Fuelcell Working – an overview

Source: http://www.esru.strath.ac.uk/

Fuel Cell System is a complex one including the interactions of mechanical, chemical, and electrochemical subsystems present, the stack being the heart of the system. The control of fuel cell systems under a variety of environmental conditions and over a wide operating range is a crucial factor in making them viable for extensive use in every-day technology. So, it is necessary to understand the heart of the system i.e. the fuel cell stack properly.

Fuel cells are chemical engines that generate electricity by converting the chemical potential of the fuel into electrical power. Since they are not based on temperature differences, they are not subjected to Carnot’s limit of efficiency. In addition, common pollutants such as sulfur dioxide and nitrous oxides are avoided since the process does not involve combustion. These advantages, together with the reduction of greenhouse gases and fuel consumption due to higher efficiencies and the possibility of alternative energy sources, have generated enormous interest in fuel cells for stationary as well as mobile applications.

A fuel cell is a class of galvanic cell based on oxidation-reduction reaction. The most basic system uses pure hydrogen as fuel, which is oxidized at the anode, producing electrons and protons:

Oxidation Reaction: H₂ –> 2H⁺ + 2e^-

The electrons are released to an external circuit, where they can be used to perform work, while the protons diffuse through an electrolyte to the cathode. At the cathode, oxygen reacts with the electrons from the external circuit and protons from the anode reaction, forming water:

Reduction Reaction: 0.5O₂+2H⁺+2e^- –> H2O

Therefore, the overall chemical reaction of the PEMFC is:

Overall Reaction: H₂+0.5 O₂-> H₂0+electricity+heat