The aim of this project was the experimental and theoretical investigation of gas purity in alkaline water electrolysis under increased system pressures and relevant operating conditions. For this purpose, both stationary and dynamic experiments were carried out by varying the current density, the system pressure, the electrolyte concentration, the electrolyte volume flow and the electrolyte guidance concepts to evaluate the product gas quality and the system behavior. With the help of these experimental results, it was possible to extend an existing process engineering model for alkaline water electrolysis to include the dynamics and the influence of pressure, thus enabling the evaluation of dynamic operating concepts to extend the partial load range of alkaline water electrolysers. It was found that the electrolyte feed has a very large influence on the resulting product gas quality. Both alternating operation between mixed and separate electrolyte circuits and a reduced electrolyte volume flow were target-oriented concepts for reducing gas contamination during partial load operation. In addition, in collaboration with other European research institutes and a material manufacturer, pre-commercial separators were compared with the current state of the art in terms of product gas permeability and ohmic voltage losses. For this purpose, both physical and electrochemical tests were carried out with the materials. This study has shown that thin separators are a good alternative for classic alkaline water electrolysis, as the cell voltage can be significantly reduced, which can save operating costs in the form of electricity costs.