This project will investigate a process for producing H2 from water for the purpose of storing solar energy as chemical energy. In the process, concentrated solar-thermal energy reduces Fe2O3 or CoO2 or Mn2O3 to a metal oxide with a lower oxidation state, which, in turn acts as a solute or anode in an electrolysis cell, enabling the production of H2 from water at ideal voltages as low as 0.21V. The low voltage is due to the anodic re-oxidation of the metal oxide. This produced oxide is then recycled in the solar step. The work required for the electrolysis is a fraction of the work that is available in a H2-air fuel cell. Thus the only energy entering the cycle is sunlight.
Valparaiso University?s partners in the project are Sandia National Laboratories, Diver Solar LLC, an industrial partner, and Professor Peter Kissinger, an electrochemist from Purdue University?s Chemistry Department. With support from the partners, undergraduate engineering and natural science students guided by faculty will conduct fundamental studies involving thermodynamics and electrochemistry. The project?s scientific objective is to obtain the requisite knowledge to assess the industrial viability of the process based on realistic estimates of the sunlight to H2 efficiency and how they compare to those from other processes reported in the solar chemistry literature. Achieving this goal requires a quantitative mechanistic understanding of the electrochemical reactions from voltammetry studies and a quantitative kinetic understanding of the solar decomposition and re-oxidation reactions from thermogravimetric analysis studies. The PIs will use our new 10kW solar furnace to conduct experiments that lead to the development of a solar thermal reactor that minimizes the irreversibilities associated with matching the incoming concentrated solar radiation to the kinetics of the decomposition reaction and the kinetics of re-oxidation to the product cool-down step.
The process resolves four major problems that have kept solar thermal chemistry from being industrially viable. (1) The process allows for the production of a solar fuel with a windowless reactor. Thus, it addresses the problem that windows must remain clean of reaction products or side products, a goal the solar chemistry research community has not yet reached with at least some of the reactions being investigated, and it improves process economics by avoiding the need to separate solar gaseous products from inert or unreacted gas. (2) It allows for a quasi-continuous process, addressing the industrial culture?s desire for nearly continuous operation. (3) The process operates at a temperature similar to those in industry. Many solar chemistry processes under investigation operate at temperatures approaching 2000 K, making the design for reliability challenging due to materials degradation, volatilization, and thermal energy management at extreme temperatures. (4) Although industry would do the solar step in the desert, the electrolysis involving water can be done wherever water is available, avoiding the need to bring water to the desert. The research will lead to a quantitative understanding of reaction kinetics for high temperature reduction and oxidation reactions of select metal oxides. The research will lead to a quantitative understanding of electrochemical reactions.
The educational component of the research program advances goal to have undergraduates aspire to be scientific leaders. The students will have the opportunity to experience the pleasure of discovery. They will synthesize concepts learned in thermal science and measurement courses in order to build up experiments and to analyze data. They will experience the process of teasing out of data new knowledge that allows us to see better the industrial potential of solar thermal electrochemistry. The students will learn rhetorical skills for communicating complex scientific ideas to the general public without compromising the science. Through the project?s outreach program, we will inspire young people in Northwest Indiana coming from underrepresented groups to consider a life in science.
