The Mechanics of PEM Fuel Cell Stack Compression

The decreasing performance of proton exchange membrane (PEM) fuel cells can be caused by changes in stack clamping pressure (i.e., compression).When the stack is compressed, the membrane electrode assembly (MEA) typically deforms 50 to 200 nm. Lee et al (Journal of Power Sources,84,45-51,1999) discusses that this nanoscale deformation causes changes to the porosity of the gas diffusion layer (GDL) which, in turn, alters the permeability and diffusion of the reactant gas and the transport of the liquid water in the MEA.However, the deformation also decreases electrical contact resistance, which suggests there is an optimization of how much the MEA should deform.The focus of the project is to assess the effects of compression and GDL nano-deformation on fuel cell performance.A testing system was constructed such that the stack compression can be altered without disassembling it.This is facilitated by a cell equipped with a compression plate with a compression adjuster and a dial gauge to measure the change in thickness of the MEA.This feature is essential since a cell's performance is altered considerably if it is disassembled and then reassembled, even if the clamping conditions are accurately reproduced.The fuel cell performance will be tested at different deformations and compared.