Aircraft manufacturers are increasingly exploring emission-free flight or emission reduction for larger passenger aircraft. The low energy density of state-of-the-art battery technology limits the application to small, electric, fixed wing aircraft up to a flight time of approximately one hour. To overcome these limits, a combination of fuel cells and batteries to exploit the benefits of battery power density and hydrogen energy density was studied. Current Lithium-Ion battery cells reach approximately 1.6 kW/kg of maximum power density, much higher than fuel cell systems. On the other hand, the energy storage capacity of suitable hydrogen storage methods is much larger than battery cells, the latter have an energy density of 240 Wh/kg.

Because most demonstrated applications are for fixed wing aircraft, the unmanned GeoCopter GC-201 helicopter was used for performance requirements, weight and volume analysis. The study focuses on the preliminary sizing of the powertrain and the optimization of fuel cell and mission profile variables for this vehicle. Helicopter performance modelling, fuel cell static behavior as well as a battery discharge simulation are combined with lower fidelity models for other components.

The study results in a comparison of battery-only and fuel cell-battery configurations through payload-range diagrams, allowing for a quick evaluation of application areas. These mainly show that batteries excel at high payload, low range applications whereas a fuel cell-battery combination shows clear advantages at low payload, longer range applications. Liquid hydrogen will be shown to be comparable to the current micro gas turbine powered rotorcraft, with 400 and 500 km range capabilities respectively. Range capabilities for 300 bar and 700 bar compressed gas tank storage options show 140 and 180 km, with battery-only reaching a maximum range of 80 km.

Following in the footsteps of the automotive industry with the successful implementation of Formula E, the E-SPARC design is the world’s first all-electric racing aircraft. E-SPARC’s mission is to proof the feasibility of a sustainable and high performance alternative for the current state-of-the-art in aerobatic racing. Thereby, the aim is to present a design worthy of competing in the popular Red Bull Air Races. Given the combination of being the world’s fastest growing international motorsport with the commitment towards reducing the carbon footprint [1], Red Bull Air Races provide the optimal platformfor the E-SPARC design. The leading design question is therefore whether an all-electric racing aircraft can be designed with performance characteristics equal to or exceeding the performance characteristics of the current competition. This report describes the design decisions and outcomes taken during the preliminary design phase, continuing upon the pusher canard configuration that was selected during the conceptual design phase...