I suppose you can equate a flow battery to a fuel cell system with similar operation but without the need for a catalyst.
Below I've linked some basics on how a Vanadium redox battery works which is a great concept but is plagued with inherent issues which limits it's
capabilities.
The beauty of it is that it has a near perfect charge efficiency,
it can operate at extremely deep cycles - overdraining it won't damage it,
it can be charged independantly while it drives a load and can be used used as a voltage coverter by tapping off the relevant electrodes and once it
is set up,
it has an indefinite lifespan and very little maintenance is needed.
The electrolyte can be charged and discharged over and over until the cows come home - so to speak.
The issues that are faced are primarily due to the electrolyte itself. From what I've read the current density is fairly low due to the concentration
limits of solubles in the electrolyte before stuff starts precipitating out and whatnot.
I would like to do a few trials on electrolyte combinations by building a single cell comprising of 2 chambers seperated by a PEM with an inert
electrode in each one. I would then add electrolyte samples to the chambers and apply a volt or 2 to the electrodes for a set time, the idea being
that applied voltage charges the electrolytes forcing half reactions in their respective directions.
After removing the charging voltage I would then connect the cell to a fixed load and monitor the voltage curve as it discharges.
I am needing help with electrolyte selection. First prize would be to use the same electrolyte in both half cells which would mean that it's oxidation
state would need to be middlepegged so that it can charge both ways. Second prize, 2 dissimilar electrolytes with the ability to reach a concentration
that optimises potential energy (watts/kg).
I am needing help with selecting electrolytes. As far as I can see the electrolyte and half reactions would need to meet the following requirement:
Precursers and products of the reactions would have to remain in solution at reasonable concentrations, no gases or precipitates.
I was wondering if it was possible to have 2 oxidation or reduction components in the same electrolyte that would hopefully increase it's
effectiveness?
I was also wondering if it was possible to have a reduction and oxidation component in the same electrolyte that would not interfere with each other?
(doubt it)
Could an answer lie in the organic chemistry side of things? I'm aware of the poor conductivity issues regarding organic compounds and the need for
catalysts in most cases - just a shot in the dark.
Could there be a resource on the web where I could select prospective chemistries to try out in the electrolytes?
I remember seeing a patent once for a flow battery that used an acid and a base as the two electrolytes.
NaOH and HCL where the two electrolytes as i recall. with the standard sort of membrane/inert electrode setup.
Im not sure if or how well it worked but id love to find out bquirky - 2-4-2009 at 07:58
Ive allso oftern wonderd about having a slurry of reactive solids either side of a membrane acting as kind of a flow battery497 - 12-11-2011 at 15:17
I'm surprised flow battery technology hasn't gained more attention on this forum. It looks like there is a lot of potential for building these things
from scratch. If low cost battery technology could be made available to the masses it could give decentralized clean energy a huge boost. It is hard
stress enough how critical cheap energy storage is to the viability of small scale wind/solar.
Rather than spend all day bickering in the global warming thread, how about we actually work toward something that could really make a difference!
There are no more appropriate forums than this to make real change happen in DIY battery technology. It's a chemistry forum not a political policy
forum!!
There are many different options for flow battery chemistry besides vanadium. Many use extremely cheap materials such as Zn, Al, S, Br, NaOH etc.
I have seen the power of this forum and its members to make real innovations (eg. hydrazine, azoclathrates, PbO2 anodes, etc) so why not direct a
collaborative effort toward something that is so undeniably important, yet unexplored by anyone but corporations?
After further research, the polysulfide/bromide pair looks nice and well documented. It looks like a good option for a DIY true redox flow cell.
Cation exchange membranes are often used, but do not have long lifetimes and are expensive or hard to find. According to this very detailed and
informative patent a properly sized porous membrane can be used without much efficiency loss and with a great improvement in life expectancy and cost.
I highly recommend reading this patent, it is one of the best pieces of literature on redox flow cells I've come across: http://www.google.com/patents?id=d2bLAQAAEBAJ&printsec=a...
Hybrid redox flow cells are much more like traditional batteries because phase changes occur, for example, a metal plating on to, and dissolving from
the electrode. That means the cell power output is coupled to the cell energy storage capicity, unlike a true redox flow cell. Hybrid systems may have
their place. They can certainly be simpler. The zinc/bromide pair is one of the better known hybrid flow cells. The zinc/polysulfide pair is
interesting but there is much less info available, can't even find a charge-discharge efficiency. Hybrid flow cells can operate without a membrane,
but at lower efficiencies. If a membrane is used, a simple porous one works.
In the following paper they were able to get over 75% efficiency using polysulfide/bromide with nickel foam and carbon felt electrodes. The efficiency
would be much better but sulfur precipitated in the pores of their nafion membrane and caused high resistive losses (a common problem apparently.) http://pemfckt.dicp.ac.cn/paper/2005_02.pdf
There is so much potential for improvement from simple trial and error experimentation with this technology. It seriously took a DOE research lab to
figure out that adding some HCl to the standard vanadium sulfate solution could increase the capacity 70%???
