Dynamic Programming-Based Mass Block Stacking Method of Gravity Energy Storage System for Minimum Energy Consumption

Stacking the mass block (MB) is a key process in maintaining the operation of a gravity energy storage system (GESS), and the energy consumption during this process directly affects the comprehensive efficiency. Currently, the rail-based MB stacking structure has significant advantages in load-bearing capacity and stability. However, minimum energy consumption is still a challenge in the application of GESS. This study first establishes an energy consumption model for a completed stacking process for a given electricity condition (GEC). With the purpose of minimum energy consumption, a dynamic programming-based stacking method for the optimal number and position of MB is proposed. Moreover, a bypass structure and the related stacking strategy are also introduced for an additional electricity condition (AEC). Secondly, for a 5-MW/20-MWh GESS, stacking site structures with the ratios of 8:1, 4:1, 2:1, and 1:1 are designed. The proposed approach achieves the average energy-saving rate of 49.9%, 41%, 39%, and 27% under GEC. When AEC is considered, the observed energy savings are about 36.5%, 25.3%, 23.5% and 24.7% of operating conditions, respectively. Finally, a laboratory-scale experimental model of a rail-based MB stacking structure is built, and experiment validation is performed on a task of 3 rails and 15 MBs. The result shows that, with the proposed stacking method, the energy consumption can be effectively reduced under GEC, with an average energy-saving rate of 41.1%. When AEC is taken into account, energy efficiency improvements are realized only in some instances while ensuring the functional capability to stack additional MBs.