The recent advancements in key materials including reactants and catalysts employed in solid-gas, gas-gas, and liquid-gas solar thermochemical energy storage (TCES) systems are reviewed. The thermochemical properties of reactants such as carbonates, hydroxides, metal hydrides, metal oxides, organics, and ammonia are examined. The research status of the modification of these reactants, new material development, and catalyst improvement are also discussed. At present, the reactant materials suitable for solar TCES exhibit various deficiencies in terms of cyclic stability, reactivity, conversion rate, energy storage density, cost or safety, which hinder the commercial viability of solar TCES technology. To further enhance the maturity of solar TCES technology, it is imperative to develop advanced composite materials on the basis of known thermochemical reaction systems, improve novel efficient catalysts, and broaden demonstration application scenarios and scales in the future. The key materials should endow TCES systems with high energy storage density, more robust cyclic stability, and rapider reaction kinetics. It is preferred that they are readily available, non-corrosive, and non-toxic and more cost-effective.

The stable operation of carbon market depends on the accuracy of carbon emission data, and the data quality of continuous emission monitoring system (CEMS), as an adjunct to the accounting method, still needs to be improved. Uncertainty assessment is an important part of the construction of CEMS and data quality control. To assess and improve the data quality of CEMS, the uncertainty assessment of the carbon emission online monitoring data of an F-class gas unit was carried out. The results show that, the extended uncertainty of carbon emissions is 4.838%~5.012% (k=2), and the main source of uncertainty is the flow rate measurement, in which the velocity field coefficient detection is the main reason for the high uncertainty in the flow rate measurement, and the operating load does not have a more obvious effect on the results. Therefore, improving the accuracy of flow rate and concentration measurement instruments or conducting regular calibration tests can effectively reduce the uncertainty and improve data quality.

Against the shortcomings of intermittency and instability of photovoltaic power generation in microgrids, a hybrid energy storage system composed of vanadium redox batteries (VRB) and super capacitors (SC) is utilized to smooth out the power fluctuations in standalone microgrids, thus to improve the power supply reliability of standalone microgrids. Considering the capacity allocation problem of the hybrid energy storage system, a multi-objective hybrid energy storage system capacity optimization model that minimizes the average annual cost of the hybrid energy storage system and the load shortage rate is developed. Aiming at the poor local search ability of the conventional elite non-dominated solution sorting genetic algorithm (NSGA-II) algorithm for solving the multi-objective optimization problem, an NSGA-II algorithm based on the improved elite retention strategy is proposed. By introducing a new fitness function, the algorithm is sorted and reasonably retains the elite individuals, so it improves the optimization effect, thus to enhance the local search ability, continuously approach the Pareto true frontier, and obtain better capacity configuration solutions. Finally, the rationality of the proposed method is verified by arithmetic examples.

With the increasingly prominent problem of load fluctuations in high proportion renewable energy grids, improving the fast load response ability of large-scaled thermal power units under full operating conditions has become an urgent need to maintain the safe and stable operation of the power system. Therefore, a rapid load change strategy combined with the high-pressure bypass transformation technology under the flexibility demand of supercritical power units is proposed. Firstly, the high-pressure bypass is added to the high-pressure regenerative system to flexibly change the steam extracted amount from turbine, thus to accelerate the energy supply rate of once-through boiler. Secondly, to adapt to the high ramping rate, a load change scheme is designed with the limitations of main steam pressure, temperature and their change rate that boiler can withstand at sliding-pressure operation mode and the decoupling of load-main steam pressure for unit. Finally, test on a 600 MW coal-fired thermal power unit shows that, the unit can successfully achieve a high load ramping rate of 3%Pe/min under full operating conditions. Moreover, the main steam pressure, position of main steam valve and other parameters are maintained stable. In addition, the load regulation ability of the unit with load ramping rate of 5% Pe/min is verified, confirming the effectiveness of the proposed load rapid regulation strategy.

Against the cooling problem of engine heat exchangers, the flow and heat transfer characteristics of hydrogen in vertical and U-shaped tubes at supercritical pressures are studied. The influence of pressure and mass flow rate on heat transfer of the pipeline is studied by numerical method, and the heat transfer law is obtained. The heat transfer mechanism of the elbow section is discussed in depth, and the effect of dimensionless force on heat transfer is analyzed. The results show that, the closer the pressure is to the quasi-critical or when the mass flow rate increases, the convective heat transfer coefficient will increase, resulting in heat transfer enhancement. The bend section of the U-shaped tube can enhance heat transfer effectively, reaching a peak near θ=90°. There is a buoyancy effect in the straight pipe section at the inlet, but when the pressure is higher than 2.0 MPa, the buoyancy effect can be ignored after the hydrogen flows through the elbow section due to the influence of density difference. The Dean vortex caused by the secondary flow is the main factor to enhance the heat transfer performance of the elbow section, and the influence on the inlet section is significantly weaker than that on the outlet section.

