Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 539141
Title Energy consumption in capacitive deionization – Constant current versus constant voltage operation
Author(s) Dykstra, J.E.; Porada, S.; Wal, A. van der; Biesheuvel, P.M.
Source Water Research 143 (2018). - ISSN 0043-1354 - p. 367 - 375.
DOI https://doi.org/10.1016/j.watres.2018.06.034
Department(s) Sub-department of Environmental Technology
WIMEK
WU Plant SciencesDepartment of Plant Sciences
Physical Chemistry and Soft Matter
Publication type Refereed Article in a scientific journal
Publication year 2018
Keyword(s) Capacitive deionization - Constant current and constant voltage operation - Minimizing energy consumption - Optimizing salt adsorption
Abstract

In the field of Capacitive Deionization (CDI), it has become a common notion that constant current (CC) operation consumes significantly less energy than constant voltage operation (CV). Arguments in support of this claim are that in CC operation the endpoint voltage is reached only at the end of the charging step, and thus the average cell voltage during charging is lower than the endpoint voltage, and that in CC operation we can recover part of the invested energy during discharge. Though these arguments are correct, in the present work based on experiments and theory, we conclude that in operation of a well-defined CDI cycle, this does not lead, for the case we analyze, to the general conclusion that CC operation is more energy efficient. Instead, we find that without energy recovery there is no difference in energy consumption between CC and CV operation. Including 50% energy recovery, we find that indeed CC is more energy efficient, but also in CV much energy can be recovered. Important in the analysis is to precisely define the desalination objective function, such as that per unit total operational time –including both the charge and discharge steps– a certain desalination quantity and water recovery must be achieved. Another point is that also in CV operation energy recovery is possible by discharge at a non-zero cell voltage. To aid the analysis we present a new method of data representation where energy consumption is plotted against desalination. In addition, we propose that one must analyze the full range of combinations of cycle times, voltages and currents, and only compare the best cycles, to be able to conclude which operational mode is optimal for a given desalination objective. We discuss three methods to make this analysis in a rigorous way, two experimental and one combining experiments and theory. We use the last method and present results of this analysis.

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