(128c) 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.