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  1. AAAA battery
  2. AAA battery
  3. AA battery
  4. A battery
  5. Absorbent glass mat
  6. Alessandro Volta
  7. Alkaline battery
  8. Alkaline fuel cell
  9. Aluminium battery
  10. Ampere
  11. Atomic battery
  12. Backup battery
  13. Baghdad Battery
  14. Batteries
  15. Battery charger
  16. B battery
  17. Bernard S. Baker
  18. Beta-alumina solid electrolyte
  19. Betavoltaics
  20. Bio-nano generator
  21. Blue energy
  22. Bunsen cell
  23. Car battery
  24. C battery
  25. Clark cell
  26. Concentration cell
  27. Coulomb
  28. 2CR5
  29. Daniell cell
  30. Direct borohydride fuel cell
  31. Direct-ethanol fuel cell
  32. Direct methanol fuel cell
  33. Dry cell
  34. Dry pile
  35. Duracell
  36. Duracell Bunny
  37. Earth battery
  38. Electric charge
  39. Electric current
  40. Electricity
  41. Electrochemical cell
  42. Electrochemical potential
  43. Electro-galvanic fuel cell
  44. Electrolysis
  45. Electrolyte
  46. Electrolytic cell
  47. Electromagnetism
  48. Electromotive force
  49. Energizer Bunny
  50. Energy
  51. Energy density
  52. Energy storage
  53. Flashlight
  54. Float charging
  55. Flow Battery
  56. Formic acid fuel cell
  57. Fuel cell
  58. Fuel cell bus trial
  59. Galvanic cell
  60. Gel battery
  61. Grove cell
  62. Half cell
  63. History of the battery
  64. Hybrid vehicle
  65. Lead-acid battery
  66. Leclanché cell
  67. Lemon battery
  68. List of battery sizes
  69. List of battery types
  70. List of fuel cell vehicles
  71. Lithium battery
  72. Lithium ion batteries
  73. Lithium iron phosphate battery
  74. Lithium polymer cell
  75. LR44 battery
  76. Luigi Galvani
  77. Manganese dioxide
  78. Memory effect
  79. Mercury battery
  80. Metal hydride fuel cell
  81. Methane reformer
  82. Methanol reformer
  83. Michael Faraday
  84. Microbial fuel cell
  85. Molten carbonate fuel cell
  86. Molten salt battery
  87. Nickel-cadmium battery
  88. Nickel-iron battery
  89. Nickel metal hydride
  90. Nickel-zinc battery
  91. Open-circuit voltage
  92. Optoelectric nuclear battery
  93. Organic radical battery
  94. Oxyride battery
  95. Panasonic EV Energy Co
  96. Peukert's law
  97. Phosphoric acid fuel cell
  98. Photoelectrochemical cell
  99. Polymer-based battery
  100. Power density
  101. Power management
  102. Power outage
  103. PP3 battery
  104. Primary cell
  105. Prius
  106. Proton exchange membrane
  107. Proton exchange membrane fuel cell
  108. Protonic ceramic fuel cell
  109. Radioisotope piezoelectric generator
  110. Ragone chart
  111. RCR-V3
  112. Rechargeable alkaline battery
  113. Reverse charging
  114. Reversible fuel cell
  115. Searchlight
  116. Secondary cell
  117. Short circuit
  118. Silver-oxide battery
  119. Smart Battery Data
  120. Smart battery system
  121. Sodium-sulfur battery
  122. Solid oxide fuel cell
  123. Super iron battery
  124. Thermionic converter
  125. Trickle charging
  126. Vanadium redox battery
  127. Volt
  128. Voltage
  129. Voltaic pile
  130. Watch battery
  131. Water-activated battery
  132. Weston cell
  133. Wet cell
  134. Zinc-air battery
  135. Zinc-bromine flow battery
  136. Zinc-carbon battery

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Flow battery

From Wikipedia, the free encyclopedia

(Redirected from Flow Battery)

A Flow Battery is a form of battery in which electrolyte containing one or more dissolved electroactive species flows through a power cell / reactor in which chemical energy is converted to electricity. Additional electrolyte is stored externally, generally in tanks, and is usually pumped through the cell (or cells) of the reactor, although gravity feed systems are also known.[1]

Fuel cells are generally defined as electrochemical devices for converting chemical energy to electricity in which the reactants are flowed through a power cell/ reactor from an external source (tank, cylinder or surrounding environment).

Under these definitions it may be concluded that the flow battery is a special type of fuel cell. However, what is rarely explicitly stated is that the electrolyte in a fuel cell remains at all times within the reactor (in the form of an ion-exchange membrane, for example). What flows into the reactor are only the electroactive chemicals, which are non-conducting (e.g. hydrogen, methanol, oxygen, etc.) This is in stark contrast to a flow battery in which at least some of the electrolyte (generally the majority in weight and volume terms) flows through the reactor.

