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Fuelling potential


Gemma Church finds out how simulation software is opening up fuel cell technology to a greater range of


commercial applications F


uel cells could, in principle, power anything that needs electrical energy to function. Yet the current commercial applications are few and


far between because of concerns about the cost and reliability of such power sources. Could simulation soſtware hold the key to unlocking the potential for fuel cells to see more widespread use? Fuel cells generate electricity and heat


most commonly through the electrochemical reactions that happen between oxygen and hydrogen to form water. Te technology has existed for almost 200 years, with the first cells invented in 1836, but the first commercial use of fuel cells came more than a century later as part of NASA’s space program – to generate power for space capsules and satellites. Te range of fuel cell technologies and their application areas have diversified since


that time. Most fuel cell designs contain the same three components: an anode, cathode and electrolyte. Electrochemical and chemical reactions that consume fuel and produce water and electricity, occur at the interfaces between electrolyte, anode and catalyst phases. Fuel cell designs differ depending on the


applications they will be used for. Proton exchange membrane fuel cells (PEMFCs), for example, are the cells that most people are familiar with and are oſten used for small, portable, fuel cell applications such as transportation. Phosphoric acid fuel cells (PAFCs) focus more on reliability over a long period of time than portability, so are oſten larger in size and provide primary and backup power for commercial, industrial and residential buildings. Both these cells are fuelled with hydrogen and are lower temperature cells, with PEMFCs operating in the 50 to 200°C range and PAFCs in the 150 to 200°C range. Tere are also a range of high temperature


cells, operating between 500 and 1,100°C, including molten carbon fuel cells (MCFCs) and solid oxide fuel cells (SOFCs) that run on fossil fuels to produce electricity for large scale applications, such as power plants.


Simulation results from a COMSOL Multiphysics model showing oxygen and fuel concentration in the channels and gas diffusion electrodes of a fuel cell


34 SCIENTIFIC COMPUTING WORLD


Solving a multiphysics challenge Tere are many challenges when simulating fuel cells caused by the intrinsic nature of such systems. For example, you are dealing with a multiphysics environment. Termodynamics and conservation of current, mass and energy – as well as the


electrochemical reactions that produce current, mass, and energy – must all be included. Termodynamics also sets the theoretical limit for the efficiency of the cell. And these systems are highly non-linear. Ed Fontes, CTO of Comsol, said: ‘Te challenge for us is that the fuel cell is a truly multiphysics problem to model because it involves so many different phenomena at different timescales. It involves fields in physics that are not usually mixed.’ Te fuel cells are also a multiscale problem


in terms of both space and time. Chris Lueth, application manager at CD-adapco, said: ‘Having thin layers next to large channels, up to modelling entire stacks requires efficient meshing and interface strategies.’ Lueth added: ‘Modelling short timescales


of chemistry and fluid dynamics, while modelling long timescales necessary for


@scwmagazine l www.scientific-computing.com


Comsol


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