Optimal Operation of Purge Valve to Reduce the H ₂ Wastage in the Fuel Cell

A Proton Exchange Membrane Fuel Cell requires the input of Oxygen from the Cathode and Hydrogen from the anode. As atmospheric air is fed into the system for power generation, nitrogen molecules enter the fuel cell along with oxygen molecules. Over time, an accumulation of nitrogen inside the fuel cell leads to an increase in the effective impedance, which in turn leads to an increase in losses inside the fuel cell, hence reducing the fuel cell efficiency. To reduce the losses, most of the PEM fuel cells have a purge valve at the anode. This purge valve is operated frequently as the impedance increases to let out the nitrogen molecules. During the purging operation, some amount of Hydrogen is let out along with nitrogen, which cannot be recovered. In other words, loss of Hydrogen could also be considered in terms of reduction in system efficiency. Conventionally, nitrogen purging operation in fuel cell takes place reactively as voltage/ power drop across the electrode increases above a defined threshold. This paper proposes an optimization-based solution, which aims at operating the purge valve by predicting load on the vehicle. This can minimize the overall losses in a fuel cell that occur due to wastage of hydrogen and conduction losses due to the presence of water and contaminants like nitrogen inside fuel cell. The predicted energy loss due to the loss of Hydrogen and the predicted energy loss due to the accumulation of nitrogen is modelled, and an optimization algorithm is developed. Optimizer suggests the time instants when the purge valve should be opened which minimizes the hydrogen loss and conduction losses.