Driving the solar thermal reforming of methane via a nonstoichiometric ceria redox cycle

This talk will be focused on a prospective solar driven methane reforming process using a nonstoichiometric ceria-based redox cycle. Compared to the traditional temperature swing process that accompanies solar-thermal redox cycles, the introduction of methane during the reduction step provides the ability to operate the cycle isothermally, or with smaller temperature swings, because the required reduction temperature decreases. As a result, the valuable solar energy that is utilized in the process is used more efficiently because sensible heating requirements are reduced, and the overall solar conversion efficiency is enhanced. Furthermore, compared to typical iron oxide based materials that are often used in similar chemical looping cycles, ceria has inherent kinetic and thermodynamic benefits that render it more suitable for isothermal operation where efficiencies are greater. Please click Additional Files below to see the full abstract

Solar Thermochemical Energy Storage Through Carbonation Cycles of SrCO₃/SrO Supported on SrZrO₃

Solar thermochemical energy storage has enormous potential for enabling cost-effective concentrated solar power (CSP). A thermochemical storage system based on a SrO/SrCO₃ carbonation cycle offers the ability to store and release high temperature (≈1200 °C) heat. The energy density of SrCO₃/SrO systems supported by zirconia-based sintering inhibitors was investigated for 15 cycles of exothermic carbonation at 1150 °C followed by decomposition at 1235 °C. A sample with 40 wt % of SrO supported by yttria-stabilized zirconia (YSZ) shows good energy storage stability at 1450 MJ m⁻³ over fifteen cycles at the same cycling temperatures. After further testing over 45 cycles, a decrease in energy storage capacity to 1260 MJ m⁻³ is observed during the final cycle. The decrease is due to slowing carbonation kinetics, and the original value of energy density may be obtained by lengthening the carbonation steps.Keywords: energy storage, strontium oxide, concentrated solar power, reactive stabilit

Thermochemical thermal energy storage

This chapter elaborates on the fundamentals of thermochemical energy storage (TCES) systems, classifications of TCES processes, and technoeconomic analysis of such systems. Then, one section for the case study is brought in which a case study TCES system is defined and analyzed in detail regarding technical indices and economic performance. Finally, like other chapters of the book, a short discussion of the future prospects of this method of thermal energy storage and its associated technologies is presented.</p

Effects of Dopant Metal Variation and Material Synthesis Method on the Material Properties of Mixed Metal Ferrites in Yttria Stabilized Zirconia for Solar Thermochemical Fuel Production

Mixed metal ferrites have shown much promise in two-step solar-thermochemical fuel production. Previous work has typically focused on evaluating a particular metal ferrite produced by a particular synthesis process, which makes comparisons between studies performed by independent researchers difficult. A comparative study was undertaken to explore the effects different synthesis methods have on the performance of a particular material during redox cycling using thermogravimetry. This study revealed that materials made via wet chemistry methods and extended periods of high temperature calcination yield better redox performance. Differences in redox performance between materials made via wet chemistry methods were minimal and these demonstrated much better performance than those synthesized via the solid state method. Subsequently, various metal ferrite samples (NiFe2O4, MgFe2O4, CoFe2O4, and MnFe2O4) in yttria stabilized zirconia (8YSZ) were synthesized via coprecipitation and tested to determine the most promising metal ferrite combination. It was determined that 10 wt.% CoFe2O4 in 8YSZ produced the highest and most consistent yields of O2 and CO. By testing the effects of synthesis methods and dopants in a consistent fashion, those aspects of ferrite preparation which are most significant can be revealed. More importantly, these insights can guide future efforts in developing the next generation of thermochemical fuel production materials