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Comparative study on the performance of capacitive mixing under different operational modes
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.ORCID iD: 0000-0002-1781-4399
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering. Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China..ORCID iD: 0000-0001-6801-9208
Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China..
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.ORCID iD: 0000-0003-4232-7944
2022 (English)In: Energy Reports, E-ISSN 2352-4847, Vol. 8, p. 7325-7335Article in journal (Refereed) Published
Abstract [en]

Capacitive mixing (CapMix) is a renewable method of extracting energy from the salinity difference between seawater and freshwater. In this study, we systematically investigate the system behavior and performance of the CapMix system under four operational modes namely, capacitive energy extraction based on double layer expansion (CDLE), capacitive energy extraction based on the Donnan potential (CDP), and CDP with additional charging of constant voltage (CDP-CV) and constant current (CDPCC). The results indicate that the application of additional charging in the CDP technique can break the limits of the Donnan potential and significantly improve the system's performance. Accordingly, in terms of energy production and average power density, CDP-CC and CDP-CV are the two superior operational modes, followed by CDP and CDLE. In addition, our results reveal that CDP-CC is determined by the accumulated charge and applied current. CDLE is dependent on the applied voltage, while CDPCV is not sensitive to the applied voltage. Increasing the external load can considerably increase the energy production of both CDLE and CDP. In summary, the findings in this study provide practical information for the optimization and application of CapMix technologies.

Place, publisher, year, edition, pages
Elsevier BV , 2022. Vol. 8, p. 7325-7335
Keywords [en]
Salinity gradient energy, Capacitive energy extraction, Double layer expansion, CDLE, CDP
National Category
Other Engineering and Technologies Renewable Bioenergy Research Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-316716DOI: 10.1016/j.egyr.2022.05.245ISI: 000836288000008Scopus ID: 2-s2.0-85131397909OAI: oai:DiVA.org:kth-316716DiVA, id: diva2:1691530
Note

QC 20220830

Available from: 2022-08-30 Created: 2022-08-30 Last updated: 2025-02-10Bibliographically approved
In thesis
1. Capacitive Mixing for Extracting Concentration Gradient Energy
Open this publication in new window or tab >>Capacitive Mixing for Extracting Concentration Gradient Energy
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Capacitive mixing (CapMix) is a renewable method of extracting energy from the salinity gradient energy (SGE) between seawater and freshwater. The classical CapMix systems using solid electrodes generate electricity by periodically circulating seawater and freshwater into the CapMix system. The major limitation of classical CapMix is intermittent energy production. Therefore, the development of a new CapMix system to solve this limitation is highly desired. This thesis aims to develope an innovative CapMix system for continuous energy production. All the work is based on four papers and can be divided into the following parts.

In Chapter 1, a brief introduction to the SGE and CapMix is presented. 

In Chapter 2, a comparative study on the four classical CapMix systems, namely, capacitive energy extraction based on double layer expansion (CDLE), capacitive energy extraction based on the Donnan potential (CDP), and CDP with additional charging of constant voltage (CDP-CV) and constant current (CDP-CC)., is discussed. The influences of experimental parameters, e.g., applied voltage, applied current, accumulated charge, and the external load on the system performance, were systematically investigated and presented. A comprehensive comparison between these four classical CapMix systems is also given in this chapter.

Chapter 3 and Chapter 4 describe two novel CapMix systems based on flow electrode (F-CapMix) configuration which were developed to realize continuous energy production. The first one is a two-cell F-CapMix system, in which the flow electrode slurry was circulated between the two cells. The second is a one-cell F-CapMix system with cross chambers, in which there are two chambers between one pair of plates in parallel; the flow electrode slurry was circulated within the two graphite plates of the cell. The feasibility of these two F-CapMix systems was examined. The effect of the experimental parameters, e.g., activated carbon loading, carbon black amount, external resistance, feedwater flow rate, and flow electrode flow rate, on the system performance were systematically investigated and presented. 

