\label{sec:dot_power} It was decided that the power storage and delivery cannot be ground supported but has to be independent. Therefore, the cable connection to the ground was mitigated, since it is not feasible. Furthermore, nuclear powered options are also not considered any further, since they are deemed too harmful to the environment and violating the sustainable spirit of the aircraft design. The next step, the design configuration, is influenced mainly by the choice of a single or distributed power source and whether a rechargeable or non-rechargeable system is selected. Thereafter, the type of storage system, batteries, fuel cells and others, are investigated and traded off.