Focusing on the photo-thermochemical water splitting hydrogen production technology, where photoreaction and thermal reaction are carried out sequentially, the CeO₂ synthesized by sol-gel method and its metal-doped catalysts were taken as the research objects to carry out experimental tests, through which the effects of photoreaction in generating oxygen vacancies and thermal reaction in hydrogen production were investigated. During the photoreaction, CeO₂ catalysts doped with three elements (Fe, Cu, Zn) at three different ratios (5%, 10%, 15%) were used. The metal-doped catalysts were characterized by several methods, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), photoluminescence (PL), ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), inductively coupled plasma (ICP), and BET specific surface area testing method. The results indicate that, the 10% Cu-doped CeO₂ catalyst exhibits the best photothermal hydrogen production performance. This is attributed to the smallest size of Cu nanoparticles, which results in the smallest bandgap width for the Cu-doped CeO₂ catalyst. Consequently, it can absorb higher energy photons, enhancing the light absorption capacity, and improving the separation and recombination rates of photogenerated charge carriers. This facilitates the formation of photogenerated oxygen vacancies, thereby enhances the hydrogen production capability during the thermal reaction process.

Large-scale hydrogen production technology from renewable energy such as solar power and wind power has become an important pathway for the consumption of renewable energy and the achievement of “dual carbon” goals. The policies and strategic layout of hydrogen energy at home and abroad are introduced, and the advantages and technical bottlenecks of water electrolysis technologies are analyzed. Moreover, the classification, coordination control optimization and energy management of large-scale renewable energy hydrogen production systems are sorted out. In view of the current development status of hydrogen energy in China, a brief analysis of the current installed capacity and the cost is performed, providing a reference for the construction of green hydrogen production system and the clean substitution of terminal energy in China.

A novel type of integrated chemical chain hydrogen production CO₂ zero emission solid oxide fuel cell/gas turbine/organic Rankine cycle hybrid power system is proposed, which achieves efficient power generation while efficiently separating and capturing CO₂. The system uses methane as fuel and generates hydrogen gas through chemical chain reactions to enter the fuel cell, avoiding carbon accumulation inside the cell. The anode outlet circuit of the cell is connected to the chemical chain, and the gas from the fuel reactor outlet and the cathode outlet of the cell enters the gas turbine to do work. The exhaust waste heat is recovered and utilized by the organic Rankine cycle system, further improving the system efficiency. A complete system model was established and thermodynamic performance analysis was conducted on the system, obtaining the variation laws of system performance with fuel flow rate, fuel utilization rate, battery working temperature, and system working pressure. The results showed that the comprehensive energy utilization efficiency of the system could reach over 74.10%, the electrical efficiency could reach over 62.42%, and the exergy efficiency could reach 57.73%. Sensitivity analysis showed that the system performance reached its optimum when the system working pressure reached 7×10⁵ Pa.

Photovoltaic power generation makes full use of the advantages of solar energy, which is green, clean, widely distributed, and abundantly available. However, the efficiency of photovoltaic (PV) modules often decreases as the operating temperature increases, severely affecting system performance. To address this issue, this paper experimentally investigates the cooling effect of phase change materials (PCM) with Y-shaped fins on PV cells. The study focuses on analyzing the effect of structural parameters such as the branching angle, position length, and length ratio of the Y-shaped fins on the system’s thermoelectric performance. The results show that, comparing with the system without fins, the system with Y-shaped fins has an average increase of 0.37% in photoelectric conversion efficiency, and the average melting rate of paraffin increased by 21.52%. The position length has the greatest impact on the melting rate. When the branching angle is 60°, the length ratio is 2, and the position length is 0, the Y-shaped fin can achieve the best temperature uniformity inside the cavity. By coupling Y-shaped fins with PCMs for PV cell cooling, this research aims to address practical application challenges such as uneven melting, internal temperature stratification, excessive local temperatures, and hotspots caused by the poor thermal conductivity of PCMs.

Ammonia-coal co-firing is one of the important ways to achieve carbon reduction of coal-fired thermal power units, but the research on high proportion ammonia co-firing is rare. In order to further explore the feasibility of high-proportion ammonia co-firing, the mechanism model of ammonia-coal co-firing is established, and the ammonia-coal co-firing and pure ammonia combustion process of 4 MW boiler is simulated by using computational fluid dynamics (CFD) method. The error between CFD calculation results and experimental data is less than 3%. The experimental results show that, when ammonia is co-fired with coal, the flame temperature decreases by about 30 ℃ and the carbon dioxide volume fraction decreases by about 20% for every 20% increase in the co-firing ratio. When the ammonia co-firing ratio is increased from 0 to 40%, the NO volume fraction at the furnace outlet increases by about 77.33%, and the carbon content in fly ash increases from 4.65% to 6.16%; when it is increased from 0 to 60%, the NO volume fraction increases by about 136.44%. When excess air ratio of ammonia-coal co-firing is 1.15, the fuel burnout and nitrogen oxide generation are optimized. The two-stage input of ammonia fuel can reduce the NO volume fraction at the furnace outlet by 31.07% compared with the ungraded input. Compared with the combustion flame of coal combustion and ammonia-coal co-firing, the flame temperature of pure ammonia combustion is lower, the ignition distance is longer and the tangent circle diameter is larger. When pure ammonia is fired, the NO mass concentration at the furnace outlet is 475 mg/m³, and the escaping ammonia concentration is close to 0.

