Electrochemical System Design for Hydrogen Production and Compression

Electrochemical System Design for

Hydrogen Production and Compression

Whitney G. Colella, Ph.D., M.B.A.

Principal Research Engineer, Gaia Energy Research Institute, Arlington, Virginia, 22203

Tel: +1-650-283-2701, Email: wgc@gaia-energy-research-institute.com, web:http://www.linkedin.com/in/wgcgaia

This research discusses electrochemical system design for hydrogen production and compression.  These devices potentially could serve the current merchant hydrogen market and industrial applications, and/or a potential future hydrogen fuel cell vehicle (FCV) fleet. 

One of the most energy-efficient ways to produce hydrogen is a by-product in a tri-generative, high temperature, stationary fuel cell system (FCSs).  Such tri-generative FCSs can produce electricity, heat, and hydrogen, simultaneously, and are sometimes also referred to as hydrogen co-production FCSs (H₂-FCSs).  This research discusses the chemical engineering process plant design of H₂-FCSs.  Special attention is paid to scenarios in which H₂-FCSs are the most energy efficient and recover heat released from the electrochemical reactions in the fuel cell stack, so as to heat the endothermic steam reforming process to generate additional hydrogen.  This approach can result in a significant reduction in primary feedstock fuel consumption per unit of hydrogen and electricity produced. Compared with stand-alone steam reformers, the H₂-FCSs can consume less primary feedstock fuel per unit of hydrogen made because fuel does not need to be combusted to provide heat to the endothermic steam reforming process; electrochemical heat from the stack is used instead.  Compared with ‘plain vanilla’ FCSs that produce only electricity and heat, the H₂-FCSs can consume less primary feedstock fuel per unit of electricity, because the endothermic steam reforming process is cooling the stack, and, consequently, the stack does not need to be cooled as much by blowing additional air across the cathode.  Hence, the ancillary load from the air compressor is less.  According to modelling results, these combined benefits result in a primary feedstock fuel savings of about ~20%.  Modelling results are discussed for the H₂-FCSs to characterize how changes in input parameters (such as steam to carbon ratio, operating temperature, etc.) impact electrical and hydrogen output, and achieving neutral system water balance.

This research also discusses the potential for electrochemical hydrogen compression systems (EHCs).  EHCs consume electricity and apply this current to forcing protons (hydrogen ions (H+)) across a proton-conducting electrolyte from a low-pressure region to a high-pressure region.  The theoretical efficiency of EHCs is higher than that of mechanical piston and/or diaphragm compressors.  This work provides an overview of their thermodynamic and economic potential.