Using energy analysis and exergy analysis methods, and considering the irreversible losses in the compression, expansion, and heat-exchange processes comprehensively, the performance indicators and irreversible loss distribution characteristics between a basic PTES (BC-PTES) system and an electric heater-integrated PTES (EH-PTES) system under defined operational conditions are compared, and the influence of key parameters on the EH-PTES system’s performance is investigated. The results indicate that both the BC-PTES and EH-PTES systems generate large exergy losses in the turbine during the discharge, with values of 456 kW and 455 kW respectively. The EH-PTES system demonstrates higher round-trip efficiency (41.50%) and energy storage density (54.1 kW·h/m³), with the exergy efficiency of the electric heater at 63%. Parameter analysis reveals that there exists an optimal discharge-phase compressor outlet pressure which can minimize the exergy loss and maximize system round-trip efficiency. For the EH-PTES system, at the optimal discharge pressure, the round-trip efficiency of the EH-PTES system initially decreases and then increases with the rising electric heater outlet temperature, and it increases with the compressor outlet temperature. For example, when the compressor outlet temperature is 550 ℃ and the electric heater outlet temperature increases from 600 ℃ to 1 000 ℃, the EH-PTES system round-trip efficiency decreases from 45.03% to 44.81% at first, and subsequently increases to 45.75%. When the electric heater outlet temperature is 850 ℃ and the compressor outlet temperature increases from 400 ℃ to 550 ℃, the system round-trip efficiency increases from 39.17% to 45.14%. Notably, the round-trip efficiency is less sensitive to the electric heater outlet temperature than to the compressor outlet temperature. By integrating electric heaters, the energy storage density can be substantially enhanced, reaching 113.9 kW·h/m³ at an electric heater outlet temperature of 1 000 ℃. These findings provide critical insights for optimizing the PTES system design.

A Carnot battery system based on coal-fired power units can efficiently absorb curtailed power of new energy while utilizing the existing infrastructure of coal-fired plants for energy release, thereby addressing the challenges posed by high-penetration renewable energy on the power supply-side flexibility. A novel supercritical carbon dioxide reverse Brayton-Rankine cycle Carnot battery system is proposed based on the concept of split-flow expansion, and a comprehensive investigation is conducted through thermodynamic modeling in EBSILON Professional, parameter sensitivity analysis, and multi-objective optimization using genetic algorithms. The results indicate that under design conditions, the turbine power output and waste heat recovery of the novel system are improved by 59.84% and 43.23%, respectively, compared to the reference system. The energy storage cycle achieves a coefficient of performance (COP) of 1.32 and a round-trip efficiency (RTE) of 57.68%, representing an increase of 0.10 in COP and 4.37 percentage points in RTE over the reference system. Both COP and RTE increase with higher pressure ratios, higher flow split ratios, and lower top-end temperature differences in recuperator 2. When the flow split ratio is 0.23, the pressure ratio is 3.09, and the top-end temperature difference in recuperator 2 is 12.60 ℃, the COP of the Carnot battery storage cycle reaches a maximum of 1.37, with a corresponding RTE of 59.87%. The study provides a technical reference for enhancing the operational flexibility of coal-fired power plants and optimizing renewable energy integration through advanced thermal storage technologies.

Current researches on advanced adiabatic compressed air energy storage (AA-CAES) systems primarily focus on optimizing designs and analyzing performance under off-design conditions based on fixed system structures, with limited attention to system-level optimization involving predefined operational modes. By taking a 300 MW-class asymmetric AA-CAES system featuring four-stage compression and three-stage expansion as the object, a novel variable-pressure (sliding-pressure) operation strategy is proposed, along with a matching design between compression and expansion stages. A quasi-dynamic thermodynamic model is developed to analyze and optimize the full charge-discharge cycle performance under fixed time constraints with sliding-pressure control. The results show that the optimized sliding-pressure mode improves the system’s round-trip efficiency to 73.32%, increases the energy density to 3.404 kW·h/m³, and reduces the required air storage volume to 440 000 m³ (only one-fourth of that under constant-pressure operation). Exergy losses are mainly concentrated in the compressors and turbines, accounting for 40.7% and 29.3% respectively. The isentropic efficiency and heat recovery capability of these components has significant influence on overall performance of the system.

