Recent advances in heat pump systems and key components: A comprehensive review

The widespread application of heat pumps in both building and industrial sectors faces scenario-specific challenges. Building heating requires addressing capacity degradation, frosting, and variable load regulation at low temperatures, whereas industrial processes must overcome the technological bottlenecks of high-temperature output. Distinct from the incremental improvement analyses common in previous reviews, this review conducts a systematic and critical review of recent advancements within an integrated component-system-application framework. Uniquely, this review identifies and scrutinizes the dynamic mismatch between component-level innovations and system-level performance—a critical yet often overlooked bottleneck. At the key component level, the focus extends beyond structural innovations to the adaptive synergy between compressors and heat exchangers under variable operating conditions. At the system configuration level, while analyzing enhanced cycle optimization strategies, the paper critically evaluates the coupling challenges between refrigerant selection and control strategies. At the application level, a heat-source-centric philosophy is proposed, elaborating on energy efficiency enhancement strategies for air-source, water-source, ground-source, and solar-assisted systems. A notable original contribution is the introduction of the Performance-to-Transport Ratio (PTR), an innovative metric designed to quantify the trade-off between pump power consumption and compressor efficiency. This review emphasizes that intelligent collaborative control and multi-source synergistic integration are pivotal directions for overcoming the limitations of single heat sources. Furthermore, it repositions the future trajectory of heat pumps as grid-interactive flexible resources, aiming to provide a systematic and forward-looking reference for both engineering applications and frontier research. © 2026 Elsevier Ltd.