Thermal and Electrochemical Performance of a High-Temperature Steam Electrolysis Stack Page: 2 of 5
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Thermal and Electrochemical Performance of a High-Temperature Steam
Electrolysis Stack
J. O'Brien', C. Stoots', J. Herring', G. Hawkes', J. Hartvigsen2
'Idaho National Laboratory, Idaho Falls, ID
2Ceramatec, Inc., Salt Lake City, UT
INTRODUCTION
Currently there is strong interest in the large-scale production of hydrogen from non-fossil sources.
This interest is driven by the immediate demand for hydrogen for refining of increasingly low-
quality petroleum resources, the expected intermediate-term demand for carbon-neutral synthetic
fuels, and the possible long-term demand for hydrogen as an environmentally benign transportation
fuel [1, 2]. Currently hydrogen is produced primarily via steam reforming of methane. From a
long-term perspective, alternatives to methane reforming are sought for large-scale production of
hydrogen as a major energy carrier since such fossil fuel conversion processes consume non-
renewable resources and emit greenhouse gases to the environment. Consequently, production of
hydrogen from water splitting via either electrolytic or thermochemical processes is under
consideration. The hydrogen production efficiency of any thermal water-splitting process increases
with temperature, so high-temperature operation is desirable.
Development of advanced high-temperature nuclear reactors could enable high-efficiency large-
scale hydrogen production, with no consumption of fossil fuels, no production of greenhouse gases,
and no other forms of air pollution. High-temperature electrolytic water-splitting supported by
nuclear process heat and electricity has the potential to produce hydrogen with high overall system
efficiencies similar to those of the thermochemical processes, but without the corrosive conditions
of thermochemical processes and without the fossil fuel consumption and greenhouse gas emissions
associated with hydrocarbon processes. Specifically, a high-temperature advanced nuclear reactor
coupled with a high-efficiency power cycle and a high-temperature electrolyzer could achieve
competitive thermal-to-hydrogen conversion efficiencies of 45 to 55% at 8500C.
A research program is under way at the Idaho National Laboratory (INL) to simultaneously address
the research and scale-up issues associated with the implementation of solid-oxide electrolysis cell
technology for hydrogen production from steam. We are conducting a progression of electrolysis
stack testing activities, at increasing scales, along with a continuation of supporting research
activities in the areas of materials development, single-cell testing, detailed computational fluid
dynamics (CFD) and systems modeling. This paper will present recent experimental results
obtained from testing of planar solid-oxide stacks operating in the electrolysis mode. The
hydrogen-production and electrochemical performance of these stacks will be presented, over a
range of operating conditions. In addition, internal stack temperature measurements will be
presented, with comparisons to computational fluid dynamic predictions.
EXPERIMENTAL APPARATUS
A schematic of the electrolysis stack-testing apparatus is presented in Fig. 1. Inlet gas flow rates of
nitrogen, hydrogen and air are established and maintained by means of precision mass-flow
controllers. Nitrogen is used as an inert carrier gas. Hydrogen is included in the inlet flow (5-10%
by volume) as a reducing gas in order to help prevent oxidation of the Nickel cermet electrode
material. The nitrogen / hydrogen gas mixture is mixed with steam by means of a humidifier. The
dewpoint temperature of the nitrogen / hydrogen / steam gas mixture exiting the humidifier is
monitored continuously using a precision dewpoint sensor. Another dewpoint sensor is located
downstream of the electrolysis stack, providing an independent measurement of the steam
consumption and corresponding hydrogen production rate. Since the vapor pressure of the water
and the resulting partial pressure of the steam exiting the humidifier are determined by the water
bath temperature, the water vapor mass flow rate is directly proportional to the carrier gas flow rate
for a specified bath temperature. Also, since the nitrogen and hydrogen flow rates are fixed by the
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
O'Brien, J.; Stoots, C.; Hawkes, G. & Hartvigsen, J. Thermal and Electrochemical Performance of a High-Temperature Steam Electrolysis Stack, article, November 1, 2006; [Idaho Falls, Idaho]. (https://digital.library.unt.edu/ark:/67531/metadc884476/m1/2/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.