Model of a Copper Spiral Solar Collector with a Concave Lens

Objective: To develop and validate a numerical model of a copper spiral solar thermal collector assisted by a Fresnel lens, aiming to simulate its optical thermal behavior, temperature evolution, and water heating efficiency under different climatic conditions. Theoretical Framework: Conventional solar collectors are limited by size requirements and thermal losses. Integrating a compact spiral copper geometry with solar concentration through a Fresnel lens provides an alternative for increasing energy density and improving solar radiation utilization in limited installation spaces. Method: A mathematical and computational model was developed in Python, integrating heat transfer phenomena, optical concentration, and energy balance principles. The system was evaluated using hourly NASA POWER meteorological data from twelve Mexican cities during 2025. Results and Discussion: The results demonstrate a strong dependence of collector performance on available solar irradiance. Hermosillo and Mexicali achieved the highest average thermal efficiencies and the shortest heating times, while central Mexican cities exhibited lower performance due to greater cloud cover and diffuse radiation conditions. Research Implications: The model provides a useful tool for the preliminary design and analysis of compact solar thermal systems for domestic water heating applications. Originality/Value: This study integrates a spiral copper collector geometry with Fresnel lens solar concentration, proposing a compact, low cost, and energy efficient alternative for residential water heating systems.