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Title: Renewable hydrogen production via thermochemical/electrochemical coupling

Abstract

A coupled electrochemical/thermochemical cycle was investigated to produce hydrogen from renewable resources. Like a conventional thermochemical cycle, this cycle leverages chemical energy stored in a thermochemical working material that is reduced thermally by solar energy. However, in this concept, the stored chemical energy only needs to be partially, but not fully, capable of splitting steam to produce hydrogen. To complete the process, a proton-conducting membrane is driven to separate hydrogen as it is produced, thus shifting the thermodynamics toward further hydrogen production. This novel coupled-cycle concept provides several benefits. First, the required oxidation enthalpy of the reversible thermochemical material is reduced, enabling the process to occur at lower temperatures. Second, removing the requirement for spontaneous steam-splitting widens the scope of materials compositions, allowing for less expensive/more abundant elements to be used. Lastly, thermodynamics calculations suggest that this concept can potentially reach higher efficiencies than photovoltaic-to-electrolysis hydrogen production methods. This Exploratory Express LDRD involved assessing the practical feasibility of the proposed coupled cycle. A test stand was designed and constructed and proton-conducting membranes were synthesized. While the full proof of concept was not achieved, the individual components of the experiment were validated and new capabilities that can be leveraged by amore » variety of programs were developed.« less

Authors:
 [1];  [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1398866
Report Number(s):
SAND-2017-10656R
657484
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN

Citation Formats

Ambrosini, Andrea, Babiniec, Sean Michael, and Miller, James E. Renewable hydrogen production via thermochemical/electrochemical coupling. United States: N. p., 2017. Web. doi:10.2172/1398866.
Ambrosini, Andrea, Babiniec, Sean Michael, & Miller, James E. Renewable hydrogen production via thermochemical/electrochemical coupling. United States. doi:10.2172/1398866.
Ambrosini, Andrea, Babiniec, Sean Michael, and Miller, James E. 2017. "Renewable hydrogen production via thermochemical/electrochemical coupling". United States. doi:10.2172/1398866. https://www.osti.gov/servlets/purl/1398866.
@article{osti_1398866,
title = {Renewable hydrogen production via thermochemical/electrochemical coupling},
author = {Ambrosini, Andrea and Babiniec, Sean Michael and Miller, James E.},
abstractNote = {A coupled electrochemical/thermochemical cycle was investigated to produce hydrogen from renewable resources. Like a conventional thermochemical cycle, this cycle leverages chemical energy stored in a thermochemical working material that is reduced thermally by solar energy. However, in this concept, the stored chemical energy only needs to be partially, but not fully, capable of splitting steam to produce hydrogen. To complete the process, a proton-conducting membrane is driven to separate hydrogen as it is produced, thus shifting the thermodynamics toward further hydrogen production. This novel coupled-cycle concept provides several benefits. First, the required oxidation enthalpy of the reversible thermochemical material is reduced, enabling the process to occur at lower temperatures. Second, removing the requirement for spontaneous steam-splitting widens the scope of materials compositions, allowing for less expensive/more abundant elements to be used. Lastly, thermodynamics calculations suggest that this concept can potentially reach higher efficiencies than photovoltaic-to-electrolysis hydrogen production methods. This Exploratory Express LDRD involved assessing the practical feasibility of the proposed coupled cycle. A test stand was designed and constructed and proton-conducting membranes were synthesized. While the full proof of concept was not achieved, the individual components of the experiment were validated and new capabilities that can be leveraged by a variety of programs were developed.},
doi = {10.2172/1398866},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month =
}

Technical Report:

