A simplified thermal and battery model for off-grid solar air conditioning in Florida’s hurricane context

Florida’s hurricane-prone climate often leaves residents without power and at risk of dangerous indoor heat conditions. This thesis examines whether an off-grid, solar-powered air conditioning system can feasibly maintain safe indoor temperatures over a one-week outage period during peak hurricane season. A simplified, lumped-capacitance thermal model and an energy-based (Coulomb-counting) battery state of charge (SoC) approach were developed in MATLAB to simulate a DC-powered air conditioner (the DC48 unit) in a single-zone space. Historical weather and solar irradiance data from Vero Beach, Florida, represent the hot and humid conditions typical of post-hurricane scenarios. The model uses an on/off plus deadband control strategy to balance comfort against limited solar availability, incorporating conduction, infiltration, internal gains, and solar loads, as well as conservative battery SoC limits (20% minimum and 70% maximum). Results from four scenario cases, varying room size and solar array capacity, indicate that near-ideal comfort (less than 12% of the time above 78 ºF) is achievable when the solar array is matched properly to the cooling demand (e.g., 1.6 kW for a 300 ft2 space). However, undersized arrays or larger enclosures lead to deeper battery depletion and more frequent excursions above the comfort threshold. These findings confirm that aligning solar capacity, battery storage, and cooling load is critical for off-grid air conditioning in disaster relief contexts. This study offers a foundational framework for future experimental validation, more advanced control schemes, and multi-zone expansions that could enhance the resilience and sustainability of emergency cooling solutions in hurricane-prone regions.