| As global hunger for energy increases and conventional energy sources begin to dwindle, a new generation of energy technologies will be necessary for the continued advancement of human society. Recent interest in solar energy technologies in particular has given rise to increasingly popular photovoltaic systems which directly convert solar energy to electricity. Another form of solar utilization lies with concentrated solar power. Instead of directly converting sunlight to usable energy, this method uses the heat from concentrated sunlight to drive chemical reactions and produce fuels. While currently less developed, concentrated solar power can offer a significant advantage over its photovoltaic counterpart in storage and portability. That is, solar fuels can be stored, transported, and converted for flexible use.;The work herein discusses thermochemical cycling, a type of concentrated solar power that harnesses the heat from sunlight to drive oxidation and reduction reactions. Oxidation of an intermediate reactive material with water and/or carbon dioxide produces hydrogen or syngas fuels. Reduction at high temperature using solar thermal energy removes oxygen and primes the material for a new oxidation cycle, thus representing a regenerative cycle that produces fuel constantly with a supply of sunlight and water/CO2. The efficacy of thermochemical cycling primarily depends upon the intermediate reactive material. Many reactive materials have been studied for their fuel-producing and thermal reduction capacities over small number of cycles. Reactivity, however, tends to decrease with increasing cycles due to effects such as sintering, thermal deactivation, or physical degradation. Thus, it is also of importance to consider materials' long term fuel production potential, or reactive stability, over many cycles. While initial fuel production is important, materials need to exhibit a stable fuel production capacity over many cycles to prove economically viable.;This work investigates the thermochemical cycling potential of iron and cerium oxide. Thermogravimetry is used to both assess their initial fuel production capabilities and characterize their reactive stability over many cycles. SEM imaging and Raman spectroscopy is utilized to characterize structure and chemical composition. Finally, a brief economic analysis is presented for a prototype modular concentrating solar reactor using cerium oxide as its reactive material. |
