小型太陽能薄膜蒸餾海水淡化系統是可紓解偏遠地區水資源缺乏問題的永續技術，然而缺乏系統化最佳設計之探討。本研究首先建立薄膜蒸餾模組，包括氣隔式、直接接觸式與真空式，以及整體系統之數學模式與實驗系統。薄膜蒸餾模組之模擬值與實驗值相對誤差約為10 %，整體系統之模擬值與實驗值變化趨勢相近，偏差主要原因是集熱器效率較模擬設定值低。藉由建立系統之數學模式，本研究提出一個擬穩態方法，結合動態最佳化搜尋，決定最低單位產水成本之設備尺寸與操作條件。本研究探討使用氣隔式、直接接觸式與真空式薄膜蒸餾模組之系統，最低之單位產水成本是使用氣隔式模組之之系統，產水量為1000 m3/day，成本為$5.16/m3。直接接觸式與真空式系統之成本接近，分別為$9.37/m3與$9.44/m3。最佳系統均採用薄膜蒸餾冷側熱回收之設計。薄膜特性影響分析結果顯示，質傳係數提升至兩倍可降低產水成本，但更高程度的改善對成本不會有更進一步的影響；熱傳導係數之降低只對直接接觸式系統有影響，50%之減低可獲單位產水成本約20%之降低。 Small-scale solar membrane distillation desalination system (s-SMDDS) is a sustainable technology for resolving the water resource problem in remote arid areas. However, the optimal design of the system has not been systematically investigated. This study developed the mathematical models and experimental systems of the membrane distillation modules, including air gap, direct contact and vacuum types, as well as the overall systems. For the membrane distillation modules, the relative deviation of the simulation results relative to the experimental results is about 10%. The trends of the simulated values and experimental values are similar, and the main reason of the deviation is that the efficiency of solar collector is smaller than the simulate setpoint. The equipment sizes and operation conditions for the water producton with minimum unit costs were determined by a systematic method. The optimization analysis employed the mathematical models, a pseudo steady state approach and the dynamic optiomization. The minimum unit costs of the systems utilizing air gap, direct contact and vacuum membrane distillation modules are $5.16/m3, $9.37/m3 and $9.44/m3 for the production rates of 1000 kg/day, 800 kg/day and 800 kg/day, respectively. For all the systems, the cold side heat recovery for the membrane distillation module should be adopted. For the membranes employed in this study, the enhancement of membrane mass transfer coefficient up to two times is beneficial for cost reduction. The 50% reduction of the thermal conductivity of the membrane can reduce the unit cost by 20% for the system using direct contact membrane distillation.
