DOI: 10.1016/j.watres.2018.07.066
Scopus记录号: 2-s2.0-85050989423
论文题名: Frequency analysis and resonant operation for efficient capacitive deionization
作者: Ramachandran A. ; Hawks S.A. ; Stadermann M. ; Santiago J.G.
刊名: Water Research
ISSN: 431354
出版年: 2018
卷: 144 起始页码: 581
结束页码: 591
语种: 英语
英文关键词: Capacitive deionization
; Dynamic system modeling
; Frequency analysis
; Performance optimization
; Resonant operation
; Water desalination
Scopus关键词: Desalination
; Effluents
; Energy efficiency
; Fourier analysis
; Frequency response
; Invariance
; Linear systems
; Time varying control systems
; Water filtration
; Capacitive deionization
; Dynamic system modeling
; Frequency Analysis
; Performance optimizations
; Resonant operation
; Water desalination
; Fourier series
; sodium chloride
; water
; degradation
; desalination
; effluent
; experimental study
; frequency analysis
; numerical model
; operations technology
; optimization
; performance assessment
; water treatment
; advection
; Article
; capacitive deionization
; chemical procedures
; concentration response
; cyclic potentiometry
; desalination
; electric potential
; electricity
; energy
; energy consumption
; energy recovery
; Fourier analysis
; frequency analysis
; impedance spectroscopy
; priority journal
英文摘要: Capacitive deionization (CDI) performance metrics can vary widely with operating methods. Conventional CDI operating methods such as constant current and constant voltage show advantages in either energy or salt removal performance, but not both. We here develop a theory around and experimentally demonstrate a new operation for CDI that uses sinusoidal forcing voltage (or sinusoidal current). We use a dynamic system modeling approach, and quantify the frequency response (amplitude and phase) of CDI effluent concentration. Using a wide range of operating conditions, we demonstrate that CDI can be modeled as a linear time invariant system. We validate this model with experiments, and show that a sinusoid voltage operation can simultaneously achieve high salt removal and strong energy performance, thus very likely making it superior to other conventional operating methods. Based on the underlying coupled phenomena of electrical charge (and ionic) transfer with bulk advection in CDI, we derive and validate experimentally the concept of using sinusoidal voltage forcing functions to achieve resonance-type operation for CDI. Despite the complexities of the system, we find a simple relation for the resonant time scale: the resonant time period (frequency) is proportional (inversely proportional) to the geometric mean of the flow residence time and the electrical (RC) charging time. Operation at resonance implies the optimal balance between absolute amount of salt removed (in moles) and dilution (depending on the feed volume processed), thus resulting in the maximum average concentration reduction for the desalinated water. We further develop our model to generalize the resonant time-scale operation, and provide responses for square and triangular voltage waveforms as two examples. To this end, we develop a general tool that uses Fourier analysis to construct CDI effluent dynamics for arbitrary input waveforms. Using this tool, we show that most of the salt removal (∼95%) for square and triangular voltage forcing waveforms is achieved by the fundamental Fourier (sinusoidal) mode. The frequency of higher Fourier modes precludes high flow efficiency for these modes, so these modes consume additional energy for minimal additional salt removed. This deficiency of higher frequency modes further highlights the advantage of DC-offset sinusoidal forcing for CDI operation. © 2018 Elsevier Ltd Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/112468
Appears in Collections: 气候减缓与适应
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作者单位: Department of Aeronautics & Astronautics, Stanford University, StanfordCA 94305, United States; Department of Mechanical Engineering, Stanford University, StanfordCA 94305, United States; Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
Recommended Citation:
Ramachandran A.,Hawks S.A.,Stadermann M.,et al. Frequency analysis and resonant operation for efficient capacitive deionization[J]. Water Research,2018-01-01,144