Advanced control strategies for air-based photovoltaic-thermal heat pump systems in residential buildings

Solar-assisted heat pump (SAHP) systems represent an effective solution for reducing the carbon footprint of buildings by integrating renewable electricity and low-temperature heat with high-performance electricity-driven heat pumps. This work investigates the design and operation of a SAHP system for heating applications, integrating air-based photovoltaic-thermal (PVT) collectors, an air-source heat pump (ASHP) and a stratified thermal energy storage (TES) tank. Three operational strategies with different control complexity are assessed: (1) an adaptive rule-based strategy, (2) a smart optimisation-based strategy inspired by model predictive control, and (3) a hybrid supervisory strategy combining optimisation with rule-based execution and representing a practically deployable control framework. The system is modelled using detailed thermodynamic and data-driven component models and evaluated for four residential case studies in Turin (IT), London (UK), Stockholm (SE) and Athens (GR). In Turin and Stockholm, the hybrid strategy provided the greatest reductions in electricity consumption (35% and 33%, respectively) and substantial cost savings (95% and 52%, respectively). In London, both smart and hybrid strategies achieved similar performance, reducing electricity consumption by 41–43% and costs by 77–79%. In Athens, the smart strategy was most effective, reducing consumption by 52%, preserving or improving electricity generation, and generating net operational revenues equivalent to a 164% reduction relative to the reference scenario. The TES tank sensitivity analysis shows that sizing the storage to match the average daily thermal demand yields near-optimal performance, while oversizing provides marginal additional benefits, making further capacity increases unjustified. The results demonstrate that coordinated control of the PVT collectors, ASHP and TES tank enables substantial energy and economic gains across different climatic and market conditions.