With the rapid advancement of renewable energy power generation, thermal power units need to take on major peaking tasks. Molten salt thermal storage technology, as a prominent method for thermal power peaking, can effectively improve peaking performance of the units. The Ebsilon software is employed to model a subcritical 300 MW unit integrated with coupled molten salt thermal storage system. Considering the operational conditions of supplying industrial steam to external entities, several indexes such as the storage/exothermic thermal efficiency, load variation and thermoelectric conversion rate of three heat storage/exothermic schemes are investigated comparatively. The results indicates that, during the heat storage process, the heat storage scheme 3 (the heat source for heat storage is the main steam, reheat steam and medium-pressure cylinder exhaust, and the exothermic medium-pressure cylinder exhaust goes directly to the condenser) exhibits the highest load variation, reaching up to 102.63 MW. Meanwhile, the heat storage scheme 1 (employing main steam and reheat steam as the heat source for storage) demonstrates the superior thermal efficiency at 28.76%. During the discharge process, exothermic scheme 2 (heat from high-temperature molten salt is used to supply industrial steam and preheat condensate) has the largest load variation, release thermal efficiency, and thermoelectricity conversion rate, which are 34.69 MW, 46.14%, and 59.07%, respectively. This study can provide theoretical guidance for the study of peak performance and thermal economy of thermal power units coupled with molten salt thermal storage system.

Compressed air energy storage is a new form of large-scale and long-term physical energy storage. Gas storage is a crucial component of compressed air energy storage system. The characteristics of common gas storage devices are summarized, and the underground artificial chamber is discussed in detail. The advantages of underground artificial chamber of compressed air energy storage system compared with other types of gas storage are summarized. The design factors such as bearing structure, sealing system and heat transfer management system of underground artificial chamber are analyzed. The key technologies affecting operation of the underground artificial chamber such as site selection, buried depth and pressure design criteria are analyzed and discussed. The evaluation method and evaluation indexes of the factors affecting stable operation of the artificial chamber are put forward. On this basis, the future development direction of compressed air energy storage underground artificial chamber is prospected, which provides a reference for rational design and stable operation of the underground artificial chamber.

To improve steam parameters for better power generation efficiency and economy and meet the development needs of nuclear power plants, a duct-type steam generator is proposed, which is suitable for high-temperature gas-cooled reactors with ultra-supercritical parameters. The main features of the duct-type steam generator’s structure are introduced, and the advantages of this structure in terms of heat transfer performance, operation safety, and production cost are analyzed. Through the establishment of a theoretical calculation model, thermal engineering analysis and heat transfer performance study of axial, radial, and quasi-three-dimensional temperature distributions and other parameters of the steam generator with direct countercurrent heat transfer mode are carried out. The calculation results show that, the duct-type steam generator is mainly based on convection heat transfer mode, with obvious temperature distribution segments and excellent heat transfer performance, which meets the relevant heat transfer requirements. This study can provide a reference for design and development of steam generators in nuclear power plants.

A new type of liquid air energy storage (LAES) system coupled with solar energy is proposed to address the issue of low round-trip efficiency (RTE) in current LAES systems. The discharging process of the new system is equipped with series-connected two-stage air heaters, which improves the RTE while allowing the system to operate in conventional ways under low solar radiation conditions. Sensitivity analysis of main parameters and exergy analysis are conducted on the new system, and the results show that, within the allowable range, the lower the liquefaction temperature, the lower the charging pressure and the higher the discharging pressure, resulting in higher RTE of the system. The optimal RTE of the system can reach 72.4%, and the system can still operate at an RTE of 53.6% when solar radiation is insufficient. The exergy efficiency of the new system is 38.0%, among which the solar collector field has the highest exergy destruction, accounting for 52.4% of the total exergy destruction, followed by the throttle valve and thermoelectric generator. In heat exchangers, there is significant exergy destruction in cold boxes and evaporators.

To accommodate grid-connected large-scale renewable power, coal-fired power plants need to undertake more peak shaving and frequency regulation tasks, so it will engage in the processes of deep peak shaving and load cycling for a long time. In this situation, the performance of wet flue gas desulfurization system (WFGD) will degradation and the auxiliary power consumption will increase significantly. To solve this problem, the dynamic model of an ultra-supercritical 660 MW coal-fired power unit and the dynamic model of the WFGD system based on the double-membrane theory are established. The performance of the desulfurization system is simulated when the slurry circulation pumps are switched under different operating conditions during the load cycling processes. It is found that the precise matching of slurry and flue gas during load cycling processes can achieve the minimum power consumption of the desulfurization system while meeting the SO₂ emission standard. Furthermore, when the slurry circulation flowrate changes stepwise during load cycling processes, the prediction model of changes in SO₂ mass concentration at the WFGD system outlet is obtained. An optimization control strategy for the slurry circulation pumps in fixed-frequency mode is proposed, which can achieve the best match between the slurry and flue gas during load cycling processes. Finally, the energy saving potential for the proposed control strategy is analyzed. When the load cycling rates are 1.0%, 1.5% and 2.0% Pe/min, the energy saving potential is 20.12%, 21.52% and 22.82% during loading down processes from 75% THA to 50% THA conditions, and that value will be 10.04%, 9.90% and 8.66% during loading up processes, respectively. The difference in flue gas flowrate during load cycling processes is found as a key factor causing the disparate of energy saving potential during loading down and loading up processes.

