• sCO 2 reverse Brayton high-temperature heat pumps are studied for industries. • Heat production temperatures up to 250 °C are examined. • Low-grade waste heat sources in the range of 50–120 °C drive the heat pump. • Internal heat exchanger increases COP by up to 8.13% and exergy efficiency by 6.54%. • Reheating and internal heat exchanger cycles improve COP by up to 15.5%. High-temperature heat pumps (HTHPs) are high-potential technologies for the decarbonization of low- and medium-temperature industrial heating processes. The conventional HTHPs can deliver heat up to 150-160 °C, while the process heat production at higher temperatures is a challenge that has attracted a lot of research in the last year. The goal of this work is to conduct a detailed investigation of different configurations of supercritical CO 2 reverse Brayton HTHPs, aiming to determine the most efficient and promising designs. This analysis investigates different process heat production from 150 °C up to 250 °C, while the HTHPs are driven by low-grade waste heat in the range of 50 –120 °C. This work is performed with developed mathematical thermodynamic models in Engineering Equation Solver, which are verified with literature data. According to the results of this analysis, the recompression is a proper solution for low heating production temperatures (mainly at 150 °C), while at higher heating production temperatures, the Reheating with an internal heat exchanger has to be selected. The application of the internal heat exchanger enhances the coefficient of performance up to 8.13% and the exergy efficiency up to 6.54%. For the typical case with source temperature at 100 °C, the average COP enhancement is found at 3.9% with internal heat exchanger, at 12.5% with Reheating with internal heat exchanger and at 15.5% with Double reheating with internal heat exchanger compared to the Simple cycle.

Improving the performance of parabolic trough collectors using waste material-based turbulence enhancers and artificial intelligence-supported models

Thermo-economic and data-driven optimization of an integrated biomass gasification system for green hydrogen, ammonia, and methanol synthesis via dual hydrogen production routes

• A moving-bed thermochemical energy storage system is experimentally investigated. • Pumice-based salt-in-matrix composite sorbents are developed and implemented. • The system achieves an energy storage density of 189.7 kWh/m 3 . • Maximum effective energy and exergy efficiencies are 52.7% and 6.8%, respectively. • A correlation between air humidity difference and temperature lift is established. In the last decade, low-grade thermochemical energy storage systems have been gaining interest due to their long-term heat storage potential and high energy storage density. Despite the advantageous aspects of this heat storage method, previously investigated fixed-bed reactors suffer from low heat and mass transfer performance and offer limited process control. In order to overcome these challenges, a new multi-layer moving bed reactor was designed, manufactured, and tested in this study. The proposed reactor consists of reaction and storage sections where eight independent sorption beds have freedom of movement between the two sections. Such a design enables a modular concept, where each sorption bed could be charged or discharged individually, while the remaining sorption beds are stored inside their own hermetically insulated chambers. In the system, two different sizes of pumice stones, namely PM1 and PM2, were used as the host matrix, and three different thermochemical materials were synthesized by impregnation of the LiCl-CaCl 2 mixture and CaCl 2 as salts into pumice. During the experiments, comparative analyses of different materials, short-cycle full-system analyses, long-cycle energy density analyses, and multi-bed performance analyses have been performed. Additionally, the impact of air velocity was investigated. The evaluations were performed based on the First and Second Laws of Thermodynamics. Study results demonstrated that each sorption bed provides an average heat output between 0.58 and 1.07 kW depending on the inlet air conditions and the composition of thermochemical material. According to the study results, the energy storage density of the system was obtained as 189.7 kWh/m 3 with the use of PM2-CaCl 2 . On the other hand, 4.2 m/s was found as the most optimal air velocity, proving the highest average heat output during the discharging process and the highest moisture desorption rate per unit of heat consumed during the charging process. A linear correlation between the air absolute humidity difference and the air temperature lift for the discharging process was also obtained, which could provide useful insights for the performance prediction of thermochemical energy storage systems.

