Glossary: Key technical terms

Mar 21, 2018

Anode: Negatively charged electrode (in the fuel cell, on the hydrogen side). The electrons flow from the anode to the consumer.

Fuel cell: Special galvanic cell that generates electricity from the chemical reaction between hydrogen and oxygen. A fuel cell consists of electrodes separated by a membrane or electrolyte (ion conductor). The fuel cell generates electric power and heat. By virtue of its high performance and efficiency, the PEM fuel cell is particularly suitable for automotive use. It has a plastic membrane as an electrolyte (PEM = Polymer Electrolyte Membrane) capable of conducting protons. Its operating temperature is around 80 degrees Celsius.

Fuel cell stack): Several fuel cells connected in series to increase the electrical voltage and put together as a sandwich construction.

Compressed hydrogen storage: Method of storing gaseous hydrogen at ambient temperature at a pressure of up to 700 bar (CGH2 = Compressed Gaseous Hydrogen).

Electrolysis: Electrochemical splitting of liquid compounds using an electrical current (example: water into hydrogen and oxygen).

Electrolyte: Medium for transporting ions - in a fuel cell this also spatially separates the reacting materials from each other. In a PEM fuel cell a special polymer membrane is used as an electrolyte (PEM = Polymer Electrolyte Membrane).

Electron: Negatively charged elementary particle. Moving electrons form an electrical current.

Ion: Positively (cation) or negatively (anion) charged particle.

Cathode: Positively charged electrode (in a fuel cell, on the oxygen side). This is where the electrons react with the oxygen and the hydrogen ions to form water.

Lithium-ion battery: Electrochemical, rechargeable voltage supply based on lithium. The advantages of lithium-ion batteries are their high energy density at a relatively low weight, their immunity to the so-called memory effect, and the low self-discharge.

Protons: Positively charged hydrogen ions.

Hydrogen (H): Smallest and lightest element in the periodic table. Hydrogen consists of a negatively charged electron and a positively charged proton. Hydrogen is the most frequently occurring element in the universe, but owing to its great reactability it occurs almost exclusively in compound form. Examples include water and hydrocarbons such as natural gas or crude oil. In its free state, hydrogen only occurs as traces in the atmosphere and in volcanic gases. Hydrogen is a colourless, odourless and tasteless gas.

Hydrogen generation: Hydrogen can be generated e.g. by fermenting biomass or the electrolysis of water. At present this energy source is mainly generated from fossil fuels, above all natural gas (by steam reformation under high pressure).