To ensure the continuously stable operation of adiabatic isothermal-compressed air energy storage system, an adiabatic-isothermal compressed air energy storage method coupled with buffer tank is proposed. The dynamic thermodynamic model of the buffer tank coupled system is established, and the experimental platform is set up to verify the model. Besides, the variation mechanism of air temperature and pressure in the buffer tank is revealed, and the influence of design parameters of buffer tank on system performance is explored. The results show that, the adiabatic-isothermal compressed air energy storage system with buffer tank exhibits favorable isotherm, and the highest temperature difference at 30 K during the cycle. The adiabatic efficiency of the compressor unit of the coupled buffer tank system increased by 8 percentage points, and the exergy loss of the compressor unit decreased. Sensitivity analysis shows that the change of energy storage power has little effect on thermodynamic parameters of the air storage room, and the volume of the buffer tank decreases with the increase of energy storage power. Moreover, the change of energy storage scale has little influence on thermodynamic parameters of the air storage room, and the change trend of air temperature shows a periodic fluctuation. When the system energy storage scale increases, the volume of buffer tank will increase with the energy storage scale. The study provides a novel scheme for the continuous, stable and efficient operation of adiabatic-isothermal compressed air energy storage system.

An axial tangentially swirl low nitrogen burner is designed based on flue gas internal circulation and staged combustion, and the effects of the burner’s load, fuel staging, and recycled high-temperature flue gas on combustion and NO_x emission characteristics are studied through industrial experiments and numerical simulations. The results indicate that, the loads and fuel staging ratios have a synergistic effect on NO_x generation. Under medium and low load conditions, the NO_x emissions increase monotonically with the secondary fuel ratio, large amount of NO_x generates in the secondary flame zone. At full load, there exists an optimal primary to secondary fuel ratio (88:12), which minimizes the NO_x emissions. When the secondary fuel ratio falls below 12%, the primary flame zone becomes dominant in NO_x production. The length of the primary fuel mixing pipe can alter the fuel and air mixing process, thereby affecting NO_x generation. When the relative length of primary fuel mixing pipe is shortened to 0.74, the main combustion zone moves upstream in the furnace, and the main flame is anchored in the middle of the furnace, resulting in a more uniform temperature distribution at the rear of the furnace. The NO_x emission mass concentration decreases by 10%~20% across all loads, all below 30 mg/m³ (with O₂ volume fraction of 3.5%, the NO_x is calculated as NO₂).

Conventional energy storage systems have high investment costs, long payback periods, and cannot be applied on a large scale in park level systems. In response to this issue, an integrated energy system in the park is established firstly, which includes hybrid virtual energy storage such as electric vehicles, air conditioning, and heating network pipelines. Moreover, the operating mechanism of the system is also analyzed. Relevant models for system and virtual energy storage are constructed. Secondly, based on correction indicators such as peak valley difference and external grid interaction scale, a hybrid virtual energy storage incentive mechanism considering dynamic time of use prices is proposed. Then, under the carbon cycle mechanism of waste incineration cogeneration flue-gas treatment-P2G, a low-carbon operation optimization model for the integrated energy system in the park is constructed with the goal of maximizing profits. Finally, a case study is performed on an integrated energy system in a certain region, and the results show that, operation optimization considering hybrid virtual energy storage can reduce external grid interaction costs. A hybrid virtual energy storage incentive mechanism considering dynamic time-sharing prices can improve the enthusiasm of virtual energy storage entities to respond to system scheduling. Considering the carbon cycle mechanism of waste incineration cogeneration flue-gas treatment-P2G can increase net revenue.

In order to build a large capacity flexible power supply and solve the dilemma of balancing winter peak shaving and heating for coal-fired units, six new “solar thermal storage” integrated power generation systems are proposed based on conventional thermal power plants (CFPP), utilizing solar energy and molten salt thermal storage to balance winter heating. The system is modeled using EBSLION software, and a comparative analysis is conducted on thermal performance and peak shaving performance of each scheme from the perspectives of thermal storage load and electricity load. The use of a “steam extraction + electric heating” thermal storage scheme significantly improves the peak shaving capability of thermal power units. Among the various schemes, Scheme W1 exhibits the maximum peak shaving depth of 92.71%, Scheme W6 shows a minimum comprehensive coal consumption of only 178.15 g/(kW·h), with a daily saving of 182 tons of standard coal. In addition, Scheme W2 achieves the highest cycle thermal efficiency of 55.2%. The use of the “light coal” storage scheme fully enhances the backup capacity of the supercritical carbon dioxide (S-CO₂) system, and the “extraction steam storage heat” drives the “small turbine” to assist the S-CO₂ system in heating, achieving the dual goal of peak shaving heating in winter. This type of system not only expands the peak shaving capacity of coal-fired units, ensuring heating for people’s livelihoods, but also fully utilizes solar energy resources, reduces coal consumption per kilowatt hour, and enhances the reserve capacity and power generation hours of S-CO₂ systems, providing theoretical and engineering guidance for the construction of high-capacity flexible regulation power sources.

Organic Rankine cycle (ORC) power systems can convert low-temperature (<150 ℃) thermal energy into mechanical energy to generate electricity. To improve the performance of small-scale ORC power systems, an ORC test-rig was built, which has a scroll expander directly connected to the generator. With a 24 kW variable-temperature heat source and the work fluid R245fa, the effects of the variations of load resistance (50~200 Ω) and the heat source temperatures (75~95 ℃) on the performance of the ORC test-rig were explored. The results indicate that, both the output shaft work and the thermal efficiency initially increase and then decrease with rising the load resistance. An optimal load resistance exists to maximize either the output shaft work or thermal efficiency, and this value varies with the heat source temperature. When the heat source temperature is 95 ℃, the output shaft work and thermal efficiency both reach the maximum at 100 Ω load resistance value, which is 722 W and 2.30%. When the heat source temperature is 75 ℃, the output shaft work reaches the maximum at 200 Ω load resistance, which is 532 W, but the thermal efficiency reaches the maximum at 150 Ω load resistance, which is 1.7%. The variation of the resistive load or the heat source temperature can change the scroll expander rotation speed and thus affect system flow rate. Therefore, the simultaneous changes of the resistance load and the heat source temperature have a synergistic effect on the system performance. The results highlight the importance of matching the resistance load and the heat source temperature. The experimental data also provide a direction for optimizing the ORC power systems.

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.

In reheat and recompression cycle system, the high-pressure carbon dioxide fluid has high temperature at outlet of the high-temperature reheater, resulting in insufficient heat absorption of the working fluid entering the heat source heater. To solve this problem, the model of a supercritical carbon dioxide (S-CO₂) cycle photovoltaic coal complementary power generation system is established using Aspen Plus software. On the basis of the reheat-recompression cycle system, a novel dual-channel S-CO₂ cycle solar hybrid coal-fired power system is proposed. Moreover, the performance of the above two systems is analyzed and compared by applying the exergy analysis method. The results indicate that, the exergy efficiency of the new system can reach 40.578%, which is 3.494 percentage points higher than that of the reheat-recompression cycle system, and the exergy efficiency of the S-CO₂ cycle subsystem increases by 11.853 percentage points. The improvement of the exergy efficiency of the novel system can be attributed to the new path layout, which brings the third stage turbine to do work through full utilization of regenerative heat from the high temperature regenerator and reduces exergy losses from the main compressor and high temperature regenerator. Additionally, the contribution of solar energy in the new system is greater, resulting in an increase in output exergy from 9.846% to 10.059%.

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.

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.

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.