Experimental investigation of steel-wool-enhanced phase change heat storage integrated air-source heat pump for winter heating applications

Improving the operational flexibility and economic viability of air-source heat pumps is critical for decarbonizing building heating. However, the widespread adoption of thermal storage to support ASHPs has been hindered by the high cost of conventional composite phase change materials. This study confronts this barrier by developing and validating a pragmatic thermal storage solution centered on two core innovations: a novel CPCM using ubiquitous and exceptionally low-cost steel wool as an effective thermal enhancer, and a ‘plug-and-play’ modular unit architecture designed for simplified scalability and integration. The optimized CPCM achieved a 47.07% increase in thermal conductivity while demonstrating excellent long-term stability, with outstanding thermal performance maintained after 100 charge-discharge cycles. At the system level, experimental validation against a non-enhanced control shows a 33.9% faster charging rate and prolonged stable room heating by 76.92%. A comprehensive techno-economic analysis, fortified by sensitivity analysis, confirmed the system's robust financial viability, projecting a 4-year payback period under a peak-shaving strategy. This research validates a cost-driven engineering philosophy, proving that steel-wool-enhanced modular storage is a commercially promising and scalable pathway toward more sustainable and resilient building energy systems.