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Effects of Electrochemical Reactions on Sustainable Power Generation from Salinity Gradients using Capacitive Reverse Electrodialysis

Oh, Yoontaek
http://orcid.org/0000-0002-7413-1033
http://rave.ohiolink.edu/etdc/view?acc_num=ucin161375277977973

Abstract Details

2020, PhD, University of Cincinnati, Engineering and Applied Science: Environmental Engineering.
Though fossil fuels have met the growing global energy demand, after three centuries of combusting fossil fuels the world is facing the environmental catastrophe: global warming and climate change. To reduce the risks of global warming and climate change, there has been an international effort to develop and improve low-carbon energy technologies, which is now driving the energy transition from fossil fuels to renewables. Among the renewable sources of energy, salinity gradient power is often overlooked. The objective of this dissertation is to both address current challenges in reverse electrodialysis (RED) which harnesses energy from salinity gradients and study on a novel capacitive reverse electrodialysis (CRED) process. When two solutions with different salinities are mixed through engineered systems, the salinity gradient can create electric power. Salinity gradient energy is estimated that theoretically 0.8 kW/m3 (equivalent to the amount of hydroelectric power from a dam higher than 280 meters) could be extracted at the point where fresh water streams into the sea. The larger the difference in concentration, the more energy becomes available. However, including natural seawater, highly saline solutions contain multivalent ions that deteriorate the RED performance significantly by increasing electrical resistance of ion exchange membranes. Some multivalent ions form precipitations in the system and these precipitations can be exacerbated at the electrode system where electrochemical reactions take place when operating voltage is high enough, such as in pilot-scale operations. These electrochemical reactions restrict the scaling up of the RED process. The CRED system is a relatively new technology in salinity gradient energy. This technology combines the conventional RED and capacitive mixing (CapMix), another new technology. The CRED process is believed to be operated even above 3–4 V without pH-changes. This indicates that this technology can control electrochemical reactions (faradaic reactions) at high operating voltages. In addition, the adopted capacitive electrodes enable the system to operate without redox chemicals that are potentially hazardous to the environment. Despite the benefits, there are very few studies about CRED that have been published. Since it is inevitable that faradaic reactions take place with RED consisting of a few hundred or more cell pairs, which are pilot-scale configurations, it is crucial to explore the maximum power density of CRED without faradaic reactions and to compare with RED. In this dissertation research, the maximum power density of the CRED system without faradaic reactions is evaluated. Results of this study show the maximum power density of CRED is nearly equal to RED. Importantly, faradaic reactions are perfectly controlled. It is revealed that the maximum power density is obtained at the lowest cutoff voltage that does not accompany the pH-changes. There is both a strong positive correlation between the extent of the pH-changes and the amount of charge transferred during discharge, and a critical point of charge transport that triggers the pH-changes. This study highlights the promise of controlled faradaic reactions in the CRED system to enhance the applications of CRED technology in power generation using salinity gradients in actual facility-scale operations.
Soryong Chae, Ph.D. (Committee Chair)
Dionysios Dionysiou, Ph.D. (Committee Member)
Junhang Dong, Ph.D. (Committee Member)
Jin-Soo Park, Ph.D. (Committee Member)
Vesselin Shanov, Ph.D. (Committee Member)
148 p.
Environmental Engineering
Capacitive Reverse Electrodialysis; Reverse Electrodialysis; Electrochemical Reactions; Capacitive Electrode; Salinity Gradient Power; Renewable Energy

Recommended Citations

Citations

  • Oh, Y. (2020). Effects of Electrochemical Reactions on Sustainable Power Generation from Salinity Gradients using Capacitive Reverse Electrodialysis [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin161375277977973

    APA Style (7th edition)

  • Oh, Yoontaek. Effects of Electrochemical Reactions on Sustainable Power Generation from Salinity Gradients using Capacitive Reverse Electrodialysis. 2020. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin161375277977973.

    MLA Style (8th edition)

  • Oh, Yoontaek. "Effects of Electrochemical Reactions on Sustainable Power Generation from Salinity Gradients using Capacitive Reverse Electrodialysis." Doctoral dissertation, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin161375277977973

    Chicago Manual of Style (17th edition)

ucin161375277977973
84
© 2020, some rights reserved.Creative Commons License Effects of Electrochemical Reactions on Sustainable Power Generation from Salinity Gradients using Capacitive Reverse Electrodialysis by Yoontaek Oh is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.