Membrane Hydration Management in Fuel Cells

An open-cathode-type fuel cell system that can humidify air coming into the fuel cell stack to prevent drying out of the electrolyte membrane. The system extracts moisture from the unreacted hydrogen and transfers it to the incoming air using a humidifying structure. This allows the fuel cell to operate without a separate humidifier.

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Monitoring humidity at the anode inlet manifold of a fuel cell stack to optimize hydrogen recirculation and manage excess fuel. By measuring the water content in the fuel stream entering the fuel cell anode, the system can determine the excess fuel ratio. This allows targeting the minimum level of excess fuel needed for optimal fuel cell performance without overloading the system. The humidity measurements can be used to determine when to operate blowers, ejectors, and bypass valves for fuel recirculation based on the target excess fuel ratio.

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A system and method for purging condensate water and hydrogen from a fuel cell stack in a way that improves operation stability and efficiency by accurately and adaptively managing the purging process. The system includes a purge valve that selectively directs the purged water/hydrogen to either the atmosphere or back into the fuel cell humidifier based on stack pressure and conditions.

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Method for operating a fuel cell to improve durability by actively managing humidity inside the fuel cell based on voltage. The humidity is decreased at high voltages to reduce catalyst degradation, but increased at low voltages to minimize ohmic losses. This involves lowering humidity when voltage exceeds a threshold, raising humidity below another threshold, and adjusting humidity in between based on voltage.

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Regulating the humidity of a fuel cell membrane by compressing the cathode gas before humidification. This involves compressing the oxygen-containing air to a pressure of at least 1 bar before humidifying it. An injection valve is used between the compressor and cathode to supply water to the compressed gas. This allows efficient and energy-saving compression since it avoids condensation of water during compression.

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A hydrocarbon-based cross-linked membrane for proton exchange membranes in fuel cells that has high proton conductivity and stability. The cross-linked composite of sulfonated polyphenyl sulfone (SPPSU) and sulfonated polyhedral oligomeric silsesquioxane (SPOSS) via sulfonic acid groups provides a membrane that retains mechanical strength while keeping high proton conductivity. Heat treating the composite cross-links the polymer chains. This prevents water swelling that can degrade performance. The cross-linked composite can be used in fuel cell proton exchange membranes.

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Fuel cell humidifier design to prevent condensate water from stagnating and flowing into the fuel cell stack. The humidifier has a membrane module to humidify air, a first cap to supply air, and a second cap to discharge humidified air. A bypass tube connects the second cap and membrane module. This bypass allows moisture-laden air from the second cap to be returned to the membrane instead of stagnating. This prevents condensate buildup and prevents water from flowing into the stack. The bypass tube is integrated into the second cap wall.

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Humidification device for fuel cell systems that improves efficiency and reduces size compared to conventional designs. The device has two membrane modules, one for exchanging moisture between exhaust gas from the fuel cells and dried air from the compressor, and another for exchanging moisture between exhaust gas and dried air separately. This allows circulating humidified air from the first module to the compressor inlet, cooling the compressor, and reducing load. It also increases relative humidity for the second module, improving humidification performance.

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Membrane humidifier for fuel cells that improves humidification efficiency and reduces the volume of the air supply system. The humidifier has separate wet air, dry air, and cooling channels in addition to the moisture exchange membrane. The cooling channel condenses wet air passing through the wet air channel using a separate channel and separators. This allows cooling water to contact and condense the wet air, improving humidification compared to just using the dry air temperature.

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An evaporative humidifier for fuel cell systems that internally recycles condensed water from the exhaust gas to humidify the supply gas without adding external water. The humidifier has separate condensation and evaporation channels with a partition wall between them. Exhaust gas is introduced into the condensation channel where it transfers heat to condense water from the supply gas. This water then drains into the evaporation channel where it evaporates to humidify the supply gas. Fins enhance heat transfer in both channels and hydrophilic coatings improve water drainage and evaporation.

