# Selected Aspects of Designing Modular PEMFC Stacks as Power Sources for Unmanned Aerial Vehicles
## 4 Conclusions  
The study provides an analysis of the feasibility of constructing multimodule power sources containing fuel cell stacks for supplying power to the electric motor and on-board equipment of an unmanned aerial vehicle. The 2-kW PEMFC stack consisted of two 1-kW PEMFC modules electrically connected in parallel. It was found that, according to the assumed electrical operation parameters in the propulsion unit, the nominal power output P\({}_{\mathrm{nom}}\) corresponded to the following pair of electrical parameters: I = \(\sim\)75 A, U = \(\sim\)28 V. Direct comparison of the electrical parameters of the 2-kW two-module PEMFC stack compared to those of the 2-kW single-module PEMFC stack indicated that construction of these power sources in modular forms enabled the acquisition of greater current density as well as a reduced need for power to supply fans and reduced hydrogen consumption. The feasibility of integrating the two-module PEMFC stack into a propulsion unit involving a BLDC electrical engine connected with a propeller was demonstrated. All of these features are important for applications and can serve as alternative solutions. A 500-W three-module PEMFC stack was designed, constructed, and tested. This stack was also characterized by electrical power output suited to the required electrical system of the BOP. Investigations of the performance of the designed hybrid power source, i.e., the 500-W PEMFC stack with an electrical battery, were also performed. The durability of the 500-W PEMFC stack was also discussed and demonstrated. Special attention was devoted to the safe operation of  
Figure 23: The waveform of electrical power (P) vs. time recorded during the operation of servomechanisms powered directly from the electric power source involving a 500-W modular PEMFC fuel cell stack.  
power sources involving hydrogen, based on redundancy, control monitoring parameters, and easier operation despite the existence of some defaults. It was concluded that the use of modular fuel cell stacks makes it possible to construct power sources adjusted to the electrical loads required for energy systems used aboard unmanned aerial vehicles.  
M.D.: conception of the paper, writing, original draft preparation, supervision and interpretation of experimental parts, contributions to all experimental parts, resources, data curation; B.L.: design and construction of modular PEMFC stacks, electrical measurements of the power sources described in the paper, graphs; A.R.: contributions to electrical measurements, analysis of cooling system, data curation; M.K. ([PERSON]): construction of PEMFCs, electrical measurements, data curation, preparation of graphs; M.K. ([PERSON]): project leader, supervision, contributions to all experimental parts. All authors have read and agreed to the published version of the manuscript.  
The National Centre for Research and Development, Warsaw, Poland, No. INNOLOT/I/3/NCBR/2013 HYBRIDIVE--\"Technology of hybrid power package for powering light or unmanned aerial vehicles\".  
Not applicable.  
It does not apply to this work.  
The study received support as part of the sector project INNOLOT HYBRIDIVE --\"Technology of hybrid power package for powering light or unmanned aerial vehicles\". Part of the research was conducted using the research infrastructure of the Centre of Energy of the AGH University of Science and Technology.  
The authors declare no conflict of interest.