Numerical analysis of transverse baffle effects on energy and exergy efficiency in an indirect solar dryer

Optimization of heat exchanger design for third generation centralized solar power generation system: CFD and thermoeconomic coupling method for improving thermal performance and reducing storage costs of batteries

Optimisation and 4E analysis of hybrid indirect solar electric dryer (HISED) for bitter gourd drying

A novel three-stage direct expansion cycle with optimal internal heat recovery and splitting-mixing processes for utilising LNG’s cold energy

Energy, exergy, economic and environmental assessments on a simple hydrogen liquefaction process under variable working conditions

Design and thermodynamic assessment of a sustainable waste to energy system for multiple useful outputs

This work examined the effects of using C-Pentane refrigerant in vapor compression refrigeration systems on energy, exergy, and Life Cycle Climate Performance (LCCP). System performance was evaluated depending on the changes in evaporator and condenser temperatures, and environmental and thermodynamic effects were analyzed at different temperature ranges. The results clearly show the effects of evaporator and condenser temperatures on the system COP. At a constant condenser temperature of 20°C, it is observed that the COP increases significantly as the evaporator temperature increases from -20°C to 0°C. Under these operating conditions, the COP increased from 3.58 to 8.24. However, raising the condenser temperature reduced the COP. When the condenser temperature was raised to 45°C, the COP decreased to 3.22. The exergy efficiency also generally increased with increasing evaporator temperature. When the condenser temperature was kept constant and the evaporator temperature increased, the exergy efficiency increased from 12.82% to 67.37%. However, increasing the condenser temperature raised exergy losses and decreased the efficiency. Especially when the condenser temperature was 45°C, the exergy efficiency decreased to 14.09%. The low GWP of C-Pentane ensured that direct emissions were minimal. Indirect emissions accounted for a significant portion of the system's electricity consumption. The results show that low condenser and high evaporator temperatures minimize the system's environmental impact by reducing the LCCP values.

This paper proposes and evaluates a novel solar-assisted multigeneration plant integrating a partial-cooling and reheated supercritical carbon dioxide (sCO2) Brayton cycle (BC) with an organic Rankine cycle (ORC), vapor compression refrigeration cycle (VCRC), thermoelectric generators (TEG), and a PEM electrolyzer to simultaneously produce electricity, cooling, and hydrogen. A comprehensive thermodynamic, economic, and environmental assessment is carried out. Parametric analyses are performed by varying solar irradiation, the turbine high pressure, and the compressor inlet pressure of the sCO2 BC to quantify their influence on subsystem interactions, irreversibilities, efficiencies, and hydrogen production. Results show that increasing solar irradiation enhances BC power from 3248.93 to 3762.02 kW and cooling capacity from 989.72 to 2997.33 kW, while the high pressure improves both energy and exergy efficiencies and lowers levelized cost of electricity (LCOE) and levelized cost of hydrogen (LCOH). On the other hand, raising the low pressure lowers BC energy output and hydrogen production but boosts heat recovery in the bottoming cycle. A genetic algorithm (GA) is used for multi-objective optimization to lower the LCOE and raise the exergy efficiency at the same time. The best setup has an exergy efficiency of 35.11% and an LCOE of 0.0471 $/kWh.

ABSTRACT Harnessing solar energy, solar water heating systems (SWH) offer a reliable and eco‐friendly way to meet hot water requirements, reducing reliance on fossil fuels and mitigating climate change. This review comprehensively assesses experimental efforts to enhance the thermal performance of SWH systems. It examines innovations in collector configurations, selective optical coatings, and advanced working fluids, such as nanofluids. The analysis evaluates key metrics, such as thermal and exergy efficiencies, by comparing experimental results with theoretical models, emphasising the importance of empirical data in addressing operational challenges. Comparative evaluations indicate that specific enhancements have improved thermal efficiency by over 60% compared to conventional designs. Nevertheless, issues related to cost, material durability, and scalability persist. The study highlights research gaps, including the need for sustainable phase change materials (PCMs), extended studies on nanofluid stability, and AI‐driven optimisation of system performance. These findings underscore the crucial role of experimental research in bridging the gap between theoretical models and practical applications, thereby supporting the broader adoption of SWH systems to promote global energy sustainability and decarbonization objectives.

