Increasing CO2 Conversion to Fuel with Optical Thermal Management in Concentrated Solar Reactors New Dual-Stage Solar Reactor Design for Reduction of Carbon Dioxide to Fuels

Direct utilization of concentrated sunlight provides a low-cost source of energy for photocatalytic chemical reactions that convert carbon dioxide to fuels and chemicals. However, the usable portion of the solar spectrum for chemical reactions is small (generally <20%), and non-used portions eventually convert to heat inside of the photochemical reactor. This thermal waste causes excessive temperature inhomogeneities that lead to photocatalyst degradation, and removal of that heat in commercial-scale reactors using standard methods is difficult and a waste of energy. New photoreactor designs and methods to manage the heat would help overcome technological hurdles for the nascent photochemical carbon dioxide conversion industry. The mature optics industry has developed a simple and efficient route to split sunlight into two components (higher- and lower-energy photons) using a single thin glass component. Integrating a solar spectrum splitting mirror would be the basis of a new solar reactor design wherein the non- used lower-energy portion of the solar spectrum is reflected away from the entrance to the photocatalytic reactor, thus diverting a significant source of thermal waste. In addition, by using this optical means of spectrum splitting, the reflected portion could be directed to a thermocatalyst that could use the heat for additional carbon dioxide conversion. This dual approach increases utilization of the solar energy spectrum and increases carbon dioxide conversion over current technologies. An examination of optical mirrors for sunlight spectrum splitting will be performed to obtain empirical data of their effects on thermal waste and heat flow in a photochemical reactor. Based on the models, a dual-stage solar catalytic reactor will be manufactured that separately uses each component of the solar spectrum to convert carbon dioxide to a major industrial feedstock for chemicals and fuels (carbon monoxide). The output for Phase I work would be a prototype lab system with increased carbon dioxide conversion and solar energy conversion than current state-of-the-art. Empirical data and modeling from prototype testing will support scale-up efforts. This proposed research will make progress toward a process identified as valuable to industrial partners: low-cost carbon dioxide conversion to feedstock chemicals and fuels. To date, we have completed two paid R&D contracts to explore photocatalysis with Royal Dutch Shell. The present work in Phase I would directly address a chemical product (carbon monoxide) requested by target customers, and the project could smoothly transition to Phase II using the obtained data to re-design a larger-scale system with integrated components. A Phase III project would entail co-location of a system for on-site usage of carbon dioxide and production of the value- added product that would be integrated into the on-site supply chain.