chapter  16
44 Pages

High-Temperature Electrolysis of Steam

ByJames E. O’Brien, Carl M. Stoots, and J. Stephen Herring

A basic thermodynamic analysis can be applied to a general thermal water-splitting process in order to determine the overall process efŒciency limits as a function of temperature. Consider the process diagram for thermal water splitting shown in Figure 16.1. Water enters the control volume from the left. Since the ultimate feedstock for any large-scale water-splitting operation will be liquid water, it is reasonable to consider the case in which water enters the control volume in the liquid phase at a speciŒed temperature T and pressure P, typically near ambient conditions. Pure hydrogen and oxygen streams exit the control volume on the right, also at T and P. Two heat reservoirs are available, a high-temperature reservoir at temperature TH and a low-temperature reservoir at temperature TL. Heat transfer between these reservoirs and the control volume is indicated in Figure 16.1

CONTENTS

16.1 Fundamentals ..................................................................................................................... 417 16.1.1 Thermodynamics of Thermal Water Splitting Processes ................................ 417 16.1.2 Thermodynamics of HTE ..................................................................................... 421 16.1.3 Thermal Requirements for Isothermal and Nonisothermal SOEC Operation ................................................................................................................427