This paper proposes an energy management system for the microgrid primarily powered by renewable energy sources, considering the thermal inertia of user-side buildings. The system aims to increase renewable energy penetration, enhance power supply reliability, and reduce operational costs. Firstly, this paper introduces a modeling approach for building thermal radiation processes. Secondly, the calculation method for determining the adjustable power of electric heating loads is proposed in this paper. Lastly, this paper outlines the energy management system to optimize microgrid operations. The EMS utilizes forecast data to formulate the pre-scheduling plan and determine the operations of the microgrid. Real-time data collection enables dynamic power scheduling, and the rolling optimization strategy is used to correct prediction inaccuracies. Adjustable load power control enhances microgrid stability during peak load periods. Simulation results demonstrate high renewable energy consumption, optimized microgrid operations, improved reliability, and reduced costs. The energy management system shows potential for effectively managing microgrid energy, leveraging renewables, ensuring reliable power supply, and optimizing costs.