Enhanced tubular solar still performance using nano beeswax/graphene phase change materials and parabolic trough collectors

The scarcity of clean water in remote areas necessitates energy-efficient and sustainable desalination solutions. This study enhances tubular solar still (TSS) performance by integrating a parabolic trough collector (PTC) and nano-phase change material (nano-PCM) based on beeswax/graphene. Beeswax offers high latent heat storage capacity, while graphene enhances thermal conductivity to improve heat transfer. Experiments were conducted under tropical conditions to evaluate clean water productivity, thermal efficiency, and exergy across three configurations: without PCM, with PCM, and with nano-PCM. The results indicate that the system without PCM produced clean water at a rate of 2.17 L/m²/day with a thermal efficiency of 31 %. The use of PCM increased productivity to 2.45 L/m²/day with a thermal efficiency of 36 %, while nano-PCM achieved 2.61 L/m²/day with a thermal efficiency of 38 %. Exergy values also improved from 3 % without PCM to 3.4 % with PCM, and 3.7 % with nano-PCM, indicating better heat transfer efficiency. Economic analysis estimates water production costs over a 10-year period as 0.081 USD/L (without PCM), 0.078 USD/L (PCM), and 0.073 USD/L (nano-PCM). The novelty of this research lies in the first-time integration of nano-PCM beeswax/graphene in a TSS-PTC system, which enhances energy efficiency, improves productivity, and ensures distillation continuity despite fluctuating solar radiation. This innovation presents a viable small-scale desalination solution for remote regions. Future research should focus on large-scale optimization and environmental performance testing to support real-world applications.