Abstract: This invention provides a cell stack for a redox flow battery that can provide battery efficiencies with high reliability over a long term, without any adhesive bonding between a bipolar plate and electrodes. In the cell stack 1 for the redox flow battery of a cell frame 2, electrodes 3, 4 and a membrane 5 being stacked in layers, the cell frame 2 comprises a frame 2A and a bipolar plate 9 arranged inside of the frame 2A, and the electrodes 3, 4 are put into close contact with the bipolar plate 9 by a clamping force, without being adhesively bonded to the bipolar plate 9. It is preferable that when the electrodes 3, 4 are compressed to a thickness corresponding to a level difference between the frame 2A and the bipolar plate 9, repulsive force of the electrodes is in the range of more than 15 kPa to less than 150 kPa (more than 0.153 kgf/cm2 to less than 1.53 kgf/cm2).

Abstract: The invention provides an operating method of a redox flow battery capable of grasping a charging state of the battery more reliably to stabilize an output capacity of the battery. The method is for operating the redox flow battery comprising a cell stack 1 comprising a plurality of cells. A selected cell(s) in the cell stack 1, to and from which positive electrode electrolyte and negative electrode electrolyte are supplied and discharged and which is/are not normally connected to a DC/AC converter 225, is/are in the form of an auxiliary cell 2 used for measuring a charging rate of the electrolyte. Also, a stop of charge of a main cell 3 and a stop of discharge of the main cell 3 are controlled with reference to a circuit voltage obtained from the auxiliary cell 2. Since the auxiliary cell 2 is integrally incorporated in the cell stack 1, the charging state of the battery can be grasped reliably without stopping the charge/discharge operation of the main cell 3.

Abstract: The present invention provides a method of designing a redox flow battery system that can prevent system efficiency loss caused by weak generation power or load power at the time of electric charge or discharge, without using any lead storage battery, and can also provide further improved system efficiency. In the present invention, generating equipment that varies irregularly in output of power generation is provided with the redox flow battery to smooth the output of power generation. An average value of output distribution of the battery with respect to the smoothed output of power generation and standard deviation are determined. Then, at least either of a specified output of the battery and a specified output of the converter for converting the battery output is determined based on the standard deviation.

Abstract: This invention provides a cell frame for a redox flow battery that prevents leakage of electrolyte out of the cell frame and also provides a good workability in assembling the redox flow battery. Also, this invention provides a redox flow battery using the cell frame. In the cell frame 30 for the redox flow battery 30 comprising a bipolar plate 21 and a frame 31 fitted around a periphery of the bipolar plate 21, the frame 31 has, on each side thereof, an inner seal and an outer seal to press-contact with a membrane and also seal electrolyte. The frame 31 has, on each side thereof, an inner seal groove 34 and an outer seal groove 35 for placing therein the inner seal and the outer seal, respectively, to prevent the electrolyte from leaking out, and O-rings are placed in the respective seal grooves.

Abstract: The invention provides an operating method of a redox flow battery capable of grasping a charging state of the battery more reliably to stabilize an output capacity of the battery. The method is for operating the redox flow battery comprising a cell stack 1 comprising a plurality of cells. A selected cell(s) in the cell stack 1, to and from which positive electrode electrolyte and negative electrode electrolyte are supplied and discharged and which is/are not normally connected to a DC/AC converter 225, is/are in the form of an auxiliary cell 2 used for measuring a charging rate of the electrolyte. Also, a stop of charge of a main cell 3 and a stop of discharge of the main cell 3 are controlled with reference to a circuit voltage obtained from the auxiliary cell 2. Since the auxiliary cell 2 is integrally incorporated in the cell stack 1, the charging state of the battery can be grasped reliably without stopping the charge/discharge operation of the main cell 3.

Abstract: The present invention provides electrolyte that can suppress reduction of battery efficiencies and capacities with increased cycles of charge/discharge of the battery, a method for producing the same, and a redox flow battery using the same electrolyte. The redox flow battery uses the electrolyte having a NH4 content of not more than 20 ppm and a relation of Si concentration (ppm)×electrolyte quantity (m3)/electrode area (m2) of less than 5 ppm·m3/m2. By limiting a quantity of contaminants in the electrolyte, a clogging of carbon electrodes to cause reduction of the battery performances with increased charge/discharge operations can be suppressed.

