Ortho-para hydrogen conversion is an indispensable process in hydrogen liquefaction system. This paper summarizes the experimental research progress of ortho-para hydrogen conversion, comprehensively compares the advantages and disadvantages of various ortho-para hydrogen conversion schemes, analyzes the differences between typical ortho-para hydrogen catalysts, such as iron hydroxide and oxide catalysts and supported nickel catalysts, in terms of the activation methods and catalytic efficiencies, and further summarizes various measurement methods for ortho-para hydrogen concentrations as well as their measurement principles. Regarding the selection of catalysts for ortho-para hydrogen conversion, the literature findings indicate that supported nickel-based catalysts have higher catalytic efficiencies, but taking full consideration of catalyst preparation, activation, deactivation, and liquefier operating requirements, iron hydroxide as well as its oxide catalysts are still the mainstream catalysts for application-oriented catalytic choices. Among the measurement methods of ortho-para hydrogen fractions, compared with spectroscopy, acoustic velocity measurement, nuclear magnetic resonance, enthalpy measurement, etc., the ortho-para hydrogen concentration measurement based on thermal conductivity method has comprehensive advantages in terms of accuracy, response speed, economy and operability, which can be used as the preferred solution for the measurement of ortho-para hydrogen concentration. As large-scale hydrogen liquefaction plants are developing towards the direction of higher efficiency, compactness and reliability, continuous conversion is the mainstream solution for ortho-para hydrogen conversion in the future hydrogen liquefaction processes. However, at present, most of the domestic studies on continuous ortho-para hydrogen conversion remain in conceptual analysis and process application, lacking data on hydrogen conversion, flow and heat transfer under cryogenic conditions, as well as relevant high-precision correlation equations. Based on the measured data of continuous catalysis and cooling of orthopara hydrogen, the development of high-precision correlations for heat transfer, pressure drop and catalysis of hydrogen eat exchangers, and the accurate design of heat exchangers for continuous ortho-para hydrogen conversion, will be an urgent task to be carried out in the future.

In view of the randomness of the initial population diversity and limited local optimal ability of the snake optimization algorithm, an Improved Particles Transmit Information Snake Optimization (IPTISO) algorithm is proposed. By using a strategy to update the worst individual in different stages of egg laying, the global search ability and local search ability of the algorithm are balanced, and Circle chaotic mapping is introduced in the initial stage to improve the diversity of the population. At the same time, a pheromone induction method was introduced to change individual characteristics during the fighting and mating stages. By using the above improved method and introducing the green certificate-carbon trading mechanism, the power system of 1 concentrated solar power station and 10 thermal power units is solved, and various scheduling scenarios are analyzed and compared with other classical algorithms. The results show that compared with other algorithms, IPTISO algorithm can obtain the optimal economic and environmental scheduling scheme, which provides a new way to solve the optimal scheduling problem of power system.

Multi-energy co-generation systems are crucial for improving energy efficiency, enhancing system flexibility, and integrating various energy sources for end users. This paper proposes a largescale, cross-seasonal, and cross-regional CO₂-based combined cooling, heating, power and fuel system. A thermodynamic model of the system is developed to investigate the effects of parameters such as CO₂ mass flow coefficient, internal waste heat, compression/expansion stages, and intercooler outlet temperature on system performance. The results show that as the ratio of CO₂ mass flow rate within the CO₂ energy storage module to that captured by the direct air capture module increases from 200 to 600, the system energy utilization factor improves from 75% to 85%. When the expansion stage number is 3, 4, 5, 6, 8, 10, 11, 13 and 15, the system begins to generate cooling energy at higher compression stages. When the compression and expansion stages are 14 and 5, the system energy utilization factor reaches its maximum value of 105%. The optimal electrical roundtrip efficiency and system energy utilization factor are 70% and 105%, respectively.

A combined cooling heating and power (CCHP) system integrated with chemical looping hydrogen generation(CLHG), molten carbonate fuel cell(MCFC) and organic Rankine cycle (ORC) is proposed. Methane is used as fuel, and hydrogen produced from chemical chain process is used to drive MCFC for power generation. The system is integrated with ORC, dual effect lithium bromide absorption refrigeration cycle, and heating subsystem to realize the energy cascade utilization and improve energy utilization efficiency. On the base of the first and second laws of thermodynamics, the study analyzes the impacts of key parameters on the new system performance. The research results show that under rated operating conditions, the energy efficiency and exergy efficiency of the new system are 67.66% and 50.47%, respectively. Compared with the MCFC-ORC CCHP system without integrating with chemical-looping hydrogen generation under the same conditions, the energy efficiency of the new system increases by 2.44%, the exergy efficiency increases by 0.65%, and the MCFC efficiency increases by 1.58%.

In order to solve the problem of the abandonment of a large number of idle oil and gas Wells and the absorption of green electricity in oil fields, the paper innovatively proposes the use of idle oil and gas Wells as gas storage devices for compressed air energy storage system. Exergic model and exergic model have been established to reveal the change law of thermodynamic performance of idle oil and gas Wells in different operating pressure ranges and injection/production flow rates under the coupling effect of air gravity and formation temperature, and exergic efficiency and energy storage of idle oil and gas Wells in 7”well shafts have been studied. The results show that in the single injection and production simulation, the temperature changes greatly in the well depth of 200 m, the temperature changes increase with the well depth of 200 m to 3000 m, and the wellhead pressure is positively correlated with the air pressure gradient in the well. At fixed injection/production flow rate, exergy efficiency of exergy in well bower is the highest and fluctuates around 100.25%, with energy storage more than 1.4 times that of conventional steel tank gas storage device of the same water volume. Exergic flow matching curve with exergic efficiency approaching 100% was selected at a fixed operating pressure interval.