What is a fuel cell?
A fuel cell is an electrochemical energy conversion system that directly converts the chemical energy of a fuel (usually hydrogen) and an oxidizing agent (oxygen from the air) into electrical energy. Unlike combustion engines, this conversion occurs without combustion – producing only water, heat, and electricity. Unlike batteries, fuel cells generate energy continuously as long as fuel is supplied, without discharging.
How a Fuel Cell works
The basic principle is based on a controlled electrochemical reaction between hydrogen and oxygen with the following three main components:
- Anode (negative pole): Hydrogen is supplied here and split into protons (H⁺) and electrons (e⁻)
- Electrolyte: An ion-conducting membrane that allows only protons to pass through while blocking electrons
Cathode (positive pole): Oxygen, protons, and electrons react here to form water
Types of Fuel Cells
Fuel cells can be classified into different categories according to their electrolyte type and operating temperature. Low-temperature fuel cells include the PEMFC (Proton Exchange Membrane Fuel Cell) operating at 60-80 degrees celsius, which is primarily used in vehicles and portable systems, as well as the DMFC (Direct Methanol Fuel Cell), which uses methanol directly as fuel and is suitable for small electronic devices. The AFC (Alkaline Fuel Cell) operates with an alkaline solution and achieves high efficiency levels but is CO₂-sensitive and is mainly used in aerospace applications.
Among high-temperature fuel cells, the PAFC (Phosphoric Acid Fuel Cell) with an operating temperature of around 200 degrees celsius is particularly relevant for decentralized building power supply. The MCFC (Molten Carbonate Fuel Cell) operates at 600-650 degrees celsius with molten carbonate and is suitable for industrial combined heat and power (CHP) applications. The SOFC (Solid Oxide Fuel Cell) with ceramic solid electrolyte achieves the highest electrical efficiencies at 600-1.000 degrees celsius and offers fuel flexibility, which is why it is increasingly being used in stationary plants and for marine applications.
Advantages of Fuel Cells
Fuel cells are particularly impressive due to their environmental friendliness and high efficiency. When operating with hydrogen, no pollutants are produced at the point of use – only water vapor is released. In combination with green hydrogen from renewable energy sources, the entire energy chain is virtually carbon-neutral. The electrical efficiency of 40–60% is significantly higher than that of conventional combustion engines, and in combined heat and power applications, total efficiencies of up to 85% can be achieved. Fuel cells also operate efficiently in the partial load range.
Another advantage lies in their practical operating characteristics: fuel cells operate almost silently without mechanical vibrations and enable fast refueling times of just 3-5 minutes in mobility applications while offering large ranges of 500-700 kilometers. Their modular design makes them flexibly scalable and enables decentralized energy generation. In addition, various fuels can be used – besides hydrogen, methanol or even natural gas after appropriate reforming. This versatility makes fuel cells an attractive technology for a wide variety of applications.
Conclusion
Fuel cells represent a mature key technology for the energy transition and enable zero-emission mobility as well as decentralized energy supply with high efficiencies. Their greatest strengths lie in local emission-free operation, short refueling times, and suitability for high-energy-demand applications. While the technology itself is already market-ready, high system costs and still inadequate hydrogen infrastructure remain the central challenges for broader market penetration.
With the progressive expansion of the hydrogen economy, decreasing production costs through economies of scale, and increasing political support, the fuel cell is expected to play an important role in the future energy mix – particularly where battery-electric solutions reach their limits. This primarily concerns heavy-duty transportation, maritime shipping, stationary long-term storage, and industrial applications. Successful establishment depends largely on the availability of cost-effective green hydrogen, which fully realizes the ecological advantages of the technology.