Solar-Driven Building-Integrated Atmospheric Water Harvesting System for Remote Island Buildings Based on MIL-101(Cr)-Coated Finned Tube Heat Exchangers

Remote island buildings often operate under isolated environmental conditions where conventional water supply infrastructures are unavailable or unreliable. However, the lack of theoretical frameworks and integrated technologies for building-scale autonomous water supply remains a critical challenge in sustainable construction and resilient building development. Existing atmospheric water harvesting technologies mainly focus on material-level adsorption capacity or short-term water production performance, while systematic principles for integrating sorption materials, heat transfer structures, and renewable energy subsystems into autonomous building water systems remain insufficiently established. This study develops and validates an active, continuous atmospheric water harvesting (AWH) system utilizing MIL-101(Cr) coated on finned tubes. The system alternates cold water (25 °C) and hot water (50–70 °C during actual experiments; 50–80 °C in simulations) through the piping, allowing the two parallel modules to independently undergo adsorption and desorption phases-thereby breaking away from the traditional daily single-cycle mode. A coupled heat and mass transfer model is developed and validated using experimental measurements obtained from the MIL-101(Cr)-coated finned tube component, with root-mean-square deviations below 8.5% for all key parameters. Under simulated coastal island conditions (75–87% RH, 29–32 °C), the dual-module system achieves a water productivity up to 1.989 kg·m−2·day−1 at a desorption temperature of 80 °C, with cycling frequencies reaching 9 cycles per module over 48 h. Parametric analysis reveals that synergy between desorption temperature (50–80 °C) and desorption extent (50–80%) governs daily water yield, while the per-cycle adsorption capacity remains stable at ≈0.91 g/g. Energy and economic analysis shows that the auxiliary electricity required ranges from 0.38 (50 °C) to 6.36 kWh·m−3 (80 °C), with a preliminary levelized cost of water of 1.85–3.2 USD·m−3 competitive with conventional island supply methods.