Operation of two mechanically driven gravity energy storage systems using one wind turbine for uninterrupted energy supply in an isolated microgrid

Abstract

Summary A novel scheme of operating two mechanically driven energy storage, namely gravity energy storage system (GESS), alternatively using one wind turbine (WT) has been proposed in this article for uninterrupted energy generation in areas with limited or no grid connectivity. However, considering its lower land requirement and nature of uninterrupted energy supply, this system can also be easily implemented in grid connected scenarios. The proposed system consisting of a WT, two GESSs, one DC motor and one inverter, describe a simplified operation of alternatively charging of two GESSs, from a single WT, using two mode changer spring and suspended weight assemblies. Mechanical power of the WT has been directly utilized to charge GESSs, omitting the requirement of WT alternator, consequently lowering the maintenance requirement. This also results in decreasing the overall loss of renewable energy and completely eliminating the reactive power requirement of the WT. The output of the system is remains unaffected from regular or general wind speed variation, thus provides a stable energy output. Operation of the proposed system is quite different from existing WTs as in most of the cases electrical energy directly gets generated from WT. The main essence of this system is its simplicity, robustness and ability to generate uninterrupted electrical energy at stable voltage. It also does not require any electrochemical battery, thus offers low maintenance expenditure. This article documents the mathematical modelling of the proposed system and performance evaluation through simulation using real wind speed data.