Empirical Study of Photovoltaic Solar Power Reliability for Life-Critical Medical Equipment in Off-Grid Health Facilities in Northern Nigeria

Solar photovoltaic power systems are increasingly deployed to provide energy independence for health facilities in off-grid northern Nigeria, but empirical data on the reliability of solar power for life-critical medical equipment loads under actual northern Nigerian operational conditions are limited, making evidence-based system sizing and clinical risk assessment difficult. This study empirically analyses the reliability performance of photovoltaic solar power systems supporting life-critical medical equipment at twelve off-grid health facilities in Kebbi, Zamfara, and Sokoto states over a twelve-month monitoring period. Real-time solar irradiance, battery state of charge, and equipment power supply voltage were monitored at each facility using ESP32-based data logging units recording at one-minute intervals. Life-critical equipment loads monitored include oxygen concentrators, delivery room lighting, vaccine refrigerators, and patient monitoring systems. Power supply interruption events, defined as supply voltage falling below equipment minimum input voltage, were recorded and characterized by duration and associated equipment shutdown. Annual irradiance data were analysed for seasonal patterns and correlation with battery bank sizing adequacy. A reliability model was developed from empirical data to predict interruption frequency as a function of system sizing parameters. Results show an overall annual power interruption frequency of 4.7 events per facility per year, with average interruption duration of 3.2 hours, predominantly occurring during the Harmattan season in December and January. Battery sizing was the primary determinant of interruption frequency, with facilities with battery autonomy below 24 hours showing significantly more frequent interruptions. The empirically derived reliability model provides an evidence base for improved solar system sizing specifications. Keywords: solar power reliability, off-grid health facilities, life-critical medical equipment, northern Nigeria, photovoltaic systems.