Use of fuel cell stacks to achieve high altitudes in light unmanned aerial vehicles

A study is presented to determine if substituting an internal combustion engine (ICE) by an electric motor powered by a fuel cell stack can be a viable option to increase the service ceiling of an available light unmanned aerial vehicle (UAV), extending it to 10,000 m. As a first condition, the stack has to be capable of supplying the minimum power required for horizontal leveled flight at this altitude, which is a function of the UAV total mass. A second step examines if the UAV can transport the energy required to reach the desired service ceiling without exceeding the maximum mass that can be loaded, considering that both hydrogen and oxygen have to be carried on-board. A particularly light PEM fuel cell stack is proposed as a suitable power source. A realistic system is described to store the required amount of reactant gases maintaining the mass below the allowable limits. Results indicate that with its aerodynamic characteristics, the UAV should be capable of ascending up to 10,000 m with the described fuel cell and gas storage system. Some multivariable maps that include service ceiling, total payload and required power are provided to perform this type of analysis.