The diffusion potential differences established between two laminar flows of electrolyte solutions of different concentrations are exploited to generate an electric current. It is shown that when a single redox couple is present in two flowing electrolyte solutions, the diffusion potential difference can induce a redox reaction at electrodes placed on the opposite walls of the cell, the electrical current being extracted in an external circuit. This hydro-voltaic cell operates solely on a salt concentration gradient and a hydrodynamic flow. In this work, we have investigated the influence of the salt concentration gradient and the concentration of the redox couple on the generated power. (C) 2003 Elsevier Science B.V. All rights reserved.