Port Westward Generating Plant (PWGP) is the newest member of Portland General Electric's (PGE's) diverse family of power-producing resources and the company's first new power plant in more than 10 years. PWGP will help PGE cope with a 2.2%/year load growth rate while reducing its need to buy wholesale power at high spot-market prices. The 400-MW plant began commercial service in June 2007. Because actual operating data were sparse at press time, an inside look at PWGP's first use of Mitsubishi Heavy Industries' (MHI's) G1 advanced gas turbine and combined-cycle technology in the U.S. must suffice for readers considering them.
PWGP (Figure 1) is located in the Port of St. Helens industrial area of Oregon's Columbia County, near PGE's 545-MW Beaver Power Plant. Mitsubishi Power Systems (MPS, www.mpshq.com) supplied all of the equipment for PWGP's 1 x 1 power island: a M501G1 gas turbine, an MHI steam turbine, generators for both units, and a triple-pressure heat-recovery steam generator (HRSG) from Deltak LLC (www.deltak.com) equipped with a selective catalytic reduction (SCR) system driven by CO and ammonia catalysts. Construction of the plant started in January 2005, and the project was finished under budget and just in time to meet PGE's summer loads.
1. Push the button. An aerial shot of Port Westward Generating Plant, taken during its start-up in June 2007. Courtesy: PGE
Prime mover and shaker
PWGP is powered by a brand-new G1-class natural gas–fired combustion turbine from MHI and boasts of a combined-cycle efficiency that's among the highest of any plant in the U.S. The plant's heat rate of 6,700 Btu/kWh takes into account all plant loads and transformer losses.
PGE's original permit application for Port Westward called for two F-class gas turbines with a combined capacity of up to 650 MW. But after carefully considering projections of consumer demand and trends in replacement power prices, the utility decided that going with a more-efficient G-class turbine in combined-cycle mode would be a better investment for both its shareholders and customers.
The target capacity of the proposed plant then had to be revised to reflect the use of one G-class machine with higher efficiency in combined-cycle mode. The G-class turbine has a 2% to 3% lower heat rate and about 100 MW more output than the F-class alternative. At average site ambient conditions, PWGP has a maximum capacity of 414 MW, of which 389 MW comes from the combined cycle and the remainder from duct firing.
MPS has a fleet of 18 G-class machines installed worldwide; the earliest entered service in 1997. To minimize operational problems, Mitsubishi thoroughly tested all final design changes incorporated into the G1 unit at PWGP at the company's verification power plant in Takasago, Japan, prior to releasing the turbine for commercial use in the U.S.
The contracting approach used on the PWGP project was typical. PGE purchased the turbomachinery directly from MPS and signed a full-wrap turnkey contract with Black & Veatch Construction Inc. (www.bv.com/services/construction/) for all other equipment. PGE also negotiated a long-term service agreement with MPS that covers gas turbine parts and planned maintenance inspections for 12 years. This and the contract agreement negotiated with assistance from Troutman Sanders LLP (www.troutmansanders.com), ensures the plant's ongoing reliability and cost predictability.
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