Thermodynamic and economic analysis and optimization of a thermal-dominated island integrated energy system in extreme cold regions

Current energy architectures are ill-suited for decarbonizing high-altitude cold regions, as they lack the capability to sustain a rigid thermal supply amidst the inherent volatility of renewable generation under harsh climatic constraints. A Thermal-Dominated Island Integrated Energy System (TD-IIES) is proposed in this paper. The TD-IIES differs by establishing a Carnot Battery as the central energy hub to decouple heterogeneous energy flows, unlike traditional electricity or hydrogen-dominated architectures. An optimization framework is developed that considers surrogate-assisted multi-objective optimization by integrating Deep Neural Networks (DNN) with the Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) for optimization of thermodynamic parameters and capacities of the equipment while executing Event-Driven Hierarchical Control Strategy (ED-HCS). A case study using real data obtained from Naqu, Tibet, is presented to compare the configurations with and without a Compound Parabolic Concentrator (CPC). The results show that the system provides a maximum Carnot Battery round-trip electrical efficiency of 64.93% and a Heat Pump COP of 4.75. The techno-economic optimum is the No-CPC scheme with a Levelized Cost of Electricity (LCOE) of 0.176 $/kW·h. The cost is 4.9% lower than the cost when CPC is included. And it also represents a reduction of around 43% compared to the mainstream off-grid design benchmarks. Resilience analysis reveals a “wind-dominated” anisotropy acting on the reliability of systems. The No-CPC scheme has better economic adaptability to the “strong wind/weak sun” scenario, while the scheme with CPC inclusion has better fault tolerance (N-1 redundancy) and can still achieve survival supply when the core heat pump is faulty. This study demonstrates that the TD-IIES framework, by leveraging the thermally coupled Carnot Battery as the central energy hub, achieves cost-competitive and resilient off-grid operation in high-altitude cold regions. The techno-economic advantage of the No-CPC scheme originates from redirecting capital from solar thermal collectors toward wind and solar generation, while the fault-tolerance advantage of the CPC-included scheme derives from its thermally autonomous backup capability.