Hybrid solar–ground source heat pump systems for net-zero energy buildings: A review of thermal management, energy storage, and optimization approaches

Hybrid solar–ground source heat pump (GSHP) systems are promising solutions for Net-Zero Energy Buildings (NZEBs), combining abundant solar energy with the thermal stability of the ground. This study presents a structured literature review and comparative analysis of 57 peer-reviewed studies on hybrid solar–ground source heat pump systems and their integration with thermal energy storage and advanced control strategies. Although solar and GSHP technologies are individually mature, their integrated operation with thermal energy storage (TES), advanced controls, and system optimization remains underexplored. This review synthesizes recent developments in hybrid solar–GSHP configurations, including solar thermal coupling, photovoltaic (PV)-assisted GSHPs, and photovoltaic/thermal (PV/T)-supported heat pump systems. Comparative analysis of case studies from Europe, Asia, Africa, the Middle East, North America, and Oceania shows consistent primary energy savings of 50–75%, significant carbon emission reductions, and improved operational resilience. However, large-scale deployment remains constrained by high upfront costs, region-specific technical constraints, and fragmented policy frameworks. Key research gaps are identified in system modeling, long-term performance assessment, and integration with smart grids and AI-based control strategies. The findings emphasize the need for regionally adaptive policies, cost-reduction pathways, and stronger experimental validation in underrepresented regions such as Africa and Latin America. The convergence of intelligent optimization, flexible TES solutions, and supportive regulatory mechanisms is expected to accelerate the role of hybrid solar–GSHP systems in climate-neutral and energy-resilient buildings.