Development of a SOFC Power System for Military Diesel and JP-8 Fuels

The contractors for this effort are the Gas Technology Institute (GTI), the Air Force Research Laboratory (AFRL) at Tyndall AFB, NexTech Materials, and the DoD Fuel Cell Test and Evaluation Center (FCTec)

Background

There are significant benefits with using fuel cells in military, aerospace, and commercial power applications. Fuel cells can provide quiet, flexible, and fuel-efficient operation that makes them suitable for use in "stealth" vehicles or quiet portable power systems. For example, the Army increasingly uses surveillance equipment, computers, and communications electronics in the battlefield. Typically, this electricity comes from either operating an engine or batteries. In a "silent watch" mode, vehicle engines cannot be operated without the vehicle being detected and battery technology alone cannot provide sufficient energy for the extended operation. Solid Oxide Fuel Cell (SOFC) power systems are also being developed for stationary power units, including stand-alone power and integrated combined heat and power designs.

A main benefit of fuel cells is their ability to convert fuel to power at high conversion efficiencies. In critical military applications, this results in a reduction in forward-deployed fuel. In non-critical applications, fuel cells represent a clean and efficient power source for base operations.

Diesel-powered SOFC power plants are envisioned for critical and non-critical military use such as auxiliary power units (APUs), portable power, and permanent stationary power. A complete development team is assembled and is expected to benefit from collaborative efforts, including the U.S. DOE Solid State Energy Conversion Alliance (SECA) program and several other key SOFC development initiatives.

Objective

The core program objective is to develop a viable diesel or JP-8 powered fuel processing system for SOFC systems for military use. The present focus is systems up to 10 kW capacity. The emphasis is on full integration of the fuel processing system with the operational requirements of the SOFC stack.

There are several challenges in the processing of military logistics fuels to make them suitable for use in an integrated SOFC power system.

  • Advancements are required to address vaporization, reformation, and contaminant control. In particular:
    • steps are needed to manage sulfur through desulfurization and use of sulfur-tolerant materials
    • steps are needed to avoid carbon/coke deposition in the system.

Mechanical and thermal integration is essential to ensure compact system design, high power density, appropriate start-up time, and maximum fuel efficiency as each system component affects parts of the system.

  • GTI is actively pursuing the development of reduced-temperature SOFC systems. This includes:
    • helping to form Versa Power Systems, Inc. (VPS) as a means of developing and commercializing SOFC technology.

The collaboration of various entities will provide expertise and development in various areas. Specifically:

    GTI will provide:
  • Sulfur tolerant steam reforming (SR) catalysts
  • Partial SR fuel conversion processes for SOFC operation and cooling strategies
  • High capacity sulfur sorbents
  • Knowledge of the construction and operation of SOFC stacks
  • Experience in process integration of fuel processors and fuel cell stacks

    AFRL will provide:
  • Know-how on diesel/JP-8 fuel fractionation, a technique to attack sulfur removal by fractionating the heavy fraction and using that sulfur-rich fuel as a heat source.
  • Heavy fuel catalytic combustion
  • Experience and design capability for compact heat exchangers and fuel processors

    NexTech Materials will provide:
  • Synthesis methods for GTI-developed catalysts
  • Samples for qualification tests
  • Scale-up catalyst production for larger quantities (e.g., in pelletized form)

    FCTec
  • Develop protocols for system testing
  • Conduct test evaluations of prototype systems
  • Provide application-based design information to support subsequent design refinements to satisfy military customer expectations for power supply systems.

Approach

The program is structured into three phases. The initial effort is focused on design and proof-of-concept, followed by an alpha system development, and finally by a beta system development and demonstration.

Phase I

Phase I work is divided into tasks covering the first twelve months. Phase I includes a parallel path fuel processor development effort and initial build of a SOFC fuel cell stack for integration with the fuel processor. Phase I fuel processor work will evaluate two fuel-processing approaches in parallel. To accomplish this, two different prototype fuel-processing systems will be built. One platform will be used to evaluate Process Options 1 (GTI). This will examine different variations, including use of sulfur tolerant steam reforming catalysts. The second platform will be used to evaluate Process Option 2 (AFRL). One distinguishing feature of this approach is the use of a novel fractionation approach.

Task 1: SOFC Fuel Processor Validation and Development

Subtask 1.1. GTI designs, builds, and tests a prototype fuel processor to evaluate Process Option One.

Subtask 1.2. AFRL, with GTI SOFC input, designs, builds, and tests a prototype fuel processor to evaluate Process Option Two.

Subtask 1.3. NexTech Materials will prepare sufficient quantities of catalyst and sulfur sorbents according to the GTI formulation and other inputs.

Task 2: Prototype Integrated Fuel Processor/SOFC Power Plant

Subtask 2.1 GTI will initiate design of a laboratory prototype SOFC system that enables thermal and mechanical integration with the fuel processor. Initial SOFC stack will look at procuring SOFC stacks from a SECA contractor or surrogate. Two SOFC stacks will be procured, assembled, and baseline data obtained on stack performance. This effort will leverage several complementary GTI SOFC programs.

Subtask 2.2. FCTec will develop testing protocols and provide preliminary information for military power system application requirements. These will be used to guide the design and development effort.

Task 3 Validation and Militarization of SOFC Power Plant

There is no worked planned in Phase I for this task. Work under this task will begin in Phase II and continue into Phase III.

Task 4. Management, Reporting, and Documentation

GTI will provide periodic reports to ERDC-CERL personnel on program progress. This task will also support participation in various technical venues to support communication and technology transfer.

    Phase I accomplishments and deliverables include:
    Hardware and Material
  • Two prototype SOFC/diesel fuel processing systems.
  • Two SOFC stacks to be used in the laboratory prototype system in Phase II.

    • Topical Reports

  • Report documenting results of testing two prototype SOFC/diesel fuel processors, including demonstrating the ability to provide ultra-low-sulfur levels and coke-free operation. This report will also include recommendations for a second-generation fuel processor system.
  • Design report for an alpha integrated diesel-powered fuel processor/SOFC system for laboratory testing and development.
  • Baseline performance testing of SOFC fuel cell stack.

Phase II

At the end of Phase I, a decision milestone will be made based on results of the two fuel processing efforts. These results will lead to a second-generation fuel processor design and development effort during Phase II (Task 1.4). This design will take the best aspects of both processes, work by others, and results from Task 2. This information will result in a fully integrated laboratory-based fuel processor/SOFC unit (alpha system, Task 2.3). The second-generation fuel processor will continue to be used for equipment, catalyst, and material evaluation in Phase II and III.

The second-generation fuel processing topology will be incorporated into the alpha system that will be developed and tested during Phase II. The alpha system will thermally and mechanically integrate the fuel processor, fuel cell stack, and balance-of-plant equipment. The current plan is to use a stack from a SECA program participant or assemble a surrogate system until SECA-based SOFC stacks are available.

Phase III

During Phase III, a detailed application-specific design will be pursued. This will target specific military applications using functional requirements to guide the overall system design. One actual military application will be used to design and build a beta system. Once proven, this effort will transition into a demonstration activity. This unit would use SOFC technology from a SECA program participant.

Phase II and III deliverables will focus on two key hardware platforms (alpha integrated system and beta integrated system, respectively) and technical reports on the results of design, development, and testing. Technical papers and presentations will be used to facilitate technology transfer.