Based on the concept of sustainable development, to promote the development and application of renewable energy and enhance the capacity of renewable energy consumption, this paper studies the design and optimization of renewable energy hydrogen production systems. For this paper, six different scenarios for grid-connected and off-grid renewable energy hydrogen production systems were designed and analyzed economically and technically, and the optimal grid-connected and off-grid systems were selected. Subsequently, the optimal system solution was optimized by analyzing the impact of the load data and component capacity on the grid dependency of the grid-connected hydrogen production system and the excess power rate of the off-grid hydrogen production system. Based on the simulation results, the most matched load data and component capacity of different systems after optimization were determined. The grid-supplied power of the optimized grid-connected hydrogen production system decreased by 3347 kWh, and the excess power rate of the off-grid hydrogen production system decreased from 38.6% to 10.3%, resulting in a significant improvement in the technical and economic performance of the system.

The safety of hydrogen storage is essential for the development of fuel cell vehicles. A mathematical model for a compressed hydrogen storage tank is established based on the mass conservation equation, the energy conservation equation and the real gas equation of state. Using the Matlab/Simulink platform, a dual-zone lumped parameter model, which divides the tank into a hydrogen gas zone and a tank wall zone, is established. The initial conditions of the MC Default method hydrogen filling from SAE J2601 are utilized in the lumped parameter model for numerical simulation. Five cases are studied, including two different tanks. One case used the Lookup table for hydrogen refueling, and four cases used the MC Default method for fueling. The hydrogen gas temperature, wall temperature, pressure in the tank and state of charge are obtained during the fueling process. The simulated results show that the dual-zone lumped parameter model can well predict the temperature, pressure and state of charge (SOC) for Type IV tanks with volumes of 249 L and 117 L during refueling. By using the averaged heat transfer coefficient (80 W/(m²·K)) between gas and wall, and the constant heat transfer coefficient (20 W/(m²·K)) between wall and environment, the gas temperature and pressure of our dual-zone lumped parameter model show good agreement with the experiment. The maximum difference between simulated and experimental wall temperatures for five cases is around 2 °C. The experimental wall temperatures were measured on the external surface of the tank, while the simulated wall temperature of the dual-zone lumped parameter model is representative of a mean temperature averaged alone with the radial direction.

The gas equation of state (EOS) serves as a critical tool for analyzing the thermal effects within the hydrogen storage tank during refueling processes. It quantifies the dynamic relationships among pressure, temperature and volume, playing a vital role in numerical simulations of hydrogen refueling, the development of refueling protocols, and ensuring refueling safety. This study first establishes a lumped-parameter thermodynamic model for the hydrogen refueling process, which combines a zero-dimensional gas model with a one-dimensional tank wall model (0D1D). The model’s accuracy was validated against experimental data and will be used in combination with different EOSs to simulate hydrogen temperature and pressure. Subsequently, parameter values are derived for the van der Waals EOS and its modified forms—Redlich–Kwong, Soave, and Peng–Robinson. The accuracy of the modified forms is evaluated using the Joule–Thomson inversion curve. A polynomial EOS is formulated, and its parameters are numerically determined. Finally, the hydrogen temperatures and pressures calculated using the van der Waals EOS, Redlich–Kwong EOS, polynomial EOS, and the National Institute of Standards and Technology (NIST) database are compared. Within the initial and boundary conditions set in this study, the results indicate that among the modified forms for van der Waals EOS, the Redlich–Kwong EOS exhibits higher accuracy than the Soave and Peng–Robinson EOSs. Using the NIST-calculated hydrogen pressure as a benchmark, the relative error is 0.30% for the polynomial EOS, 1.83% for the Redlich–Kwong EOS, and 17.90% for the van der Waals EOS. Thus, the polynomial EOS exhibits higher accuracy, followed by the Redlich–Kwong EOS, while the van der Waals EOS demonstrates lower accuracy. This research provides a theoretical basis for selecting an appropriate EOS in numerical simulations of hydrogen refueling processes.