Micro-nano particle doping is an important method for the modification of molten salt thermal storage materials. By taking a binary carbonate molten salt mixture of 40Li₂CO₃-60Na₂CO₃ (mass fraction) as the base molten salt, CuO and CuCl₂ as the dopants, three composite molten salt phase change thermal storage materials, namely CuO-Li₂CO₃-Na₂CO₃, CuCl₂-Li₂CO₃-Na₂CO₃, and CuO-CuCl₂-Li₂CO₃-Na₂CO₃, were re prepared separately using a high-temperature melting method. Moreover, the thermal properties of these compounds were tested, and the effects of additives on the modification of binary carbonate molten salts and composite molten salt phase change thermal storage materials were investigated. The results show that, the melting point of the Li₂CO₃-Na₂CO₃ molten salt with 0.24% CuO addition decreased by 5.2 ℃, the latent heat of phase change decreased by 98.1 J/g, the average specific heat capacity of the solid phase decreased by 0.39 J/(g·℃), and the average specific heat capacity of the liquid phase decreased by 0.77 J/(g·℃). The upper limit of the operating temperature increased by 4 ℃. For the Li₂CO₃-Na₂CO₃-CuCl₂ molten salt with 0.06% CuO addition, the melting point increased by 9.6 ℃, the latent heat of phase change decreased by 15 J/g, the average specific heat capacity of the solid phase increased by 0.07 J/(g·℃), and the average specific heat capacity of the liquid phase increased by 0.12 J/(g·℃). The upper limit of the operating temperature increased by 17 ℃. Both molten salts exhibited improved thermal conductivity performance after the addition of CuO.

To study the effect of inlet temperature and flow step changes on dynamic performance of supercritical carbon dioxide (S-CO₂)/lead-bismuth coupled heat exchanger, a segmental model was established for numerical simulations. Based on the simulation results, a transfer function model was developed and validated to quantitatively assess the effect of inlet step disturbances on the cold-side outlet temperature. The results show that, under inlet temperature step disturbances, the heat exchanger responds quickly, but the temperature field changes with a smaller amplitude. The time constant for the temperature step change at the hot-side inlet is 22.1 s. When the cold-side inlet temperature decreases by 50 K, the temperature at the midpoint of the heat exchanger only drops from 795.23 K to 793.17 K. Under flow step disturbances, the heat exchanger responds with a delay, but the temperature field changes with a larger amplitude. The time constant for the cold-side inlet flow step change is 30.08 s. When the cold-side flow increases to 0.002 kg/s, the temperature at the midpoint of the heat exchanger drops from 795.23 K to 779.08 K. The transfer function established in this study shows good agreement with the results from the segmental model. The findings provide useful insights for the operational strategy of intermediate heat exchangers in the S-CO₂ power cycle and the lead-bismuth fast reactor coupling system.

In the context of building a new type of power system with new energy as the main body, it is required that thermal power units undertake more peak shaving tasks, and coupling heat storage tanks is one of the effective ways for units to improve the peak shaving capability. In order to solve the operation scheduling problem of heat storage tanks and units in the context of peak shaving auxiliary service market, thermal system simulation is conducted on combined heat and power (CHP) units to obtain coal consumption and operational safety zones that reflect the actual operating conditions of the units. After that, an optimization model for the CHP system coupled with heat storage tank is established. Aiming to maximize the net profit of the system, this article intelligently optimizes the hourly operation scheduling of a certain CHP and heat storage tank. The results show that, the heat storage process of the thermal storage tank occurs during the electricity price period, and the heat release process varies depending on the heating load. During the high cold period with high heat load, heat is only released during the electricity price valley period, while during the early and late stages with low heat load, heat is released during the valley and peak periods. The net income of the system decreases with the increase of heating load. Running the entire heating season with the optimized scheduling in this article can increase revenue by 21.13 million yuan per year, with a static investment payback period of 5.22 years.

In order to study the effect of molten salt thermal storage schemes on peak shaving capacity and economy of double reheat condensing units, by taking a 660 MW double reheat condensing unit as an example, seven bypass thermal storage schemes are designed by combing thermal storage with bypass system, considering different thermal storage sources. Through simulation, the changes in indicators of different schemes, such as the minimum power generation load rate, thermal storage load reduction number, compensation for increased peak shaving capacity and coal consumption costs, are studied in the heat storage initial range from 30%THA to 50%THA. The results show that, the minimum power generation load rate of the schemes with multiple parallel heat storage sources are lower than that of the schemes using a single heat source. Scheme VII with three parallel heat storage sources can reduce the minimum power generation load rate to below 18% under different initial heat storage conditions. However, in the Scheme I with superheated steam heat storage, the load reduction number of heat storage exceeds 2.00, and the load reduction capacity per unit of heat storage power is the largest. As the load rate of the initial heat storage condition decreases, there is a maximum compensation for the annual increase in peak shaving capacity, and the compensation for multiple thermal storage heat source schemes is greater than that for a single heat source scheme. The annual increase in coal consumption cost of the scheme including low-pressure bypass heat storage is much higher than other schemes, but it will decrease with the initial working condition of heat storage.

With the grid-connection of renewable energy systems, more coal-fired units are required to participate in deep-peak-shaving and quickly respond to the automatic generation control command. Therefore, the controllers of coal-fired units should not only have satisfactory dynamic performance but also have strong robustness. However, the tuning of proportional-integral (PI) controllers which are widely applied to coal-fire units usually takes the dynamic performance into account and robustness in the application of PI controller parameter tuning is lack. Thus, the maximum-sensitivity-constrained desired dynamic equation (DDE) PI is proposed to obtain good dynamic performance and strong robustness. Simulations and field tests on the hot primary air system of the coal pulverizer indicate that, the proposed control method has better disturbance rejection performance and stronger robustness, which can effectively handle with uncertainties caused by the wide load variation of the unit.