Abstract
The combined use of waste heat (WH), ground-source heat pumps (GSHPs), and district heating (DH) offers an effective pathway to decarbonize urban heating. Taking a system-integration perspective, this review synthesizes technical, operational, and policy dimensions of WH-assisted GSHPs coupled to DH. Both centralized and decentralized configurations are examined, focusing on thermal energy storage (TES) and advanced control strategies to maintain long-term ground thermal balance (under climate- and load-dependent annual heat-balance constraints) and to mitigate seasonal mismatches between WH availability and heat demand. Evidence from campus- and city-scale studies indicates that hybrid WH–GSHP–DH systems can enhance seasonal performance, widen recoverable low-grade WH sources, and improve ground balance, while TES and demand-side management enhance flexibility and curb peak electricity demand. Effective integration depends on low-temperature DH operation, appropriate temperature matching between sources and loads, and price-responsive control that optimally dispatches large heat pumps and maximizes direct WH use and storage flexibility. However, deployment is often constrained by high capital investment, coordination among multiple actors, and market designs that undervalue thermal flexibility and third-party WH. Supportive measures—two-way heat markets, dynamic electricity and heat pricing, and spatial planning that co-locates WH sources, demand, and favorable geology—can address these barriers. Future research priorities include integrated multi-domain modeling, optimization-based control with long-term ground monitoring, market and tariff designs that monetize flexibility, and advances in high-temperature heat pumps and durable borehole materials. Under supportive technical and policy conditions, WH–GSHP–DH integration represents a scalable route toward efficient, flexible, and low-carbon urban heating.