An integrated energy system for residential communities based on hydrogen-blended natural gas and geothermal energy: Synergistic optimization for deep decarbonization and grid flexibility

Facing the challenges of global climate change and carbon neutrality, the large-scale utilization of clean energy sources such as hydrogen and geothermal energy is a key strategy for achieving a deep energy transition. This paper proposes a novel integrated energy system for low-carbon residential communities, which deeply couples hydrogen separated from the hydrogen-blended natural gas network with shallow geothermal energy. To achieve the dual objectives of deep decarbonization and grid flexibility, this paper develops a multi-objective synergistic optimization model aimed at minimizing both total system carbon emissions and peak grid load. Furthermore, a day-ahead rolling optimization framework is employed to simulate the year-round operation, thereby revealing the synergistic operational mechanism between hydrogen and geothermal energy. Taking a representative residential community in a cold region as a case study, the results indicate that: 1) Compared to a conventional energy system, the proposed synergistic optimization strategy can achieve an annual carbon reduction of up to 14.84% while maintaining grid-friendliness. In contrast to a strategy that solely pursues maximum emission reduction, this synergistic approach significantly reduces the daily average peak grid load by 29.71% at the cost of a mere 1.91% increase in carbon emissions; 2) The mechanism analysis further reveals that multi-timescale energy management is key to achieving the dual objectives. Specifically, the ground source heat pump covers the base heat load to provide flexibility for multi-energy scheduling. The temporal decoupling of hydrogen allows for off-peak accumulation and critical-peak power release. The synergy of multi-energy storage devices rapidly responds to the system's demands. This study provides a new paradigm and valuable insights for the planning and dispatch of energy systems in future low-carbon communities, especially in the context of high renewable energy penetration.