Investigating the Role of Geometry in Solar Water Heating: A Case Study of Cylindrical and Frustum Buckets

ABSTRACT This study studies the effect of bucket shape and geometry on the performance of solar water heating systems. Three plexiglass (PMMA) buckets were chosen: cylindrical, frustum, and inverted frustum. Each bucket has a capacity of 13 L and 3 mm wall thickness. The primary objective is to identify the most effective bucket shape and surface treatment for maximizing thermal efficiency under winter solar conditions. The buckets were evaluated in two configurations: with black‐painted bases and with half the lateral surface painted black. Experiments measured solar intensity, water temperature, and heat transfer parameters using thermocouples and a solar power meter. Results revealed that the frustum‐shaped bucket achieved the highest water temperature increase, reaching 47.5°C after 4 h, compared to 43.2°C and 41.8°C for the inverted frustum and cylindrical shapes, respectively. Numerical analysis validated the experimental results and provided insights into convective, evaporative, and radiative heat transfer. The outcomes emphasize the critical role of geometric optimization and surface modification in solar thermal design, offering a cost‐effective and sustainable alternative for rural energy needs.