.27, 25.53 to 64.59, 1.13 to 4.10 × 107 CNY and 5.77 to 2.22 years, respectively. Besides, the thermo-economic performance of R1233zd(E) HPAAC under optimum working conditions in terms of subcooling degree varying with the evaporation temperature is also investigated. [ABSTRACT FROM AUTHOR]

Organic Rankine cycle (ORC) has been considered as one of the most promising technologies in industrial waste heat utilization and power generation. During the actual operation of ORC system, due to the fluctuation of cooling and heat sources, the system operates under off-design conditions in most cases. In this paper, thermodynamic model, heat transfer process description and power equipment model are established to evaluate the operating parameters of ORC for the off-design conditions. Evaporation temperature and condensation temperature are taken as independent parameters for the operation of ORC system. Genetic algorithm is adopted to optimize the independent parameters under the maximum net output power. The results show that the effect of optimizing independent parameters is to make the working fluid at the outlet of the preheater as close as possible to a saturated liquid state, and the working fluid at the inlet of the screw expander should be in a saturated gas state. With the optimal power output increasing by 19.1% for every 5 °C increase in hot water inlet temperature, 9.2% for every 20 kg/s increase in hot water mass flow rate, and 3.9% for every 1 °C decrease in cooling water temperature. The optimization method of off-design operating conditions has good system performance and good engineering application prospects. [ABSTRACT FROM AUTHOR]

Fiber‐based thermoelectric (TE) device that can collect waste heat of human body and convert it into electricity is growing fast and is of great significance for sustainable development. Although ionic thermoelectric (i‐TE) ionogels are considered to be the next generation of TE materials, to construct ionogel fiber with synergistically enhanced mechanical and i‐TE performances remains big challenge. Herein, the poly(vinylidene fluoride‐co‐hexafluoropropylene)/1‐ethyl‐3‐methylimidazolium dicyanamide/ethanol/NaTFSI/SiO2 (PH/ED‐E‐Na‐SiO2) ionogel with ultrahigh ionic Seebeck coefficient of 47.5 mV K−1 and ionic conductivity of 43.7 mS cm−1 is constructed by a proposed antisolvent‐doping‐hybrid synergistic strategy. The enhanced i‐TE performances are mainly attributed to the low crystalline structure and the improvement in ions dissociation, migration, and diffusion difference. The corresponding power factor of the PH/ED‐E‐Na‐SiO2 ionogel film is as high as 9845.8 µW m−1 K−2, which is almost the highest value ever reported. Based on this, the ionogel fiber with comparable i‐TE performances and significantly enhanced tensile strength and strain (from 327 KPa and 47% of film to 17.7 MPa and 70% of fiber) is prepared by a simple coating process. It can be weaved into wearable i‐TE device that generates high thermovoltage and lights the light‐emitting diode (LED) bulb, demonstrating its great application potential as wearable energy supply device. [ABSTRACT FROM AUTHOR]

This paper presents a novel green combined heat and power generation system for industrial applications. It composes of a hydrogen-fueled combined cycle power plant and a battery energy storage. Firstly, the hydrogen-air rich mixture enters the combustion chamber of the gas turbine cycle for generating electricity, while recovering the heating energy from the exhausted flue gases for driving a steam turbine cycle. The heating energy extracted from the condenser heat exchanger is also used to supply the heating demand of the end-user. Moreover, a comprehensive thermodynamic model and analysis of H 2 combustion process is provided to estimate the adiabatic flame temperature based on enthalpies of reactants and products. The optimum operating point of the cogeneration system is found by solving a mixed-integer nonlinear problem using MATLAB and GAMS over a 24-h study horizon aiming to minimize its daily operation cost considering all technical constraints of system components and load-generation balance criterion. It is found that the energy efficiency of the hydrogen-fueled combined cycle changes from 46 to 58 % while generating 11.331–12.982 MW electricity and 4.436–4.984 MW heat. Two cases are studied without and with participation of battery in energy procurement strategy. It is demonstrated that the objective function of the optimization problem improves from 18 $ cost in case 1 to 29 $ revenue in case 2. • Thermodynamic model and analysis of a H 2 -fueled CHP plant is presented. • Adiabatic flame temperature is obtained based on enthalpies of reactants and products. • A high-temperature heat exchanger is used to produce steam from waste heat of gas turbine flue gases. • Optimal charge and discharge of battery is scheduled for higher cost savings. [ABSTRACT FROM AUTHOR]

Torrefaction is an effective method to improve the quality of biomass feedstocks for a subsequent thermal conversion process. Torrefaction has been widely developed for biomass upgrading in terms of increasing bulk and energy densities, reducing water and oxygen contents, and improving hydrophobic properties, which are favorable for transportation and storage. Moreover, the torrefied biomass can be easily ground to even particle sizes, which favor the downstream thermochemical conversion process such as gasification. This paper reports on the progress in the dry and wet torrefaction of biomass sources. Key findings and challenges of torrefied biomass gasification are highlighted as well. In general, the properties of biomass feedstocks can be improved by the torrefaction process. Torrefaction for biomass gasification can improve the quality of syngas. In particular, gasification of torrefied biomass involves a merit of volatile matter (tar precursor) removal prior to the gasification process. The properties of torrefied biomass are significantly affected by the torrefaction conditions mainly including atmosphere, temperature, and pressure. The presence of an appropriate amount of oxygen gas leads to a superior performance for biomass torrefaction. The oxygen-containing gas and the waste heat from industrial flue gas can be utilized to reduce the operating cost, thus making the biomass torrefaction pretreatment more commercially feasible. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid thermoelectric (TE) materials have attracted tremendous interest for harvesting waste heat energy. Due to their mechanical flexibility, inorganic‐organic hybrid TE materials are considered to be promising candidates for flexible energy harvesting devices. In this work, enhanced TE properties of Tellurium (Te) nanowires (NWs)‐ poly (3‐hexylthiophene‐2, 5‐diyl) (P3HT) hybrid materials are reported by improving the charge transport at interfacial layer mediated via controlled oxidation. A power factor of ≈9.8 µW (mK2)−1 is obtained at room temperature for oxidized P3HT‐TeNWs hybrid materials, which increases to ≈64.8 µW (mK2)−1 upon control of TeNWs oxidation. This value is sevenfold higher compared to P3HT‐TeNWs‐based hybrid materials reported in the literature. MD simulation reveals that oxidation‐free TeNWs demonstrate better templating for P3HT polymer compared to oxidized TeNWs. The Kang–Snyder model is used to study the charge transport in these hybrid materials. A large σE0 value is obtained which is related to better templating of P3HT on oxygen‐free TeNWs. This work provides evidence that oxidation control of TeNWs is critical for better interface‐driven charge transport, which enhances the thermoelectric properties of TeNWs‐P3HT hybrid materials. This work provides a new avenue to improve the thermoelectric properties of a new class of hybrid thermoelectric materials. [ABSTRACT FROM AUTHOR]

