- 學位論文
河川流態與水力發電潛域之研究
Site Selection and Theoretical Potential of Small Hydropower Plant over Time-series Flow Regime Analysis and Hydrodynamic Model Simulations
摘要
面對氣候變遷的威脅及能源短缺的困境，永續能源的發展已是國際趨勢。其中，水力能源因其轉換效率高、價格低廉等因素而於各類綠色能源中佔有一席之地，在世界能源占比與日俱增。然而，傳統上水力發電案場的潛力評估僅著重水頭與流量兩個水利參數，常忽略水流動量及其產生的動壓對發電裝置的驅動效果，且考量時間參數的流態分析也相當缺乏，因此水力發電潛力評估系統仍有進一步的改善空間。本研究旨在建立一套完整的水力發電潛域評估模式，透過數學模式決定目標流量，並搭配CFD軟體計算以提出用以評估裝置受力之關係式。本研究以台灣北部景美溪支流永定溪為例，收集自1998年至2019年共22年的時流量資料，透過連續時間的超越機率進行流量時變分析，同時搭配小波模式進行流態分析的結果，決定具備發電潛力的目標流量。決定流量後，透過Flow3D模式模擬高流速區域的三維細部流場，同時於河道中放置阻礙物，用以模擬水力發電裝置放置於該發電潛域所受之合力。最後，將大小型阻礙物受力情形與河道原始流速、水深進行迴歸分析，提出定量關係式，用以推估阻礙物放置於河道中的受力特性。 本研究根據連續時間參數的超越機率分析結果，採用Q10與Q5作為永定溪代表流量。而小波模式的分析結果顯示此區域小波能量整體有逐年下降的趨勢，且以1年為主週期、3.5年為次週期變化。透過前後11年的小波能量對比，決定使用震盪幅度較小、流態改變不大的Q4.4作為第三種目標流量。本研究同時針對日流量與時流量的小波分析進行比較，結果顯示日流量能一定程度反應時流量的分析結果，可作為時流量的替代資料使用。Flow3D與定量分析的結果發現當小型阻礙物置入於河道時，流速為阻礙物受力的主導參數，相反的，大型阻礙物的受力大小雖亦為流速主導，然水深的影響不可忽略。有別於傳統水利方法，本研究全面性地考量水力發電裝置運作之機制，搭配頻譜分析與三維模擬，提出一套創新的選址方法。
並列摘要
Green energy development has become emergent because of the threat of global climate change and the rapid consumption of energy storage. Hydroelectric stands out from all renewable energy sources due to its higher conversion efficiency and lower cost. However, traditional site selection of small hydropower (SHP) only considers hydraulic head and flow rate. The momentum and the dynamic pressure caused by moving water and the continuous duration of the target flow rate were usually ignored, making the limitations on estimating the SHP capacity. The historical hourly flow rate data in Yongding River was collected from 1998 to 2019 in the present study. The target flow rate was determined by incorporating continuous duration into exceedance probability and using wavelet analysis to identify the flow regime of the Yongding basin. This study established a model to assess the suitable site of SHP and provided a regression equation that can compute the total force acting on SHP devices. A CFD model, Flow3D, was conducted to understand the complex flow fields and related momentum forces. Blocks of two different sizes were placed in the river to calculate the SHP device's situation in the potential site. The target flow rate was decided to be Q10 and Q5 according to exceedance probability with continuous duration. Besides, the results of wavelet analysis show that wavelet energy has decreased gradually and was oscillating by one year as a primary temporal change and 3.5 years as a secondary period. By comparing wavelet energy before and after 2009, the third target flow rate was determined to be Q4.4 because of its slight change in flow regime. The results of wavelet analysis indicated that daily data could offer similar results as those of hourly data analysis. The results of Flow3D simulation and quantitative analysis show that when small blocks are put in the river, flow velocity dominates the force acting on blocks. In contrast to small blocks, water depth significantly affects the total force. We suggested refining and revising conventional assessment procedures according to the present study basis on practical evaluation of the site selection and theoretical potential of in-river small hydropower.
參考文獻
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