Direct-Coupled Improvement of a Solar-Powered Proton Exchange Membrane Electrolyzer by a Reconfigurable Source

This paper deals with proton exchange membrane (PEM) electrolyzers directly coupled with a photovoltaic source. It proposes a method to increase the energy delivered to the electrolyzer by reconfiguring the electrical connection of the arrays according to solar radiation. Unlike the design criterion proposed by the literature, the suggested approach considers a source obtained by connecting arrays in parallel depending on solar radiation based on a fixed photovoltaic configuration. This method allows for the optimization of the operating point at medium or low solar radiation, where the fixed configuration gives poor results. The analysis is performed on a low-power plant (400 W). It is based on a commercial photovoltaic cell whose equivalent model is retrieved from data provided by the manufacturer. An equivalent model of the PEM electrolyzer is also derived. Two comparisons are proposed: the former considers a photovoltaic source designed according to the traditional approach, i.e., a fixed configuration; in the latter, a DC/DC converter as interface is adopted. The role of the converter is discussed to highlight the pros and cons. The optimal set point of the converter is calculated using an analytical equation that takes into account the electrolyzer model. In the proposed study, an increase of 17%, 62%, and 93% of the delivered energy has been obtained in three characteristic days, summer, spring/autumn, and winter, respectively, compared to the fixed PV configuration. These results are also better than those achieved using the converter. Results show that the proposed direct coupling technique applied to PEM electrolyzers in low-power plants is a good trade-off between a fixed photovoltaic source configuration and the use of a DC/DC converter.