To comply with the trend of emission reduction and energy-saving in the industrial sector, a novel integration of the hydrogen liquefaction process based on reversed Brayton cycle (RBC) with the organic Rankine cycle (ORC), for waste heat recovery is proposed. The high temperature gas in the compressor outlet of RBC, which is typically wasted in air-coolers, is recovered in ORC and used as the heat source for power generation for the hydrogen liquefaction process. Thermodynamic analysis showed that compared to the conventional system COP increased by 17.95% from 0.11 to 0.14 and specific energy consumption (SEC) decreased by 16.33% from 10.84 to 9.07 kWh/kg LH2. Parametric analysis was conducted to evaluate the impact of pressure ratio, evaporator temperature and minimum temperature difference (M Δ T) in heat exchangers, on system performance. Changes in these variables affect the system performance and heat transfer area in opposite directions, thus multi-objective optimization by the genetic algorithm was performed to determine the optimum operating conditions. The SEC and the net present value (NPV) were selected as objective functions and were optimized simultaneously. Results from the optimization process indicate that the SEC and NPV were found to be 9.165 kWh/kgH 2 and 1.55 million dollars with the optimal evaporator temperature of 365 K, pressure ratio of 2.85, and the M Δ T of 7.79. • A novel design of hydrogen liquefaction process with heat recovery is examined. • Reversed Brayton cycle is integrated with organic Rankine cycle for the process. • The specific energy consumption is decreased by 16.33% than the conventional one. • Multi-objective genetic algorithm is used to evaluate techo-economic viability. [ABSTRACT FROM AUTHOR]

The energy sector is essential in the transition to a more sustainable future, and renewable energies will play a key role in achieving this. It is also a sector in which the circular economy presents an opportunity for the utilisation of other resources and residual energy flows. This study examines the environmental and social performance of innovative energy technologies (which contribute to the circularity of resources) implemented in a demonstrator site in Luleå (Sweden). The demo-site collected excess heat from a data centre to cogenerate energy, combining the waste heat with fuel cells that use biogas derived from waste, meeting part of its electrical demand and supplying thermal energy to an existing district heating network. Following a cradle-to-gate approach, an environmental and a social life cycle assessment were developed to compare two scenarios: a baseline scenario reflecting current energy supply methods and the WEDISTRICT scenario, which considers the application of different renewable and circular technologies. The findings indicate that transitioning to renewable energy sources significantly reduces environmental impacts in seven of the eight assessed impact categories. Specifically, the study showed a 48% reduction in climate change impact per kWh generated. Additionally, the WEDISTRICT scenario, accounting for avoided burdens, prevented 0.21 kg CO2 eq per kWh auto-consumed. From the social perspective, the WEDISTRICT scenario demonstrated improvement in employment conditions within the worker and local community categories, product satisfaction within the society category, and fair competition within the value chain category. Projects like WEDISTRICT demonstrate the circularity options of the energy sector, the utilisation of resources and residual energy flows, and that these lead to environmental and social improvements throughout the entire life cycle, not just during the operation phase. [ABSTRACT FROM AUTHOR]

This study investigates the enhancement of vehicle warm-up performance using phase-change materials (PCMs) and various thermal storage methods. The primary objective is to utilize the thermal energy lost during engine cooling to improve the cold-start performance, thereby reducing fuel consumption and emissions. Thermal storage devices incorporating PCMs were developed and tested by measuring temperature changes and energy transfer over soaking periods of 4, 8, 16, and 24 h. The results show energy transfers of 591, 489, 446, and 315 kJ at 4, 8, 16, and 24 h, respectively. In terms of the warm-up time, the use of thermal storage devices reduced the time required to reach 70 °C by up to 24.45%, with significant reductions observed across all soaking periods. This reduction in the warm-up time directly contributes to faster engine stabilization, leading to proportional improvements in fuel efficiency and a corresponding decrease in exhaust emissions, including CO2. The findings highlight the effectiveness of PCMs in improving the engine warm-up performance and emphasize the importance of optimizing thermal storage systems to balance energy efficiency and practical application considerations. Additionally, the experimental data provide useful benchmark information for computational simulation validation, enabling the further optimization of automotive thermal management systems. Integrating a PCM-based thermal storage device can significantly enhance a vehicle's warm-up performance, leading to reduced fuel consumption and lower emissions. [ABSTRACT FROM AUTHOR]

The issue of energy supply for wireless sensors is becoming increasingly severe with the advancement of the Fourth Industrial Revolution. Thus, this paper proposed a thermoelectric self−powered wireless sensor that can harvest industrial waste heat for self−powered operations. The results show that this self−powered wireless sensor can operate stably under the data transmission cycle of 39.38 s when the heat source temperature is 70 °C. Only 19.57% of electricity generated by a thermoelectric power generation system (TPGS) is available for use. Before this, the power consumption of this wireless sensor had been accurately measured, which is 326 mW in 0.08 s active mode and 5.45 μW in dormant mode. Then, the verified simulation model was established and used to investigate the generation performance of the TPGS under the Dirichlet, Neumann, and Robin boundary conditions. The minimum demand for a heat source is cleared for various data transmission cycles of wireless sensors. Low−temperature industrial waste heat is enough to drive the wireless sensor with a data transmission cycle of 30 s. Subsequently, the economic benefit of the thermoelectric self−powered system was also analyzed. The cost of one thermoelectric self−powered system is EUR 9.1, only 42% of the high−performance battery cost. Finally, the SEPIC converter model was established to conduct MPPT optimization for the TEG module and the output power can increase by up to approximately 47%. This thermoelectric self−powered wireless sensor can accelerate the process of achieving energy independence for wireless sensors and promote the Fourth Industrial Revolution. [ABSTRACT FROM AUTHOR]

