Randomly firing jet arrays can be used for large-scale electrodeposition from dilute solutions for which tertiary current distribution prevails, for example, the electrodeposition of Cu-In-Se layers, which are promising compounds for thin-layer solar devices. For this type of electrodeposition, a stirring system is needed to enhance the mass-transfer rate toward the cathode. The studied stirring system is a modular jet array firing in the horizontal direction, submerged in the tank containing the electrolyte. A dilute Cu electrolyte was used to investigate and optimize the hydrodynamic conditions determined by the stirring system. Two parameters were investigated to vary the hydrodynamic conditions: the mesh of the jet nozzles and the distance between the jet nozzles and the cathode. An optimized configuration was found, allowing the jets to merge and create a homogeneous tertiary distribution. Random sequential activation of the jets was used with the optimized configuration, and the resulting copper layer exhibited higher homogeneity than those resulting from continuous activation of the jets. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3208057] All rights reserved.