Hydrogen distribution, Chapter

Chapter 12 discusses and analyses the different options for hydrogen distribution -pipelines and trailers (including liquefaction) - from a technical and economic point of view, in the same way as the hydrogen production technologies in Chapter 10. Further, different hydrogen refuelling station concepts are described and the necessity for the development of codes and standards addressed. 

To provide cathodic protection, the entire surface must remain within a specified potential range of protection. Furthermore, the current density must exceed the protection current density at each point, but it should not become too high in areas close to an anode because this could lead to excessive hydrogen formation, which could damage the coating or create a risk of hydrogen embrittlement (Chapter 11). For the design of cathodic protection systems it is therefore important to consider the various factors that influence the current and potential distributions at an electrode. 

Hydrogen bonding stabilizes some protein molecules in helical forms, and disulfide cross-links stabilize some protein molecules in globular forms. We shall consider helical structures in Sec. 1.11 and shall learn more about ellipsoidal globular proteins in the chapters concerned with the solution properties of polymers, especially Chap. 9. Both secondary and tertiary levels of structure are also influenced by the distribution of polar and nonpolar amino acid molecules relative to the aqueous environment of the protein molecules. Nonpolar amino acids are designated in Table 1.3. 

The effect of molecular interactions on the distribution coefficient of a solute has already been mentioned in Chapter 1. Molecular interactions are the direct effect of intermolecular forces between the solute and solvent molecules and the nature of these molecular forces will now be discussed in some detail. There are basically four types of molecular forces that can control the distribution coefficient of a solute between two phases. They are chemical forces, ionic forces, polar forces and dispersive forces. Hydrogen bonding is another type of molecular force that has been proposed, but for simplicity in this discussion, hydrogen bonding will be considered as the result of very strong polar forces. These four types of molecular forces that can occur between the solute and the two phases are those that the analyst must modify by choice of the phase system to achieve the necessary separation. Consequently, each type of molecular force enjoins some discussion. 

Studies of the electron distributions around outer atoms consistently show that hydrogen is always associated with two electrons (one pair). All other outer atoms always have eight electrons (four pairs). The reason for this regularity is that each atom in a molecule is most stable when its valence shell of electrons is complete. For hydrogen, this requires a single pair of electrons, enough to make full use of the hydrogen 1 S orbital. Any other atom needs four pairs of electrons, the maximum number that can be accommodated by an .S p valence shell. Details of these features can be traced to the properties of atoms (Chapter 8) and are discussed further in Chapter 10. 

An area-wide supply of hydrogen will, in the medium to long term, require the implementation of an extensive transport and distribution infrastructure. In addition, a dense network of refuelling stations will have to be put in place. This chapter first addresses the various options for hydrogen transport and their characteristics. Subsequently, different fuelling station concepts will be discussed. 

For the limitations of this publication, it is not possible to present a comprehensive set of the data used as input to the model. In principle, the model is based on the technoeconomic characteristics of hydrogen production and distribution technologies, as presented in Chapters 10 and 12, respectively, such as specific investments for certain plant sizes, full load hours, process efficiencies, maintenance and labour costs, etc. 

---