Enhancing peak shaving capability of supercritical carbon dioxide (S-CO₂) boiler is the key to realize flexible operation of S-CO₂ coal-fired power plants. Research on dynamic characteristics of S-CO₂ boiler is beneficial to optimize the boiler operation control strategies. A dynamic simulation model of S-CO₂ boiler is established by the principles of thermodynamics and heat transfer based on the boiler of a 5 MW S-CO₂ cycle power unit designed and built by Xi’an Thermal Power Research Institute, and the reliability of the model is validated with operational data from unit. Based on the simulation model, dynamic characteristics of the above S-CO₂ boiler under step disturbance of different boundary conditions, such as fuel flow rate, working fluid flow rate, and working fluid temperature, are analyzed. The results show that, the S-CO₂ boiler has large thermal inertia, stability times of working fluid temperature at the boiler outlet are different under disturbance of different boundary conditions. With the increase of disturbance range of boundary conditions, stability times become longer. With the increase of boiler heat load, the working fluid pressure at the S-CO₂ boiler outlet decreases, and the working fluid flow rate at the S-CO₂ boiler outlet increases instantaneously in the initial stages of a dynamic process.

In response to significant increase in energy consumption caused by low-grade waste heat and energy waste in coal-fired power plants, a 350 MW unit is selected as the research object, the Ebsilon software is used to model and simulate different deep recovery schemes for low-grated waste heat and residue. The operating data of the unit under two schemes of “organic Rankine cycle (ORC)” and “Heater” are calculated. The energy consumption characteristics, revenue characteristics and differences are analyzed, and the mechanism and optimization plan for deep recovery of waste heat and energy are obtained. The results show that, the energy consumption characteristics of the unit improve significantly under both schemes, and the “heater” scheme has lower energy consumption. As the organic working fluid flow rate increases, the power generation of the ORC system gradually increases, but the thermoelectric efficiency of the ORC system gradually increases at first and then tends to stabilize and has a downward trend, with a range of 6.94%~7.75%. The organic working fluid flow rate has a relatively small effect on circulation efficiency of the ORC system. Both schemes are technically and economically feasible. The “ORC” scheme can bring direct electricity benefits to the power plant, while the “Heater” scheme is slightly more economical.

With the rapid development of renewable energy, the demand for grid-scale energy storage solutions is increasing to address the challenges posed by intermittent and variable power generation. As an integration of various mature electrothermal conversion and storage technologies, Carnot battery is gaining increasing attentions due to its scalability and independence from geographical constraints. The fundamental principles, key technologies, application prospects and current research status of Carnot battery are reviewed. The definition of high-temperature Carnot battery technology and the operational characteristics and technical challenges of related key equipment such as compressors and expanders are discussed. Additionally, practical application cases and technological prospects of Carnot battery systems based on electric heating and bidirectional cycles (such as Brayton and Rankine cycles) are analyzed, providing a reference for future research and technological development.

Aiming at the characteristics of complex and variable load and strong coupling of integrated energy system, a combined forecasting model based on variational mode decomposition (VMD), Prophet model, long- and short-term memory network (LSTM) and autoregressive integrated moving average (ARIMA) model is proposed for short-term electrical load prediction. Firstly, the electric load eigen mode functions with different center frequencies and relatively stable ones are obtained by VMD. Then, after calculating the value of zero cross rate, the modal components of each group are superimposed respectively to form the high-frequency and low-frequency timing components, and the Prophet model is used to extract the high-frequency components for timing features. Finally, the ARIMA prediction model is used to predict the low frequency component, and the LSTM neural network model is applied to predict the high frequency component. The final predicted electric load is obtained by superimposing the respective prediction results. The proposed method is applied to the actual integrated energy system, and the example analysis shows that the combined forecasting method presented above has good forecasting performance for the integrated energy system

The cost of underwater assets in offshore wind farms is relatively low compared with the total cost of offshore wind power projects, yet the quality of these assets is vital for safe and stable operation of the offshore wind farms. The quality issues that can arise with wind turbines, underwater steel structures and foundations of offshore substations, and submarine cables during the construction and operation and maintenance phases are analyzed. Based on cases from practical offshore wind power generation projects, the inspection requirements and methods stipulated by relevant standards are evaluated, and comprehensive and effective underwater inspection methods for various types of quality defects are put forward. These methods have been verified in real cases, forming industry standards and specifications, which provides significant technical guidance and reference value for quality control and operational maintenance of underwater assets in offshore wind farms.