The Power of Design: Product Innovation in Sustainable Energy Technologies

3.4 Fuel Cells

Frank de Bruijn

Nedstack fuel cell technology B.V., Westervoortsedijk 73, The Netherlands Energy and Sustainability Research Institute Groningen University of Groningen, Nijenborgh 4, Groningen, the Netherlands

3.4.1 Fuel Cell Principles and Characteristics

Fuel cells are electrochemical devices that convert chemical energy into electricity and heat. Like batteries, fuel cells are so-called galvanic cells: Because of a negative change in Gibbs free energy, the electrochemical reaction is a spontaneous process. The counterpart of the fuel cell is the electrolyzer, which is a forced process.

The core of the fuel cell consists of an electrolyte and two electrodes, the anode and the cathode. Oxidation takes place at the anode, and reduction at the cathode. The electrolyte separates the two electrodes, while at the same time it facilitates the transport of ions to prevent the accumulation of charge at either side of the fuel cell.

In comparison to batteries, fuel cells are open systems: A continuous feed of reactants is needed to sustain the electrochemical process, while the products have to be expelled. The increase of power density is often a combination of optimizing the activity of the electrodes, minimizing ohmic resistances, and maximizing the rate at which reactants can reach the reaction interface. A schematic drawing of a series of three cells in a fuel cell stack is shown in Figure 3.4.1, including the flows of gas, ions, and electrons.

Figure 3.4.1 Schematic ...