Abstract: An ancillary Ce+3/Ce+4 redox couple is added to the positive electrolyte solution containing the V+4/V+5 redox couple of an RFB energy storage system in a mole content sufficient to support charge current in case of localized depletion of oxidable V+4V ions in the anode double layer on a wetted carbon electrode surface at a polarization voltage approaching 1.5 V, thus restraining any further increase that would lead to massive OH? discharge on the carbon electrode. Such a “buffering” function of the fraction of oxidable of C+3 ions, substitutes of no longer present oxidable V+4 ions, may eventually continue after a substantially complete oxidation to V+5 of the vanadium of the main redox couple V+4/V+5 in the positive electrolyte solution and to this end a balancing mole amount of a reducible redox couple is also added to the negative electrolyte solution.

Abstract: A Method and device for measurement is disclosed in operation, an undivided cell sensor immersed at any desirable point of the positive electrolyte circuit is constantly supplied at a controlled fixed DC bias voltage between the positive metal electrode and the porous carbon counter-electrode by an appropriate voltage regulator of adequate power capability, or cyclically at two or more different voltages, all within a range that includes the region between 0.35V and 0.45V, measuring simultaneously the current flowing across the undivided cell sensor at the fixed voltage or voltages bias. By correlating the paired voltage and current values, using a look up table compiled at calibration, estimated values of the degree of oxidation or state of charge of the redox ion couple of the positive electrolyte solution are produced.

Abstract: A novel multi cell stack architecture has specific features allowing deployment of simple electrical instrumentation of data collection/monitoring of crucial hydraulic, electrical and electrochemical quantities, on the basis of which the operator or electronic controller is able to gather/process critical information of such a depth and enhanced reliability, for immediately identifying any cell in “state of sufferance” and eventually to exclude it from the system and possibly substitute it with a spare cell. A method of monitoring/controlling the operation of an all-vanadium redox flow battery system is also disclosed.

Abstract: A Method and device for measurement is disclosed in operation, an undivided cell sensor immersed at any desirable point of the positive electrolyte circuit is constantly supplied at a controlled fixed DC bias voltage between the positive metal electrode and the porous carbon counter-electrode by an appropriate voltage regulator of adequate power capability, or cyclically at two or more different voltages, all within a range that includes the region between 0.35V and 0.45V, measuring simultaneously the current flowing across the undivided cell sensor at the fixed voltage or voltages bias. By correlating the paired voltage and current values, using a look up table compiled at calibration, estimated values of the degree of oxidation or state of charge of the redox ion couple of the positive electrolyte solution are produced.

Abstract: An ancillary Ce+3/Ce+4 redox couple is added to the positive electrolyte solution containing the V+4/V+5 redox couple of an RFB energy storage system in a mole content sufficient to support charge current in case of localized depletion of oxidable V+4V ions in the anode double layer on a wetted carbon electrode surface at a polarization voltage approaching 1.5 V, thus restraining any further increase that would lead to massive OH? discharge on the carbon electrode. Such a “buffering” function of the fraction of oxidable of C+3 ions, substitutes of no longer present oxidable V+4 ions, may eventually continue after a substantially complete oxidation to V+5 of the vanadium of the main redox couple V+4/V+5 in the positive electrolyte solution and to this end a balancing mole amount of a reducible redox couple is also added to the negative electrolyte solution.