To answer the OP's question, yes the catholyte and anolyte can be identical before charging if vanadium is used.
[Edited on 13-11-2011 by 497]IrC - 23-11-2011 at 01:15
I like to use Free Patents because they list and link (a real time saver) a wealth of related patents for further study in PDF format. Link:
20100136455 Common Module Stack Component Design June, 2010 Winter
20100094468 Level Sensor for Conductive Liquids April, 2010 Sahu
20100092843 VENTURI PUMPING SYSTEM IN A HYDROGEN GAS CIRCULATION OF A FLOW BATTERY April, 2010 Conway
20100092813 Thermal Control of a Flow Cell Battery April, 2010 Sahu
20100092807 Magnetic Current Collector April, 2010 Sahu
20100092757 Methods for Bonding Porous Flexible Membranes Using Solvent April, 2010 Nair
20100003586 Redox flow cell January, 2010 Sahu
7227275 Method for retrofitting wind turbine farms June, 2007 Hennessy et al.
20070111089 ELECTROCHEMICAL CELL FOR HYBRID ELECTRIC VEHICLE APPLICATIONS May, 2007 Swan
7220515 Pressure fluctuation prevention tank structure, electrolyte circulation type secondary battery, and redox flow type secondary battery May,
2007 Ito et al.
20070080666 Methods and apparatus for coupling an energy storage system to a variable energy supply system April, 2007 Ritter et al.
7199550 Method of operating a secondary battery system having first and second tanks for reserving electrolytes April, 2007 Tsutsui et al.
20070072067 Vanadium redox battery cell stack March, 2007 Symons et al.
7078123 High energy density vanadium electrolyte solutions, methods of preparation thereof and all-vanadium redox cells and batteries containing high
energy vanadium electrolyte solutions July, 2006 Kazacos et al. 429/105
7061205 Method for operating redox flow battery system June, 2006 Shigematsu et al.
6986966 Battery with bifunctional electrolyte January, 2006 Clarke et al.
20050260473 Electrical power source designs and components November, 2005 Wang
20050181273 Method for designing redox flow battery system August, 2005 Deguchi et al.
20050164075 Method for operating redox flow battery and redox flow battery cell stack July, 2005 Kumamoto et al.
20050158615 Redox flow battery July, 2005 Samuel et al.
20050156432 Power generation system incorporating a vanadium redox battery and a direct current wind turbine generator July, 2005 Hennessy
20050156431 Vanadium redox battery energy storage and power generation system incorporating and optimizing diesel engine generators July,
2005 Hennessy
6905797 Porous mat electrodes for electrochemical reactor having electrolyte solution distribution channels June, 2005 Broman et al.
20050074653 Redox cell with non-selective permionic separator April, 2005 Broman et al.
20040241544 Cell stack for flow cell December, 2004 Nakaishi et al.
20040202915 Cell frame for redox-flow cell and redox-flow cell October, 2004 Nakaishi et al.
20040170893 Cell frame for redox flow cell and redox flow cell September, 2004 Nakaishi et al.
6764789 Redox flow battery July, 2004 Sekiguchi et al.
6761945 Electrolyte tank and manufacturing method thereof July, 2004 Adachi et al.
6759158 System for proclusion of electrical shorting July, 2004 Tomazic
6692862 Redox flow battery and method of operating it February, 2004 Zocchi
20030091886 Polyelectrolyte, polyelectrolyte film, and fuel cell May, 2003 Tanioka et al.
6562514 Stabilized vanadium electrolyte solutions for all-vanadium redox cells and batteries May, 2003 Kazacos et al.
6555267 Membrane-separated, bipolar multicell electrochemical reactor April, 2003 Broman et al.
6524452 Electrochemical cell February, 2003 Clark et al.
20030008203 Leak sensor for flowing electrolyte batteries January, 2003 Winter
6509119 Carbon electrode material for a vanadium-based redox-flow battery January, 2003 Kobayashi et al.
6475661 Redox flow battery system and cell stack November, 2002 Pellegri et al.
6461772 Battery diaphragm October, 2002 Miyake et al.
20020127474 Proton-selective conducting membranes September, 2002 Fleischer et al.
6387964 Water based grafting May, 2002 D'Agostino et al.
6225368 Water based grafting May, 2001 D'Agostino et al.
6086643 Method for the fabrication of electrochemical cells July, 2000 Clark et al.
6040075 Electrolytic and fuel cell arrangements March, 2000 Adcock et al.
6005183 Device containing solar cell panel and storage battery December, 1999 Akai et al.
5919330 Method for bonding a porous medium to a substrate July, 1999 Pall et al.
5854327 Mineral-filled roofing membrane compositions and uses therefor December, 1998 Davis et al.
5851694 Redox flow type battery December, 1998 Miyabayashi et al.
5759711 Liquid-circulating battery June, 1998 Miyabayashi et al.
5665212 Flexible, conducting plastic electrode and process for its preparation September, 1997 Zhong et al.
5656390 Redox battery August, 1997 Kageyama et al.
5648184 Electrode material for flow-through type electrolytic cell, wherein the electrode comprises carbonaceous material having at least one
groove July, 1997 Inoue et al.
