Cortney Mittelsteadt

PEM Electrolyzers and PEM Regenerative Fuel Cells Industrial View

Abstract Electrolysis of water with hydrogen storage is one of the few methods available for grid-scale energy storage. Stored hydrogen has many applications: as a fuel to add peak power back to the grid, a bioreactor feedstock, or direct feed to existing natural gas infrastructures. Although alkaline electrolyzers are the state of the art, polymer electrolyte membrane (PEM) polymer electrolyte membrane electrolyzers (PEMELs) are gaining considerable attention as an ideal replacement due to their ability to respond rapidly to intermittent power sources with large transients, operate at high current density, and generate high and differential pressure. This chapter focuses on the principles and considerations governing operation and installation of PEMEL technology. Current research and development efforts along with economies of scale have significantly reduced the cost of hydrogen production and storage, greatly increasing the viability of this technology as well as increasing the fraction of intermittent, renewable power acceptable to the grid. Advancements in coupling fuel cells and electrolyzers into discrete polymer electrolyte membrane-regenerative fuel cells and unitized regenerative fuel cell systems allow for improved versatility of the technology for energy storage and other cutting-edge applications.

Synthesis and Membrane Properties of Sulfonated Poly(arylene ether sulfone) Statistical Copolymers for Electrolysis of Water: Influence of Meta- and Para-Substituted Comonomers

Two series of high molecular weight disulfonated poly(arylene ether sulfone) random copolymers were synthesized as proton exchange membranes for high-temperature water electrolyzers. These copolymers differ based on the position of the ether bonds on the aromatic rings. One series is comprised of fully para-substituted hydroquinone comonomer, and the other series incorporated 25 mol % of a meta-substituted comonomer resorcinol and 75 mol % hydroquinone. The influence of the substitution position on water uptake and electrochemical properties of the membranes were investigated and compared to that of the state-of-the-art membrane Nafion. The mechanical properties of the membranes were measured for the first time in fully hydrated conditions at ambient and elevated temperatures. Submerged in water, these hydrocarbon-based copolymers had moduli an order of magnitude higher than Nafion. Selected copolymers of each series showed dramatically increased proton conductivities at elevated temperature in fully hydrated conditions, while their H2 gas permeabilities were well controlled over a wide range of temperatures. These improved properties were attributed to the high glass transition temperatures of the disulfonated poly(arylene ether sulfone)s.

Novel Current Distribution Board for PEM Devices

Distribution Board is only 1.5mΩ for a 50cm 2 cell. The printed board circuit designed consists of a Kapton base layer, copper deposit, nickel deposit, and gold flash to prevent oxidation. The design is based on a tripleserpentine flow field plate such that a negligible amount of material interferes with the flow channels. The only material that interferes with the flow field is that of thin copper strips that run perpendicular to the flow pattern. This small amount of material is added to prevent overheating from occuring. The Current Distribution Board consists of 10 individual current collecting areas that match the triple serpentine flow field separated by thin sections of Kapton from the base layer. Adaptors are attached to both sides of the board which collect the current through 12 AWG wires threaded thru hall-effect sensors. By using somewhat thick wires in the adaptors, the external resistances are minimized such that an internal resistance from an MEA will be detected. The hall-effect sensors output an analog signal that is proportional to the amount of current detected. This analog signal is routed to a Data Acquisition Board which is connected to a computer in order to collect and record data. During use, the Current Distribution Board is separated from the MEA by a Gas Diffusion Layer (GDL) which contains continuous conductive fibers. This means some of the current will smear throughout the 10 individual current collecting areas thus giving a false current reading. However, this is effect is compensated for by applying a set of mathematical equations for each of the sections in order to collect and record the true current. Additionally, a mathematical model is being developed based on experimental results. This model will help determine the fuel cell’s performance based on different testing conditions but ultimately be used as a tool for water management of the cell. Acknowledgement