Key Parameters Design of Chain-Rail Based Slope Gravity Energy Storage System for Optimal Efficiency

A chain-rail based slope gravity energy storage system (SGESS) has significant advantages in mountainous and hilly regions due to the merit of highly efficient and reliable operation performance. However, designing SGESS requires balancing multiple structural and operational parameters. Given the interdependent constraints of electrical and mechanical components, selecting key parameters and optimizing them to maximize the system's comprehensive efficiency remains a major challenge in industrial applications. To solve this issue, this study establishes the dependency constraints of electrical and mechanical components and the key parameters of the SGESS are also selected. Then, a complete mathematical model for loss analysis in each component of the chain-rail based SGESS is developed, and the impact of key parameters on the system's comprehensive efficiency is investigated. With the objective function of system efficiency, an optimization method of key parameters based on nonlinear programming is proposed. Furthermore, with three chain-rail based SGESSs with the capacities of 1-kW, 500-kW and 5-MW, the key parameters, such as mass and number of mass block (MB), moving speed, slope angle, ratio of gearbox, etc, are systematically optimized for the highest efficiency. Experimental validation is performed on a 1-kW chain-rail based SGESS prototype with the slope angle of 34.6°. With the given number of MB and ratio of gearbox, the mass and moving speed of MB are optimized. The results show that the designed and measured charging efficiencies are 46.42% and 43.8%, respectively, and the effectiveness of the proposed design method is validated well.