5366824 Flow battery November, 1994 Nozaki et al.
5258241 Rebalance cell for a Cr/Fe redox storage system November, 1993 Ledjeff et al.
5188911 Tapered manifold for batteries requiring forced electrolyte flow February, 1993 Downing et al.
5162168 Automatic voltage control system and method for forced electrolyte flow batteries November, 1992 Downing et al.
5126054 Venting means June, 1992 Matkovich
5061578 Electrolyte circulation type secondary battery operating method October, 1991 Kozuma et al.
5026479 Fluid separation device June, 1991 Bikson et al.
4956244 Apparatus and method for regenerating electrolyte of a redox flow battery September, 1990 Shimizu et al.
4948681 Terminal electrode August, 1990 Zagrodnik et al.
4945019 Friction welded battery component July, 1990 Bowen et al.
4929325 Removable protective electrode in a bipolar battery May, 1990 Bowen et al.
4894294 Electrolytic solution supply type battery January, 1990 Ashizawa et al.
4882241 Redox battery November, 1989 Heinzel
4874483 Process for the preparation of redox battery electrolyte and recovery of lead chloride October, 1989 Wakabayashi et al.
4849311 Immobilized electrolyte membrane July, 1989 Itoh et al.
4828666 Electrode for flow-through type electrolytic cell May, 1989 Iizuka et al.
4814241 Electrolytes for redox flow batteries March, 1989 Nagashima et al.
4786567 All-vanadium redox battery November, 1988 Skyllas-Kazacos et al.
4784924 Metal-halogen energy storage device and system November, 1988 Savinell et al. 429/109
4732827 Process for producing electrolyte for redox cell March, 1988 Kaneko et al.
4543302 Negative electrode catalyst for the iron chromium REDOX energy storage system September, 1985 Gahn et al.
4496637 Electrode for flowcell January, 1985 Shimada et al.
4485154 Electrically rechargeable anionically active reduction-oxidation electrical storage-supply system November, 1984 Remick et al.
4468441 Separator membranes for redox-type electrochemical cells August, 1984 D'Agostino et al.
4454649 Chromium electrodes for REDOX cells June, 1984 Jalan et al.
4414090 Separator membranes for redox-type electrochemical cells November, 1983 D'Agostino et al.
4312735 Shunt current elimination January, 1982 Grimes et al.
4309372 Method of making formulated plastic separators for soluble electrode cells January, 1982 Sheibley
4159366 Electrochemical cell for rebalancing redox flow system June, 1979 Thaller
4133941 Formulated plastic separators for soluble electrode cells January, 1979 Sheibley
3996064 Electrically rechargeable REDOX flow cell December, 1976 Thaller
3540934 MULTIPLE CELL REDOX BATTERY November, 1970 Boeke
A few more:
5496659 Electrochemical apparatus for energy storage and/or power delivery comprising multi-compartment cells March, 1996 Zito 429/105
4786567 All-vanadium redox battery November, 1988 Skyllas-Kazacos et al. 429/19
4784924 Metal-halogen energy storage device and system November, 1988 Savinell 429/15
5318865 Redox battery Kaneko et al.
4370392 Chrome-halogen energy storage device and system January, 1983 Savinell et al.
4362791 Redox battery December, 1982 Kaneko et al.
3996064 Electrically rechargeable REDOX flow cell December, 1976 Thaller
3279949 Fuel cell half-cell containing vanadium redox couple October, 1966 Schaefer et al.
2986592 Alkaline primary cells having anodes of niobium, vanadium, or molybdenum May, 1961 McCallum et al.
[Edited on 11-23-2011 by IrC]497 - 11-4-2012 at 15:59
I'm not sure how this works considering ZnO is practically insoluble in water and I would expect it to be less so in an ionic liquid unless we bring
colloidal suspensions into this, the aim being to take it to the anode to reduce it when charging and doing it efficiently.
Another way to charge would be to do it indirectly. The concept I'm going for is to extract the ZnO from the electrolyte and reduce it using
solar/wind energy back to Zinc after which this Zinc is simply added back to the anode.
A bench-top system up to an 1- kW stack and 1-kWh tanks will be demonstrated at the end of FY12.
Interesting if you have nafion membrane...and other resistant items...and the electrical components. How many years would it take for a practical DIY
version to pay off? Very heavy units are being increasingly sold worldwide.
