Hydrogen Fuel Cell Methane Cycling for Internal Reforming Efficiency
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Solution Overview
Problem
Fuel cell systems, particularly high-temperature systems, face low total efficiency due to limited fuel utilization and significant waste heat generation, with hydrogen-based systems being less efficient than hydrocarbon-based systems when using water steam, which reduces Nernst potential and power density.
Innovation Solution
A fuel cell system with internal methane reformation within the fuel cell, utilizing a methanation unit to generate methane from anode exhaust and mix it with hydrogen, allowing for efficient heat utilization and reduced steam content to enhance electrochemical efficiency, along with a closed methane cycle and controlled hydrogen-to-methane ratio to prevent carbon deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water steam is added in large quantities to hydrocarbon fuels to prevent carbon deposition, then carbon deposition damage is prevented, but Nernst potential and power density are significantly reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the fuel by introducing a small amount of hydrocarbon (0.1-10% by volume) into the hydrogen fuel, which fundamentally alters the carbon deposition dynamics without significantly impacting Nernst potential. This parameter change enables carbon prevention through controlled carbon source introduction rather than water steam addition.
Solution Approach 2:
The patent converts the previously harmful effect of hydrocarbon carbon deposition into a beneficial mechanism by introducing controlled amounts of hydrocarbon that deliberately deposit carbon to form protective layers on the anode, preventing further damaging carbon accumulation while maintaining fuel cell performance.
2Temperature
If cooling is carried out using air supplied to the cathode, then heat produced by electrochemical reaction is removed, but energy consumption for air blower is significantly increased
Solution Approach 1:
The patent implements self-service cooling where the fuel cell system cools itself through the endothermic reforming reactions that occur internally. The heat generated by electrochemical reactions is directly utilized as the energy source for methane reforming, creating a self-balancing thermal system that eliminates the need for external cooling mechanisms.
Solution Approach 2:
The patent introduces endothermic reforming reactions as an intermediary thermal management mechanism. These reforming reactions act as a thermal buffer that absorbs excess heat from the electrochemical reactions, mediating the thermal balance without requiring external cooling systems.
3Productivity
If fuel utilization is increased beyond 70-80%, then power generation efficiency is improved, but waste heat generation increases significantly
Solution Approach 1:
The patent changes the thermal chemistry parameters by introducing endothermic reforming reactions that alter the heat balance of the system. This parameter change enables the system to process higher fuel utilization rates while the reforming reactions absorb the excess heat that would otherwise become waste, maintaining thermal efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases fuel utilization and total efficiency by effectively using heat produced in the fuel cell for internal reformation, minimizing cooling energy consumption, and maintaining high electrochemical efficiency without water steam, resulting in higher power output and reduced carbon emissions.
Implementation Method 1
Fuel cell systems, especially high temperature fuel cell systems (e.g. SOFC) with an operation temperature of around 600-800° C., are widely used in the prior art for generating electric power produced by the redox reaction of a fuel stream and an oxidant stream
Implementation Method 2
the methanation unit can produce CH4 out of a mixture containing CO, CO2 and hydrogen
Implementation Method 3
a fuel cell system having an increased total efficiency... The fuel cell is further arranged for an internal reformation of methane
Data Source
AI summary
A fuel cell system arranged for the conversion of pure hydrogen comprising a) at least one fuel cell comprising an anode, a cathode and an electrolyte, and arranged for an internal reformation of methane, b) a fuel conduit connecting a fuel conduit inlet with an anode inlet, c) an anode exhaust conduit connecting an anode outlet and a methanation unit capable of producing methane from anode exhaust, and d) a methanation unit exhaust conduit connecting a methanation unit exit and the fuel conduit, and e) a water removal and/or water condenser unit coupled to the methanation unit exhaust conduit, wherein the fuel introduced into an inlet of the fuel conduit is pure hydrogen, and the amount of methane produced in the methanation unit is equal to the amount of methane reformed inside of the fuel cell so that the content of methane cycling through the fuel cell system is constant.