DEVELOPMENT AND EMPIRICAL PERFORMANCE EVALUATION OF A LOW-COST PASSIVE THERMOSYPHON SOLAR WATER HEATER USING LOCALLY SOURCED MATERIALS

This study presents the design, fabrication, and empirical performance evaluation of a cost-effective domestic solar water-heating prototype operating by passive thermosyphon circulation. The system uses locally sourced materials: an insulated wooden casing, a matte black aluminium absorber plate, 10 mm copper riser pipes, a 4 mm tempered-glass cover, and a 5 L insulated storage tank. The collector casing measured 63.5 cm by 30.8 cm, providing an aperture area of approximately 0.196 m². During a representative outdoor test from 08:00 to 18:00, water outlet temperature increased from 25.0 °C at 08:00 to 66.5 °C at 14:00; the largest recorded inlet-to-outlet temperature difference was 40.0 °C. A theoretical thermal-energy equivalent of approximately 837 kJ was calculated by applying this maximum temperature difference to the nominal 5 kg water inventory; it is not a direct measurement of energy stored in the tank. The estimated material and fabrication cost was NGN 120,000. The results demonstrate the practical feasibility of a locally fabricated passive solar heater for small domestic applications. Because solar irradiance, calibrated uncertainty, and repeat-day measurements were not recorded, collector efficiency and economic payback are not reported.