Impacts of Hydrogen-Natural Gas Mixtures on a Commercial Solid Oxide Fuel Cell System

In this study, the emissions and performance of a commercial Solid Oxide Fuel Cell system with micro-combined heat and power (SOFC mCHP) capabilities are analyzed at various power output levels and with various hydrogen (H2) - natural gas (NG) fuel mixture concentrations. The SOFC mCHP system, although designed to be fueled by pure NG, is intentionally fueled with mixtures between 0 and 30% vol of H2 mixed with NG (balance) and is operated between 0.5 and 1.5 kW. Since these units are used in residential and commercial applications, it is important to ensure that if H2 becomes widely injected into the NG system that the corresponding H2-NG mixtures would not negatively impact the emissions or performance of the system. The performance of the system is characterized by measurement of major exhaust species concentrations (carbon dioxide, carbon monoxide, methane, water, nitric oxide, nitrogen dioxide, etc.). These measurements confirm that NOx emissions are extremely low and that adding hydrogen to the NG system does not increase NOx emissions. In addition, the system's efficiency at part load experienced a small reduction with increasing H2 concentrations in the mixture, compared to pure NG operation.