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The fuel cell

In a fuel cell, an electrochemical process converts hydrogen and oxygen into electricity. The only waste product released by this is water. A fuel cell can be compared to a battery, but it is not a closed system. Because hydrogen and oxygen are fed in continuously, a fuel cell can produce a continuous supply of electricity, The electricity is used for driving an electric motor, which moves the vehicle. The electricity can be stored in a battery, of course.

A fuel cell contains two electrodes. Hydrogen is supplied to one (the anode), and oxygen to the other (the cathode). The electrodes are separated by an electrolyte, which carries the electrical charge through the cell. Hydrogen electrons are released at the anode, generating approximately 0.7 volts. A fuel cell also contains grooves, just a few millimetres deep, that help convey the hydrogen and oxygen to the electrodes better. The amount of electricity is increased by linking a series of these cells together, into what is called a fuel cell stack. The dimensions of a stack can vary, depending on the power required.

There are different types of fuel cell, usually named after the type of electrolyte used in them. There are polymer electrolyte fuel cells (PEMFC), direct methanol fuel cells (DMFC), alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC). The electrochemical process occurs at a high or a low temperature, depending on the type of electrolyte.

A catalyst is used to speed up the chemical reactions in a fuel cell. This is particularly important in low-temperature fuel cells. Platinum is the catalyst most often used in DMFC and PEMFC types. Extremely pure oxygen (with a low carbon monoxide concentration) is used in order to get the catalyst to work properly.

The type of fuel cell most commonly used in the automobile industry is based on the polymer electrolyte membrane (PEM) fuel cell. A PEM fuel cell works at low temperatures and uses pure hydrogen. The PEM fuel cell used in the HyMove bus is supplied by NedStack and generates 30 kW of power.

Hydrogen can be used in an internal combustion engine in any case, but technical modifications to the engine and the vehicle are required because of the properties of the gas. The efficiency of a fuel cell is higher and, in contrast to an engine, it makes scarcely any noise.