溫度與奈米孔道的尺寸對鹽濃差發電的影響

Abstract

海水鹽差能是種具有前景、挑戰性而可立即取得的再生能源，在多種取得這種乾淨能源的方法中，運用奈米通道的逆電透析法尤其具有潛力。由於離子傳輸受到溫度以及奈米通道尺寸的影響，進而影響到海水鹽差能的發電及其效率，所以在這篇論文中，我們對溫度與奈米通道尺寸對海水鹽差能的影響做了理論分析，第一章節中主要探討溫度效應，第二章節則討論奈米通道的尺寸效應。在第一章節中，結果顯示最大可得的鹽差能會隨增溫度的增加而增加，然而發電效率幾乎不受溫度影響。第二章節中，一般而言無論是具有正電荷密度或負電荷密度的奈米通道，奈米孔道的管徑較窄、管長較短以及兩端的鹽濃差梯度較大可以得到較大的海水鹽差能，然而一個管徑較窄且管長較長的奈米孔道，兩端施加較小的鹽濃差梯度則可得到較高的發電效率，再比較具有正電荷密度以及負電荷密度的奈米通道的表現，具有正電荷密度的奈米通道在相同的條件下，可提供較大的發電功率以及發電效率，主要因為正電荷密度的奈米孔道所吸引的反離子更容易擴散通過孔道。最後我們提供了最大可得的海水鹽濃差能以及此時效率的迴歸式作為後續實驗設計的參考，其變數包括奈米孔道的管徑、管長以及兩端的鹽濃差梯度。

Salinity gradient power is a promising, challenging, and readily available renewable energy. Among various methods for harvesting this clean energy, the reverse elecrtodialysis based on charged nanochannels/nanopores (NRED) is of great potential. Since ionic transport depends highly on the temperature, so is the efficiency of the associated power generated. In this thesis, we conduct a theoretical analysis on the influences of temperature and nanopore size on NRED, focusing on temperature in Chapter 1 and nanopore size in Chapter 2. In Chapter 1, results gathered reveal that the maximum power increases with increasing temperature, but the conversion efficiency dependents weakly on temperature. In Chapter 2, a larger power density can be obtained by choosing a narrower and/or shorter nanopore, and a larger salt gradient for both a negatively and a positively charged nanopore generally. In contrast, a narrower and/or longer nanopore, and a smaller salt gradient should be adopted for a higher efficiency. The performance of a positively charged nanopore is better than that of a negatively charged one because it is easier for counterions to diffuse through in the former, thereby enhancing both power and efficiency. Regression relationships for the dependence of the maximum power density and the corresponding efficiency on the radius and length of a nanopore, and the salt gradient across it are recovered for design purposes.