Given the low projected demand for new coal-fired generating capacity prior to 2005, the U.S. market for Group 1 systems will likely be small. These systems are essentially based on proven components and do not offer an efficiency advantage over state-of-the-art pulverized coal systems. Projected performance and cost enhancements come from improved systems design and integration. There may be opportunities to market these technologies overseas, where demands for new coal-based power generation capacity are greatest. Despite their limited commercial potential, the first-generation PFBC and IGCC systems constitute important steps toward the development of higher-efficiency Group 2 and Group 3 systems. In contrast, the LEBS does not offer comparable growth potential, since it employs a simple steam (Rankine) cycle, whereas all of the Group 2 and Group 3 systems use combined-cycles with potentially higher efficiencies.

The committee recommends that future investment of DOE resources in first-generation systems be based on realistic market expectations and value as an entry into new technology with high growth potential. At least 50 percent industry cost sharing should be required to demonstrate private sector confidence in these technologies.

Group 2 and Group 3 power generation systems depend on the successful development of several critical components, including high-temperature gas turbines, high-temperature heat exchangers, advanced high-temperature furnaces, fuel cells, hot gas cleanup technology, and high-efficiency gasification. The riskiest components appear to be the high-temperature ceramic heat exchanger required for the externally fired combined-cycle system and the hot gas cleanup systems required for advanced PFBC and needed for maximum-efficiency IGCC and IGFC systems. The 1370 °C to 1430 °C (2500 °F to 2600 °F) gas turbine required for Group 3 systems is within the state of the art for aviation systems but requires further development, demonstration, and testing for power generation applications. Fuel cells hold significant promise for efficiency advantages, but their high cost may be a barrier to widespread use of IGFC systems.

Gas cleanup is necessary to comply with environmental requirements and to protect advanced gas turbines from corrosive impurities, notably chlorine, volatile alkali metals, and particulates. Commercially available cold gas cleanup technology could be used for IGCC and IGFC systems, although this would incur higher costs and an efficiency penalty of approximately 2 percentage points for air-blown second-generation systems. In contrast, advanced PFBC systems require hot gas filtration since cooling the high-temperature, high-pressure combustion products would eliminate the advantages of PFBC. Thus, IGCC is a somewhat less risky technology than PFBC. Environmentally, IGCC has the advantage of producing by-product sulfur or sulfuric acid, whereas the use of limestone or dolomite for in-bed sulfur capture in PFBC systems can as much as

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