Energy storage technologies are essential to overcome the temporal variability in renewable energy. The primary aim of this thesis is to develop reactor solutions to better analyze the potential of thermochemical energy storage (TCES) using non-stoichiometric metal oxides, for the multi-day energy storage application. A TCES system consists of a reduction reactor and an insulated MOx storage bin. The reduction reactor heats (to ~ 1100 °C) and partially reduces the MOx, thereby adding sensible and chemical energy (i.e., charging it) under reduced pO2 environments (~10 Pa). Inert gas removes the oxygen generated during reduction. The storage bin holds the hot and partially reduced MOx (typically particles) until it is used in an energy recovery device (i.e., discharge). Irrespective of the reactor heat source (here electrical), or the particle-inert gas flows (here countercurrent), the thermal reduction temperature and inert gas (here N2) flow minimize when the process approaches reversibility, i.e., operates near equilibrium. This study specifically focuses on developing a reduction reactor based on the theoretical considerations for approaching reversibility along the reaction path. The proposed Zigzag flow reactor (ZFR) is capable of thermally reducing CAM28 particles at temperatures ~ 1000 °C under an O2 partial pressure ~ 10 Pa. The associated analytical and numerical models analyze the reaction equilibrium under a real (discrete) reaction path and the mass transfer kinetic conditions necessary to approach equilibrium. The discrete equilibrium model minimizes the exergy destroyed in a practical reactor and identifies methods of maximizing the energy storage density () and the exergetic efficiency. The mass transfer model analyzes the O2 N2 concentration boundary layers to recommend sizing considerations to maximize the reactor power density. Two functional ZFR prototypes, the -ZFR and the -ZFR, establish the proof of concept and achieved a reduction extent, Δδ = 0.071 with CAM28 at T~950 °C and pO2 = 10 Pa, 7x higher than a previous attempt in the literature. The -ZFR consistently achieved  > 100 Wh/kg during >10 h. runtime and the -ZFR displayed an improved  = 130 Wh/kg during >5 h. operation with CAM28. A techno-economic model of a grid-scale ZFR with an associated storage bin analyzes the cost of scaling the ZFR for grid energy storage requirements. The scaled ZFR capital costs contribute < 1% to the levelized cost of thermochemical energy storage, which ranges from 5-20 ¢/kWh depending on the storage temperature and storage duration.

As the need for environmentally friendly and renewable fuel sources rises, many are considering alternative fuel sources, such as solar power. The device explored in this report uses solar power, in theory, to heat a metal oxide, cerium oxide, to a desired temperature. At specific temperatures and pressures, a reaction between an input gas, carbon dioxide or water vapor, and the metal oxide may produce fuel in the form of hydrogen or carbon monoxide. In order to reach the temperatures required by the reaction, a filament inside a high-temperature radiant heater must be heated to the desired temperature. In addition, the system’s pressure range must be satisfied. A pressure and temperature measurement device, as well as a voltage control, must be connected to an interface with a computer in order to monitor the pressure and temperature of different parts of the system. The cerium oxide element must also be constructed and placed inside the system. The desired shape of the cerium oxide material is a tube, to allow the flow of gas through the tubes and system and to provide mechanical strength. To construct the metal oxide tubes, they need to be extruded, dried, and sintered correctly. All the manufactured elements described serve an essential purpose in the system and are discussed further in this document.
This report focuses on the manufacturing of ceria tubes, the construction of a high-temperature radiant heater filament, and the implementation of a pressure measurement device. The manufacturing of ceria tubes includes the extrusion, the drying, and the sintering of the tubes. In addition, heating element filament construction consists of spot-welding certain metals together to create a device similar to that of a light bulb filament. Different methods were considered in each of these areas, and they are described in this report. All of the explorations in this document move towards the final device, a thermochemical reactor for the production of hydrogen (H2) and carbon monoxide (CO) from water (H2O) and carbon dioxide (CO2).
The results of this report indicate that there are several important manufacturing steps to create the most desirable results, in terms of tube manufacturing and heating element design. For the correct tube construction, they must be dried in a drying rack, and they must be sintered in V-groove plates. In addition, the results of the heating element manufacturing indicate that the ideal heating element filament needs to be simple in design (easily fixed), cost-effective, require little construction time, attach to the ends of the system easily, provide mechanical flexibility, and prevent the coil from touching the walls of the tube it lies in. Each aspect of the ideal elements, whether they are tubes or heating elements, is explored in this report.