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Liquid air energy storage (LAES) technology is a promising large-scale energy storage solution due to its high capacity, scalability, and lack of geographical constraints, making it effective for integrating renewable energy sources. The core unit of the LAES system is the cold energy storage (CES) unit, which significantly influences its overall efficiency. However, the current mainstream liquid-phase and solid-phase CES methods have inherent drawbacks, including safety, environmental issues, and the dynamic effect of the thermocline. Moreover, previous research has often over-idealized the CES unit and neglected the actual heat transfer processes during the CES and cold energy release (CER) processes. In the innovative study, a gravity-driven moving packed bed (MPB) based LAES system (MPB-LAES) adopting quartz sand as the CES medium is proposed. A thermodynamic model for the LAES system is constructed, and the gas-solid counterflow coupling heat transfer model for the MPB is developed based on the continuous solid-phase model and finite difference method. The accuracy of the model is validated through experimentation using the constructed test apparatus. The research findings reveal the gas-solid coupling heat transfer characteristics in the low-temperature region of −180 ° C to 30 ° C , particularly the asymmetry during the CES and CER processes. The cold energy transfer mechanism within the CES unit is also uncovered, and the analysis of exergy destruction within various components is carried on. Through design parameter analysis and optimization of the MPB-LAES system, an impressive round-trip efficiency of 57.0% is achieved. This marks a significant breakthrough as it is the first report that a LAES system based on solid-phase CES has attained a round-trip efficiency (RTE) of over 55.0% while considering the actual heat transfer processes. • The LAES system utilizing moving packed beds is proposed. • The gas-solid coupling heat transfer model is established and verified. • The cold energy transfer mechanism in the CES is uncovered. • Irreversible analyses are performed in the CES and CER processes. • An RTE of 57.0% is achieved considering actual heat transfer for the first time. [ABSTRACT FROM AUTHOR]

Since trains usually have long travel mileage requirements, designing an optimal energy management strategy has great potential for reducing energy consumption. First, a hybrid train power component model was developed, and the train operating efficiency, as well as a map of the optimal integrated efficiency of the entire vehicle operation, was derived for each mode from simulation calculations by analyzing the power flows in different operating modes. Next, the overall optimal efficiency of the entire vehicle was used to determine the mode division rules, and proportional integral control was used to ensure that the engine and motor operated at the target speed under the target torque. Finally, with the optimization objectives of reducing the fuel consumption of the entire vehicle and maintaining a balanced battery state of charge, a forward simulation model for the overall efficiency optimization of the entire vehicle was built in the MATLAB/Simulink software. Then, the trajectories of the engine and motor operating points, the fuel consumption, and the battery SOC were obtained for certain operating conditions. The effectiveness of the energy management strategy based on integrated efficiency optimization was verified by comparing the simulation results for the hybrid train with those of a conventional internal combustion engine train. [Display omitted] • Models are created for the hybrid train's dynamics and power components. • A comprehensive efficiency optimization diagram for hybrid trains is constructed. • Optimization of power and torque distribution based on optimal efficiency • The suggested energy management approach can enhance dynamics and the economics. [ABSTRACT FROM AUTHOR]

This paper conducts research on the fuel accommodation control of a fuel-flexible engine. Blended fuels from gasoline and diesel are tested on a compression ignition engine. Two problems with the fuel-flexible engine are studied. One problem is that the engine brake torque output is different with different fuels, and the other problem is that the thermal efficiency deteriorates without recalibration. One open-loop control method and one closed-loop control method based on cylinder pressure sensor are proposed to deal with the fuel accommodation control problems. The open-loop control method features fuel blend ratio detection, which is a new dimension of input for the conventional MAP based engine management system. Gasoline and diesel blend ratio detection methods are studied, and the result also provides information for the closed loop control method as a feedforward controller. An indicated mean effective pressure based method is proposed for the engine brake torque difference problem, and a feedback controller with indicated mean effective pressure maximum seeking algorithm is used to optimize engine efficiency. The fuel injection amount and timing will be adjusted according to the fuel estimation result and the feedback control algorithms. Results show that the methods proposed could identify fuel blend ratio quite accurately, the engine brake torque output could follow the target value well, and the engine thermal efficiency could be optimized. [ABSTRACT FROM AUTHOR]

In this work, we propose the use of a genetic algorithm (GA) for the determination of the optimal fraction of mass flow rate to be extracted from each stage of the turbines of a typical pressurized-water reactor (PWR) secondary side, in order to increase cycle efficiency. Here, we show some preliminary results obtained in a case study in which the PEPSE® system was used as simulation tool. [Copyright &y& Elsevier]