Solar‐driven water‐electricity co‐generation (WEC) emerges as a viable solution to address global freshwater and energy scarcity. Phase change materials (PCMs)‐based WEC systems have been proposed to solve intermittent solar radiation issues. Nevertheless, WEC performances decline significantly leading to limited operating durations in dark. The study proposes a new concept of directional‐thermal‐conductive PCMs to address above challenges. By precisely regulating hydrophilicity/hydrophobicity distribution of Cu substrates, the structural disorder of boron nitride‐based PCMs is effectively tuned to achieve directional thermal transport. These directional‐thermal‐conductive PCMs exhibit a high phase transition enthalpy of 250.4 J g−1 and a large thermal‐conductivity anisotropy index of 3.24, which improves heat exchange between PCMs and photothermal/thermoelectric, and minimizes transverse heat dissipation simultaneously. Consequently, the directional‐thermal‐conductive PCMs‐based WEC achieves evaporation rates of 2.51 kg m−2 h−1 with power outputs of 1759.7 mW m−2 at 1 sun, among the best performance reported in the state‐of‐the‐art studies. More impressively, its evaporation rate still reaches 0.93 kg m−2 h−1 with a superior power output of 411.0 mW m−2 and a prolonged operation time of 90 minutes in nighttime, significantly surpassing previously‐reported devices with nondirectional‐thermal‐conductive designs. Finally, an omniphobic PVDF membrane is demonstrated that can improve the anti‐fouling performance of WEC systems for prolonged lifespan. [ABSTRACT FROM AUTHOR]

• The mechanism of carbonation of steel slag was explored. • Process simultaneously carbon sequestration, CO 2 capture and waste heat recovery. • Directly use the lime kiln gas as the gas source without purification. • Average treatment cost of 0.68 MWh for 1 t of steel slag for the process. The iron and steel-making industries have garnered significant attention in research related to low-carbon transitions and the reuse of steel slag. This industry is known for its high carbon emissions and the substantial amount of steel slag it generates. To address these challenges, a waste heat recovery process route has been developed for molten steel slag, which integrates CO 2 capture and fixation as well as efficient utilization of steel slag. This process involves the use of lime kiln flue gas from the steel plant as the gas quenching agent, thereby mitigating carbon emissions and facilitating carbonation conversion of steel slag while simultaneously recovering waste heat. The established carbonation model of steel slag reveals that the insufficient diffusion of CO 2 gas molecules within the product layer is the underlying mechanism hindering the carbonation performance of steel slag. This finding forms the basis for enhancing the carbonation performance of steel slag. The results of Aspen Plus simulation indicate that 1 t of steel slag (with a carbonation conversion rate of 15.169 %) can fix 55.19 kg of CO 2 , process 6.08 kmol of flue gas (with a carbon capture rate of 92.733 %), and recover 2.04 GJ of heat, 0.43 GJ of exergy, and 0.68 MWh of operating cost. These findings contribute to the development of sustainable and efficient solutions for steel slag management, with potential applications in the steel production industry and other relevant fields. [ABSTRACT FROM AUTHOR]

As China's economy and society continue to advance, there has been a notable enhancement in the quality of life for its people. However, the escalating energy consumption in buildings, particularly for heating and cooling purposes, has emerged as a pressing concern, accounting for nearly 60% of the overall energy consumption. In response to this challenge, heat pumps have emerged as a promising solution by efficiently meeting the demand for heating and cooling. Among these options, wastewater-source heat pumps (WWSHP) have garnered attention as an innovative choice, harnessing the waste heat in available wastewater resources in China to provide efficient heating and cooling services. The objective of this study was to comprehensively investigate the decarbonisation potential associated with sewage source heat pumps in China. By employing both techno-economic analysis and life cycle assessment methods, we conducted a thorough comparison between conventional heating and cooling systems and various heat pump systems. The results of our analysis demonstrate that WWSHPs not only exhibit the lowest greenhouse gas (GHG) emissions but also yield the lowest production costs. Our findings reveal that the potential capacity of WWSHPs amounted to a total of 2.4 EJ in 2020, with the capability to mitigate 99 Mt CO2-eq emissions and achieve cost savings of 24 billion RMB. Importantly, WWSHPs' maximum potential cannot be fully realised by replacing heating alone. However, by replacing both heating and cooling options, WWSHPs unlock substantial decarbonisation potential and cost savings. [ABSTRACT FROM AUTHOR]

One of the primary concerns with fuel combustion in internal combustion engines is the significant quantity of energy that is dissipated as waste heat, which leads to thermal pollution and reduced engine efficiency. To address this issue, a new integrated system incorporating a natural gas fueled homogeneous charge compression ignition (HCCI) engine for different hydrogen fractions (0%–20%) in fuel blends and its exhaust heat is recovered to drive the NH 3 –H 2 O based absorption refrigeration cycle (ARC) and process heat exchanger has been developed, which encompasses the generation of electricity, heating, and cooling. A comprehensive energy-exergy model was built and the impact of some key operating variables on the performance of combined system are investigated. Simulation of the proposed system was performed using Engineering Equation Solver (EES) software and REFPROP toolbox library data. The energy and exergy efficiencies of HCCI engine resulted in an increase from 45.26% to 55.45% and from 41.15% to 46.14%, whereas the combined system efficiencies were increased by 15.90% and 10.13% when hydrogen addition is promoted from 0% to 20%. Utilization of 10% hydrogen resulted in energy efficiency of 49.57% for electrical, 11.89% for cooling, and 4.51% for heating. Illustration of exergy flow diagram identified HCCI engine (118.29 kW, 32.11%) as the most fuel exergy destructive component, followed by ARC cycle (30.86 kW, 8.37%), catalytic converter (27.24 kW, 7.39%) and process heat exchanger (11.103 kW, 3.01%). Impressive exergetic results from the system include a power exergy of 158.91 kW (43.14%), heating exergy 10.697 kW (2.90%), and cooling exergy 3.92 kW (1.06%). • H 2 enriched natural gas fueled HCCI engine based trigeneration system was developed. • HCCI engine's exhaust waste heat was harnessed through the ARC cycle and PHE. • A single effect NH 3 –H 2 O absorption chiller was employed for cold production. • Energy and exergy-based assessment was carried out to analyze the proposed system. • HCCI engine (32.11%) were identified as the primary exergy destructive components. [ABSTRACT FROM AUTHOR]