Flow batteries are also distinguished from fuel cells by the fact that the chemical reaction involved is often reversible, i.e. they are generally of the secondary battery type and so they can be recharged without replacing the electroactive material. In this sense fuel cells, as sources of electricity, and flow batteries, for storage of electricity, may be seen as complementary in achieving a hydrogen economy.

To add to the confusion the European Patent Organisation classes redox flow cells (H01M8/18C4) as a sub-class of regenerative fuel cells (H01M8/18).

Classes of flow batteries

Various classes of flow batteries exist including the redox (reduction-oxidation) flow battery, in which all electroactive components are dissolved in the electrolyte. If one or more electroactive component is deposited as a solid layer the system is known as a hybrid flow battery.[2] The main difference between these two types of flow battery is that the energy of the redox flow battery can be determined fully independently of the battery power, because the energy is related to the electrolyte volume (tank size) and the power to the reactor size. The hybrid flow battery, similarly to a conventional battery, is limited in energy to the amount of solid material that can be accommodated within the reactor. In practical terms this means that the discharge time of a redox flow battery at full power can be varied, as required, from several minutes to many days, whereas a hybrid flow battery may be typically varied from several minutes to a few hours.

Another type of flow battery is the redox fuel cell.[3] This has a conventional flow battery reactor, which only operates to produce electricity (i.e. it is not electrically recharged). Recharge occurs by reduction of the negative electrolyte using a fuel (e.g. hydrogen) and oxidation of the positive electrolyte using an oxidant (typically oxygen or air).

Examples of redox flow batteries are the vanadium redox flow battery, polysulfide bromide battery (Regenesys), and uranium redox flow battery.[4] Hybrid flow batteries include the zinc-bromine, cerium-zinc and all-lead flow batteries. Redox fuel cells are less common commercially although many systems have been proposed.[5][6][7][8]

Advantages and disadvantages

Redox flow batteries, and to a lesser extent hybrid flow batteries, have the advantages of flexible layout (due to separation of the power and energy components), long cycle life (because there are no solid-solid phase changes), quick response times (in common with nearly all batteries), no need for "equalisation" charging and no harmful emissions (in common with nearly all batteries). Some types also offer easy state-of-charge determination (through voltage dependence on charge), low maintenance and tolerance to overcharge/ overdischarge.

On the negative side, flow batteries are rather complicated in comparison with standard batteries as they may require pumps, sensors, control units and secondary containment vessels. The energy densities vary considerably but are, in general, rather low compared to portable batteries, such as the Li-ion.


Taking the above considerations together it should be apparent that flow batteries are normally considered for relatively large (1 kW - many MW) stationary applications. These are load levelling, where the battery is used to store cheap night-time electricity and provide electricity when it is more costly, as well as storing energy from renewable sources such as wind or solar for discharge during periods of peak demand; peak shaving, where spikes of demand are met by the battery; and UPS, where the battery is used if the main power fails to provide an uninterrupted supply.

Because flow batteries can be rapidly "recharged" by replacing the electrolyte, they have been proposed for electric vehicles, and the use of vanadium redox flow batteries for load levelling in wind farm applications is already showing promise.

A further potential application for redox flow batteries lies in the fact that all cells share the same electrolyte/s. Therefore, the electrolyte/s may be charged using a given number of cells and discharged with a different number. Because the voltage of the battery is proportional to the number of cells used the battery can therefore act as a very powerful dc-dc converter. In addition, if the number of cells is continuously changed (on the input and/ or output side) power conversion can also be ac-dc, ac-ac or dc-ac, with the frequency limited by that of the switching gear.[9]

See also

  • Hydrogen technologies
  • Redox electrode


  1.   T. Fujii, T. Hirose, and N. Kondou, in JP Patent 55096569 (1979), to Meidensha Electric Mfg. Co. Ltd.
  2.   M. Bartolozzi, "Development of redox flow batteries. A historical Bibliography," J. Power Sources, vol. 27, pp. 219-234, 1989.
  3.   L. H. Cutler, in US Patent 3607420 (1969), to E.I. du Pont de Nemours and Co.
  4.   Y. Shiokawa, H. Yamana, and H. Moriyama, "An application of actinide elements for a redox flow battery," J. Nucl. Sci. Tech., vol. 37, pp. 253-256, 2000.
  5.   W. Borchers, in US Patent 567959 (1894)
  6.   W. Nernst, in DE Patent 264026 (1912)
  7.   R. M. Keefer, in US Patent 3682704 (1970), to Electrocell Ltd.
  8.   J. T. Kummer and D.-G. Oei, "A chemically regenerative redox fuel cell," J. Appl. Electrochem., vol. 12, pp. 87-100, 1982
  9.   P. M. Spaziante, K. Kampanatsanyakorn, and A. Zocchi, in WO Patent 03043170 (2001), to Squirrel Holdings Ltd.

External links

  • research on the uranium redox flow battery




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