• Modelling the overall system efficiency of PEM water electrolyzers. • PEM water electrolysis efficiency can be significantly improved by temperature optimization. • Optimal temperature depends on the applied cell voltage. • Safety issue caused by hydrogen crossover is prevented by temperature optimization. Most of the hydrogen produced today is made using fossil fuels, making a significant contribution to global CO 2 emissions. Although polymer electrolyte membrane water-electrolyzers can produce green hydrogen by means of excess electricity generated from renewable energy sources, their operation is still not economical. According to industry experts, the necessary cost reductions can be achieved by 2030 if system efficiency can be improved. The commonly stated idea is to improve efficiency by increasing the stack temperature, which requires the development of more resistant materials. This study investigates not only the efficiency of an electrolysis cell, but of the entire electrolysis process, including gas compression of hydrogen. The results indicate that an optimal stack temperature exists for every operating point. It is shown that the optimal temperature depends solely on the electrode pressure and cell voltage and can be analytically calculated. In addition, the temperature optimization leads to significantly reduced hydrogen permeation at low current densities. In combination with the pressure optimization, the challenging safety issues of pressurized electrolysis can be eliminated for the entire load range and, at the same time, the efficiency of the overall system be maximized. [ABSTRACT FROM AUTHOR]

• Optimization of power, durability, and performance of PV modules for desert areas. • 9.58% gain in efficiency by proper choice of materials and module design. • Encapsulant suggestions to reduce UV degradation on front and rear side of PV cells. • Reduction of cell movement due to the temperature cycles and risk of tab breakage. • Up to 35% reduced soiling losses by using a new anti-soiling coating. The global share of photovoltaic plants in desert locations increases continuously due to inexpensive land and higher yield due to higher irradiation levels. However, PV modules suffer from harsh environmental conditions that influence their lifetime and, consequently, the levelized cost of electricity. Environmental factors such as high temperature differences between nights and days, high ultraviolet doses, high ambient temperatures, and high airborne dust lead to durability and performance issues such as delamination, discoloration, fatigue of interconnection, breakage of solar cells, hot-spots, and power loss due to the soiling. In this work, different bills of materials and module designs are evaluated, targeting optimum PV output power while increasing the service life and performance of the PV modules in desert climates. A stepwise optimization of module components (solar cells, glass coating and polymers/encapsulation) and module design (full vs. half cells, tab widths) are performed by simulation and experimental approaches. Simulations results analyzes the loss mechanisms and electricity production of PV modules by considering the impact of module material and design Experimentally, ultraviolet stress tests and thermal cycling tests are performed for polymer durability and interconnection fatigue analysis. The soiling reduction potential of a newly developed glass coating is investigated by outdoor exposure tests in Saudi-Arabia. It is shown by proper choice of materials and optimized interconnection design, the efficiency of the module is increased by 9.58% rel. relative to the reference module. Furthermore, the choice of encapsulant and module design strongly affect the expected service-life, and soiling losses could be reduced up to 35%. [ABSTRACT FROM AUTHOR]

• A model has been developed to simulate CO 2 reforming of methane in reactors. • Our model is more accurate than the laminar finite-rate model in the reference. • A 10% increase in the energy efficiency is achieved with an optimization study. In CO 2 reforming of methane solar thermochemical energy storage, much research has been conducted to enhance the thermochemical performance of the reactor. However, there has been little research conducted to investigate the effects of dimensions on the reactor thermochemical performance. Moreover, little innovation has occurred on optimizing reactor dimensions and operating conditions simultaneously. In this paper, a model has been developed to simulate CO 2 reforming of methane reaction in a tubular packed reactor. By comparing with experimental and simulation data from another publication, the model is validated to be more accurate. A parametric study has been performed to investigate the effects of dimensions and operating conditions on the reactor thermochemical conversion and energy storage efficiency. The result shows that there is a trade-off between achieving a higher energy storage efficiency and decreasing the conversion by having smaller reactor with larger gas flow rate. An optimization study of all the design parameters, based on the reaction model coupled with a multistart optimization algorithm, is performed to find the maximum energy storage efficiency for a fixed required conversion. Without sacrificing the conversion, an energy storage efficiency of 0.77, which is 10% higher than the highest established experimental data, is obtained through optimization. The study provides a baseline for further thermodynamic analysis of the entire system. [ABSTRACT FROM AUTHOR]