To improve the accuracy of carbon emission accounting and make the effect of carbon emission reduction more intuitive, it is proposed to associate power plant generation with carbon emission intensity. Firstly, the carbon emission performance of the gas-steam combined cycle unit is calculated based on Aspen Plus. Then, the carbon emission performance is analyzed from the aspects of four influencing factors: unit load, environmental temperature, heat network input and natural gas composition. The results show that, the established Aspen Plus model can simulate the operation of the power plant accurately. Taking the S106FA multi-axis gas-steam combined cycle unit of a power plant as an example, the calculated carbon emission performance is 342.66 g/(kW·h). The carbon emission is calculated by comparing the measured method and the emission factor method. The carbon emission performance accounting is closer to the measured method, and the deviation between the carbon emission performance method and the measured method is 0.20%. The deviation between the measured method and the emission factor method applying the measured low calorific value and the saved and deficient low calorific value are 5.24% and 19.66%, respectively. Unit load has the most obvious effect on carbon emission performance of the combined cycle unit, followed by heat network input, ambient temperature and natural gas composition. To reduce the carbon emission performance of the combined cycle unit, the power plant needs to arrange the peak regulation time and heat network heating reasonably, and using renewable energy as an alternative or supplementary fuel can be considered.

The intermittency and volatility of renewable energy poses significant challenges to stable operation of power grids. Energy storage technology can address these issues effectively. Liquid air energy storage technology offers significant advantages of high energy storage density, being unconstrained by geographical conditions and atmospheric pressure storage. However, its round-trip efficiency is relatively low. To solve this problem, a liquid nitrogen and liquid air hybrid energy storage system (N-LAES) is proposed. By charging liquid nitrogen during energy release process, the gas flow in the expander increases, and gas pressure in front of the expander rises as well, thus the system’s round-trip efficiency increases. A thermodynamic model is developed, and the analysis results indicate that, for a typical scale N-LAES, the round-trip efficiency is increased to 66.47% compared with 56.90% for a standalone LAES. The net present value at the 30th year increases to 120 213 500 yuan, compared with 58 077 400 yuan for a standalone LAES, and the levelized cost of storage decreases to 0.809 4 yuan/(kW·h) from 0.897 2 yuan/(kW·h) for a standalone LAES. These findings demonstrate that both the thermodynamic and economic performance of the N-LAES is superior to that of the standalone LAES, offering a new approach for development of the liquid air energy storage technology.

To explore the heat and mass transfer process in a solid-state hydrogen storage reactor, a two-dimensional numerical calculation model for the reactor is developed. The radial reaction rate distribution characteristics of the solid-state hydrogen storage material within the reactor is investigated, and the influence laws of bed thickness of the hydrogen storage material and diameter of the heat exchange tube on saturation radius are also studied. Based on this, the arrangement of the heat exchange tube bundle is optimized. The results show that, the heat exchange tube has the corresponding maximum saturation radius, and it increases with the tube radius. When the tube radius is 1.00~6.00 mm with single-tube arrangement, the maximum saturation radius is 2.60, 3.30, 3.50, 3.70, 3.80 and 3.90 mm, respectively. The volume fraction of heat exchange tubes with radius of 1.00, 2.00 and 3.00 mm is relatively small, which is 7.72%, 14.24% and 21.30%. The optimal bed thickness between tubes is 4.86, 6.09 and 6.38 mm when arranging the above three types of tubes in a tube bundle. Moreover, adding heat exchange tube bundles can effectively improve the hydrogen storage performance of reaction dead zone in the reactor. In the reactor equipped with heat exchange tube bundles with radius of 2.00 mm, adding 12 heat exchange tubes with radius of 2.00 mm in the reaction deadzone can reduce the hydrogen storage time to 267 s (by 40.00%), while the volume fraction of tube bundle only increases by 1.92%, and the hydrogen storage capacity just decreases by 2.17%. The research findings can establish a fundamental basis for the optimal design of solid-state hydrogen storage reactors and offer valuable guidance for subsequent engineering applications.

Liquid air energy storage (LAES) is a promising technology for large-scale energy storage due to its geographical flexibility and high energy storage density. To further improve the round-trip efficiency and economic benefits of LAES, a novel integrated system combining liquid natural gas (LNG) cold energy utilization and organic Rankine cycle (ORC) with LAES is proposed. Thermodynamic and economic analysis methods for the integrated system are established, and the effects of key parameters on the system’s thermal performance are investigated based on simulations. An economic analysis of the system is also conducted. The results show that, as the system’s expansion pressure increases, both efficiency and power output rise, but at a decreasing rate. The system’s round-trip efficiency increases with more expansion stages up to a point, then decreases. With four-stage expansion, the system efficiency reaches 62.26%, which is 7%~12% higher than that of the conventional LAES system. When the difference between peak and valley electricity prices is 0.848 yuan/(kW·h), the net present value, dynamic payback period, and levelized cost of electricity are 119 058 500 yuan, 4.48 years, and 0.893 yuan/(kW·h), respectively. The results of this study can provide a reference for engineering application and efficiency improvement of LAES systems.

The arrangement of micro adiabatic compressed air energy storage (A-CAES) system is flexible and suitable for typical distributed energy systems. By accurately modelling a typical device of the miniature A-CAES system based on pneumatic motors, a thermodynamic model that can reflect its system performance is constructed. The experimental bench of the A-CAES system is built, and the average error rate between the simulation model and the experiment is around 5.38%, which verifies the reliability of the model. The round-trip efficiency and comprehensive efficiency of the system are 4.81% and 27.23%, respectively, verifying the necessity of the existence of thermal energy storage devices in the A-CAES system. The effects of compression level and compression ratio on the system performance are analyzed by using this model. The results show that, as the compression level increases, the round-trip efficiency and comprehensive efficiency of the system both increase, and the optimal efficiency of the system can reach 6.10% and 35.81%, respectively. Taking the combination of compression ratios of 2, 3, and 5 as an example, reasonable distribution of compression ratios can improve the round-trip efficiency and overall efficiency of the system by 1.27% and 4.38%, respectively.