Abstract: A simplified, pressure-variation preventing tank structure capable of preventing pressure variations in a gas phase portion resulting from temperature variations, without bringing stored liquid into contact with air. This pressure-variation preventing structure includes a breather bag arranged in a gas phase portion of a tank and inflating/deflating in communication with outside air, and a manhole to which the breather bag is attached to suspend in a gas phase portion, including a communication hole for the breather bag to communicate with outside air. The breather bag has air-blocking, acid-resistant and expandable characteristics.

Abstract: The invention provides a secondary battery system that allows a high overload operation regardless of discharging condition during a steady operation, and an operating method thereof. The secondary battery system comprises first tanks 31, 32 for reserving electrolytes required for a steady operation, and second tanks 33, 34 for reserving electrolytes required for an emergency operation. Valves 41–48 are opened and closed for allowing selective switching between the electrolytes in the first tanks 31, 32 and the electrolytes in the second tanks 33, 34 to circulate the selected electrolytes through a cell stack 100. The electrolytes reserved in the second tanks 33, 34 are electrolytes having a proportion of a quantity of active material produced in a charging reaction to a total quantity of active material of not less than 50%.

Abstract: An operating method of a redox flow battery system that can provide a stabilized output to a system from a redox flow battery system annexed to a wind power generator, to produce an improved battery efficiency. The redox flow battery system comprises the wind power generator 10, a redox flow battery 30 annexed to the wind power generator, and an AC/DC converter 40 connected to the redox flow battery.

Abstract: The present invention provides a method of designing a redox flow battery system that can prevent system efficiency loss caused by weak generation power or load power at the time of electric charge or discharge, without using any lead storage battery, and can also provide further improved system efficiency. In the present invention, generating equipment that varies irregularly in output of power generation is provided with the redox flow battery to smooth the output of power generation. An average value of output distribution of the battery with respect to the smoothed output of power generation and standard deviation are determined. Then, at least either of a specified output of the battery and a specified output of the converter for converting the battery output is determined based on the standard deviation.

Abstract: The invention provides an operating method of a redox flow battery capable of grasping a charging state of the battery more reliably to stabilize an output capacity of the battery. The method is for operating the redox flow battery comprising a cell stack 1 comprising a plurality of cells. A selected cell(s) in the cell stack 1, to and from which positive electrode electrolyte and negative electrode electrolyte are supplied and discharged and which is/are not normally connected to a DC/AC converter 225, is/are in the form of an auxiliary cell 2 used for measuring a charging rate of the electrolyte. Also, a stop of charge of a main cell 3 and a stop of discharge of the main cell 3 are controlled with reference to a circuit voltage obtained from the auxiliary cell 2. Since the auxiliary cell 2 is integrally incorporated in the cell stack 1, the charging state of the battery can be grasped reliably without stopping the charge/discharge operation of the main cell 3.

Abstract: An operating method of a redox flow battery system that can provide a stabilized output to a system from a redox flow battery system annexed to a wind power generator, to produce an improved battery efficiency. The redox flow battery system comprises the wind power generator 10, a redox flow battery 30 annexed to the wind power generator, and an AC/DC converter 40 connected to the redox flow battery.

Abstract: A modified vanadium compound characterized in that vanadium sulfate (III), or a mixed vanadium compound of vanadium sulfate (III) and vanadyl sulfate (IV) contains excessive sulfuric acid other than sulfate group composing the vanadium sulfate (III) or the vanadyl sulfate (IV), and when the modified vanadium compound is used, a redox flow battery electrolyte can be prepared easily.

