Standalone versus grid-connected? Operation mode and its economic and environmental assessment of railway transport microgrid

Abstract

The microgrid is a necessary complement to the energy system, allowing flexible and effective utilization of distributed energy sources. This study explores the prospects of microgrid applications in railway transport and designs proper operation modes for standalone and grid-connected microgrids. To evaluate the economic and environmental effects of microgrids, a comprehensive analytical framework based on system dynamics, life cycle analysis, and life cycle cost analysis is developed. An empirical study using relevant data from the Guangzhou Metro is carried out to verify the feasibility of the proposed operation mode. There are three main findings: (1) The operational mode of the designed microgrid is implementable, in which the standalone microgrid could be applied to cover a part of the electricity loads of the enterprise, while the grid-connected microgrid could significantly participate in the electricity spot market. (2) In the two microgrids, the economic and environmental benefits increase with the increased installed photovoltaic capacity. And the economic and environmental benefits are the highest in the grid-connected microgrid when no battery is installed. (3) By comprehensive comparison, the grid-connected microgrid is more suitable for the railway transport industry. This study could provide a reference for decision-making for designing the railway transport microgrid.