Wolf Hollow offers early glimpse into H-machine performance

Two of the biggest, bad-ass gas turbines currently operating in the US are proceeding through their paces at Exelon Generation’s 2 × 1 Wolf Hollow II facility, Granbury, Tex, southwest of Fort Worth. CCJ editors stopped in to visit with Plant Manager Jeff Klier during a recent swing through the state.

Of utmost importance to the combined-cycle community is the effort Klier and other early adopters of the H technology, including Tennessee Valley Authority (TVA) and Florida Power & Light Co, are making to form a users group. Klier is hoping to schedule the inaugural meeting in the late August/early September timeframe at a hotel near his plant, with the opportunity of a tour of Wolf Hollow. CCJ staff will be assisting Klier in that endeavor.

The GE 7HA.02 machines, together with a D600 steam turbine/generator and two HRSGs (delivered under the new GE ownership of Alstom), anchor the 1160-MW powerplant. Most facility’s most striking feature, according to Klier, is its cycling flexibility. The plant is expecting to turn down to 350 MW and to ramp up to 1160 at 80 MW per minute.

The site currently is working with the OEM to optimize performance around the facility’s typical load points. Results of inspections to date, including removal of certain components at different intervals typical of early days with fleet-leader units, suggest critical parts will have the lifecycle durations anticipated.

After 6000 combined operating hours between the two gas turbines, Klier reports “no deal-breakers” on performance, which he says is impressive for fleet-leader machines. To date, equivalent forced outage rate (EFOR) issues tend to be exhibited in the ancillary systems, not the turbine itself and not the new-technology components.

Klier concluded the discussion by noting that “we’re making history here, with respect to the evolution of advanced GT technology, and based on our early experience, this machine has a very bright future.” Exelon is also operating the same engine at its Colorado Bend facility near Houston.

GE and Exelon are full partners at Wolf Hollow II. Exelon has a contractual services agreement for service and maintenance, and Exelon partnered with GE to apply the OEM’s Predix monitoring, diagnostics, and knowledge-management platform.

7HA.02 backgrounder

The gas turbines installed at Wolf Hollow II are GE’s largest and most-efficient 60-Hz engines. They were ordered in 2014 and began commercial operation in late 2016. Here are some bullet points from GE’s 7HA.02 highlight reel:

  • Fuel-flexible design accommodates the use of a wide range of gaseous and liquid fuels—including high-ethane (shale) gas and LNG.

  • Simplified dual-fuel system uses less water, eliminates recirculation, and uses an enhanced liquid purge for improved reliability and dependability.

  • Simpler configuration and modular design saved more than 10,000 installation hours compared to the 7F.03 gas turbine. Reasons include 40% fewer field connections and welds, and a 98% reduction in field-installed valves.

  • Quick-removal turbine roof, field-replaceable airfoils, and full borescope inspection coverage of all airfoils streamlines maintenance.

  • Four-stage air-cooled turbine with single-crystal airfoils protected by advanced thermal-barrier coatings.

  • Advanced compressor has 14 stages (three with variable stator vanes) and field-replaceable super-finished blades.

  • Fuel-gas pressure requirements are as low as 435 psig.

  • DLN 2.6+ combustor with axial fuel staging is proven through tens of thousands of starts and more than 2 million hours of operation.

  • Fast 10-min ramp-up from start command to full load; turndown to 25% of the baseload rating within emissions compliance.

  • An air-cooled generator is available to simplify installation and maintenance.

  • Wolf Hollow is GE’s first-ever application of its D600 side exhaust steam turbine—a design that translates to less complexity and lower construction costs.

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