Compressed carbon dioxide energy storage (CCES) technology has garnered considerable interest in compressed gas energy storage due to its broad applicability and high efficiency. However, differences in carbon dioxide (CO₂) storage phase states lead to variations in system configuration, efficiency, and energy density, which remain insufficiently studied. This study systematically investigates six CCES configurations with distinct storage forms: supercritical-supercritical (SC-SC), supercritical-liquid (SC-L), liquid-supercritical (L-SC), liquid-liquid (L-L), supercritical-liquid with pumping (SC-L-P), and liquid-liquid with pumping (L-L-P). A thermodynamic framework integrating energy and exergy analysis is established, with the work ratio and round-trip exergy efficiency proposed as key metrics for efficiency assessment. The performance of these configurations under variable operating conditions caused by dual-tank structures is analyzed, with emphasis on density variations of CO₂ within tanks and exergy loss distribution. Results demonstrate that the SC-L-P system achieves the highest work ratio of 78.17% by elevating the expander inlet pressure. The SCSC system exhibits the highest round-trip exergy efficiency of 68.20% due to the absence of phase transitions. The L-SC system achieves energy density of 0.96 kWh/m³ with 74.95% tank utilization leveraging gas-liquid phase conversion of saturated liquid. The findings provide critical theoretical guidance for storage-phase selection and integrated system design in CCES technology under diverse application scenarios.

High-temperature heat pump applications can be extended beyond building heating to encompass a wider range of industrial heating sectors, representing a significant avenue for advancing heat pump technology. A comprehensive investigation was conducted on four distinct transcritical CO₂ heat pump cycles: the basic cycle, the reheat cycle, the ejector cycle, and the ejector reheat cycle. The thermodynamic models and multi-objective optimization models of each cycle were established considering the temperature difference of heat transfer pinch point of heat exchanger and the phenomenon of non-equilibrium phase change of the ejector. A cycle optimization method for solving the phase equilibrium problem was proposed for the ejector cycle and the ejector reheat cycle. The study shows that: the reheat process is necessary for the production of high temperature hot water. The maximum heating temperature of each cycle is limited by the compressor discharge pressure and discharge temperature, with a peak heating temperature reaching up to 124.0°C in an environment of 20°C. At a heating temperature of 90°C, the COP of each cycle is equal, at about 4. When the heating temperature is higher than 90°C, the cycles with an internal heat exchanger have better performance; when the heating temperature is lower than 90°C, the cycles with an ejector have better performance.

In order to solve the problems of poor performance of prime power equipment running at off-design condition and insufficient utilization of the exhaust waste heat of the power equipment in traditional combined cooling heating and power (CCHP) system, a powercooling- heating-compressed air multi-generation system coupled with compressed air energy storage (CAES) and thermal energy storage was proposed. The system model was established, and the sensitivity analysis of key parameters that affect the performance of system was carried on, such as isentropic efficiency of compression/expansion, maximum/minimum pressure of compressed air reservoir, compressed air production pressure and flue gas flow rate. Sensitivity analysis revealed the existence of an optimal compressed air production pressure and demonstrated that increasing the flue gas flow rate enhances system performance across all operating conditions. The results showed that proposed system represents excellent thermodynamic performance, of which the primary energy ratio, the primary energy saving rate (PESR) and the exergy efficiency is 3.78, 6.11and 4.33 percentage point higher, respectively. Furthermore, the T-Q diagram analysis of exhaust gas cascade utilization elucidated the fundamental mechanisms behind performance improvement.

Under the global energy transition and the “Dual Carbon” goals, enhancing the efficiency of traditional energy systems and cutting carbon emissions is crucial, to reduce waste heat in CCHP systems, this paper presents a low-carbon CCHP system using heat pump technology, combined with an MEA carbon capture system, to recover and use low-temperature waste heat from flue gas and carbon capture. Through thermodynamic analysis, models for energy and exergy balance of the system are built. The results show that the heat pump boosts system efficiency and waste heat usage by recovering flue gas waste heat and carbon capture regeneration tower waste heat, with energy efficiency rising from 74.25% to 81.22%, and waste heat recovery increasing from 73.59% to 89.85%. Compared to the traditional system, the exergy loss of the designed system decreases by 182.53 kW, and the exergy efficiency improves from 53.95% to 65.07%. Also, the compressor power has a small impact on system performance, but when the waste heat boiler flow is fixed, the efficiency drops rapidly with increasing input power. This study offers new ideas for designing and optimizing low-carbon, high-efficiency CCHP systems.

To accelerate the construction of satellite internet, flat-panel satellites offer significant advantages due to their modular design and stackable launch capabilities. This paper addresses the requirements for temperature stability and uniformity in the thermal control system of flat-panel satellites. Through thermal simulation analysis and thermal balance testing, the rationality of the heat pipe network layout is validated, and a new heat pipe layout is proposed. The impact of different heat pipe network layouts on the overall satellite’s temperature stability and uniformity is analyzed. The study demonstrates that adopting the new heat pipe network layout significantly improves the satellite’s temperature levels and stability: the maximum temperature of the main radiating surface facing the sky panel decreases from 49.7°C to 38.1°C, and the maximum temperature difference across the cabin panel is reduced from 41.8°C to 28.2°C. Based on the proposed short-path heat dissipation method for the heat pipe network, the maximum temperature difference across the cabin panel can be further reduced. The highest temperature of the cabin panel decreases by 7.9°C, temperature fluctuations are substantially reduced, and the required mass of heat pipes is also minimized.