HydroBot is a demonstration platform that showcases the practical application of fuel cells. Its drive concept corresponds to that of commercial fuel cell vehicles.
The Helmholtz-Institute Erlangen-Nürnberg for Renewable Energy (HI ERN) investigates electrochemical energy converters such as fuel cells and water electrolyzers, which can help to store and release energy from renewable sources. Researchers from the department of Electrocatalytic Interface Engineering focus primarily on single fuel cells and water electrolysis cells, which must be better understood and require further development to enable cost-efficient and long-term stable devices.
However, these single cells cannot operate independently. They are investigated in detail in complex test systems in everyday research. Yet, in doing so, one can easily lose sight of the big picture:
What is actually needed to move from a single hydrogen fuel cell in the research lab to a vehicle that allows emission-free propulsion using fuel cells?
The HydroBot showcases the practical application of fuel cells.
Development of a demonstration platform
With this question in mind, researchers at HI ERN developed HydroBot. This demonstration platform is a remote-controlled robot whose drive concept has been designed analogously to commercial fuel cell vehicles: A hydrogen fuel cell converts chemical energy stored in gaseous hydrogen into electrical current, which in turn is used to supply the vehicle’s electronics and motors with energy.
HydroBot is intended to serve as demonstration material for the practical use of fuel cells for both students and doctoral candidates at HI ERN, as well as interested members of the public from outside the institute. For this reason, the project will be presented at the Long Night of Science 2025 in the three cities of Nuremberg, Fürth, and Erlangen, among other venues.
A fuel cell is an electrochemical energy converter that converts chemical energy from a fuel such as hydrogen into electrical energy, i.e., it generates electricity. However, a single fuel cell delivers a voltage of less than 1 V, less than that of a conventional AA battery. Therefore, several cells must be connected in series to form a so-called stack to generate usable voltages, similar to battery-powered electrical appliances that require more than one battery cell, or battery packs in e-bikes and e-cars.
What is required to operate a fuel cell?
In addition to the stack, which consists of individual cells connected in series, a fuel cell requires several other components for operation: The gaseous hydrogen must be stored safely and fed into the stack in a controlled manner, the stack must be actively cooled during operation, and the fuel cell must be monitored and controlled. These functions require both the appropriate electronics and an external power source, because the electronics must be supplied with energy before the fuel cell is started, i.e., before the fuel cell can provide energy.
Why does a fuel cell vehicle contain a buffer battery?
Although fuel cells can adapt quickly to changing loads, it is helpful to use a buffer battery to deliver the required power peaks during rapid acceleration. Hence, the size of the fuel cell can be reduced so that it only needs to provide the average power required for the vehicle. The fuel cell charges the battery at low loads, and the battery can provide additional energy to cover peak loads when needed. The buffer battery also serves as an external power source to start the fuel cell safely. In addition, using a buffer battery enables energy to be stored during braking. Since a fuel cell can only generate electricity but not store it, the fuel cell vehicle benefits from the electric drive’s regenerative braking (recuperation). Thus, by appropriately dimensioning the fuel cell and battery, it is possible to achieve an energy supply system that is as space- and weight-saving as possible and optimized in terms of efficiency and cost.
What is the goal of the HydroBot project?
HydroBot aims to illustrate the general concept behind a fuel cell vehicle as clearly as possible. To this end, the robot uses a 60 W stack from Horizon Educational as its fuel cell, which is supplied with hydrogen from metal hydride storage cartridges. This fuel cell is integrated into the robot’s on-board power supply system using custom-built electronics. A 12.8 V lithium iron phosphate battery is the buffer battery and defines the vehicle’s on-board voltage. HydroBot uses so-called Mecanum wheels for propulsion. These enable four-wheel drive with special wheels that allow the car to turn on the spot and drive in any direction without conventional steering to change the wheel angle. Four brushed DC electric motors drive the wheels.
How does HydroBot allow a look behind the scenes?
HydroBot is controlled using an in-house developed remote control, which allows users to monitor the relevant sensor data for the battery and fuel cell and to switch the fuel cell on and off at the touch of a button, enabling HydroBot to clearly demonstrate how fuel cells and batteries are interconnected to power an electric vehicle. The documentation of the robot is freely accessible, allowing interested parties to look at the details and enabling further developments on this platform at any time.
