Extraction and optimization for modeling ofdesalination by capacitive deionization

Abstract: Water scarcity is set to become a big challenge in the 21st century and more efficient desalinationtechnologies will be needed in the future. In this project, one desalination method called capacitivedeionization (CDI) is explored and we used a model called the ELC model to simulate CDI withComsol. The goal of this project focuses on evaluating the performance of CDI and how changingdifferent operational parameters of the process affects other aspects of desalination. Some examplesare power consumption, desalination rate and water usage. With the gathered information, the process of CDI can be optimized in some way. Even though our project simulates a specific model ofCDI, the hope is to have come to general conclusions regarding CDI so that the results can be usedfor other models. If the correlations between parameters are known, it will be easier to calibrate anysetup of CDI. The gathered data is exported, stored, processed, and plotted using Matlab functionsintegrated with Comsol. The results consist of two sets, the first for constant voltage and the secondfor constant current. Both have results on how desalination rate and energy efficiency are related toparameters such as internal voltage intervals controlling how long the desalination cycle is running,external voltage, and inflow salt concentration in the water. The key conclusions drawn are as thefollowing for constant voltage. High external voltages are effective in increasing both desalinationrate and energy efficiency but will degrade the CDI electrodes. The internal voltage span should bepretty long with high max internal voltage and the minimum internal voltage the same as the external voltage. The energy efficiency increase with lower salt concentrations in the inflow water up toa point. The best setup for the desalination rate is at quite a high maximum internal voltage withvaried low minimum internal voltage. For constant current, low current is generally efficient, whilethe maximum external voltage depends on the current. Avoid a high current with a low externalvoltage. By relating all these parameters, we get more insights into what an energy-efficient and fastadsorbing CDI setup looks like.