地埋熱交換器與能源筏式基礎的熱–水行為之分析

Abstract

台灣夏季氣候炎熱，導致冷氣使用頻繁，造成用電量上升與供電壓力增加。此外，冷氣運轉所產生的廢熱排放至周遭環境，進一步加劇以台北市為代表的都市熱島效應。能源基礎 (Energy Foundation) 作為一種兼具結構支撐與熱交換功能之新興綠能技術，提供有效解決方法。其原理係於基礎構造內部埋設地熱交換管，藉由地源熱泵系統 (Ground Source Heat Pump, GSHP) 驅動流體在管中循環，將冷房系統產生之廢熱傳導至地層中與低溫土壤進行熱交換，進而達到節能降耗並緩解熱島效應。 本研究以 COMSOL Multiphysics 建立熱–水力耦合數值模型，模擬分析台北地區一處實際能源筏式基礎案例。該案例採用HDPE 地熱交換管共40迴圈，總長達6720 m，埋設於筏基板中，並結合現地溫度監測資料進行模型驗證。研究進一步探討地下水條件（地下水位與流速）對出口流體溫度、土壤熱擴散效能與系統性能係數 (COP) 之影響。 此外，為驗證垂直式地源熱泵系統之可模擬性與模型可靠性，本研究以臺大農場實地設置之垂直熱交換井進行熱響應試驗 (Thermal Response Test, TRT)，作為垂直系統數值模型之驗證依據。並採用與筏式基礎案例相同之土壤參數與初始地溫條件，進一步模擬不同鑽孔數量配置之垂直地埋熱交換器 (Borehole Heat Exchangers, BHE)，並與水平筏式系統進行效能比較，探討兩種配置在不同地下水條件下之熱傳行為與COP表現，提供地熱系統實務應用與設計策略之參考。

Taiwan’s hot summers lead to heavy air－conditioning use, increasing electricity demand and intensifying the urban heat island effect–especially in Taipei. Energy foundations, which combine structural support with geothermal heat exchange, present a sustainable cooling strategy. This study employs COMSOL Multiphysics to build a coupled thermo－hydraulic model simulating an energy raft foundation in Taipei, featuring 40 loops of HDPE geothermal pipes (6720 m total length). Field data were used to validate the model, and parametric studies examined the effects of groundwater level and flow on outlet temperature and COP. To verify vertical ground heat exchanger (BHE), modeling, a Thermal Response Test (TRT) was conducted at the NTU experimental farm. Using soil properties identical to those of the Taipei raft foundation site, simulations of various borehole configurations were performed and compared to the horizontal system. Results offer practical insights into optimizing geothermal system design under urban soil and groundwater conditions. environments.