Passive solar membrane distillation (MD) is an emerging technology to alleviate water scarcity. Recently, its performance has been enhanced by multistage design, though the gains are marginal due to constrained temperature and vapor pressure gradients across the device. This makes condenser cooling enhancement a questionable choice. We argue that condenser heating could suppress the marginal effect of multistage solar MD by unlocking the moisture transport limit in all distillation stages. Here, we propose a stage temperature boosting (STB) concept that directs low-temperature heat to the condensers in the last stages, enhancing moisture transport across all stages. Through STB in the last two stages with a heat flux of 250 W m−2, a stage-averaged distillation flux of 1.13 L m−2 h−1 S−1 was demonstrated using an 8-stage MD device under one-sun illumination. This represents an 88% enhancement over the state-of-the-art 10-stage solar MD devices. More notably, our analysis indicates that 16-stage STB-MD devices driven by solar energy and waste heat can effectively compete with existing photovoltaic reverse osmosis (PV-RO) systems, potentially elevating freshwater production with low-temperature heat sources. Multistage solar membrane distillation is facing challenges with current system designs due to constrained temperature and vapor pressure gradients. Here, the authors propose a stage temperature-boosting concept that enhances moisture transport with up to 88% improvement in overall distillate flux. [ABSTRACT FROM AUTHOR]

Harvesting low‐grade waste heat into electrical energy is recognized as a promising solution for sustainable energy supply. In parallel, thermotropic smart windows have emerged as an efficient way to reduce building energy consumption. It is posit that thermotropic smart windows with inherent thermoelectric property may offer unique advantages for practical applications. Herein, the preparation and characterization of a series of ionic hydrogels that exhibit temperature‐sensitive phase transition behavior is reported, which are suitable for both thermotropic smart windows and thermoelectric generators. Notably, the lower critical solution temperature (LCST) of this ionic hydrogels can be feasibly modulated, and the thermoteopic phase transition also induces a sharp increase in their Seebeck coefficient, reaching up to 39.03 mV K−1 with a power factor (PFi) value up to 0.838 mW m−1 K−2. A prototype dual functional thermotropic smart window that simultaneously works as an ionic thermoelectric generator is further demonstrated, achieving both efficient phase transition driven by solar heat at ≈26 °C and an energy density up to 250 mJ m−2. This study offers new opportunity for the development of smart materials that can bridge the gap between thermal comfort and energy sustainability for energy harvesting and smart building applicat. [ABSTRACT FROM AUTHOR]

Harvesting waste heat efficiently with thermoelectric energy conversion requires materials with low thermal conductivity. Recently, it was demonstrated how dynamic lone pair expression in thermoelectric InTe is responsible for giant anharmonicity leading to a very low lattice thermal conductivity. InTe also contains correlated disorder of intrinsic defects due to vacancies, and this contributes to additional lowering of the thermal conductivity. Here we use the three‐dimensional difference pair distribution function (3D‐ΔPDF) to analyze 25 K single crystal diffuse X‐ray scattering from InTe to unravel the local defect structure, and propose a microscopic structural model. Extended off‐centering of In+ ions induced by vacancies allows for the local expression of stereochemically active lone pairs. The associated electronic stabilization is proposed to be a driving force for the formation of In+ vacancy defects in InTe. [ABSTRACT FROM AUTHOR]

Maritime propulsion is recognized as a hard-to-abate sector and its decarbonization will therefore require transversal efforts, including the introduction of alternative fuels to reduce CO 2 emissions. Both ammonia and hydrogen could provide clean power; however, forecasts hint that ammonia will be especially useful for longer routes, while hydrogen suffers from low volumetric energy density. This paper evaluates the feasibility of a cargo ship with a SOFC powertrain equipped with LOHC-based hydrogen storage and compares the sizing and heat management requirements of four LOHC systems, namely N-ethylcarbazole (NEC), dibenzyltoluene (DBT), methylcyclohexane (MCH), decaline (DEC), with an ammonia-based one. The size of the 8.4 MW SOFC system is similar for the five carriers as expected. The dynamic performance of the LOHC system shows that the hydrogen flow rate can be effectively controlled by acting on the LOHC flow rate, reactor temperature, and pressure. However, LOHC systems are heavier (by a factor of 1.6 to 2.1) and larger (by 1.6 to 2.3 times) than ammonia systems. The decalin system results in the lowest mass and volume, while NEC is the heavier, and MCH is the least dense of the evaluated LOHCs. Similarly, the utilization of SOFC waste heat to cover dehydrogenation heat ranges from 45.6 % (NEC) to 27.9 % (ammonia). Overall, even considering the lower reaction temperature, LOHCs do not appear to be competitive with ammonia as hydrogen storage systems in the maritime sector. • Liquid organic hydrogen carrier (LOHC) systems discussed for maritime applications. • Different LOHC systems are sized, and the heat demand is evaluated. • Control strategies are devised to meet instantaneous hydrogen demand. • The dynamic response of LOHC-based systems is more than satisfactory. • Comparison with ammonia is unfavorable in terms of mass, volume and heat demand. [ABSTRACT FROM AUTHOR]

Reforming ammonia to hydrogen using engine exhaust waste heat is a promising technology to improve the combustion performance and reduce the exhaust emissions of ammonia-fueled engines. However, there are still a research gap between the laboratory-level catalytic reforming tests and the practical application in engine systems. In particular, there are urgent needs to further understanding the ammonia reforming characteristics and developing the simulaiton models for the engine system optimization. In this paper, we conducted the experiments of catalytic reforming NH 3 to H 2 to study the effects of the reaction temperature, gas hour space velocity (GHSV) and pressure on the thermo-catalytic decomposition characteristicsxin. The results indicate that both the ammonia catalytic conversion and reforming efficiency exhibit an increasing trend with the rise in reaction temperature, while these two parameters demonstrate a decreasing trend with the increase in GHSV and pressure. The rate of hydrogen production is directly proportional to temperature, GHSV, and reaction pressure. Conversely, the energy required per unit of hydrogen production decreases with temperature but increases with GHSV and reaction pressure. The energy flow analysis shows that increasing the reforming temperature increases the reforming losses, but the total calorific value of the reformate increases, which is expected to improve the overall efficiency of ammonia fueled engines and reduce the unburned ammonia emissions. Simulation results show that, the improved Temkin-Pyzhev global rate model can significantly improve the accuracy of the ammonia catalytic decomposition process prediction. [Display omitted] • A novel energy flow analysis method for thermo-catalytic reforming is presented. • A precise predictive model for thermo-catalytic characteristics is established. • The thermo-catalytic system has a system efficiency of up to 94%. • The thermo-catalytic system has a reforming efficiency of up to 112%. [ABSTRACT FROM AUTHOR]

