Sugar alcohols are gaining attention as highly promising medium-temperature phase change materials (PCMs) due to their superior overall performance. Currently, the evaluation of the comprehensive performance of sugar alcohol composite PCMs optimized for a single objective remains incomplete. In this study, erythritol (Ery) was used as a PCM, combined with expanded graphite (EG) and Al₂O₃ as additives. A ternary composite PCM was prepared using the melt blending method, and its comprehensive performance was assessed. The results showed that the components of the ternary composite PCM exhibited excellent physical compatibility. Among them, the ternary composite PCM with 0.5%(wt) Al₂O₃ / 1.5%(wt) EG/Ery demonstrated the best overall performance. This ternary composite PCM maintained a high melting enthalpy of 312.9 kJ/kg and, compared to Ery, achieved a thermal conductivity of 1.083 W/(m·K), an increase of 54%. In the isothermal cooling test, its supercooling degree was reduced by 9.3°C, in the non-isothermal cooling process, its supercooling degree was reduced by 16.7°C. The pyrolysis temperature increased by 20°C, and the maximum pyrolysis rate temperature increased by 8.3°C, significantly enhancing thermal stability. Additionally, after 40 isothermal cycling tests, its supercooling degree and melting enthalpy remained essentially unchanged, demonstrating excellent cycling stability.

The International Maritime Organization (IMO) and port States have increasingly stringent requirements for ship energy efficiency, and the improvement of ship energy efficiency based on waste heat recovery is one of the most effective ways to meet this challenge. TEG-ORC combined cycle is a new method to realize the utilization of multiple waste heat steps in ships, but the effect of bottom cycle ratio on the performance of combined cycle system has not been studied in detail. The theoretical model is optimized and the influence of variable bottom cycle ratio on the performance of the main parameters of the combined cycle system is studied experimentally. The experimental results show that under the conditions of ORC bottom cycle working medium R245fa, working medium mass flow rate m = 0.079 kg/s and evaporation pressure P = 0.7 MPa, with the gradual increase of bottom cycle ratio, the system output power and flue gas waste heat utilization rate of the main engine increase, and the cost of combined power generation decreases. When the bottom cycle ratio of TEG/ORC is 0.885, the flue gas waste heat utilization rate of the main engine is 85.07%, the total output power of the system is 688.4 W, the thermal efficiency of the system is 7.07%, and the power generation cost of the combined cycle system is 3.338 CNY/kWh.

The efficiency of the supercritical carbon dioxide (SCO₂) Brayton cycle is closely related to the parameters of the components in the cycle system. Based on the MATLAB/Simulink platform, a modularized calculation procedure for the SCO₂ Brayton cycle was established. The design and analysis of a large capacity coal-fired power generation system were carried out using split flow recompression and secondary reheating schemes, and the influence of relevant parameters of components was investigated, such as turbines, compressors, and flue gas coolers. The results showed that the optimal split ratio of the recompressor decreased with the increase of turbine inlet pressure; The power distributions of the heater exchangers in boiler were significantly affected by the split ratio of the flue gas cooler; The circulation efficiency of the system reached its highest level at 35 MPa and 600°C , when the primary reheat pressure and secondary reheat pressure were 25 MPa and 16 MPa, respectively, and the split ratio of the recompressor and the flue gas cooler is 0.3 and 0.05, respectively; As the inlet temperature and pressure of the compressor increased, the circulation efficiency gradually decreased. The research results of this article have important reference value for the establishment and optimization of the large-scale coal-fired SCO₂ power generation systems.

Owing to their favorable thermodynamic performances, transcritical power cycles utilizing carbon dioxide (CO₂)-based mixtures have emerged as an optimal choice for the power cycle part in medium to low-temperature trough-type concentrating solar power (CSP) systems. This study introduces a two-layer decision-making framework grounded in multi-objective optimization to facilitate the selection of appropriate CO₂-based mixtures. The analysis assesses the effects of diverse key parameters on the thermodynamic performance, economic feasibility, and environmental dimensions of the system. The research findings reveal that the CO₂/R32 mixed working fluid maximizes the net power output, achieving 253.77 kW. Simultaneously, the CO₂/R161 mixed working fluid exhibits superior thermal efficiency (9.80%), economic viability (0.6444 USD/kWh), and reduction in carbon emissions (0.0329 kg/kWh). Moreover, TOPSIS decision-making results suggest that, across various thermal storage tank temperatures, the selection of the CO₂/R161 mixed working fluid is of paramount importance.

To address the challenges of carbon dioxide capture in hydrogen production and electricity generation from fossil fuels, as well as the supply-demand mismatch in the utilization of intermittent and unstable solar energy, this paper proposes a solar-driven hydrogen and electricity cogeneration system with source decarbonization. The system employs an iron-nickel mixed oxygen carrier, which reduces the reduction reaction temperature while achieving efficient carbon dioxide capture. The results indicate that under a solar irradiance of 750 W/m², the system achieves a solar energy input ratio of 30.80%, with energy utilization rates of 67.23% and 59.47% for hydrogen production and electricity generation under design conditions, respectively. In addition, by regulating the sensible heat of the inlet oxygen carrier and its oxidation degree during the reaction process, the system can operate stably under varying irradiation conditions and flexibly adjust hydrogen and electricity outputs. When the solar irradiation intensity is 750 W/m², the adjustable hydrogen-toelectricity ratio ranges from 0.17 to 0.59 m³/kWh, demonstrating excellent adaptability to varying operating conditions. This study offers a novel technological pathway for highly efficient hydrogen and electricity co-production and source decarbonization through the complementary use of solar energy and natural gas.