Performance Evaluation of A Hybrid Photovoltaic–Thermal–Battery System Integrated with An Unreliable Grid for Residential Buildings in Nigeria

Unreliable electricity supply remains a persistent challenge for residential buildings in many developing countries, including Nigeria, where frequent grid outages undermine energy security and quality of life. This study presents a comprehensive simulation-based evaluation of a hybrid photovoltaic–thermal (PVT)–battery system integrated with an unreliable national grid for a typical residential building in Bauchi State, Nigeria. The system was modelled using the Transient System Simulation Tool (TRNSYS) under local climatic conditions and realistic electrical and domestic hot water demand profiles obtained through structured energy audits. A rule-based energy management strategy was employed to coordinate energy flows among the PVT system, battery storage, and grid supply. Results indicate that the hybrid system supplied approximately 60% of the annual electrical demand from renewable sources, reduced grid electricity consumption by about 52%, and met nearly 68% of the annual domestic hot water requirement. Battery storage provided up to 8 hours of autonomy during grid outage periods. The findings demonstrate the technical feasibility and resilience of hybrid PVT–battery systems for enhancing residential energy reliability in regions characterized by weak and intermittent grid infrastructure.