基於奈米孔道之發電:側流對濃差發電之影響與溫度梯度對壓差發電之影響

Abstract

隨著人口增加，人類對於能源的消耗與需求日益成長，加上近年來環保、永續意識抬頭，綠色能源無疑已成為我們這個世代最重要的課題之一。其中，奈米流體裝置用於轉換綠色能源深具潛力。當流體侷限於帶電奈米孔道中流動時，將具有離子選擇性等特殊的離子傳輸現象，這些現象可以被利用來將濃度差、壓力差等天然能量梯度轉換成電能的形式，達到永續綠能的目的。 第一章節中，我們使用側流來提升多孔薄膜濃鹽差發電的效能。奈米孔道薄膜應用於濃鹽差發電的一大挑戰是嚴重的濃度極化，當孔密度上升時，伴隨而來的濃度極化會大幅降低薄膜兩側的有效濃差，使得電能下降。我們發現，需要透過正確的方式加入側流，才可以有效的消除濃度極化並且提升電能。此外，我們也探討了側流讓電能提升的機制，並比較了不同情況下加入側流的效益。以上的研究成果已發表於國際期刊Journal of Membrane Science. 第二章節中，我們針對奈米孔道壓差發電系統，探討了將其加入溫度梯度後的離子輸送現象。和文獻中相關研究最大的不同在於，我們使用的模型同時考慮了薄膜的熱傳導和孔道表面的解離反應。我們發現，由於溫差造成的孔道表面不均勻帶電，將會影響孔道中離子的輸送現象。此外，對系統施以和壓力差梯度相反的溫度梯度，將有助於提升壓差發電的效能。

Due to the growing population on earth, the demand and consumption of energy have increased rapidly. Along with the pursuit of sustainable ecosystem, green energy has become one of the most important topic in this era. Nanofluidic device has a potential to serve as a platform for clean and sustainable energy conversion. When the electrolyte solution is confined to a charged nanopore, some special ion transport phenomena can be found, such as ion selectivity. These phenomena can be used to transform natural gradient (e.g., salinity gradient, hydraulic pressure gradient) into electricity. In chapter 1, we apply a cross flow to improve the osmotic energy conversion performance of a multipore membrane. One of the critical challenges for using such a system in practice is ionic centration polarization (ICP). When the pore density is high, ICP becomes severe and undermines the effective concentration difference across the membrane surface. This causes the energy conversion performance to degrade. We find that if we apply the cross flow in a right way, ICP will be alleviated and the electric power will increase. The mechanism behind this is investigated. We also compare the effectiveness of applying cross flow under various conditions. The above results were published in Journal of Membrane Science. In chapter 2, we investigate the ion transport behavior of a nanopore subject to simultaneously applied pressure and temperature gradient. The feature of our model is that we consider both the thermal conductivity of the membrane and surface reaction of the nanopore. We find that the nanopore will be unevenly charged due to the temperature distribution, and this will affect the ion transport. Additionally, we find that applying the pressure and temperature gradient in an opposite direction will enhance the performance of the electrokinetic energy conversion system.