Concurrent Technologies Corporation (CTC), operators of the Department of Defense (DoD) Fuel Cell Test and Evaluation Center (FCTec ), under contract to the U.S. Army Engineer Research and Development Center - Construction Engineering Research Laboratory (ERDC-CERL) and in collaboration with FuelCell Energy (FCE), modified a FCE carbonate Direct Fuel Cell (DFC)-300 power plant to operate on natural gas as a primary fuel and HD-5 propane as a secondary fuel.  Engineered in conjunction with FCE, the ability to rapidly switch between fuels while maintaining base load electricity generation was successfully demonstrated at various loads during testing.  This validates the systems' capacity to guard against fuel supply interruptions from natural disasters or security issues at mission-critical facilities.