Solar water heater (SWH) systems represent an effective strategy for reducing residential fossil fuel consumption; however, conventional flat-plate solar collectors often rely on metallic components and multi-circuit configurations that increase cost and system complexity. This work presents the long-term performance assessment of a passive SWH featuring a flat-plate solar collector fabricated from Polypropylene Random Copolymer (PPR) and operating under a simplified single-circuit thermosiphon configuration. The proposed design avoids the need for auxiliary components such as circulation pumps, heat exchangers, and antifreeze loops, enabling a robust and cost-effective architecture for domestic applications. The system was evaluated through a one-year field case study in a four-person household located in Santiago, Chile, characterized by high solar resource availability. Results show a 55% reduction in liquefied petroleum gas (LPG) consumption, corresponding to an annual solar fraction of 55% and an annual system-level solar thermal efficiency of 58.1%. The system delivered annual energy savings of approximately 2,904 kWh, resulting in an estimated payback period of 6 years under projected fuel prices. Seasonal performance analysis revealed higher solar contributions during summer months, while winter performance remained supported by auxiliary heating. A sensitivity analysis further demonstrated that user behavior parameters – shower flow rate and duration – significantly influence the system’s effective solar contribution. Furthermore, projecting the SWH's thermal performance in San Pedro de Atacama (northern Chile) and Temuco (southern Chile) demonstrated its potential applicability across diverse climatic conditions, underscoring the dominant influence of regional solar radiation profiles on system efficiency. Additionally, a thermomechanical comparison of collector materials indicates that PPR offers advantageous flexibility, durability, and ease of installation compared with conventional materials such as copper and polyvinyl chloride (PVC). Overall, the results demonstrate that this work’s PPR-based passive SWHs with simplified hydraulic architecture can provide reliable thermal performance and attractive economic returns in sun-rich regions. The findings support the broader adoption of cost-effective solar thermal technologies and highlight opportunities to optimize systems based on user demand profiles.
Alvarez et al. (Wed,) studied this question.