The start-up energy consumption of parabolic trough concentrated solar power (PTCSP) systems is high due to the characteristics of their daily start-up and shut-down processes. To reduce this energy consumption, quasi-steady state models for a 50 MW PTCSP are established, and a daily optimal operating mode is proposed by replacing the start-up and shut-down processes with low-load operation. The critical shut-down time is derived theoretically to determine whether the optimal operating mode could reduce energy consumption. The results show that, the daily accumulated electricity production of a PTCSP can be improved by 16.3~26.3 MW·h with the optimal operating mode when the electricity production decreases from 25% to 10% of the rated production under low-load condition. When the initial energy storage duration in the thermal energy storage system increases from 0 to 3.0 h, the daily accumulated electricity production of the PTCSP system can be improved by 7.2~8.1 MW·h. Additionally, the critical shut-down time of the PTCSP system is 14.0 h when the load is 15% of the rated electricity production under low-load operating conditions. The start-up energy consumption of the PTCSP system with the optimal operating mode can be reduced when the practical shut-down time is shorter than the critical shut-down time. The annual electricity production of the PTCSP system can be increased by 0.9% with the optimal operating mode.

As a key component of air source heat pump, the thermodynamic performance of scroll compressor has an important influence on the heat pump system. A three-dimensional transient simulation model of the scroll compressor is established, and the accuracy of the model is verified through experiments. Based on computational fluid dynamics method, the non-uniformly distributed flow characteristics of internal flow field of the scroll compressor under the influence of tangential leakage flow are investigated. The influence of different operating conditions on thermodynamic performance of the scroll compressor is explored. The sensitivity analysis method is used to discuss the sensitivity of thermodynamic performance of the scroll compressor under different operating conditions. The results show that, with the increase of pressure ratio, the isentropic efficiency increases at first and then decreases, the heat production decreases, the maximum increase in time-averaged exhaust temperature is 11.26 K. When the suction temperature increases to 311.65 K, the isentropic efficiency grows by 16.72 percentage points. The increase of rotational speed will weaken the phenomenon of reflux and reduce the exhaust temperature, when the rotational speed rises to 4 500 r/min, the volumetric and isentropic efficiencies increase to 86.61% and 46.86%, respectively.

For helical coiled tube steam generator for liquid metal reactor, the working medium at the first side is liquid metal and that at the second side is water, and its thermal and hydraulic characteristics are significantly different from those of conventional pressurized water reactor natural circulation saturated steam generators. The helical coiled tube steam generator of liquid metal reactor is equivalent as flow network system and divided into flow circuits, pressure nodes, and other components. The mathematical model for calculating thermal hydraulic parameters such as pressure drop, flow rate and temperature, and mathematical model for calculating the metal wall temperature of tube bundles are established, based on the mass, momentum and energy conservations. Moreover, the profile of flow rate, pressure drop, working medium temperature, outlet steam temperature, wall temperature, vapor quality and heat transfer coefficient in helical coiled tubes are obtained through the direct solving of nonlinear equations composed of unknown flow rate and pressure nodes in the flow circuit. The flow and heat transfer characteristics of the helical coiled tubes in steam generator are obtained. Besides, one-dimensional system analysis and calculation programs are proposed other than RELAP5 and the thermal hydraulic calculation method of helical coiled tube steam generator has been improved.

When operating at low loads, W-flame boilers may encounter various problems, such as low reheated steam temperature, which requires combustion adjustments and other measures. To solve these problems, numerical simulations are conducted to investigate the combustion adjustment of a W-flame boiler under low load conditions. In order to deal with the low steam temperature at low loads, the influence of the position of the recycled flue gas injection and the presence of wall-attached air on the velocity field and temperature field inside the furnace were analyzed. The research results show that introducing recycled flue gas into the furnace by extracting 16% of the total flue gas flow at the air preheater inlet increases the amount of flue gas and improves the convective heat transfer on the heating surfaces. Combined with adjusting the opening of the reheater flue gas baffle, this approach can solve the problem of low reheated steam temperature at low loads. Injecting recycled flue gas from the SOFA air nozzle into the furnace has a minimal impact on the temperature in the primary combustion zone, which benefits the stability of coal combustion at low loads. Introducing 40% of the recycled flue gas as wall-attached air from the side walls of the lower furnace can lower the temperature of the side wall flue gas and transform it into an oxidizing atmosphere, reducing the possibility of side wall coking and high-temperature corrosion.

The intermittency and volatility of renewable energy generation poses significant challenges to grid integration. A waste heat-coupled Carnot battery system, based on heat pumps and organic Rankine cycles, is considered a potential solution. However, the system’s power-to-power efficiency is greatly affected by waste heat temperature. To address this issue, a novel high-efficiency Carnot battery system is proposed, utilizing vapor injection and regeneration technologies in the charging and discharging modules, respectively. A thermodynamic model is developed to investigate the cycle performance of the system under various operating conditions. Additionally, the energy consumption and economic viability of the system are analyzed in three representative cities: Guangzhou, Nanjing, and Harbin. The results indicate that, the power-to-power efficiency increases with higher heat source temperatures and lower ambient temperatures. Moreover, the new system features an optimal intermediate pressure during both the charging and discharging processes, maximizing efficiency. Compared with the conventional Carnot battery systems, the new system demonstrates a 21.8%, 22.5%, and 23.6% increase in daily average power to power efficiency in Guangzhou, Nanjing, and Harbin, respectively. Furthermore, the annual net income increases by 45.6%, 52.8%, and 50.2% in these cities, respectively. This study provides theoretical guidance for enhancing the efficiency of Carnot battery systems.

