Closed Loop Thermochemical Energy Transport Based on CO₂ Reforming of Methane: Balancing the Reaction Systems

The objective of the Closed Loop Efficiency Analysis (CLEA) Project at Sandia National Laboratories is to develop the data base, the calculational tools, and the operational experience necessary for the design of cost-effective energy transport systems based on reversible chemical reactions. The primary application of interest is the transport of solar energy either from the collectors of a distributed system to a central site or from a solar energy plant of any type located in an area of high solar insolation to a population or industrial center a few to several hundred kilometers away. A series of experiments and analysis have been carried out to explore the effect of catalyst selection, starting composition, reactor temperatures, system pressure, and water recycle on the operation and the efficiency of an energy transport system based on the reversible carbon dioxide reforming of methane. Both the experiments in the CLEA laboratory facility and the analyses indicate that the carbon dioxide/methane thermochemical energy transport system can be operated in a stable, closed-loop mode and that the system can be started up and shut down, as it must be daily in a solar application, without triggering either catastrophic instabilities or carbon deposition. Based on the success of the CLEA project, two new hardware projects have been initiated to address scale-up and direct solar interfacing.