Unlocking the grid flexibility potential of fifth-generation district heating and cooling systems through user-level demand-side strategies

The increasing penetration of renewable energy sources is intensifying the need for energy flexibility solutions capable of supporting power grid stability. In this context, fifth-generation district heating and cooling (5GDHC) systems represent a promising yet still underexplored interface between urban thermal demand and electricity grids. This work investigates the potential of 5GDHC systems to provide energy flexibility services through demand-side management strategies implemented at building-user level. A physics-based dynamic modelling framework is developed, integrating building thermal demand calculation, heat pump performance modelling, and the representation of thermal energy storage and electrical batteries. Flexibility-oriented control strategies, including indoor temperature setpoint modulation, battery-assisted heat pump operation, and thermal energy storage integration, are simulated and assessed using dedicated flexibility indices for downward and upward load modulation and load shifting. The methodology is applied to a multi-user 5GDHC case study considering three alternative thermal balancing configurations: ground-coupled, groundwater-based, and solar-assisted solutions. The results of the simulative case study show that setpoint modulation enables short-term flexibility, achieving electricity load reductions of up to 37% and load increases of up to 26%. Battery integration enhances flexibility further, enabling load variations of 51–60%, while thermal energy storage achieves the highest performance, with load modulation exceeding 99% and load shifting fractions up to 54%. Flexibility provision is accompanied by primary energy savings of up to 11% and operating cost reductions of up to 14%, with groundwater-based configurations yielding the best overall performance. The proposed framework provides a robust tool to support the design and operation of flexible, low-carbon district energy systems.