000213651 001__ 213651
000213651 005__ 20181205220143.0
000213651 0247_ $$2doi$$a10.5075/epfl-thesis-6813
000213651 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis6813-9
000213651 02471 $$2nebis$$a10567796
000213651 037__ $$aTHESIS
000213651 041__ $$aeng
000213651 088__ $$a6813
000213651 245__ $$aRedox flow battery and indirect water electrolysis
000213651 269__ $$a2015
000213651 260__ $$aLausanne$$bEPFL$$c2015
000213651 300__ $$a271
000213651 336__ $$aTheses
000213651 502__ $$aProf. Lothar Helm (président) ; Prof. Hubert Girault (directeur de thèse) ; Prof. Christos Comninellis, Dr Leonard Berlouis, Dr Richard G. Wills (rapporteurs)
000213651 520__ $$aThe progressive integration of renewable energy sources such as wind turbines and photovoltaic pannels in the current electrical network, and the rise of the electrical mobility, provoke a change of paradigm in the sector of energy management. The increasing variability of the electricity production and consumption profiles, together with the requirement for a reliable supply of energy, necessitates the implementation of energy storage means of different scales and for a wide range of applications. Redox flow batteries (RFBs) are well adapted for buffering the fluctuations of solar or wind energy production. They present a fast response time, can withstand a large number of charge-discharge cycles and their ouput power is independant of their energy capacity. The main limitation of RFBs resides in their low energy density. The objective of the present work was to test a mean to overcome this low energy density. A new concept was developed, which rests on the addition of a second pathway to discharge the RFB. This pathway allows to generate hydrogen and oxygen, without affecting the functioning of the RFB. This concept was called dual-circuit RFB and was patented. RFBs are based on two liquids electrolytes, each stored in a reservoir, and flowing through an electrochemical cell for their electrochemical conversion. Each electrolyte contains one redox couple and Ce(IV)/Ce(III) and V(III)/V(II) were selected as positive and negative redox couples in the RFB developed here. Charge-discharge curves of a V–Ce RFB were measured for characterisation purposes and for the preparation of the charged electrolytes. The latter ones can be discharged electrochemically in the RFB to generate electricity (electrochemical discharge mode), or they can be directed in a secondary circuit where they are discharged for the production of hydrogen or oxygen (chemical discharge mode). The chemical discharge of the negative electrolyte consists of the reaction of V(II) with protons to produce hydrogen and V(III). Mo2C was selected as heterogenous catalyst for the characterisation of the reaction. A conversion close to 100% suggested no loss of current. A kinetic analysis provided some insights into the catalytic mechanism of this reaction. The chemical discharge of the positive electrolyte aimed at the conversion of Ce(IV) to Ce(III) by the oxidation of water to oxygen and also necessitates a catalyst. Iridium dioxide (IrO2) and ruthenium dioxide (RuO2) were evaluated in terms of conversion and kinetics. The composition of the positive electrolyte was shown to be of importance for this reaction. To show the feasibility of this concept, a larger-scale demonstrator system was designed based on a 10 kW (40kWh) commercially available vanadium RFB. A characterisation of this RFB was first performed. The design a suitable Mo2C catalyst and its corresponding catalytic bed is also discussed. As a conclusion, the concept developed and experimentally tested in the present work leads to a RFB system which is characterised by two discharge modes, increasing its energy storage capacity and energy density. The dual-circuit RFB also represents a crossing between electrical grid and hydrogen mobility as the hydrogen produced by surplus electricity could be delivered to fuel cell cars. The application of this system in a local distribution electrical network, close to a wind or solar source seems a promising approach.
000213651 6531_ $$aDual-circuit redox flow battery
000213651 6531_ $$awater electrolysis
000213651 6531_ $$ahydrogen
000213651 6531_ $$arenewable energy storage
000213651 6531_ $$amolybdenum carbide
000213651 700__ $$0245346$$aAmstutz, Véronique$$g181373
000213651 720_2 $$0242739$$aGirault, Hubert$$edir.$$g105258
000213651 8564_ $$s35603293$$uhttps://infoscience.epfl.ch/record/213651/files/EPFL_TH6813.pdf$$yn/a$$zn/a
000213651 909C0 $$0252090$$pLEPA$$xU10100
000213651 909CO $$ooai:infoscience.tind.io:213651$$pDOI$$pSB$$pthesis$$pthesis-bn2018$$qDOI2
000213651 917Z8 $$x108898
000213651 917Z8 $$x108898
000213651 918__ $$aSB$$cISIC$$dEDCH
000213651 919__ $$aLEPA
000213651 920__ $$a2015-11-20$$b2015
000213651 970__ $$a6813/THESES
000213651 973__ $$aEPFL$$sPUBLISHED
000213651 980__ $$aTHESIS