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%.

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.

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.

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.

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.

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.

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.

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.

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.

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.