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  • Hydrogen fuel is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world's hydrogen is currently derived from fossil fuels through some type of reforming processes. Nuclear hydrogen production is an emerging and promising alternative to the reforming processes for carbon-free hydrogen production in the future. This report presents the main results of a research program carried out by a NERI Consortium, which consisted ofmore » Penn State University (PSU) (lead), University of South Carolina (USC), Tulane University (TU), and Argonne National Laboratory (ANL). Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. While previous studies have identified over 200 possible thermochemical cycles, only a few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes. The Cu-Cl cycle has a significant advantage over other cycles due to lower temperature requirements – around 530 °C and below. As a result, it can be eventually linked with the Generation IV thermal power stations. Advantages of the Cu-Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input). Other advantages include common chemical agents and reactions going to completion without side reactions, and lower demands on materials of construction. Three university research groups from PSU, USC, and TU as well as a group from ANL have been collaborating on the development of enabling technologies for the Cu-Cl cycle, including experimental work on the Cu-Cl cycle reactions, modeling and simulation, and particularly electrochemical reaction for hydrogen production using a CuCl electrolyzer. The Consortium research was distributed over the participants and organized in the following tasks: (1) Development of CuCl electrolyzer (PSU), (2) Thermodynamic modeling of anolyte solution (PSU), (3) Proton conductive membranes for CuCl electrolysis (PSU), (4) Development of an analytical method for online analysis of copper compounds in highly concentrated aqueous solutions (USC), (5) Electrodialysis as a means for separation and purification of the streams exiting the electrolyzer in the Cu-Cl cycle (USC), (6) Development of nanostructured electrocatalysts for the Cu-Cl electrolysis (USC), (7) Cu-Cl electrolyzer modeling (USC), (8) Aspen Plus modeling of the Cu-Cl thermochemical cycle (TU), (9) International coordination of research on the development of the Cu-Cl thermochemical cycle (ANL). The results obtained in the project clearly demonstrate that the Cu-Cl alternative thermochemical cycle is a promising and viable technology to produce hydrogen efficiently.« less
  • Water decomposition cycles, of the hybrid type, involving an electrochemical cell producing hydrogen, and an oxide, and a subsequent thermochemical process loop which liberates oxygen and regenerates the lower oxide (or metal), are evaluated. A prototype cycle based on the oxides of lead: H/sub 2/O + PbO H/sub 2/ + PbO/sub 2/ (electrolysis) PbO/sub 2/ PbO + /sup 1///sub 2/O/sub 2/ (thermal decomposition) is presented. In principle, such cycles would allow the positive characteristics of conventional water electrolysis and those of thermochemical water-splitting cycles to be exploited to give higher enegy efficiencies. An equation correlating the energy efficiency to severalmore » of the process operating parameters has been developed. The calculated efficiencies of 28 percent to 46 percent for the hybrid cycles compare favorably to the 20 percent to 25 percent range for conventional water electrolysis. The hybrid processes are proported to offer comparable energy efficiencies to the thermochemical cycles. However, the hybrid processes offer increased flexbility since many reactions can be performed in electrolysis which could not ordinarily be accomplished by thermal means. Less difficult separations and fewer corrosion problems may be additional advantages offered by hybrid cycles. Certain physical and economic limitations of hybrid cycles are identified and discussed. The major problems facing the hybrid processes are the short supply and expense of the reactant material, high solubility of the anodic reactant (or product), incomplete reactions, difficult material handling, poor heat exchange characteristics, and difficult filtration due to degradation of the solid material. Although the hybrid cycles presented in this study are theoretically equal or superior to the other methods for water decomposition, their technological feasibility and economic promise are, nevertheless, not sufficient to contemplate their practical implementation.« less
  • This assessment was prepared to determine what impacts would result from (further) materials research for thermochemical hydrogen production. In this context, materials are those materials of construction that would be used for plant equipment such as heat exchangers, reactors, and the like. Process chemicals and catalysts are not within the scope of this study.
  • The Thermochemical Hydrogen Program at the Los Alamos Scientific Laboratory is continuing its investigation of practical schemes to decompose water thermochemically for production of hydrogen. Current efforts were directed to experimental studies of reactions relevant to the sulfuric acid-hydrogen bromide thermochemical cycle. The use of insoluble bismuth sulfate as a means of concentrating aqueous sulfuric solutions is also under investigation. Preliminary calculations show a significant cycle efficiency increase if solid sulfate and subsequent sulfur trioxide decomposition steps replace the sulfuric acid concentration and decomposition steps proposed in other cycles.
  • This study examines the energy resources required to produce 4-10 million metric tonnes of domestic, low-carbon hydrogen in order to fuel approximately 20-50 million fuel cell electric vehicles. These projected energy resource requirements are compared to current consumption levels, projected 2040 business as usual consumptions levels, and projected 2040 consumption levels within a carbonconstrained future for the following energy resources: coal (assuming carbon capture and storage), natural gas, nuclear (uranium), biomass, wind (on- and offshore), and solar (photovoltaics and concentrating solar power). The analysis framework builds upon previous analysis results estimating hydrogen production potentials and drawing comparisons with economy-wide resourcemore » production projections« less