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Operating method for a humidifier in a fuel cell system to ensure proper function under various conditions. The humidifier enriches the fresh air supply to the cathode with moisture. It uses a moisture exchanger with a permeable membrane between the inlet and exhaust air paths. The moisture from the exhaust air is transferred onto the inlet air. This prevents excessive drying of the air supply and maintains optimal humidity levels for the cathode reaction.

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Fuel cell system with a mechanism to prevent performance degradation due to low moisture content in the polymer electrolyte membrane without reducing energy efficiency. When the membrane moisture level is low, the anode gas pressure is reduced to replenish moisture from the cathode side. This maintains electrolyte hydration without increasing anode pressure and pump power consumption. The system has a sensor to detect low membrane moisture and a regulator to selectively lower anode pressure when needed.

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A method for removing residual water in a fuel cell to enhance durability of the membrane by selectively controlling the humidity of purge gases. The method involves reducing the water content in the fuel cell while maintaining the relative humidity of the membrane by supplying dry gas to the anode and fully humidified gas to the cathode. This prevents excessive drying of the membrane that can degrade its performance. The amounts of fuel and purge gases supplied during operation and after shutdown are also controlled to optimize water removal.

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Membrane humidifier design for fuel cells that minimizes mass transport resistance and pressure drop. The humidifier has multiple stages with perpendicular flow channels in wet and dry sides. Water vapor transfers from wet to dry via diffusion media between the plates and a central membrane. This cross-flow configuration allows efficient humidification with low resistance compared to parallel flow.

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A humidification system for fuel cells that can adjust the humidification of air supplied to the fuel cell stack based on load conditions to prevent flooding and starvation issues. The system uses parallel membrane humidifiers with hollow fiber membranes of different sizes and configurations. This allows selectively engaging certain humidifiers based on load to match the required humidity level.

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Controlling relative humidity in fuel cells to optimize performance and prevent damage. The method involves setting target relative humidity levels for the cathode gas entering and exiting the fuel cell stack. These targets are achieved by adjusting factors like coolant flow, cathode gas flow, and temperatures. By precisely managing humidity, it prevents over-hydration issues like liquid water blockages or freezing damage when the cell shuts down, while still avoiding dry stack operation penalties.

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Improving humidity management in fuel cells to prevent dryout and degradation of cells in a stack. The method involves exchanging humidity between the fuel streams entering and leaving the cathode and anode areas of the fuel cell stack. This is done by connecting the supply and exhaust channels for the fuel streams through the stack. Humidity is removed from the exhaust and added to the supply to maintain optimal humidity levels inside the fuel cell stack. This prevents dryout and degradation of cells at the inlet due to insufficient humidity. The method uses the stack itself as a humidity management system without additional external circuits.

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Evaporator for a polymer electrolyte membrane fuel cell system that allows utilizing waste heat from the fuel cell stack to evaporate fuel or water, instead of using external heat sources. The evaporator is integrated with the fuel cell system and heated by the fuel cell waste heat. The evaporator has chambers for evaporation and heat transfer. It lowers the partial pressure of the medium to be evaporated below saturation to increase evaporation rate. This allows efficiently extracting waste heat from the fuel cell stack to evaporate fuel or water without external heat sources.

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Fuel cell with a solid polymer membrane that doesn't require a separate humidifier and has compact size. The fuel cell has separate fuel and air supply paths through the cell frame. It also has additional moisture supply paths through the frame walls at different locations from the fuel and air supply openings. This allows direct moisture injection into the membrane without interfering with the fuel or air paths. This prevents drying of the membrane on the fuel side while avoiding excessive moisture that could clog the fuel and air paths.

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A fuel cell system with humidification membranes to improve performance and reduce contamination compared to prior art systems. The system uses membranes to humidify the reactant gas streams without introducing contaminants from the water source. This prevents contamination of the fuel cell components like the gas diffusion layers and membrane electrode assembly. The humidifier has a membrane with separate paths for the reactant gas and humidifying liquid to flow over opposite sides. This allows humidification without mixing the two streams and potential contamination. The humidified gas is then fed into the fuel cell.

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