Ovepotentials | 12/14 | UPV

Título: Ovepotentials Descripción: El objetivo es conocer las curvas de polarización de las pilas de combustible, y los fenómenos que causan el descenso en la eficiencia energética (ovepotentials). Ribes Greus, MD. (2010). Ovepotentials. http://hdl.handle.net/10251/8160 Descripción automática: In this video, the presenter discusses the loss of efficiency in fuel cells due to various types of overpotentials. The first type of overpotential mentioned is activation polarization, which occurs at low current densities and requires extra energy, known as activation energy, for electrochemical reactions to begin. This is followed by ionic polarization, which arises due to resistances within the cell's components and affects the cell at intermediate current densities. Lastly, concentration polarization is explained to occur at very high current densities, where the rapid reactions create a concentration gradient that hinders the access of fuel molecules to the reaction surface, thus requiring more energy for the reactions to proceed. The presenter goes on to describe the polarization curve that represents the sum of all three types of polarization. The overpotential is defined as the difference between the operating point on the curve and the reversible potential. To understand these effects, equations that characterize activation polarization and concentration polarization are used. Activation polarization is studied through graphical analyses, which can yield electron transfer coefficient and exchange current density parameters. Similarly, concentration polarization is examined with fixed law equations to understand mass transfer efficiency. The overall voltage of a fuel cell is finally depicted as the reversible potential minus the cumulative overpotentials from activation, concentration, and ohmic losses. The presenter emphasizes employing a semi-empirical approach to fit real polarization curves with these equations to predict fuel cell behavior. Autor/a: PoliMedia Administrador Curso: Este vídeo es el 12/14 del curso Introduction to Fuel Cells Course | Universitat Politècnica de València (UPV). https://www.youtube.com/playlist?list=PLB618851272E238D8 + Universitat Politècnica de València UPV: https://www.upv.es + Más vídeos en: https://www.youtube.com/valenciaupv + Accede a nuestros MOOC: https://upvx.es #Fuel cells #Ovepotential #Polarisation curve #MAQUINAS Y MOTORES TERMICOS