Abstract: This invention provides a cell stack for a redox flow battery that can provide battery efficiencies with high reliability over a long term, without any adhesive bonding between a bipolar plate and electrodes. In the cell stack 1 for the redox flow battery of a cell frame 2, electrodes 3, 4 and a membrane 5 being stacked in layers, the cell frame 2 comprises a frame 2A and a bipolar plate 9 arranged inside of the frame 2A, and the electrodes 3, 4 are put into close contact with the bipolar plate 9 by a clamping force, without being adhesively bonded to the bipolar plate 9. It is preferable that when the electrodes 3, 4 are compressed to a thickness corresponding to a level difference between the frame 2A and the bipolar plate 9, repulsive force of the electrodes is in the range of more than 15 kPa to less than 150 kPa (more than 0.153 kgf/cm2 to less than 1.53 kgf/cm2).

Abstract: A cell frame for a redox-flow cell excellent in sealability between a frame member and a dipole sheet and a redox-flow cell having it are disclosed. The cell frame is composed of a dipole sheet (9) and a frame member (2A) attached to the periphery of the dipole sheet (9). The frame member (2A) contains 50 mass % or more of vinyl chloride. The dipole sheet is made of a conductive plastic containing 40-90 mass % of graphite and 10-60 mass % of a chlorinated organic compound. Chloride.

Abstract: The present invention provides electrolyte that can suppress reduction of battery efficiencies and capacities with increased cycles of charge/discharge of the battery, a method for producing the same, and a redox flow battery using the same electrolyte. The redox flow battery uses the electrolyte having a NH4 content of not more than 20 ppm and a relation of Si concentration (ppm)×electrolyte quantity (m3)/electrode area (m2) of less than 5 ppm·m3/m2. By limiting a quantity of contaminants in the electrolyte, a clogging of carbon electrodes to cause reduction of the battery performances with increased charge/discharge operations can be suppressed.

Abstract: This invention provides a cell frame for a redox flow battery that prevents leakage of electrolyte out of the cell frame and also provides a good workability in assembling the redox flow battery. Also, this invention provides a redox flow battery using the cell frame. In the cell frame 30 for the redox flow battery 30 comprising a bipolar plate 21 and a frame 31 fitted around a periphery of the bipolar plate 21, the frame 31 has, on each side thereof, an inner seal and an outer seal to press-contact with a membrane and also seal electrolyte. The frame 31 has, on each side thereof, an inner seal groove 34 and an outer seal groove 35 for placing therein the inner seal and the outer seal, respectively, to prevent the electrolyte from leaking out, and O-rings are placed in the respective seal grooves.

Abstract: The invention provides a secondary battery system that allows a high overload operation regardless of discharging condition during a steady operation, and an operating method thereof. The secondary battery system comprises first tanks 31, 32 for reserving electrolytes required for a steady operation, and second tanks 33, 34 for reserving electrolytes required for an emergency operation. Valves 41-48 are opened and closed for allowing selective switching between the electrolytes in the first tanks 31, 32 and the electrolytes in the second tanks 33, 34 to circulate the selected electrolytes through a cell stack 100. The electrolytes reserved in the second tanks 33, 34 are electrolytes having a proportion of a quantity of active material produced in a charging reaction to a total quantity of active material of not less than 50%.

Abstract: An electrolyte tank which allows effective use of existing space of various shapes is provided. An electrolyte tank is formed by laminating one or more layers of coated fabric provided by coating a woven fabric of organic fiber with rubber or plastic and processing the laminated coated fabric to a bag-shape.

Abstract: The present invention provides method of producing a trivalent and tetravalent mixed vanadium compound having excellent solubility with sulfuric acid directly from a tetravalent or pentavalent vanadium compound by using a reducing agent,and a method of producing a vanadium electrolyte. For example, a vanadium compound mainly containing a pentavalent vanadium compound; sulfur and concentrated sulfuric acid in molar ratios with respect to (one mol of vanadium atom in the pentavalent vanadium compound) 0.35 to 0.4:1.2 to 1.9 are kneaded into paste form, and the paste-form mixture is calcined at a temperature of not less than 150° C. to less than 440° C. so that a trivalent and tetravalent mixed vanadium compound is obtained, and a redox flow battery-use vanadium electrolyte is obtained by dissolving the trivalent and tetravalent mixed vanadium compound in a sulfuric acid solution.