(Invited) Hydrogen Generation and Compression

Abstract

Compression of hydrogen has the same importance then producing the same, since hydrogen applications require hydrogen on elevated pressure levels, however, those levels are quite divers. As hydrogen generation, also compression is possible on various ways. Next to mechanical compression, also electrochemical hydrogen compression, in the generation unit itself (direct co-compression) or in additional unit (electrochemical hydrogen compressor (EHC)), is seen as a promising alternative in the context of power-to-gas plants.This contribution summarizes the different options and lists the pro and cons of the different techniques, whereas the focus is on the electrochemical systems. It shows that the decision also depends on the application. Herein, the specific energy demand for hydrogen generation and compression is used as measure.The study analyses hydrogen generation and compression pathways using water electrolysis and hydrogen compression pathways, based on proton exchange membrane (PEM) technology, for pressures up to 1000 bar. Energy demands are systematically investigated as a function of design parameters such as pressure, current density, temperature and membrane thickness. The analysis looks deeper into the underlying reasons and intrinsic difference of one or the other pathway, considering aspects on overpotential and gas-crossover.The study shows that the water splitting process itself causes large energetic disadvantages. Also, using EHC enables design parameters to be optimized separately regarding hydrogen generation and compression, giving an important degree of freedom for system design.