ABSTRACT This paper details a hybrid operational and computational study for improving the thermodynamic performance of a Gas-Steam Combined Cycle Power Plant (CCGT) through a novel hybrid optimisation framework Adaptive Annealed NSGA (AANSGA. This framework integrates Non-Dominated Sorting Genetic Algorithm II (NSGA-II) and Simulated Annealing (SA). The study applies second-law (exergy) analysis and optimised heat integration approaches such as the pinch point method and the approach temperature difference method to reduce exergy destruction and improve thermal efficiency. Operational results were obtained from a laboratory-based CCGT study, where the gas turbine inlet temperature was 1400 K, the Heat Recovery Steam Generator (HRSG) outlet steam pressure was 20 bar, and the steam mass flow rate was 25 kg/s. The results show an increase in thermal efficiency from 46.96% to 54.12%, and an increase in the exergy efficiency from 84.95% to 85.55%. Similarly, fuel consumption improved from 2.425 to 2.405 kg/s, and CO2 emissions stabilised at 352 kg/MWh. The HRSG pinch point temperature difference was improved between 9.35°C − 9.47°C. The hybrid AANSGA approach achieved a reduction in total exergy destruction per cycle and improved operational stability. Overall, AANSGA provides a useful decision-support tool for the development of sustainable, high-performance power systems under dynamic conditions.

ABSTRACT The energy, exergy and emission performance of a four‐stroke diesel engine fueled with diesel (D100), Waste cooking oil (WCO30), waste plastic oil (WPO30), and their blend (WCO15WPO15) is compared. Energy and exergy analyses showed that the WCO15WPO15 mixture has the highest energy efficiency, approximately 20% (full load), compared to D100, which is 18% (full load). In addition, WCO15WPO15 exhibited higher exergy efficiency and more favorable combustion characteristics, attributed to the interaction between WCO's oxygenation and WPO's increased calorific value. This alternative shows a considerable trade‐off between particulate matter (PM) and nitrogen oxides (NOx) emissions. D100 had PM emissions of more than 2.5 g/kWh at full load, whereas the WCO15WPO15 blend demonstrated less than 2 g/kWh, corresponding to a 20% improvement. At full load, NOx generation of the WCO15WPO15 blend was above 800 ppm, 15% more than D100, due to higher combustion temperature. It was concluded that the WCO and WPO blends, particularly WCO15WPO15, are promising alternative fuels for diesel engines, increasing energy efficiency and reducing PM emissions. Future studies will focus on parameter optimization and exhaust aftertreatment to reduce NOx emissions, enabling cleaner, more sustainable combustion solutions.

The growing demand for clean and efficient fuels, along with the need to reduce environmental impacts and operational risks, has driven the development of sustainability strategies in refining processes such as gas oil hydrocracking. This paper evaluates the sustainability of an industrial gas oil hydrocracking process with mass and energy integration, using the Safety and Sustainability Weighted Return on Investment (SWROIM) metric. This metric integrates economic, energy, environmental, technical, and safety criteria into a single quantitative indicator. The process was modeled and simulated considering heat exchange networks and direct water recycle to improve the overall system efficiency. The main objective was to calculate the SWROIM of the integrated process and analyze the relative influence of each sustainability indicator through a sensitivity study based on varying weighting factors. The results show that the process achieves an SWROIM value of 127.39%, significantly higher than the return on investment (ROI), demonstrating favorable sustainable performance. This behavior is attributed to high exergy efficiency, a reduction in potential environmental impact, improvements in water management, and a decrease in the inherent risk of the process. Sensitivity analysis confirmed that the energy indicator has the greatest influence on SWROIM, while the technical criterion has a relatively minor impact. Overall, the results demonstrate that mass and energy integration, evaluated using advanced metrics such as SWROIM, is a robust tool to support decision-making in the sustainable design and optimization of hydrocracking processes, opening opportunities for future applications in other complex systems within the refining industry.