The influence of main-auxiliary combined indirect air-cooling tower at different ambient wind speeds and with different directions on flow heat transfer characteristics of the unit under normal working conditions in summer is investigated via numerical simulation. The results show that, as the ambient wind speed increases from 4 m/s to 16 m/s, the pressure in windward fan section of the main-auxiliary combined indirect air-cooling tower will increase, while the pressure on both sides of the fan section will decrease. The pressure on the inner side of the back fan section will increase and high-temperature zones which will decrease in quantity when the wind speed exceeds 8 m/s will form. The pressure on the outer side will decrease, and the pressure change in the upwind and backwind sections will be greater than that on both sides of the fan section. The total heat transfer in the main fan section will continue to decrease, while the auxiliary fan section will continue to increase slowly and be less affected by environmental wind. In different environmental wind directions, when the wind direction angle is 0° or 180°, the heat transfer of the blocked tower will increase significantly. When the wind direction angle is 45° or 135°, some fan sections between the two towers will be blocked, and the heat transfer of the blocked tower will decrease slightly. The maximum heat transfer of the main fan section occurs in the direction where the environmental wind is completely blocked, and the maximum heat transfer of the auxiliary fan section occurs at a 90° environmental wind direction angle, which is directly facing the auxiliary fan section.

Overdue service of thermal power units has become a trend, but fatigue crack of turbine rotor steel seriously affects the operation safety of steam turbine units. Due to the lack of the fatigue crack growth (FCG) test data of rotor steel, and large computation cost for stochastic model modeling and solution, the estimation of fatigue crack remaining useful life (RUL) is currently insufficient. On the basis of fatigue crack growth tests and analysis on its random models, a modified Gaussian membership information expanded (GMIE) sample domain method is proposed to generate virtual samples based on mega trend diffusion (MTD). Meanwhile, an extreme machine learning (ELM) neural network combined with the expective regression (ER) model is used to predict the RUL of fatigue crack propagation. The RUL of fatigue crack propagation under a specific cycle is calculated. By comparing the results with the RUL probability density function (PDF) curve and fatigue crack propagation curve of the existing numerical analysis methods, it shows that mean absolute percentage error (δ_MAPE) is 2.78%, which verifies the effectiveness of the proposed method and provides robust support for safe operation of the turbine rotor systems.

To investigate the effect of blending ratio on co-combustion characteristics of sludge hydrothermal carbon and municipal solid waste, and reveal the interaction between the two materials, thermogravimetric analyzer is used to test the combustion characteristics of sludge hydrothermal carbon, municipal solid waste and mixed samples. The combustion kinetics of the samples were analyzed by Coats-Redfern method. Based on the difference between the experimental combustion characteristics and the theoretical combustion characteristics of the mixed samples, the interactions between the two materials was revealed. The results showed that, the ignition temperatures and burnout temperatures of the mixed samples decreased with the increase of sludge hydrothermal carbon blending ratio, but the combustion rate also decreased, resulting in a decrease of the comprehensive combustion characteristic index. As the blending ratio of sludge hydrothermal carbon increased from 0% to 80%, the comprehensive combustion characteristic index of mixed sample decreased by 71.8%. With the increase of sludge hydrothermal carbon blending ratio, the activation energy of volatile combustion stage decreased, while the activation energy of char combustion stage increased. There was a significant interaction between sludge hydrothermal carbon and municipal solid waste, which can inhibit the combustion of volatiles. In the blending ratio range of 20%~80%, the comprehensive combustion characteristic index of the mixture decreased by 12.9% on average. The research results can provide data reference and theoretical basis for the control of the working condition and the design of ACC automatic control system in the municipal solid waste incineration plant.

The recent advancements in key materials including reactants and catalysts employed in solid-gas, gas-gas, and liquid-gas solar thermochemical energy storage (TCES) systems are reviewed. The thermochemical properties of reactants such as carbonates, hydroxides, metal hydrides, metal oxides, organics, and ammonia are examined. The research status of the modification of these reactants, new material development, and catalyst improvement are also discussed. At present, the reactant materials suitable for solar TCES exhibit various deficiencies in terms of cyclic stability, reactivity, conversion rate, energy storage density, cost or safety, which hinder the commercial viability of solar TCES technology. To further enhance the maturity of solar TCES technology, it is imperative to develop advanced composite materials on the basis of known thermochemical reaction systems, improve novel efficient catalysts, and broaden demonstration application scenarios and scales in the future. The key materials should endow TCES systems with high energy storage density, more robust cyclic stability, and rapider reaction kinetics. It is preferred that they are readily available, non-corrosive, and non-toxic and more cost-effective.

In the context of global energy transition towards cleaner, more efficient, and sustainable energy sources, nuclear power is recognized as a critical base-load power source that serves as a substitute for fossil fuels, playing a pivotal role in transformation of energy structure. Key advancements in integration of large-scale energy storage technologies with nuclear power are introduced, with an emphasis on analyzing the coupling modes of thermal storage, mechanical energy storage, and electrochemical energy storage with nuclear power, as well as their potential to enhance the performance of nuclear power stations. Various methods of coupling energy storage technologies with nuclear power stations are explored, encompassing thermal, mechanical, and electrical coupling, and the effects of these methods on operation of nuclear power plants are discussed. Additionally, solutions for the integration of energy storage systems are presented, such as the redundant design of turbines and the design of heat exchanger-based energy storage. The research points out that, the development of energy storage technologies will offer a broader array of flexible technological options for nuclear power stations, aiding nuclear power in playing an even more critical role in the global energy transition.