FUEL CELL Technology

Development of a PEM Fuel Cell at Isfahan Engineering Research Center

Proton Exchange Membrane (PEM) is well known among other types of the fuel cells. In theses types of fuel cells, the electrolyte is a polymer and they operate at temperature of about 80 ^oC with high efficiency. PEM fuel cell is a chosen to be the viable fuel cell for a wide range of applications, from low-Watt (e.g., cellular phones, lap-top computers) to high-Watt (e.g., stationary power plants). A unit-cell can produce about 0.6-07 Volts and is considered to be the building block of a fuel cell stack.
	The current obtained by a fuel cell depends on the area of each cell and the quality of the materials used and their assembly. Each unit cell consists of different subsections, like MEA (Membrane-Electrode-Assembly), bipolar plates, seals, and catalyst. MEA by itself has three subsections: like membrane, catalyst and gas-diffusion-layers).
MEA: is a major part of the PEM and is considered as the heart of the cell. All chemical and electro-chemical reactions happen in MEA. A polymeric membrane with layers of catalyst (usually Pt) is sandwiched by two carbon papers or GDL (Gas-Diffusion-Layer). A GDL is a porous carbon paper and its function is to feed the active gases to the catalyst layer and transport the bi-product (mainly water) to the outside of the cell.
	The H₂ gas is supplied to the anode side of the MEA and the O₂(or air) to the cathode side. Hydrogen is then electrochemically decomposed to electrons and protons. The membrane is conductive to protons and prevents electrons to pass through. Hence the electrons (i.e., electricity) go around and reacts electrochemically with Oxygen on the cathode side to produce water.
The development of MEA is a complex one and needs establishing several processes in the laboratory. At IERC, we have developed MEA with active areas from 3x3 cm² to 14x14 cm². Test results for these MEA�s are satisfactory and further improvements are optimizations are scheduled.
	Bi-polar plates: these plates have several functions, like distributing the feeding gases, transferring the heat, marinating the structural rigidity of the cell, conducting electricity. The MEA is sandwiched between two bi-polar plates to form a unit-cell. On the surfaces of these plates flow fields are machined (or molded) to distribute the gases. Different flow field designs are investigated and designed for plates with 3x3 cm² to 16x16 cm² surface areas. Fluent software package in addition to analytical techniques are used for design and optimization of the flow fields. Temperature distributions, heat transfer and effects of coolants are also investigated. We are also investigating different production and manufacturing techniques for fabricating the bi-polar plates.
End-plates and seals: In order to seal the leakage of the gases and the liquid water as well as preventing electrical shorts between unit-cells in a stack, we need to develop seals that are resistive and durable enough in the cell environment. We are also working on developing the end plates, which should conduct the current, & voltage produces by the stack.

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