Towards power-to-X and carbon capture technologies for decarbonized green cities: A multi-layer cost-effective energy scheduling approach in integrated energy systems for targeting carbon footprint reduction

The increasing energy demand and the urgency of carbon reduction have driven the need for efficient decarbonization strategies. This study proposes a multi-layer optimization framework integrating Power-to-X (P2X) and Carbon Capture, Utilization, and Storage (CCUS) technologies within Integrated Energy Systems (IES) to minimize costs, enhance renewable energy utilization, and reduce emissions in green cities. The bi-level scheduling model optimizes natural gas network operations at the upper level and electricity market dispatch at the lower level, incorporating a ladder-based carbon trading mechanism for incentivized emission control. Simulation results demonstrate a 16.2 % cost reduction (from $10.52M to $8.825M), a 51.9 % decrease in carbon emissions (from 6,450 to 3,100 metric tons), and a 71.8 % drop in carbon trading costs (from $330,000 to $93,000). The Power-to-Gas (P2G) system facilitates the integration of surplus wind energy, producing 1.21 million cubic feet of synthetic natural gas (SNG) to enhance system flexibility. The bi-level model outperforms single-level approaches, achieving 8.6 % lower costs, 6.6 % fewer emissions, and 12.39 % more SNG production. Additionally, the ladder-based carbon trading mechanism reduces emissions by 20.3 % at a 0.44 % marginal cost increase, proving its effectiveness in balancing economic and environmental goals. This study provides a scalable framework for low-carbon urban energy systems by optimizing CCUS-P2X integration, improving cost-efficiency, and leveraging market-driven carbon strategies. Future research should explore real-time carbon pricing, sector-wide energy integrations, and large-scale pilot implementations to advance decarbonization efforts. Policymakers must support financial incentives and regulatory frameworks to accelerate the transition to cost-effective, sustainable, and carbon-neutral cities.