Using molten salt as a heat medium to form a high-temperature molten salt heat exchange system, a set of molten salt heat storage and carbonization device was designed. The structure and rated working conditions of the molten salt-carbonization furnace were designed, and the Nu empirical formula was applied to calculate the composite surface heat transfer coefficient of the molten salt-cylinder wall, and the relevant small-scale carbonization tests were carried out. The results showed that the convective heat transfer coefficient hti of the molten salt in the pipeline was much greater than the convective heat transfer coefficient ho1 of the molten salt heating layer of the carbonization furnace. The theoretical thermal efficiency and the measured thermal efficiency of the biomass carbonization device increased with the carbonization temperature. With the increase in carbonization temperature, decrease in material handling capacity, and extension of carbonization time, the calorific value of the products increased, but the solid energy yield decreased. Compared with rice husks, the organic components of pine wood shavings were more likely to escape into tar and even the vapor phase during the carbonization process. The designed experimental device can realize the carbonization of biomass under the condition of storing molten salt as a heat medium, which achieves the purpose of energy saving and carbon dioxide emission reduction.

A stand-alone liquid air energy storage (LAES) system with a water-oil combined heat storage system was constructed, and the effects of compression stages, expansion stages, and heat-storage water temperature on the system’s round-trip efficiency and compression heat utilization were analyzed. The results indicate that increasing the number of compression stages will reduce the round-trip efficiency, and the optimal number of compression stages is two. The optimal number of expansion stages is one more than the number of compression stages. Within the temperature range of 25~65 ℃, increasing the heat-storage water temperature can improve the system’s round-trip efficiency and the utilization degree of compression heat. However, the system efficiency will no longer increase when the temperature of the heat-storage water exceeds 65 ℃. Under optimal conditions, the system with two compression stages, three expansion stages, and a heat-storage water temperature of 65 ℃ has a compression heat surplus ratio of 0.349 and a round-trip efficiency of 0.622. The study provides a theoretical reference for optimizing the compression heat utilization process in LAES systems.

The high-temperature and high-pressure steam control valves in steam-heated molten salt thermal energy storage systems have to withstand high temperature, high pressure, and high pressure difference, and require frequent and high-precision adjustments. In view of these design and manufacturing challenges, a steam-heated molten salt thermal energy storage demonstration project was taken as the research object. Focusing on the actual application requirements of high-temperature and high-pressure steam control valves, systematic calculation and analysis were conducted on their flow capacity under different selection working conditions. An innovative technical scheme was proposed, which involves designing different stages of throttling and pressure reduction for different opening ranges of the control valve. This scheme effectively achieves good adaptability of the valve under full working conditions. It can accurately match the regulation requirements of the system in different operation stages, and significantly improves the adjustment accuracy. When the upstream steam flow rate is low, the use of steam-assisted atomizing nozzles is recommended, as they can make the atomized water particles finer, achieve a better atomization effect, reduce thermal shock and thermal stress on the pipeline, and ensure the safety of the device after desuperheating. This study sorts out the key considerations in the selection process of high-temperature and high-pressure steam control valves, which can provide important reference for the selection and design of high-temperature and high-pressure steam control valves in subsequent similar steam-heated molten salt heat storage projects.

The large-scale integration of renewable energy poses significant challenges to the peak-shaving capacity of coal-fired units. To enhance operational flexibility and address energy flow conflicts in typical coal-fired systems coupled with compressed air energy storage systems during peak shaving, this study investigates a 660 MW coal-fired unit using EBSILON software. Three energy storage schemes and two energy release schemes are proposed and evaluated through thermo-economic analysis, focusing on thermal-time decoupling capability, peak-shaving paradox elimination, and system performance. The results show that during energy storage, the scheme utilizing intermediate-pressure cylinder exhaust for thermal oil heating achieves the highest thermal storage gain ratio (1.370) and the lowest heat rate (8 814.976 kJ/(kW·h)). During energy release, the scheme absorbing heat from No.3 high-pressure heater drain outlet yields the minimum heat rate (7 547.945 kJ/(kW·h)). After 8 hours of operation, the system retains 38.503 MW·h of utilizable thermal energy and reduces the peak-shaving paradox index to –0.041. Parameter optimization improves the round-trip efficiency of the compressed air energy storage system by 2.702 percentage points and increases the unit’s peak-shaving depth by 2.481%. This study provides a viable solution for synergistic optimization of coal-fired units and energy storage systems.

Applying the molten salt heat storage technology to condensing thermal power units can enhance the flexibility of peak shaving. A bypass two-stage heat-storage peak shaving scheme was proposed and applied in an ultra-supercritical 660 MW unit. Taking 30% THA as the design condition for the thermal storage system, four heat storage capacity schemes were designed. The EBSILON software was used to analyze the peak regulation range, heat storage and release duration, peak regulation cost, and the change of net profit from heat-storage peak-shaving under different market rules. The results show that during off-design operations, there exist feasible domains for both heat charging and discharging. During the charging process, when the initial operating condition is between 40%~50%, the decrease in minimum generation load ratio is most significant, with the high-temperature thermal storage system reaching its design capacity first. During the discharging process, when the initial operating condition is 94.6%, the load ratio equivalent to VWO condition can be achieved, with the high-temperature thermal storage system completing discharge first. Regardless of the implementation approach, peak-shaving through thermal storage achieves maximum electricity revenue growth while minimizing lifespan depreciation costs and overall system expenses. In the peak-shaving ancillary service market, net profit peaks at 40% heat-storage starting condition, whereas in the capacity market scenario, the maximum net profit occurs at 45% heat-storage starting condition. The scheme with the smallest heat storage capacity demonstrates the lowest total cost increase, with both market mechanisms yielding optimal net profits.

