Abstract
This study aims to evaluate a hybrid energy system combining solar photovoltaic panels, ground-source heat pumps (GSHPs), and battery storage, within a unified university-based model applied to three distinct Tunisian climate zones: Beja, Gabes, and Borma. The methodology relied on a dynamic integration of OpenStudio and TRNSYS to accurately simulate annual thermal and electrical loads. A total of 35 design configurations per city were investigated, varying in borehole number and spacing, while system components were standardized to 1,137 photovoltaic panels rated at 450 W and 120 LiFePO₄ batteries with a storage capacity of 13.44 kWh. Results revealed that the imbalance between cooling and heating demands leads to gradual thermal accumulation in the ground, reducing system efficiency over time.To assess mitigation strategies, a composite objective function incorporating four indicators was employed: thermal accumulation, ground field volume, instantaneous operating cost rate, and grid dependency. The optimization process identified configurations capable of limiting ground temperature rise and supporting stable operation. Sensitivity analysis showed that increasing the weight of economic and spatial indicators reshuffles the ranking of certain configurations, highlighting the importance of prioritization based on design goals. The selected configurations demonstrated the ability to cover more than 70% of annual demand, with levelized cost of energy (LCOE) ranging from 0.023 to 0.114 USD/kWh and payback periods between 23 and 44 years, depending on whether the system operates under Tunisia’s restrictive grid policies or more supportive international frameworks. Annual loads ranged from 965 to 1,135 MWh, with peak cooling reaching 660 kW and heating between 324 and 416 kW. Simulations also revealed seasonal variations in battery performance, with average daily charge levels exceeding 50–55% in July and dropping to 17–20% in January, depending on location. The study emphasizes the need to align technical configurations with regulatory reforms to ensure economic viability and accelerate the transition to sustainable energy systems in academic institutions.

Key words: solar–geothermal systems, thermal imbalance, energy policy, energy modeling, multiobjective optimization.