R-015

Marina Becker

marina.becker@tu-clausthal.de

Henning Becker, Maik Becker

Research Center Energy Storage Technologies, Clausthal University of Technology, Germany

Stray currents in industrial alkaline water electrolysis stacks –  Current commercial systems and their optimization

Many, if not most, applications of alkaline water electrolysis systems require the cells to be arranged in stacks to increase productivity and reduce system costs. In all cases where a liquid is pumped to the electrodes from a shared tank, the conductivity of the liquid will cause a stray current that is a fraction of the main current passing from cell to cell. Therefore, especially in alkaline water electrolysis and even in proton exchange membrane electrolysis, stray currents affect the efficiency, cause side reactions, corrosion or lead to a degradation of the active surface. To quantify the stray currents in alkaline water electrolysis, we have developed a Python-based script that automatically creates resistance networks and implements voltage sources to account for electrochemical potential differences. To solve the model, a system of linear equations is generated by creating an incidence matrix from the network and combining it with Kirchhoff’s circuit laws. In this presentation, we would like to share the results of our analysis of the expected stray currents in commercial alkaline water electrolysis stacks using the developed model and discuss the advantages and disadvantages of different stack designs. Furthermore, we will utilize the model to optimize channel design, which, with the correct choice of length and diameter, can lead to low stray currents even under partial load. In addition, non-uniform channel and distributor parameters along the stack (e.g., multiple distributor lines, branch lines, varying lengths, and diameters) enable further reduction of stray currents compared to uniform design. An analysis and explanation of these design optimization strategies to reduce stray currents while considering pressure loss and investment cost effects will be presented in this work.