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Title: SECA Coal-Based Systems - LGFCS

LGFCS is developing an integrated planar (IP) SOFC technology for mega-watt scale power generation including the potential for use in highly efficient, economically competitive central generation power plant facilities fuel by coal synthesis gas. This Department of Energy Solid-State Energy Conversion Alliance (SECA) program is aimed at achieving further cell and stack technical advancements and assessing the readiness of the LGFCS SOFC stack technology to be scaled to larger-scale demonstrations in subsequent phases. LGFCS is currently in Phase 2 of the program with the Phase 1 test carrying over for completion during Phase 2. Major technical results covering the initial Phase 2 budget period include: Metric Stack Testing: 1. The Phase I metric test is a ~7.6 kW block test (2 strips) in Canton that started in March 2012 and logged 2135 hours of testing prior to an event that required the test to be shutdown. The degradation rate through 2135 hours was 0.4%/1000 hours, well below the Phase I target of 2%/1000 hours and the Phase 2 target of 1.5%/1000 hours. 2. The initial Phase II metric test consisting of 5 strips (~19 kW) was started in May 2012. At the start of the test OCV was low andmore » stack temperatures were out of range. Shutdown and inspection revealed localized structural damage to the strips. The strips were repaired and the test restarted October 11, 2012. 3. Root cause analysis of the Phase 1 and initial Phase 2 start-up failures concluded a localized short circuit across adjacent tubes/bundles caused localized heating and thermal stress fracture of substrates. Pre-reduction of strips rather than in-situ reduction within block test rigs now provides a critical quality check prior to block testing. The strip interconnect design has been modified to avoid short circuits. Stack Design: 1. Dense ceramic strip components were redesigned to achieve common components and a uniform design for all 12 bundles of a strip while meeting a flow uniformity of greater than 95% of the mean flow for all bundles. The prior design required unique bundle components and pressure drops specifications to achieve overall strip fuel flow uniformity. 2. Slow crack growth measurements in simulated fuel environments of the MgO-MgAl2O4 substrate by ORNL reveal favorable tolerance against slow crack growth. Evidence as well of a high stress intensity threshold below which crack growth would be avoided. These findings can have very positive implications on long-term structural reliability. More testing is required, including under actual reformate fuels, to gain a deeper understanding of such time dependent reliability mechanisms. 3. A next generation (Gen2) substrate from the LGFCS supplier has been qualified. The substrate incorporates cost reductions and quality improvements. Cell Developments: 1. Subscale testing of the epsilon technology under system relevant conditions surpassed 16,000 hours with a power degradation rate of <1%/1000 hours. Key degradation mechanisms have been identified: (1) MnOx accumulation near the cathode-electrolyte interface and cathode densification (2) metals migration across the anode-ACC bilayer and general microstructure coarsening at high temperatures and peak fuel utilizations and (3) metal migration into primary interconnect (lesser mechanism) 5 2. Alternate LSM cathodes show slightly lower ASR and lesser free MnOx and chromium contamination. Long-term durability screening of three alternate cathodes is being performed. 3. Single layer anodes show very significant improvement in microstructure stability after 5000 hours testing at aggressive conditions of 925C and bundle outlet, high utilization fuel. 4. New primary interconnect designs are being tested that achieve lower ASR. Modeling performed to further balance ASR and cost through optimized designs.« less
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Resource Type:
Technical Report
Research Org:
Lg Fuel Cell Systems Incorporated
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Country of Publication:
United States