A fuel cell system includes a fuel cell that generates electric power using fuel gas and oxidant gas, a fuel gas supply path through which the fuel gas is supplied to an anode inlet of the fuel cell, a recycle gas path through which anode off-gas discharged from an anode outlet of the fuel cell returns to the fuel gas supply path, and a pressure booster arranged in the recycle gas path, and the pressure booster is arranged above a confluence portion where the fuel gas supply path and the recycle gas path meet each other when gravity acts downward from above.

This invention provides a system and a method for safe production of electrolyte at required concentration on site on demand where occasionally only water is needed to be filled up. The system includes two main units: a saturated electrolyte unit and a diluted electrolyte unit.

Molten carbonate fuel cells (MCFCs) are operated to provide enhanced CO.sub.2 utilization. This can increase the effective amount of carbonate ion transport that is achieved. The enhanced CO.sub.2 utilization is enabled in part by operating an MCFC under conditions that cause transport of alternative ions across the electrolyte. The amount of alternative ion transport that occurs during enhanced CO.sub.2 utilization can be mitigated by using a more acidic electrolyte.

A reforming element for a molten carbonate fuel cell stack and corresponding methods are provided that can reduce or minimize temperature differences within the fuel cell stack when operating the fuel cell stack with enhanced CO.sub.2 utilization. The reforming element can include at least one surface with a reforming catalyst deposited on the surface. A difference between the minimum and maximum reforming catalyst density and/or activity on a first portion of the at least one surface can be 20% to 75%, with the highest catalyst densities and/or activities being in proximity to the side of the fuel cell stack corresponding to at least one of the anode inlet and the cathode inlet.

Methods and systems are provided for a rebalancing reactor of a flow battery system. In one example, a pH of a battery electrolyte may be maintained by the rebalancing reactor by applying a negative potential to a catalyst bed of the rebalancing reactor. A performance of the rebalancing reactor may further be maintained by treating the catalyst bed with deionized water.

A system includes one or more redox flow batteries and includes a stack of several electrochemical cells. The electrochemical cells include a cathode compartment and an anode compartment. The cathode compartment is in fluidic communication, via a feed circuit, with one or more tanks of electrolyte called catholyte. The anode compartment is in fluidic communication, via a feed circuit, with one or more tanks of electrolyte called anolyte. The feed circuit of the catholyte, respectively the anolyte, includes a pump for circulating the catholyte, respectively the anolyte, from the tank to the cathode, respectively the anode compartments. The system includes a catholyte drainage pump and an anolyte drainage pump, the catholyte, respectively. The anolyte drainage pump is controlled by a catholyte, respectively anolyte presence detector, in at least a part of the feed circuit of catholyte, respectively anolyte.

A method of evaluating a movement tendency of ions in an electrolyte membrane includes counting inter-movement ions, counting intra-movement ions and calculating the ratio of the intra-movement ions and inter-movement of ions. The movement tendency of ions is predicted based on the ratio. In the case of evaluating a movement tendency of ions using the method, since the structure of the electrolyte membrane in which the ratios of intra-movement and inter-movement are maximized is predicted through measurement of the ratios of the intra-movement and inter-movement of ions, ohmic resistance that may occur in a membrane-electrode assembly (MEA) may be reduced. The electrolyte membrane having the optimal structure predicted by the method can be applied to a fuel cell to increase its performance.

Molten carbonate fuel cells (MCFCs) are operated to provide enhanced CO.sub.2 utilization. This can increase the effective amount of carbonate ion transport that is achieved. The enhanced CO.sub.2 utilization is enabled in part by operating an MCFC under conditions that cause transport of alternative ions across the electrolyte. The amount of alternative ion transport that occurs during enhanced CO.sub.2 utilization can be mitigated by using a more acidic electrolyte.

A method for a redox flow battery may include, interrupting cycling of the redox flow battery, including charging the redox flow battery to a threshold charge condition, draining positive and negative electrolyte from the redox flow battery, circulating a wash solution through the redox flow battery, and returning the positive and negative electrolyte to the redox flow battery, and resuming cycling of the redox flow battery. In this way, contamination of the redox flow battery system can be reduced, thereby prolonging the life and increasing performance of the redox flow battery system.

A fuel cell system includes a fuel cell stack having a plurality of fuel cells that each contain a plurality of fuel electrodes and air electrodes. The system includes a fuel receiving unit connected to the fuel cell stack, which receives a hydrocarbon fuel from a fuel supply. The system includes a fuel exhaust processing unit fluidly coupled to the fuel cell stack by a slip stream, where the fuel exhaust processing unit processes fuel exhaust from the fuel cell stack, and the slip stream is fluidly connected to an exhaust stream flowing from the fuel cell stack. The fuel processing unit removes a first portion of carbon dioxide (CO.sub.2) from fuel exhaust within the slip stream, outputs the first portion of CO.sub.2 in a first stream, and outputs a second portion of CO.sub.2 remaining from the fuel exhaust in the slip stream into a second stream, which includes hydrogen.