In Chapter 5, a thorough study of the theoretical models related to the thermodynamic properties of the electric double layer at equilibrium, e.g., the Gouy-Chapman-Stern (GCS), Modified Poisson-Boltzmann-Stern (MPBS), modified Donnan (mD) and improved modified Donnan (i-mD) models is presented. The rationality and the physical interpretation of the parameters used in these models were detailed investigated and presented.

Abstract [sv]

Kapacitiv blandning (CapMix) är en förnybar metod för att utvinna energi från salthaltsgradientenergin (SGE) mellan havsvatten och sötvatten. De klassiska CapMix-systemen som använder solida elektroder genererar elektricitet genom att periodiskt strömma havsvatten och sötvatten in i CapMix-systemet. Den största begränsningen för klassisk CapMix är den intermittenta energiproduktionen. Därför är utvecklingen av ett nytt CapMix-system för att lösa denna begränsning mycket önskvärt. Detta examensarbete syftar till att utveckla ett innovativt CapMix-system för kontinuerlig energiproduktion. Allt arbete bygger på fyra papper och kan delas upp i följande delar. 

I kapitel 1 presenteras en kort introduktion till SGE och CapMix. 

I kapitel 2, en jämförande studie av de fyra klassiska CapMix-systemen, nämligen kapacitiv energiextraktion baserad på dubbelskiktsexpansion (CDLE), kapacitiv energiextraktion baserad på Donnan-potentialen (CDP) och CDP med ytterligare laddning av konstant spänning (CDP) -CV) och konstant ström (CDP-CC). Inverkan av experimentella parametrar, t.ex. pålagd spänning, pålagd ström, ackumulerad laddning samt extern belastning på systemets prestanda undersöktes och presenterades systematiskt. Den omfattande jämförelsen mellan dessa fyra klassiska CapMix-system ges också i detta kapitel. 

I kapitel 3 och kapitel 4 utvecklades två nya CapMix-system baserade på flödeselektrodkonfiguration (F-CapMix) för att realisera kontinuerlig energiproduktion. Den första är ett F-CapMix-system med två celler, i vilket flödeselektrodsuspensionen cirkulerade mellan de två cellerna. Den andra är en encell med tvärkammare F-CapMix-system, i vilket det finns två kammare mellan ett par plattor parallellt, flödeselektrodsuspensionen cirkulerades inom cellens två grafitplattor. Genomförbarheten av dessa två F-CapMix-system undersöktes. Effekten av de experimentella parametrarna, t.ex. aktivt kol, mängd kimrök, externt motstånd, matarvattenflöde och flödeselektrodflödeshastighet på systemets prestanda undersöktes och presenterades systematiskt.

I kapitel 5, en grundlig studie av de teoretiska modellerna som relaterade till de termodynamiska egenskaperna hos det elektriska dubbelskiktet vid jämvikt, t.ex. Gouy-Chapman-Stern (GCS), Modified Poisson-Boltzmann-Stern (MPBS), modifierad Donnan (mD) och förbättrade modifierade Donnan (i-mD) modeller gavs. Rationaliteten och den fysiska tolkningen av parametrarna som används i dessa modeller undersöktes och presenterades i detalj.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 74
Series
TRITA-CBH-FOU ; 2022:50
Keywords
capacitive mixing, salinity gradient energy, salt difference energy, electric double layer, flow electrode CapMix, kapacitiv blandning, salthaltsgradientenergi, saltskillnadsenergi, elektriskt dubbelskikt, flödeselektrod CapMix.
National Category
Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-319620 (URN)978-91-8040-365-8 (ISBN)
Public defence
2022-11-03, F3, Kollegiesalen, Brinellvägen 8, via Zoom: https://kth-se.zoom.us/meeting/register/u5Apdu6gqj4qH9JEeQ2pGyUr3U_E1A8jLWY9, Stockholm, 10:00 (English)
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Online defense

Available from: 2022-10-04 Created: 2022-10-04 Last updated: 2022-10-24Bibliographically approved

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Zou, ZhiLiu, LongchengBian, Xiaolei

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