Evaluated in conjunction with Concurrent Technologies Corporation (CTC), operators of the Department of Defense (DoD) Fuel Cell Test and Evaluation Center (FCTec) in Johnstown, Pa., the power plant continued to generate base load electricity on a secondary fuel supply (propane) when the loss of its primary fuel source (natural gas) was triggered during testing. This rapid fuel switch was successfully demonstrated more than 40 times during operations exceeding 3,000 hours.

The R&D project is being sponsored by the federal government to demonstrate the dual-fuel capability of Direct FuelCell® (DFC®) power plants. CTC is the primary contractor to the U.S. Army Corps of Engineers, involving its Engineer Research and Development Center's Construction Engineering Research Laboratory (ERDC-CERL). FuelCell Energy and CTC operated a sub-megawatt DFC power plant on HD-5 propane fuel at full load achieving an electrical efficiency of 46 percent. The Johnstown plant continues to operate, having accumulated a total of 3,060 hours on propane and generated 425 Megawatt hours (MWh) of electricity as of June 28, 2006. The plant also operated 550 hours on natural gas, generating an additional 45 MWh.

"Successful dual-fuel testing demonstrates DFC power plants can be a vital part of our nation's homeland security efforts by providing ultra-clean, firm base load power at mission-critical facilities," said Christopher R. Bentley, executive vice president of government research and development operations. "On-the-fly switching among fuel sources enhances the flexibility and value of our DFC products."

Propane, a readily available fuel that can easily be stored onsite, is used as a primary fuel in isolated or sensitive locations such as islands, remote sites, national parks, data centers, military bases, hotels, and hospitals, and, therefore, is an ideal backup fuel for DFC power plants, said the company.

Rapid fuel switching from natural gas to propane and back again was achieved on more than 40 fuel swaps at various load levels while the plant was generating power. The fuel swap to backup propane occurs instantaneously when the system detects natural gas pressure dropping below a predetermined trigger point. Improved in-line fuel utilization measurement technology was also successfully tested, improving fuel flow control. This is important for propane operation since a rapid change in fuel composition occurs when filling the propane fuel tank. This technology played a key role in achieving the rapid validation of the instantaneous fuel switching.

"With increasing focus on establishing effective homeland security measures, the rapid fuel switching capability of FuelCell Energy's DFC products can provide enhanced on-site power generation options for facilities where reliable 24/7 power is essential," said Franklin H. Holcomb, CERL's fuel cell team project leader. "Multiple fuel operation is part of the rapid evolution of fuel cells as a replacement for conventional electric power where high efficiency, increased reliability, reduced harmful emissions, and lower noise levels are key requirements for installation."

Testing validated the DFC power plant is capable of continuous long-term high-load high-efficiency operation on propane, as well as instantaneous fuel switching from natural gas to propane in the event of loss of natural gas supply without loss of power. The unit can also switch back to natural gas from propane, instantaneously and on-load, once natural gas service is restored.

The project is supported by funding through DoD, the U.S. Army, and ERDC-CERL.

Publication date: 07/31/2006