good-to-know
A brief guide: How the Flying Fuel Cell™ works
The FFC does not produce any emissions of CO2 or NOx or particulates. Since its only emission is water, this propulsion concept is virtually emissions-free.
06.2022 | author: Isabel Henrich | 3 mins reading time
author:
Isabel Henrich
studied political science and communications. At MTU, she coordinates the editorial process of AEROREPORT and is responsible for the conception and development of its content.
What is the Flying Fuel Cell™?
The Flying Fuel Cell™ (FFC) is an MTU propulsion concept in which hydrogen and oxygen from the air react within a fuel cell to form water, thereby releasing electric energy. A highly efficient electric motor then uses this energy to drive the propellor via a gearbox.
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What are the benefits of the FFC?
This propulsion system does not produce any emissions of CO2, NOx or particulates—its only emission is water. In this way, the FFC reduces the climate impact of aviation by as much as 95 percent—i.e., to virtually zero. And since the propeller is then the sole source of noise, the Flying Fuel Cell will also help achieve massive noise reductions.
The core of the system is the fuel cell stacks. The electrochemical conversion of hydrogen into electricity is highly efficient. Moreover, the electrochemical reaction takes place under considerably cooler conditions than conventional combustion. While this fact clearly calls for an efficient cooling system, it also makes things a little simpler, for example regarding the choice of materials and integration options. The platinum used in the fuel cell is highly recyclable— when processed properly, it and other metals can be reused almost indefinitely. Also, this energy conversion takes place in the stacks, effectively without moving parts.
What components go into the FFC?
The core components of a high-performance flying fuel cell system are the stacks and an intelligent integration of all lines.
Wie ist die FFC aufgebaut?
- Fuel cell stacks: Conversion of hydrogen and oxygen into water and electrical energy.
- LH2-Tank: Storage and supply of liquid hydrogen for the electrochemical process in the fuel cell. Liquid hydrogen is converted into gaseous hydrogen and then sent to the hydrogen line.
- Hydrogen line: Conditions the gaseous hydrogen coming from the LH2 tank system to give it the appropriate temperature, desired pressure and ideal humidity before conversion in the fuel cell stacks.
- Heat exchangers: Serve to dissipate heat so as not to exceed the permissible temperature in the fuel cell and all subsystems.
- Air line: Streams of air are directed precisely to where they can provide the necessary oxygen for the electrochemical reaction. The air line, too, must supply air to the stacks at the appropriate pressure, temperature and humidity.
- Power line: Takes the electrical energy from the fuel cell stacks and converts it into mechanical energy using a motor control unit (MCU) and an electric motor. The power line is also a separate network that supplies all of the system’s electrical consumers.
- Cooling line: All equipment is cooled or heated depending on the flight phase and the flight conditions in order to optimize system thermodynamics and aircraft energy management. The heat is regulated in the system by way of a cooling liquid and the smart interconnection of devices. The excess heat is then released to the outside air through a heat exchanger.
- Electric motor: Converts electrical energy from the fuel cell into mechanical energy and is part of the power line.
- Propeller: Converts mechanical energy from the electric motor into thrust.
- Control line: The control line is almost invisible, but it is a key to success with the FFC, because it ensures the intelligent interaction of all components in all phases of flight. The control line is the system’s brain. It combines all sensors, data and actuators to form a perfectly harmonious orchestra.
How does the fuel cell work?
Each fuel cell contains two plate-shaped electrodes (anode and cathode). At the anode, hydrogen molecules (H2) release electrons to become positively charged hydrogen ions (H+). The free electrons flow as usable electricity via a conductor to the cathode, where they join with oxygen atoms to form negative oxygen ions (O2-).
The hydrogen ions combine with the oxygen ions at the cathode to form water while releasing heat.
Where can the FFC be used?
The FFC is set to be deployed soon on short-haul routes in regional air traffic. The next-generation FFC is set to be in operation on short- and medium-haul routes, further reducing the climate impact of commercial aviation.
How is the FFC being developed?
MTU is developing the FFC technology as a highly integrated system using state-of-the-art development methods and tools. In addition to technology development, MTU is collaborating with DLR to fly a Do228 as a technology platform and flight demonstrator. The goal is to replace one of the two conventional gas-turbine engines with a 600 kW electric powertrain, with energy supplied by a hydrogen-powered fuel cell. The partners are aiming for this flying lab to complete its first flight by mid-decade. This will be preceded by extensive ground tests and preliminary trials.
MTU’s job is to develop the entire hydrogen-powered fuel cell powertrain, including the liquid hydrogen fuel system and control functions. DLR is heading the Do228 research project, providing the research aircraft and performing the flight experiments. The research center is also responsible for integrating the powertrain into the aircraft.
While this work is going on, MTU is drawing up certification requirements in conjunction with the European Union Aviation Safety Agency (EASA). This involves exploring potential ways of certifying a Flying Fuel Cell™ in the future; new standards, certification guidelines and verification methods must be defined to ensure safe operation of the new Flying Fuel Cell™ propulsion concept.
