Analysis of Fuel Options for SOFC-Based Power Systems in Undersea Vehicles

Abstract

In a departure from NUWCDIVNPT's original focus on diesel-type (logistics) fuels, methane is looking more attractive for Unmanned Undersea Vehicle (UUV) applications, at least for first generation SOFC-powered UUVs. Even though the energy density for methane is roughly half that of diesel-type fuel, the savings in oxygen and carbon dioxide sorbent storage result in system energy metrics similar to those for S-8-based systems. In addition, the fuel processor control and system start-up can be greatly facilitated by using methane instead of a liquid hydrocarbon fuel. Switching to a methane fuel feed has the following advantages: • High Hydrogen-to-Carbon ratio (this lowers O2 and CO2 sorbent storage requirements) • Facilitates steam reforming versus diesel-type fuels • Greater ease of start-up and system power transient control • Risk mitigation for potential SOFC coking • Low boiling point, thus avoiding logistics of vaporizing diesel-type fuels and producing carbon residue.