This paper provides the groundwork for the most efficient design of freshwater generating systems that take advantage of waste heat from the main engines. In the desalination process, freshwater generators, whether in the form of shell and tube-type or plate-type, are employed. Merchant vessels primarily utilize submerged shell and tube-type evaporators to generate fresh water. The foundation for comprehending separation processes, energetics, and economics lies in the quantitative interpretation of the second law of thermodynamics, with a specific focus on exergy and its dissipation. This research suggests employing exergy analysis to utilize waste heat as a valuable resource in a single-effect desalination process to meet freshwater needs, considering practical aspects. The study involves analyzing a freshwater generator of the Shell and tube type situated at the Tolani Maritime Institute in Pune, India. Thermal properties are calculated and visually represented through a flow diagram using a C++ program. The assessment of exergy unveils the extent and distribution of unattainable work within a freshwater generator employing a shell and tube design, particularly concentrated in its key components: the evaporator, condenser, and brine section. These findings are contrasted with those from a Plate Type Heat Exchanger (PTHE) freshwater generator. The rate of exergy destruction in Plate Type Heat Exchanger freshwater generators is 29.33%, whereas in shell and tube-type freshwater generators, it is higher at 44.88%. [ABSTRACT FROM AUTHOR]

A solid desiccant-based novel dehumidification technique in indoor cooling is a viable substitute for a traditional dehumidification system in regions with high humidity levels. The ozone layer is being steadily destroyed by vapour compression-based conventional dehumidification systems, which also have a number of other disadvantages such as excessive power consumption and a rise in the amount of chlorofluorocarbons type refrigerant leakage in the atmosphere. As compared to traditionally used vapour compression type refrigeration air conditioners, solid desiccant-integrated novel cooling may be more advantageous as it provides more easily accessible, cost-effective, and ecologically sound cooling. It can be more competitive when it is reactivated by freely available renewable heat available from solar power and industrial waste heat. Not only marginally saving energy, but it can also help in drastically lower operational costs. Recently, many studies have been carried out with aim of ameliorating desiccant air conditioners' overall performance through the development of novel system configurations, enhanced system designs and better controls, and the integration of hybrid energy sources for desiccant reactivation as well as sub-systems technological advancements. By this means, the present study offers a thorough analysis of the previously described investigations. This offers detailed study on possible suggestions and recommendations for possible future work direction based on the most recent investigations in the field of the desiccant-powered novel cooling techniques. These recommendations can help to amplify the efforts to find better solutions to concurrent technological issues, which will definitely ameliorate the overall performance of desiccant-integrated dehumidification and hybrid cooling in the field of heating, ventilation and air conditioning. [ABSTRACT FROM AUTHOR]

• The performance of AHTs using {H 2 O+ILs} working pairs are evaluated. • Simulated the performance of ILs in AHTs under high heat source temperature. • {H 2 O+ILs} working pairs can achieve greater temperature lift compared to {H 2 O+LiBr}. • The exergy loss of {H 2 O+LiBr} in each component of AHT is lower than {H 2 O+DMIMDMP}. The study investigated six sets of ionic liquid (IL) working pairs based on high-temperature vapor-liquid equilibrium data. These sets were modeled using the NRTL activity coefficient model and integrated into a single-stage absorption heat transformer (AHT) for system cycle simulation analysis. A comparison was made with traditional H 2 O + LiBr working pairs commonly used in AHTs. The study aimed to assess the feasibility of using IL working pairs in high-temperature AHTs to achieve higher output temperatures when dealing with heat sources exceeding 120 °C. Compared to the traditional H 2 O + LiBr working pair, which has strong COP and ECOP but a limited temperature range, IL pairs offer advantages under various conditions. For instance, H 2 O + [HMIM][Cl] and H 2 O + [BMIM][Br] can operate at higher condensation temperatures, providing broader temperature ranges. H 2 O + [HMIM][Cl] has a wider operational temperature range, suitable for unstable waste heat sources. It also has the highest optimal ECOP value of 0.64 at 197 °C absorption temperature, and shows good cyclic performance, achieving temperature rises of about 78 °C. ILs can maintain stable COPs and circulation ratios over a wide range of absorption temperatures, thus achieving higher temperature rises or meeting the need for higher absorption temperatures. Notably, although the H 2 O + IL combination exhibits slightly higher exergy loss than the traditional H 2 O + LiBr pair when comparing exergy losses in the AHT system among different working pairs, its low corrosiveness, lack of crystallization, and wide operating temperature range make these drawbacks insignificant. [ABSTRACT FROM AUTHOR]

The current energy crisis is causing a transformation of tremendous scope and complexity. The natural gas, coal, and electricity sectors have experienced the largest tremors. In this regard, an effort was made to conserve energy by providing a compact heat exchanger that may be utilized to recover waste heat from power plants and industries. This article explores the effect of combined passive techniques on the performance of a CTHE fitted by twisted tapes at hot-side and Al2O3 nanofluid used as cold-side fluid. The experiments were conducted by incorporating the differently configured PVTTs and CFTTs (TR: 20, 13.3, and 9.8) in the inner tube with fixed flowrate (Re = 2500) of hot water and using different volume fractions of Al2O3 nanofluid (Vol.%: 0.05, 0.1 and 0.15) as cold fluid with varied flow rates (500 ≤ Re ≤ 5000) in the annulus. The results reveal that the PVTT (TR = 20) and 0.05% nanofluid combination increases the Nusselt number by 12.28% and the TPF by 1.127, while the CFTT (TR = 9.8) and 0.15% nanofluid combination increases the Nusselt number by 24.27% and the TPF by 1.263. Hence, CFTT (TR = 9.8) with 0.15% of Al2O3 nanofluid provided greater performance in the combinations tested, albeit at the expense of a little pressure loss. [ABSTRACT FROM AUTHOR]