In humid climates, effective moisture control is essential for thermal comfort and reducing building cooling loads. This study experimentally evaluates a solar-regenerated solid desiccant cooling system integrated with an indirect liquid-to-air heat exchanger. The system uses a parabolic trough collector and a modified evacuated tube receiver for regeneration. Performance was analyzed under varying regeneration temperatures (60–90 °C), cooling water flow rates (50–125 liters/hour), desiccant wheel speeds (5–25 revolutions/hour), and ambient conditions. Results show that increasing regeneration temperature enhanced dehumidification by 27%, reducing humidity ratio from 18.5 to 13.5 g/kg, but also raised desiccant exit air temperature from 44 °C to 50 °C. Higher water flow maintains supply air temperatures 8–13 °C lower than at lower flow. Faster wheel speeds improved moisture removal (20.3 to 15 g/kg) but increased supply air temperature by 5.7 °C at 80 °C. Coefficient of performance (COP) improved with regeneration temperature and wheel speed, though exergy efficiency declined by 41% at high speeds. Optimal performance occurred at 80 °C regeneration, 100–125 liters/hour cooling flow, and 15–20 revolutions/hour wheel speed, achieving 0.67 COP and 31% exergy efficiency. Further, the potential of passive desiccant cooling was also confirmed through energy and exergy analysis, demonstrating the system’s viability as an energy-efficient solution for hot-humid regions, aligning with sustainable cooling demands.

ABSTRACT Atmospheric water harvesting (AWH) has emerged as a promising decentralized solution, enabling water generation directly from the air without depending on traditional water sources. The aim of present study is to analyze the effect of regeneration temperature and desiccant material quantity on the performance parameters of AWH system. Initially, single-bed configuration with 20 kg of silica gel is tested at regeneration temperatures of 80°C, and 120°C, and later dual-bed system with a total of 40 kg is evaluated to enable alternate sorption and desorption operation. During sorption process, the average ambient temperature and humidity ratio varies between 27.4–27.6°C and 16.1–18.6 g/kg of dry air. The results show that higher regeneration temperatures significantly enhance the desorption rate (0.76–1.52 kg/h) and reduce the desorption time (7 h at 80°C to 4 h at 120°C). With two desiccant beds, the system achieved a water uptake of 302.5 g per kg of desiccant material and a desorption rate of 1.04 kg/h, resulting in a daily water production of 10.4 L/day. The corresponding energy and exergy efficiencies are 26.5% and 6.1%, respectively. These findings demonstrate that increasing both regeneration temperature and desiccant mass significantly improves the water harvesting capability and thermodynamic performance of AWH system.

Freshwater scarcity remains a major challenge in arid and coastal regions, and conventional solar stills often suffer from low productivity, limited thermal efficiency, and high operational costs, highlighting the need for improved designs. This work examines a new form of the oval tubular solar stills, OTSS. This study focuses on enhancing the daily, nighttime, and overall (diurnal) productivity of freshwater by employing advanced materials. In the present investigation, paraffin wax (PW) was used as a phase change material (PCM), while nano-alumina-enhanced paraffin wax (NAPW) was applied to improve the thermal conductivity of PW. The OTSS is a simply distinguish design, lower cost, and high production rate of desalinated water. The OTSS is used with PW, without PW, and with NAPW. The experiments were conducted under Cairo, Egypt climatic conditions (Latitude 30.10 N longitude 31.29E) with varying basin water depths (0.5–2 cm) and Al2O3 concentrations (0.1–0.3 wt%). Results show that OTSS with PW achieved a maximum productivity of 6.53 L/m2/day, while the addition of NAPW further increased productivity to 7.26 L/m2/day and thermal efficiency to 68.24%. Daily thermal exergy efficiency improved from 3.41% (without PW) to 4.52% (with NAPW), and the production cost decreased from $0.0208 to $0.0163 per liter. The study demonstrates the effectiveness of integrating PCM and nanoparticles in OTSS to improve freshwater yield, thermal performance, and economic feasibility.

Study on the exergy efficiency and hydrogen production rate in biomass gasification process based on pilot-scale