Mark C. Thies, Ph.D., P.E. -- Research Activities

Producing Hydrogen “Carbon Free” by the Splitting of Water

Ironically, most hydrogen today is produced by using the very fossil fuels that we are trying to replace.  But we can also produce hydrogen by splitting water into its two elements, hydrogen and oxygen.  The trick is to find the most energy-efficient manner for carrying out that splitting process.  Proposed "thermochemical processes" have the potential to be much more efficient – and far more amenable to scale-up for the large-scale production of hydrogen – than classic electrolysis, which uses an electric current to split the water.  Thermochemical cycles use coupled chemical reactions to indirectly split the water, and heat input via nuclear or solar power has been proposed – thus eliminating the production of any greenhouse gases.  A truly clean fuel for transportation could become a reality. 

One of the leading international candidates from the 100+ proposed thermochemical cycles for the production of hydrogen via water splitting is the sulfur-iodine (S-I) cycle (See Fig. 1).  However, this cycle involves complex, highly nonideal phase behavior that is poorly understood, so performance projections and efficiency calculations are currently being made with little confidence.  Therefore, the Department of Energy has identified thermodynamic measurements and physical property models for the S-I cycle as a basic research need for the Hydrogen Economy.  To this end, Prof. Thies and his research team have been awarded an $856,000 grant from DOE to carry out this research effort, so that the true potential of the S–I cycle can be assessed.

Fig. 1.  The Sulfur-Iodine Cycle for splitting water to produce hydrogen and oxygen.

The work in this project is divided into three focus areas: Thermodynamic Measurements, Physical Properties Modeling, and Process Modeling.  In a unique integrated approach between Clemson University, the University of Virginia, and Savannah River National Laboratory, initial properties and process modeling efforts are being used as a guide for the selection of high-priority phase-equilibrium measurements.  As measurements of the system become available, property models for the system will be refined and provided to the process modeling effort.  Lastly, updated process modeling results will be used to identify additional experiments that are most crucial for minimizing any remaining process uncertainties. 

Fig. 2.  Continuous-flow apparatus for experimental phase-behavior measurements.

Related Presentations and Publications

O’Connell, J. P.; Murphy, J.; Gorensek, M.; Thies, M.; Crosthwaite, J. Thermodynamic Analysis and Properties Modeling of the S–I Process for Massive Hydrogen Production. PPEPPD 2007 [CD-ROM]; Hersonissos, Crete, Greece, May 2007, paper HYD1.

Crosthwaite, J. M.; Edling, M. A.; Thies, M. C. Liquid-Liquid Equilibrium Measurements for the Sulfur-Iodine Cycle: the Iodine-Water System. AIChE 2006 Annual Meeting, San Francisco, CA, Nov 2006, paper 207e.

O’Connell, J. P.; Bellezza, K. P.; Murphy, J. E.; Gorensek, M. B.; Mathias, P. M.; Thies, M. C.; Crosthwaite, J. M. Investigation of the Reactive Distillation Separation for HI-I2-H2 in the S-I Process for Thermochemical Hydrogen Production. AIChE 2006 Annual Meeting, San Francisco, CA, Nov 2006, paper 126e.

Crosthwaite, J.M.; Thies, M. C. Experimental Studies of the Iodine-Water System for the Sulfur-Iodine Thermochemical Cycle. AIChE 2006 Spring National Meeting, Orlando, FL, April 2006, paper 182b.

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