In response to escalating environmental concerns and the imperative to institute effective energy management strategies, the pursuit of alternative fuels has emerged as a pivotal endeavor for realizing sustainable energy solutions. Methanol and ammonia have surfaced as particularly promising and environmentally friendly liquid fuels, holding significant potential for aiding in the attainment of decarbonization objectives and addressing global energy requirements. This research proposes and scrutinizes a sophisticated cogeneration system integrating solid oxide fuel cells (SOFCs), gas turbine (GT), steam Rankine cycle, and organic Rankine cycle. Direct utilization of ammonia and methanol as fuel in this intricate system is examined, with the design and modeling facilitated through the utilization of Aspen HYSYS V.12.1. The thermodynamic performance of the proposed system is rigorously assessed by employing the foundational principles of the first and second laws of thermodynamics. The direct SOFCs fueled by ammonia and methanol exhibit notable energy efficiencies of 64.25 % and 58.42 %, respectively. Remarkably, the amalgamated systems showcase heightened energy efficiencies, witnessing a commendable increase of 12.64 % and 10.66 % when powered by ammonia and methanol, respectively, as compared to individual SOFC systems. Examination of exergy destruction reveals the SOFC as the principal contributor, with electrochemical and chemical processes constituting the primary sources of irreversibility. Additionally, explicit values for exergy destruction in the GT, afterburner, and heat exchanger components are provided. A comprehensive parametric study underscores the pivotal role of the fuel utilization factor (Uf), identifying a value of 0.85 as optimal and significantly augmenting the thermodynamic efficiency of the system. This analysis not only substantiates the potential of ammonia and methanol as effective carriers for hydrogen but also underscores the efficacy of waste heat recovery as a viable strategy for enhancing the overall thermodynamic performance of an SOFC system. The findings presented herein contribute valuable insights, paving the way for the strategic utilization of alternative fuels and cogeneration systems in the broader context of sustainable and environmentally conscious energy solutions. [ABSTRACT FROM AUTHOR]

Traditional internal combustion engines (ICEs) have garnered considerable attention due to their high emissions and low efficiency issues. In this study, a novel ICE–fuel cell hybrid power system based on a single‐methanol fuel is proposed to address these concerns. The system utilizes methanol as fuel, directly supplying it to the methanol engine, and generates hydrogen for the fuel cell through methanol reforming technology. The structural design of the system fully exploits engine exhaust, first using waste heat for methanol reforming to produce hydrogen and then utilizing exhaust inertial potential energy to drive a dual turbocharging structure for air compression entering the fuel cell, thereby achieving self‐thermal balance. Thermodynamic analysis and cost evaluation indicate that the thermal efficiency of this system is improved by 8.34% compared to traditional diesel engine setups. Compared to engine‐fuel cell hybrid systems that do not utilize waste heat, the thermal efficiency is increased by 5.81%. In terms of economics, the cost of the methanol engine system is ≈.1466$ kW h−1$\left(\text{kW h}\right)^{- 1}$, which is 44.05% lower than the 0.262 $ kW h−1$\left(\text{ kW h}\right)^{- 1}$ fuel cost of traditional diesel engine systems. This study presents an innovative solution that significantly enhances thermal efficiency and offers economic advantages, providing a viable approach to address the low efficiency and high emissions issues of traditional ICEs. [ABSTRACT FROM AUTHOR]

A thermal efficiency analysis of an organic Rankine cycle (ORC) system enables its performance to be evaluated; for this purpose, critical system components, including the turbine and the boiler, must be scrutinized. ORC plants can operate under various regimes, such as simple, regeneration, and reheat work modes. Organic fluids such as R-245fa integrate low-temperature sources such as solar radiation. However, a literature review revealed limited research on the impact of a solar collection system on the overall thermal efficiency of an ORC system during the regeneration stage. In this study, we examined the thermal efficiency behavior of an ORC plant with a 1 kW generator operating in simple and regeneration modes with a solar collection stage. The results show that the thermal efficiency in simple mode was 35.27%, while in regeneration mode with solar collection it reached 51.30%. Improving the thermal efficiency of a thermodynamic cycle system can reduce CO2 emissions. The operating temperature ranges facilitate the development of a methodology for industries to implement ORC systems in their manufacturing processes, thereby utilizing waste heat from industrial operations. [ABSTRACT FROM AUTHOR]

The objective of this study is to perform a thermodynamic analysis on a marine diesel engine waste heat-assisted cogeneration power plant modified with regeneration onboard a ship. The proposed system utilizes the waste heat from the main engine jacket water and exhaust gases to generate electricity and heat, thereby reducing the fuel consumption and CO2 emissions. The methodology includes varying different turbine inlet pressures, extraction pressures, and fractions of steam extracted from the turbine to evaluate their effects on the efficiency, utilization factor, transformation energy equivalent factor, process heat rate, electrical power output, saved fuel flow rate, saved fuel cost, and reduced CO2 emissions. The analysis demonstrates that the proposed system can achieve an efficiency of 48.18% and utilization factor of 86.36%, savings of up to 57.325 kg/h in fuel, 65.606 USD/h in fuel costs, and 180.576 kg/h in CO2 emissions per unit mass flow rate through a steam turbine onboard a ship. [ABSTRACT FROM AUTHOR]

This article aims to examine a novel combined power and refrigeration system, using renewable and waste heat sources suitable for low-temperature applications. The present system is an integrated Kalina cycle and ejector refrigeration system to generate power and refrigeration simultaneously. To improve the vapour generation, the separator vapour fraction is used as a decision variable. Relative irreversibility and efficiency defect as two important parameters considered in this system for an investigation to identify the weaker components. The combined system generates power and refrigeration with two different mediums by the incorporation of the heat exchanger at the turbine exhaust. The novel system's energy and conventional exergy evaluation are carried out through Python Software. The optimum values of decision variables: turbine concentration, separator vapour fraction, entrainment ratio, expander ratio, split ratio and turbine concentration are identified using Python software from an opted range of variables. The maximum value of net power output, first law efficiency for power generation system, combined system, second law efficiency for power generation system, combined system, refrigeration effect and coefficient of performance are obtained as 113 kW, 8.85%, 11.83%, 93.44%, 81.29%, 38.07% and 0.118, respectively, at higher separator vapour fraction. Among the components considered in the combined power generation system, the condenser and LTRGN account for the higher exergy destruction rate of 30.41% and 25.53%. The coefficient of performance is maximized at a higher value of the refrigeration effect. The turbine pressure at the inlet is increased with increments in turbine work on choosing the higher value of the expander ratio. The higher exergetic value components are not emphasized to focus on improvement. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials can effectively convert waste heat into electricity, which is a key technology for solving energy shortage problems. Poly(3,4‐ethylenedioxythiophene) (PEDOT), as a promising energy conversion material, has attracted much attention due to its easy doping, low toxicity, and high flexibility. However, the TE performance of PEDOT still needs further improvement. In this work, vapor phase polymerization (VPP) and ionic liquid (IL) post‐treatment are combined to obtain high‐performance PEDOT film. It is demonstrated that by varying the polymerization conditions, the optimal conductivity and Seebeck coefficient of PEDOT‐Tos are 947 S cm−1 and 18.3 µV K−1, respectively. Furthermore, after treatment with 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIM BF4), its power factor can be further enhanced to a maximum value of 154.58 µW m−1 K−2, which is 4.9 times higher than that without treatment (31.67 µW m−1 K−2). The enhanced TE performance of PEDOT is largely due to changes in doping levels and morphology, which have been confirmed through different characterization methods. These results will contribute to the preparation of high‐performance PEDOT films by the VPP method. [ABSTRACT FROM AUTHOR]

