Continuing the work from previous projects, I have developed this prototype from scratch (except for the fuel cell stacks): a fuel cell system designed as a range extender for a small rover. The purpose of the rover is to evaluate this technology and to semi-autonomously reach predefined waypoints, making it an excellent platform for testing additional UAV-related technologies such as flight controllers, GNSS antennas, and batteries.

                                             Figure 1. Rover architecture  schematics

The rover integrates multiple telemetry systems. One system uses MAVLink to command the rover, leveraging the ArduPilot suite, while a separate WiFi-based system collects real-time data from the fuel cell stack. This second telemetry system interfaces with LabVIEW (Community Edition) and an Arduino Nano ESP32, which handles fine control of the fuel cell.

As mentioned in previous projects, a fuel cell is an electrochemical device that converts a fuel — in this case, hydrogen and air — into water vapor, heat, and electricity. There are several types of fuel cells based on their operating temperatures. Low-temperature fuel cells include Proton Exchange Membrane Fuel Cells (PEMFC), which are used in this project. In PEMFCs, a membrane separates the anode and cathode, conducting H⁺ ions. Other types include Alkaline Fuel Cells (AFC), which exchange OH⁻ ions through an alkaline electrolyte, separated either by a diaphragm or an anionic membrane. AFCs were extensively used in space applications like the Apollo missions (whereas Gemini missions interestingly used PEM cells).

High-temperature fuel cells, such as High-Temperature PEM (HT-PEM) and Solid Oxide Fuel Cells (SOFCs), operate at temperatures exceeding 100°C and 800°C respectively. SOFCs, with their ceramic-metal (Cermet) electrolytes, are particularly interesting for cogeneration applications and better performance.

                                                 Figure 2. Figure 2. PEM fuel cell overview

For this project, several PEM stacks were combined to form the range extender. Each stack was independently characterized by generating voltage-current (polarization) curves using a custom-built test bench that utilized Arduino Nano and LabVIEW for serial communication. From these curves, simple models were created to simulate the behavior of the stacks, aiding in system design and optimization.

                         Figure 3.  PEM Stack on test bench with model correlation

The stacks were upgraded and controlled to deliver a nominal combined output of 5W, with optimized airflow and hydrogen purging strategies, managed by the Arduino Nano ESP32. One of the most exciting features was the integration of WiFi telemetry using a Ublox patch antenna, providing real-time monitoring with low power consumption. A DC/DC converter was installed at the fuel cell output to stabilize the voltage at 12V, ensuring compatibility with the rover’s battery management system (BMS).

                                                Figure 4. Fuel cell range extender architecture

To integrate the control systems and fuel cells, a PLA housing was designed and 3D printed, miniaturizing the entire assembly into a robust, real-world working module but miniturized.

                                              Figure 5.  Video of range extender assembly and first test