As the power supply structure gradually shifts toward a diversified pattern, the risk of regional renewable energy consumption increases. In order to maximize the utilization of the existing adjustment capacity of hydropower and thermal power and improve the consumption level of wind power and photovoltaic power, a multi-energy complementary energy base including wind power, photovoltaic power, hydropower, thermal power and energy storage is constructed, and the advantages of complementary power generation among wind power, photovoltaic power, hydropower, thermal power and energy storage compared to other power generation modes are analyzed. Based on 8 760 time series points throughout the year, a multi-objective power generation capacity planning model that takes into account system reliability, economic benefits, environmental benefits, and the consumption level of renewable energy is constructed, and multi-objective optimization is achieved through the linear weighting method of unit standardization of the objective function. Finally, the annual historical wind and solar data of a certain place are selected for simulation experiments. The results show that, compared with single-objective optimization, multi-objective optimization can effectively balance the equilibrium points among different optimization objectives, avoid the limitations of single-objective optimization, and by rationally adjusting the output of hydropower, thermal power and energy storage, the complementary coordination of wind power, photovoltaic power, hydropower, thermal power and energy storage on multi-time scales can be achieved.

A model for hydrogen production and storage during deep peak-shaving (less than 30% of rated capacity) was established by coupling a gas turbine combined cycle (GTCC) unit with a solid oxide electrolysis cell (SOEC), demonstrating the feasibility of efficiently matching electrothermal resources within the system to accommodate renewable energy. Machine learning was used to predict GTCC variable-load power output, heat recovery boiler models were used to calculate steam parameters, and SOEC thermochemical models were applied to determine hydrogen production electricity and heat consumption. Results show that SOEC electrolysis voltage and hydrogen production can quickly respond to changes in input electrical energy, with the thermal inertia temperature difference of hydrogen production stabilizing at 25~27 ℃. When the peak shaving depth (the ratio of accommodated renewable energy to rated capacity) increased from 50% to 100%, the overall efficiency of the energy storage peak shaving system rose from 47.8% to 55.3%. Using GTCC-SOEC to accommodate renewable energy reduced the total energy consumption of hydrogen production from 6.7 kJ/m³ to 5.8 kJ/m³, with a reduction of 13.4%. SOEC hydrogen production heat consumption is about 80% of the electricity consumption, and the efficiency of the coupled hydrogen production system is only approximately 3.15%～3.34% lower than the efficiency of GTCC standalone peak-shaving power generation. For every 1% increase in peak shaving depth, hydrogen production increases by about 0.1 t/h, and CO₂ emissions from natural gas combustion decrease by 0.64 t/h. Considering storage costs and weather impacts, when the unit operates for 8 hours per day, as the peak periods for wind and solar generation increase from 0 to 1.5 hours, the hydrogen blending volume ratio increases to 30%, and the average efficiency of the hydrogen storage-release cycle increases from the baseline 56.7% to 62.5%; When the daily online duration of renewable energy reaches 2.5 hours, the average efficiency within the cycle can reach 67.1%. When the ratio of peak-shaving subsidy to electricity price is less than 0.2, the cost-to-output ratio initially decreases and then increases with the ratio of stored to grid electricity. When the subsidy-to-electricity price ratio is greater than 0.2, the cost-to-output ratio continuously increases with the stored-to-grid electricity ratio.

An efficient and feasible primary-side control method is proposed for the hybrid energy storage system (HESS) and wireless power transfer (WPT) system. This method can enable the system to dynamically maintain maximum power transfer under different charging states of the hybrid energy storage unit and keep the switching transistors of the Class E power amplifier (Eop) in a soft-switching operating state, ensuring stable and efficient wireless energy supplementation for the hybrid energy storage system. The system topology consists of an Eop, a series-series (S-S) type WPT circuit, and HESS. Based on the analysis of WPT transmission characteristics and Eop soft switching characteristics under different charging modes, the Eop optimal frequency tracking control and Eop soft switching duty cycle control strategies for HESS wireless charging are proposed. The key advantage is that all control mechanisms are located on the transmitting side, which can effectively reduce the volume of additional circuits in the energy storage unit on the receiving side and improve the volumetric energy density of the system. Finally, an experimental prototype is built based on the ZYNQ controller, and the experimental results show that the system can achieve efficient and stable wireless power transfer under different charging states and coupling conditions of the hybrid energy storage.