In some scenarios, electric heavy-duty trucks with battery swapping mode (ETBSm) are more cost-effective than battery charging mode. The viability of battery swapping stations is contingent upon the operational requirements and range capabilities of the ETBSm. Low temperatures have the effect of reducing the range of the ETBSm, thereby creating difficulties for battery swapping. This article proposes the use of motor waste heat recovery (MWHR) to heat batteries, which would improve range. A number of subsystem models have been established, including the ETBSm, battery, motor, and thermal management system (TMS). The calibration of battery temperature and motor efficiency is achieved with a model error of less than 5%. Comparison of performance, such as temperature, energy consumption, and range, when using only positive temperature coefficient (PTC) heating and when using both PTC heating and motor waste heat. The results indicate a 15% increase in the rate of rise in battery temperature and a 10.64 kW·h reduction in energy consumption under Chinese heavy-duty vehicle commercial vehicle test cycle (CHTC) conditions. Then, the motor waste heat percentage, energy consumption, and range are analyzed at different ambient temperatures. At an ambient temperature of −20 °C, −10 °C, and 0 °C, the percentage of the motor waste heat is 32.1%, 35%, and 40.5%; when 75% of the state of charge (SOC) is consumed, the range is improved by 6.55%, 4.37%, and 4.49%. Additionally, the effect of the PTC heater on temperature characteristics and power consumption is investigated by changing the target temperature of the coolant at the battery inlet. In accordance with the stipulated conditions of an ambient temperature of −20 °C and a target coolant temperature of 40 °C at the battery inlet, the simulation results indicated a battery temperature rise rate of 0.85 °C/min, accompanied by a PTC power consumption of 15.6 kW·h. This study demonstrates that as the ambient temperature increases, the utilization of motor waste heat becomes more effective in reducing PTC heating power consumption. At the lowest ambient temperature tested, the greatest improvement in driving range is observed. It is important to note that while an increase in the target heating temperature of the PTC helps to raise the battery temperature more rapidly, this is accompanied by a higher energy consumption. This article provides a reference for the ETBSm with MWHR. [ABSTRACT FROM AUTHOR]

In this paper, copper slag is used as the heat carrier of coal gasification reaction, and CaO is used as the CO 2 adsorbent of syngas to solve the problem of high cost of heat source and high proportion of CO 2 produced by coal gasification. When copper slag is used as the heat carrier, the adsorption effect of CaO on CO 2 is most pronounced at temperatures of 600 °C and 700 °C, with CO 2 proportion reduced to 8% and H 2 proportion reaching 65%. Additionally, CaO exhibits a significant promotion effect on carbon conversion rate and gasification efficiency at temperatures above 800 °C, with the maximum carbon conversion rate reaching 89% and the highest gasification efficiency reaching 78%. At low temperatures, CaO primarily functions in gas phase reaction, such as WGS reactions, hydrocarbon reforming reactions, tar reforming reactions, and pyrolysis reactions. As the temperature increases, CaO primarily functions in gas-solid reactions such as oxidation reactions and secondary water gas reactions. In high-temperature environments, iron compounds present in copper slag undergo iron reduction reactions, while the Ca 2 Fe 2 O 5 compound formed from the reaction of CaO and Fe significantly promotes reforming reactions. • The copper slag is used as the heat carrier, and the waste heat in the copper slag is utilized. • CaO was selected as the adsorbent, and the synergistic effect with copper slag was found during adsorption. • The proportion of H 2 in syngas can be increased to 89 %. • The reaction mechanism of different temperature stages was analyzed. [ABSTRACT FROM AUTHOR]

Hydrometallurgy is a novel metallurgical methodology that employs hydrogen as a reducing agent, thereby facilitating efficient, low energy consumption, and eco-friendly metal smelting processes. This study establishes a new fluidized bed hydrogen direction reduction system, which encompasses hydrogen production by water electrolysis, hydrogen direct reduction iron, waste heat utilization, and hydrogen recovery with Aspen Plus. The impact of the hydro-to-iron ratio and reaction temperature on the iron reduction and the energy and exergy efficiencies of the system is investigated. The results indicate that, the higher the hydro-to-iron ratio or reaction temperature, the higher the reduction rate. The energy efficiency of the system exhibits a non-linear trend with respect to temperature and the exergy efficiency demonstrates an overall increase with temperature or the hydro-to-iron ratio. • A new fluidized bed hydrogen reduction system with hydrogen recycling is established. • Increasing temperature and hydro-to-iron ratio enhances iron oxide reduction by hydrogen. • The energy efficiency of the system shows a non-linear trend with temperature. • The exergy efficiency increases with temperature or the hydro-to-iron ratio. [ABSTRACT FROM AUTHOR]

This paper focuses on proton exchange membrane fuel cell (PEMFC) operation at current densities in the order of 6 A/cm2. Such high current densities are conceivable when the traditional carbon fiber papers are replaced with perforated metal plates as the gas diffusion layer to enhance waste heat removal, and at the same time the relative humidity inside the fuel cell is kept below 100% by applying appropriate operating conditions as was found in previous one-dimensional modeling work. In the current paper, we applied a three-dimensional, multi-phase computational fluid dynamics model based on Ansys-CFX to obtain additional insight into the underlying physics. The calculated pressure drops are in very good agreement with previous one-dimensional modeling work, and the current densities in all case studies are in the order of 5–6 A/cm2, but different from the previous one-dimensional study, the results suggest that the relative humidity is very close to 100% throughout the entire channel length when the inlet relative humidity is 100%, ensuring best hydration cell conditions and hence best performance. Importantly, the model results suggest that fuel cell performance at a high current density in conjunction with relatively low stoichiometric flow ratios around 1.5–2 is possible. [ABSTRACT FROM AUTHOR]

