In order to solve the problem of mismatch between heat source temperature and evaporation pressure in low-pressure stage, a double gas-liquid separator (DS-DPORC) system was proposed based on the basic dual-pressure organic Rankine cycle (DPORC) system. The thermal performance of DPORC and DS-DPORC system is compared and analyzed. Both traditional and advanced exergy analysis methods were used to study the improvement potential and interaction relationship of the optimized DS-DPORC system and its components. It is shown that there is an optimal evaporation pressure at high and low-pressure stages, respectively, which enables the thermal performance of both systems to reach the optimal level. At that time, DS-DPORC had a 10.02% increase in net output compared to DPORC, while the exergy efficiency increase was 10.4%. There are differences between traditional and advanced exergy analysis methods. The former thinks that the preheater with the highest exergy destruction has the greatest potential for improvement, while the latter thinks that the high-pressure turbines has the highest priority for improvement considering both the exergy destruction rate and the exergy destruction. In addition, exergy destruction of various components in the DS-DPORC system mostly belongs to internal exergy destruction, and the exergy destruction of components is relatively poor in inter dependency.

Calcium cycle technology (CaL) is highly compatible with concentrated solar power (CSP) plants due to its high temperature resistance and high heat storage density. However, the poor stability of CaO cycle and poor light absorption performance limit the overall efficiency of the system. In this study, steel slag was used as a raw material to prepare novel calcium-based materials by acetic acid impregnation and doping with different ratios of manganese. The results showed that the material doped with 5% manganese had the best performance. Through thermogravimetric tests and 30 cycles of thermal storage experiments, the adsorption rate is increased by 85% and the energy storage density is increased by 73% compared with CaO. In addition, its light absorption rate is 9.5 times that of CaO. The light-driven simulation experiments also further validate its potential for application in the system, demonstrating a wide range of prospects for use in next-generation CaL-CSP systems.

A simulation study has been conducted on a water-based Photovoltaic-Thermal (PVT) heat pump system using different types of solar cells. An energy loss model for photovoltaic (PV) modules and a thermodynamic model for the PVT heat pump system are established and experimentally validated. The energy distribution of three high-efficiency monocrystalline silicon (c-Si) PV modules—PERC (Passivated Emitter and Rear Cell), TOPCON (Tunnel Oxide Passivated Contact), and HJT (Heterojunction with Intrinsic Thin-film)—is analyzed at different temperatures, and the temperature coefficients are calculated. The temperature sensitivity varies for different types of PV cells. The HJT module exhibits the lowest temperature coefficient at −0.27% among them. The performance of the PVT heat pump system based on three c-Si solar cells is compared on typical days throughout the year. The results indicate that the power generation efficiency of the HJT module is improved by 12%∼15% compared to PERC, while the average COP is slightly reduced by 0.8%∼1.3% compared to the PERC system. Therefore, using high-efficiency photovoltaic modules is an effective way to improve quality and efficiency in PVT heat pump systems. The system’s COP in summer could reach 7.11, while the COP in winter is 4.62.

When the supercritical carbon dioxide(S-CO₂) Brayton cycle is applied to low temperature cold source scenarios such as deep sea and polar regions, the compressor inlet temperature is limited by the critical point of CO₂ (30.98°C) and cannot be further reduced, the critical temperature of CO₂ can be adjusted by adding the second component of working medium to CO₂, which is expected to improve the cycle thermal efficiency while adapting to the low ambient temperature. In this paper, the thermodynamic performance of S-CO₂ mixed-work mass Brayton cycle system under low-temperature environment is analyzed, and SF₆, Xe, Kr, and Ar gases are selected as the additive work masses to analyze the effects of main compressor inlet temperature, turbine inlet temperature, turbine inlet pressure, and diversion ratio on the thermal efficiency of the system cycle with different work masses and different critical temperatures. The results show that the addition of the above additives can improve the thermal efficiency of the cycle, among which the addition of Xe and Kr has the greatest improvement on the cycle thermal efficiency. The optimal cycle thermal efficiency of CO₂-Xe and CO₂-Kr are increased by 2.4% and 2.3% compared with pure CO₂ at a critical temperature of 14°C for the mixture working fluid.

In this study, a mathematical model of a static hybrid power generation system composed of a cesium thermionic energy converter (CTEC) and a thermoelectric generator (TEG) was established. The model takes into account the irreversible heat loss and additional energy barriers of the CTEC module, as well as the Thomson effect of the TEG module. The effects of the CTEC output voltage, anode work function, and TEG current on the system’s output power and conversion efficiency were investigated. The results show that the output power and conversion efficiency of the hybrid power generation system exhibit a parabolic relationship with the increase of the CTEC output voltage. Reducing the anode work function is beneficial for improving system performance, while the TEG current has a minor impact on the system. The optimal operating region of the system was determined by analyzing the relationship between efficiency and output power, providing a reference for the optimal design and application of CTEC-TEG hybrid power generation systems in the future.