By Teresa Hansen
What started as home to a 42-MW gas turbine peaking plant in 1994 has grown into a four-unit power park with a total capacity of 742 MW, much of it baseload. Nearly 100 POWER-GEN Week attendees loaded onto buses Monday morning to visit Florida Municipal Power Association’s (FMPA) Cane Island Power Park, located in Kissimmee. They heard not only about each unit’s history, but got an up-close view of each plant during the tour. Power plant workers from Kissimmee Utility Authority (KUA), the plants’ operator, hosted small groups, guiding them to all four units, the water demineralization unit, the site’s substation, and—the heart of the site—the control room, which controls all four units. One group was even allowed to climb to the top of one of the units to get a bird’s-eye view of the entire facility.
After learning about water demineralization, Tim Yelverton, KUA’s instrumentation and electrical supervisor onsite, took attendees to Unit 1, the first unit to be built at the site. The dual fuel (natural gas and fuel oil), simple-cycle GE LM6000 gas turbine was built as a peaking unit and began operation in 1994. At 23 years old, the plant doesn’t operate much anymore, but is still called upon when peaking power is needed, Yelverton said.
“Our peak load is growing much faster than our baseload,” he said. “The gap between the two is steadily getting larger.”
For this reason, Unit 1 is still important to FMPA and the public power companies it serves, Yelverton added
“This unit can ramp to full load in only 11 minutes,” he said.
Unit 2, which was commissioned in 1995, is a GE 7EA dual-fuel,combined-cycle unit with an output of 120 MW. The unit, which is currently shut down for control system upgrades, was originally built to be a baseload unit. According to Yelverton, it was operated as such for many years. Now, however, the plant runs only about half the time each year. It is slower to start up than Unit 1, but is called upon for extra generation during times of high electricity demand.
“It [Unit 2] is not as cheap to operate as some of the newer units, so it is no longer a baseload plant,” Yelverton said.
Unit 3 was added five years later. The GE 7FA combined-cycle unit was commissioned in 2000 and, like its two predecessors, is a dual-fuel unit.
Yelverton pointed out that all three of the dual-fuel units on site run primarily on natural gas, but can operate on fuel oil as a backup, if needed. Natural gas is available to the site from two sources: Florida Gas Transmission and Gulf Stream.
The 270-MW Unit 3 was built as a baseload plant and still operates that way.
Unit 4, also a GE 7FA machine, is almost a twin to Unit 3. The differences are that Unit 4 is not dual-fuel capable and was built with a duct burner to increase the temperature of the steam that is fed into the steam turbine. The addition of this duct burner gives the plant the ability to generate an additional 40 MW, increasing its total capacity to 310 MW and making FMPA’s largest generating unit.
“The duct burners increase the steam temperature, which increases the plant’s output,” Yelverton said. “But, the duct burners are used only when peaking power is needed.”
The demand for electricity changes frequently in central and eastern Florida, Yelverton said. Therefore, the output of the baseload units, Units 3 and 4, at Cane Island Power Park fluctuate almost constantly, he pointed out.
To handle this fluctuation, the two baseload units are equipped with GE Mark VIe governors that automatically signal the gas turbines when capacity requires change. A set point is sent to the GE governors from the Florida Municipal Power Pool. The governors then automatically send a signal to the gas turbines that adjusts the fuel amount, which in turn adjusts the electricity output of Units 3 and 4.
Yelverton said that so far adjusting the electricity output of the two baseload units has not had much of an impact on the plants’ efficiencies. He said, however, lowering their output has the potential to create air permit compliance issues.
When asked if Cane Island Power Park will see another unit in the near future, Yelverton said there are no plans at this time to add Unit 5.