Top Plant: West County Energy Center, Palm Beach County, Florida
The 3,600-MW West County Energy Center, with two recently commissioned power blocks and a third just entering start-up, is the first “greenfield” combined-cycle plant constructed by FPL since the 1970s. Thanks to FPL’s long history with repowering projects, the project team commissioned Unit 2 seven months early, with no operator errors during start-up. At just over $600/kW, the cost of the plant was a bargain.
NextEra Energy Inc. (formerly FPL Group) has two operating subsidiaries: Florida Power & Light Co. (FPL) and NextEra Energy Resources, a competitive energy subsidiary that produces electricity using wind, solar, hydro, natural gas, oil, and nuclear energy. FPL, the regulated utility, serves about 4.5 million customers in 35 counties with the lowest residential rates of Florida’s 55 utilities.
Over the past 10 years, FPL’s average annual customer growth has soared 1.8%, much higher than the national average of about 1.2% over the same period. Power sales have dropped over the past couple of years, as at the majority of utilities across the nation, yet FPL still set a new system demand record of 24,354 MW on January 11, 2010, due to the coldest weather in decades. Today, FPL’s total installed capacity is 24,530 MW, plainly showing the immediate need for additional generation to reliably serve its customers.
For much of the past decade, FPL has pursued either repowering existing or constructing new power generation facilitates with high-efficiency combined-cycle technology. In 2003, POWER recognized the Fort Myers Repowering Project as a Top Plant for adding an incremental 960 MW to the grid. In 2004, the Sanford Repowering Project was named a Top Plant for completing a 1,150-MW plant upgrade. FPL next added 1,900 MW with the 2005 Martin and Manatee plant additions, followed by the 1,150-MW Turkey Point 5 combined cycle in 2007. Today, natural gas fires over 75% of FPL’s generation, followed by nuclear (12%), oil (8.7%), and coal (3.7%).
FPL has christened the next fleet of combined-cycle projects “Next Generation Clean Energy Centers.” These new plants include the twin power block 2,400-MW West County Energy Center (WCEC) and its third 1,200-MW power block now undergoing start-up. On the same day as the new system peak record was set, WCEC exceeded its cold winter expected output by 50 MW per unit by producing 2,717 MW net from the first two power blocks a month after Unit 2 entered service.
Up next in the FPL combined-cycle queue are the 1,250-MW Cape Canaveral Energy Center (2013) and the 1,250-MW Riviera Energy Center (2014).
An Enormous Project
The sheer scale of the West County Energy Center project is impressive. When all three units are completed, WCEC will assume the title of largest combined-cycle power plant in the U.S. and will be FPL’s first “greenfield” power plant since the 1970s. The plant is located on a 220-acre industrial site in western Palm Beach County adjacent to the water storage ponds where the South Florida Water Management District is processing water for restoration of the Everglades. The estimated cost of the WCEC when Unit 3 is complete is $2.2 billion.
Each of the three power blocks consists of a 3 x 1 combined-cycle configuration with Mitsubishi Power Systems 501G1 combustion turbines, each producing a nominal 250 MW. Each of the 501G1s has 16 separate steam-cooled, dry low-NOx combustors for high efficiency and low emissions (Figure 1). The three Nooter/Eriksen triple-pressure heat-recovery steam generators (HRSGs) produce steam for the single Toshiba reheat condensing steam turbine, nominally rated at 500 MW. Emerson Process Management’s Ovation digital control system integrates power block and plant operations.
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| 1. Building for efficiency. Each power block uses three Mitsubishi Power Systems 501G1 combustion turbines (1C is shown), each producing a nominal 250 MW. Courtesy: FPL |
The combustion turbines use natural gas as a primary fuel with ultra-low-sulfur (<0.0015%) distillate oil as emergency backup. Operation on distillate is limited to 500 hours per year per combustion turbine. The turbines are also fitted with inlet evaporative coolers to maintain or boost plant output when the ambient temperature exceeds 60F. The HRSGs are configured with an integral selective catalytic reduction system to tame NOx emissions and duct burners to peak steam flow during periods of high energy demand.
Each power block has a GEA 24-cell mechanical draft cooling tower to condense the steam turbine exhaust. The South Florida Water Management District and the Floridan Aquifer wells, drilled to a depth of 1,400 to 1,700 feet, supply plant makeup water. The plant will transition to reclaimed water recovered from five municipal plants in early 2011. Plant process liquid wastes, such as cooling tower blowdown, are pumped into another set of wells that reach 3,200 feet below ground.
Three Primary Goals
According to Roxane Kennedy, vice president of FPL Power Generation Operations, the goals of the WCEC project were threefold: to complete construction on an ambitious schedule, build one of the cleanest and most efficient combined-cycle natural gas power plants in the country, and operate the new plant safely and efficiently.
Beat an Already Ambitious Schedule. The schedule for constructing WCEC was ambitious, even for FPL’s experienced combined-cycle project teams. FPL received approval for construction of WCEC’s first two units in December 2006 and construction began only two months later. However, when a proposed 1,960-MW coal plant tentatively sited near the Everglades got the thumbs down from the Florida Public Service Commission in July 2007, FPL immediately resubmitted an application to add a third unit to WCEC. FPL received the necessary approvals in November 2008 and construction of Unit 3 began the following February.
FPL selected the team of Zachary-Black & Veatch to build all three units under an engineer-procure-construct contract but with the FPL operations team leading the commissioning process. WCEC also leveraged the hard-earned knowledge and experience of its engineers and operations teams from the earliest stages of planning and construction to prevent later operational, safety, and maintenance issues.
Unit 1 entered commercial service in August 2009, followed by Unit 2 in November 2009, seven months ahead of the original project schedule. As this article was written (late July), Unit 3 was beginning start-up work and had just finished fuel gas piping blows. Current projections show that the team will achieve schedule goals for the remaining unit, scheduled to come online in June 2011.
A key measure of the team’s productivity was the time it took to commission each unit. The average time between completing steam blows and commercial operation on the three previous combined-cycle projects was 140 days. On WCEC, the time for Unit 1 was 76 days, and Unit 2 was squeezed to just 38 days.
Exceptional Plant Performance. WCEC’s full-load heat rate is 5,850 Btu/kWh net (LHV), representing 58.3% thermal efficiency. Since entering commercial service, Units 1 and 2 have operated “in the high 90s” for availability.
WCEC is economically dispatched, although, as the FPL fleet’s most efficient gas-fired plant, each power block is usually baseloaded. However, the design of the plant allows each 3 x 1 power block to operate in a 1 x 1 configuration. This is especially helpful for dispatchers when winter loads dip to less than 5,000 MW at night. FPL’s four nuclear units have 3,064 MW of capacity, so efficient low-load operation of gas-fired assets is critical for best economy and stable grid operation.
Put People First. WCEC project leaders championed a number of innovative management practices that enabled the team to achieve its excellent results, including these:
- Development and operations employees worked together from the earliest stages of the project to consider and solve operational issues, including safety and maintenance challenges, throughout planning and construction.
- Skilled operators and maintenance personnel reviewed and learned from simulation training and system assessments, including three-dimensional virtual plant walkdowns.
- Operator training was more robust with a Unit 1 simulator motivating operators to quickly become proficient before the start of plant commissioning.
The result was a record-breaking start-up and commissioning of Unit 1 and Unit 2 without a single operator human error.
— Dr. Robert Peltier, PE is POWER’s editor-in-chief.