Carbon dioxide energy storage is a new type of long-duration large-scale physical energy storage technology that combines high efficiency, decoupled power and capacity, unrestricted geography, and low-carbon safety. This article presents for the first time an experiment on a hundred kilowatt level transcritical carbon dioxide energy storage system, and conducts research on the theoretical basis, design key points, system construction, and testing involved in the experiment. The experimental results show that under a typical experimental condition, the system’s energy storage efficiency, thermal utilization efficiency, and energy storage density reach 46.1%, 86.2%, and 0.40 kWh/m³, respectively. Due to the idealization of the model and the performance constraints of actual equipment, the actual energy storage efficiency is 67.2% lower than the ideal theoretical value. Considering the lack of objectivity in the experiment, further scaling up the system, increasing the total pressure ratio, and improving the heat storage temperature will be important optimization directions for the system. This study can provide some reference for the theoretical and applied research of carbon dioxide energy storage.

The pressure variations during the gas release process in the high-pressure storage tank will cause the turbine to significantly deviate from its design conditions, thereby reducing the energy storage efficiency of the system. To address this issue, this paper proposes a novel constant-volume isobaric discharging compressed CO₂ energy storage system (CVID-CCES). Utilizing the thermophysical property distortion characteristics of CO₂ in the pseudo-critical region, the system recovers low-grade energy within the system to heat the high-pressure storage tank, compensating for pressure drop caused by working fluid outflow, thereby achieving isobaric discharging process. Based on thermodynamic analysis and multi-objective optimization, the optimal energy storage efficiency and energy density of the system are 66.11% and 0.29 kW·h·m⁻³, respectively. Dynamic models of high-pressure storage tank and key components based on real-gas isobaric discharging are established to investigate dynamic characteristics. The results show that near the pseudo-critical point, a small temperature increase can maintain high-pressure storage tank isobaric, while away from this region, continued heating diminishes the isobaric maintenance effect, accompanied by significant output power reduction and a system energy storage efficiency of 47.96% during dynamic operation.

This study investigates inorganic phase change materials (PCMs) with high supercooling characteristics for controllable heat release through external crystallization triggering. The system demonstrates three key advantages: long-term phase stability, minimal heat loss, and rapid controllable heat release, making it particularly suitable for building heating applications. We prepared a composite PCM using sodium acetate trihydrate (SAT) as the base material and sodium carboxymethyl cellulose (CMC) as the thickening agent, with the resulting SAT/CMC composite exhibiting a 57°C melting point while maintaining stable supercooling at room temperature. Experimental analysis showed the material reaches its 56°C phase equilibrium temperature within 5 s after triggering, enabling rapid on-demand latent heat release. The established Mixture-Lee model accurately described the controlled crystallization process, with simulations revealing that increased supercooling enhances phase transition driving force, significantly influencing available thermal energy and heat release rate. Under convective boundary conditions, high supercooling(ΔT=27°C)achieved up to a significantly higher transient heat release rate and approximately 46% higher total heat output within 1000 s compared to low supercooling (ΔT=12°C), though requiring more latent heat for PCM rewarming. These findings provide crucial theoretical guidance for developing efficient thermal storage systems using supercooled PCMs with controllable crystallization heat release.

Coal-fired power generation produces nitrogen oxides (NO_x) that are extremely harmful to the environment. Selective catalytic reduction (SCR) denitrification technology effectively reduces NO_x emissions of coal-fired units. However, in the frequent load-cycling processes, it is difficult to accurately control the NH₃ injection rate of SCR system, resulting in large fluctuation of NO_x emission. In this paper, the dynamic simulation model of thermal system and SCR system model of coal-fired units are developed, and the denitrification performance in load-cycling processes are analyzed. It is found that the NO_x emission in the load-lifting process of coal-fired units is lower than the set value of 45 mg·m⁻³, and the average NO_x emission concentration is 42.124 mg·m⁻³. While in the load-shedding process, NOx emission is higher than the set value, which is 52.536 mg·m⁻³, but NH₃ escape is significantly lower than that in the load-lifting process. The study shows that in the transient process, the NH₃ storage effect of SCR catalyst layer leads to the difference between the NO_x reduction reaction rate and the transfer rates of heat and mass of fluegas, which results in the instability of denitrification performance in load-cycling processes. The research results provide a theoretical basis for the optimization of NH₃ injection control logic of SCR system.

This paper addresses the temperature fluctuations and uneven temperature transfer characteristics of the cryocooler in the 2∼5 K thermodynamic temperature measurement device. It focuses on temperature control by conducting simulation and experimental studies on the structural parameters and installation methods of thermal link. The simulation results based on the response surface method show that the optimal length, width and thickness of the thermal link structure parameters are 36 mm, 50 mm and 12 mm, respectively. Experimental results indicate that this structure can reduce the temperature fluctuation from 2.000 mK at the helium pot to 0.630 mK at the third stage flange, with a fluctuation attenuation rate of 68.50%. The temperature only increases from 1.5690 K at the helium pot to 1.5734 K at the third stage flange, rising by 0.30%, with almost no impact on the cooling transfer. The optimal installation method for the thermal link is to place the installation point as close as possible to the center of the flange, ensuring a uniform temperature distribution across the flange.