This study proposes an innovative hybrid system that integrates a phosphoric acid fuel cell (PAFC) with an absorption refrigeration system (ARS) to enhance overall exergy efficiency. Waste heat from the PAFC is used in ARS generation. An evaluation is made of the energy efficiency, economic aspects, and the influence of the operating pressures of the two working fluid pairs, LiBr/H2O and R134a/DMF. In the combined PAFC-ARS, the absorption refrigeration unit incurs the highest exergy loss: 157 kW (R134a/DMF) and 146 kW (LiBr/H2O). The second-largest loss is experienced by the pure electrical generation PAFC unit at 117 kW. From an economic perspective, PAFC-ARS (LiBr/H2O) systems incur costs of USD 2.4/t for both hot water and cooling water, and USD 0.13 kW/h for electricity, with an 8 year payback period. In comparison, the R134a/DMF system entails costs of USD 2.1/t for hot water and cooling water and USD 0.16 kW/h for electricity. The PAFC exhibits a net output power of 434 kW, considering both energy and exergy perspectives. The corresponding maximum net electric energy efficiency (ηI) of the PAFC is 52%, while the overall exergy efficiency of the cooling model (ηII,dc) of the PAFC-ARS peaks at 56%, and the overall exergy efficiency of the heating model (ηII,dh) reaches its maximum at 61%. In conclusion, the PAFC-ARS (LiBr/H2O) demonstrates superior economic viability. [ABSTRACT FROM AUTHOR]

Despite the many benefits of greenhouses, it is challenging to meet their heating demand, as greenhouses belong to the most energy‐intensive production systems in the agriculture sector. Industrial symbiosis can bring an effective solution by utilizing waste heat from other industries to meet the greenhouse heat demand. This study proposes an optimization framework by which optimum symbiotic relationships can be identified. For this aim, the spatial analysis is integrated into an optimization model, in which geographical, technical, and economic parameters are considered simultaneously to identify the optimal location for developing new agricultural greenhouses. The objective function is to minimize the heating costs, that is, the investment cost of piping and electricity cost for pumping heat‐carrying fluid from supplier to demand. The model is applied to the case study of Switzerland, and currently existing municipal solid waste incinerators, cement production plants, and biogas plants are considered potential waste heat sources. Results show that the import of tomato, cucumber, and lettuce to Switzerland can theoretically be replaced by vegetable production in new waste‐heat supplied greenhouses (zero import scenarios). Accounting for the economy of scale for pipeline investment costs leads to selecting large‐scale greenhouses with a cost reduction of 37%. The optimization results suggest that 10% of the greenhouses needed to satisfy the total domestic demand for lettuce, tomato, and cucumber could be placed on a suitable land plot in the direct vicinity of a waste heat source, with low costs of waste heat supply. [ABSTRACT FROM AUTHOR]

Due to increasing emissions and global warming, in parallel with the increasing world population and energy needs, IMO has introduced severe rules for ships. Energy efficiency on ships can be achieved using the organic and inorganic Rankine cycle (RC) driven by exhaust heat from marine diesel engines. In this study, toluene, R600, isopentane, and n-hexane as dry fluids; R717 and R718 as wet fluids; and R123, R142b, R600a, R245fa, and R141b as isentropic fluids are selected as the working fluid because they are commonly used refrigerants, with favorable thermal properties, zero ODP, low GWP and are good contenders for this application. The cycle and exergy efficiencies, net power, and irreversibility of marine diesel engine exhaust-driven simple RC and RC with a recuperator are calculated. For dry fluids, the most efficient fluid at low turbine inlet temperatures is n-hexane at 39.75%, while at high turbine inlet temperatures, it is toluene at 41.20%. For isentropic fluids, the most efficient fluid at low turbine inlet temperatures is R123 with 23%, while at high turbine inlet temperatures it is R141b with 23%. As an inorganic fluid, R718 is one of the most suitable working fluids at high turbine inlet temperatures of 300 °C onboard ships with a safety group classification of A1, ODP of 0, and GWP100 of 0, with a cycle efficiency of 33%. This study contributes to significant improvements in fuel efficiency and reductions in greenhouse gas emissions, leading to more sustainable and cost-effective maritime operations. [ABSTRACT FROM AUTHOR]

Featured Application: The work in this paper provides some basic theoretical and practical reference value for the energy and exergy analysis, calculation, process optimization, and energy conservation research of the hydrogen-based direct reduction shaft furnace process, which is helpful for promoting its further industrial application. The traditional production mode using coal as the main energy source is not conducive to the sustainable development of the iron and steel industry (ISI). The hydrogen-based direct reduction shaft furnace (HDRSF) process is a feasible technical route for promoting the green development of the ISI. However, there is a lack of comprehensive analysis with respect to the energy utilization and process flow of the HDRSF method. To address these issues, a systemic material–energy–exergy model of HDRSF is established. An improved HDRSF process incorporating waste heat recovery is also proposed, and energy consumption intensity and exergy intensity are used as assessment metrics. This study's findings indicate that the proposed waste heat recovery can considerably lower gas demand and energy consumption intensity, but exergy intensity has little effect. The reducing gas demand drops from 2083 m3 to 1557 m3, the energy consumption intensity drops from 2.75 × 107 kJ to 1.70 × 107 kJ, and the exergy intensity drops from 1.08 × 107 kJ to 1.05 × 107 kJ when the reducing gas temperature is 900 °C, H2:CO = 1:1; meanwhile, the recovery rate of waste heat reaches 40%. This study can serve as a reference for actual HDRSF process production. [ABSTRACT FROM AUTHOR]

This study presents the potential of using a natural ventilation system integrated with different combinations of enhancement techniques. The focus was on the perspective of using such configurations of passive ventilation systems (PVSs) in buildings located in different European cities. This work presents the results of obtaining the level of volumetric air flow rate for considering natural ventilation systems. Furthermore, the influences of local weather conditions (temperature, solar radiation, wind speed) were analyzed. Moreover, the year-round operation of all systems was presented. Also noted was the limitation of using PVSs based on the natural draft effect, additionally assisted by wind turbine ventilators in all European localizations. However, for the cities located in the northern part of Europe, it was confirmed that such a system can still meet minimum hygienic recommendations. It was also noted that a system additionally supported by a solar chimney is a much better solution. The best system was a PVS supported by a wind turbine ventilator and solar chimney integrated with PCM accumulation mass. The system should be additionally supported by waste heat from low-temperature sources. In the presented study, a high potential to reduce CO2 emission from building stock by the recommended system is additionally highlighted. However, there is still a need to analyze the proposed solutions by additional field tests and experimental investigations. [ABSTRACT FROM AUTHOR]