Hydrogen is emerging as a promising energy carrier for storing renewable energy sources. Water electrolysis provides a clean and efficient production method, with alkaline water electrolysis being one of the technologies. However, a major limitation of this process is the low current density, which is partly caused by the formation of bubbles that affect the efficiency of the system. Understanding bubble dynamics and their impact on performance is important for optimizing hydrogen production. In this project, an attempt was made to predict the hydrogen bubble size distribution in the cathode- electrolyte interface using population balance modeling (PBM). Previous research focuses on using an experimentally determined bubble size distribution or a constant bubble size coming out from the surface of electrode, and using this as an input to the multiphase modeling of the electrolysis cell.