proton exchange membrane fuel cell advantages and disadvantages
Proton-exchange membrane PEMFCs contain advantages over other types of fuel cells such as solid oxide fuel cells (SOFC). PEMFCs operate at a lower temperature, are lighter and more compact, which makes them ideal for applications such as cars. However, some disadvantages are: the ~80 °C operating temperature is too low for cogeneration like in SOFCs, and that the electrolyte for PEMFCs must be water-saturated. However, some fuel-cell cars, including the Toyota Mirai, operate without humidifiers, relying on rapid water generation and the high rate of back-diffusion through thin membranes to maintain the hydration of the membrane, as well as the ionomer in the catalyst layers. High-temperature PEMFCs operate between 100 °C and 200 °C, potentially offering benefits to electrode kinetics and heat management, and better tolerance to fuel impurities, particularly CO in reformate. These improvements potentially could lead to higher overall system efficiencies. However, these gains have yet to be realized, as the gold-standard perfluorinated sulfonic acid (PFSA) membranes lose function rapidly at 100 °C and above if hydration drops below ~100%, and begin to creep in this temperature range, resulting in localized thinning and overall lower system lifetimes. As a result, new anhydrous proton conductors, such as protic organic ionic plastic crystals (POIPCs) and protic ionic liquids, are actively studied for the development of suitable PEMs.[6][7][8]
Nuclear membrane Exactly how the nuclear membrane reforms during telophase of mitosis is debated. Two theories exist[7]â€”
Vein Veins are less muscular than arteries and are often closer to the skin. There are valves in most veins to prevent backflow.
Capability Maturity Model Integration Maturity Level 5 - Optimizing
Catalytic converter As an alternative, catalytic converters were moved to a third of the way back from the engine, and were then placed underneath the vehicle.
Fire Once ignited, a chain reaction must take place whereby fires can sustain their own heat by the further release of heat energy in the process of combustion and may propagate, provided there is a continuous supply of an oxidizer and fuel.