The growing share of renewable energy leads to increased load volatility and uncertainty in power system, necessitating greater flexibility in cogeneration systems. The utilization of molten salt thermal storage equipment can enhance the performance of cogeneration systems. Against the main-pipeline cogeneration system consisting of four boilers and two steam turbines which is integrated with a coupled molten salt thermal storage equipment, the EBSILON simulation software is used to establish mechanism model for power supply and heating. The influence of molten salt heat storage equipment on combined heat and power system performance is analyzed, and the optimization scheduling methods for coupled systems are also investigated. The results show that, the coupling of molten salt thermal storage equipment in cogeneration systems can increase the system’s peak shaving capacity, expand the system’s operating range, and broaden the unit’s operating area. After estimation, the amount of coal saved in one day can be about 4.16 tons, the carbon emissions can be reduced by about 8.25 tons, and the pollutant emissions can be decreased by about 1.76 kg. The molten salt thermal storage equipment has improved the system’s economy and environmental friendliness.

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.

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%.

In response to the current problems of high volatility in wind and photovoltaic power generation and difficulties in consumption in typical areas, a new hybrid energy system optimization scheduling method for promoting wind and solar consumption through geothermal power generation is proposed by incorporating reliable and rapidly climbing geothermal power generation into the hybrid energy system. Taking into account both operational costs and risks, and constrained by physical characteristics of the power units, a multi-objective optimization dispatch model for the new hybrid energy system is established. A rolling repair strategy is introduced to correct the initial values of the population, and the model is solved based on the adaptive trade-off model and the non-dominated sorting genetic algorithm II. This algorithm is more suitable for solving high-dimensional, complex constraint problems compared with the conventional algorithms and offers a faster convergence rate. Through a comparative analysis of two scenarios during typical winter days in a specific region of Tibet, geothermal power is found to enhance the absorption rates of wind and solar energy by 8.0% and 7.9%, respectively. Simultaneously, the system’s operating costs decreases by 2.5%, and risk indices decreases by 7.1%. These findings underscore the role of geothermal power in promoting the integration of wind and solar energy and improving the overall reliability of the power system. The research provides valuable theoretical support for decision-making and scheduling in hybrid energy systems.

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.

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).

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.

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.

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.