Florida Power & Light (FPL), the largest electric utility in the US, marked June 1, 2022 as the commercial operation date for the world’s first GE 7HA.03 gas turbines at FPL’s new Dania Beach Clean Energy Center near Fort Lauderdale.
Nominal 1200MW natural gas combined cycle plant, with ultra-low sulfur distillate oil fuel back-up, is powered by two of GE’s latest version of their HA-class gas turbines, each ISO rated at 430MW. Single steam turbine generator, driven by steam raised by two triple-pressure level reheat HRSGs, is rated at 437.6MW (ISO conditions) at base load output. Key combined cycle plant features:
Fast Restart. Hot plant restart from zero to full power in 30 minutes.
Emissions. Less than 2.5 ppm NOx and 9 ppm CO at 15% to 100% plant output.
Hydrogen. Capable of operating on up to 50% (vol) hydrogen and natural gas blend.
At the commercial operation day ceremony, FPL Chairman and CEO, Eric Silagy noted FPL has been working for over two decades to systematically modernize its fleet by replacing aging, inefficient plants with ultra-efficient, clean energy centers.
“With GE’s latest HA technology, the Dania Beach Clean Energy Center is now one of the most fuel-efficient plants in the world,” says Silagy, “and will save customers even more money while further reducing our environmental footprint.”
Fleet modernization
According to FPL, the new plant replaced an aging plant retired in 2018 and demolished to clear the site. The new plant will reduce fuel consumption by almost 30 percent per kWh, resulting in savings of more than $60 million per year in fuel cost compared to continued operation of the old plant.
The plant replaced was a nominal 1000MW early-1990s vintage combined cycle with an efficiency of nearly 50% (LHV). For its time it was a pioneering project in its own right, as it included four original 501F (155MW) gas turbines supplied by Westinghouse to repower two existing steam turbine generators. (On the site of FPL’s first power station built in 1927!) Not only is there a big improvement in efficiency, says FPL, but there is also a great reduction in plant air emissions. The old gas turbines used steam injection for controlling NOx emissions to 42 ppm on natural gas fuel, without selective catalytic reduction (SCR) for further minimizing NOx.
The new 7HA.03 plant will feature GE’s latest dry low NOx combustion technology (DLN2.6e) which will limit gas turbine NOx emissions to less than 25 ppm (at 15% O2) and will also include the installation of an SCR system designed to reduce NOx emissions to less than 2.5 ppm. The DLN2.6e combustor also features low CO emissions at part load, remaining compliant with permitted levels even at turndown to as low as 20% load. Overall, FPL says, the new plant will result in a 70% reduction in the level of primary emissions at the site.
Around-the-clock power
FPL says the new Dania Beach plant is designed to produce around-the-clock power, with rapid response to changing demand and grid conditions. This will enable the company to continue its brisk solar expansion, already the largest in the United States.
Regarding the plant’s fast restart capability this has emissions and economic benefits as well as providing fast energy supply to the grid to support renewable regulation. In its 2018 project approval application to the Florida Public Service Commission, FPL submitted an estimate of $888 million as the plant’s cost, less than $700 per kW at the ISO rated power output. Existing infrastructure at the plant site to be reused included the cooling water intake and discharge structures and liquid fuel storage tanks.
In approving the project, the PSC showed strong support for the project saying it agreed that closing the existing Lauderdale power plant and reusing some of its infrastructure for the new plant was the most cost-effective way to go forward and meet increasing needs for electricity in South Florida. The regulator further said that the new Dania Beach plant will have significant benefits in terms of its environmental impact by reducing nitrogen oxide and carbon dioxide emissions by 95% and 22%, respectively. On top of this, the PSC acknowledged that new plant will result in a substantial reduction in water usage for power generation at the site, by as much as 1.7 million gallons per day.
Hydrogen ready
FPL believes that with some future modifications, natural gas-fueled gas turbines like the units at Dania Beach will burn hydrogen instead of natural gas. Natural gas already results in the lowest carbon emissions possible burning fossil fuel, they explain, but hydrogen would result in zero carbon emissions.
FPL is developing a pilot project that will test the use of green hydrogen to replace a portion of the natural gas used at its 1,600MW (3×1 7HA.02) combined cycle power plant in Okeechobee County. The hydrogen will be generated by a 20MW electrolyzer being installed at the site powered by surplus solar energy. Operation is expected to begin in 2023.
It is noted that a 20MW electrolyzer can produce about 800 lb/hr of hydrogen. The actual portion of natural gas to be replaced with hydrogen during test operation would depend on the hydrogen storage capacity installed at the site and duration of test runs.
GE says it is making big strides toward decreasing carbon emissions. For instance, the 7HA.03 gas turbines at Dania Beach, enabled by the DLN2.6e combustion system, can already burn up to 50% (vol) hydrogen when blended with natural gas.
“Developments in hydrogen-based power generation mean that gas turbines offer great potential for reducing their carbon intensity and can represent a destination technology, not just a bridging technology,”
Evolution of HA technology
The 7HA.03, introduced in 2019 along with the launch order from FPL for the Dania Beach plant, is the culmination in evolution of GE’s advanced aircooled HA platform. The 7HA (60Hz) and 9HA (50Hz) were introduced in 2014 as next generation H-class gas turbines which originally (2003) featured steam cooling of critical hot gas-path parts.
Key design features maintained across the fleet of all HA machines include:
- 14-stage compressor with a set of electrically driven variable inlet guide vanes, three sets of variable stator vanes, and titanium first-stage rotating blade row,
- 12-can dry low NOx combustor with axial fuel staging and “unibody” construction, 1,282MW (2×1), representing about 12% increase over the 7HA.02 ratings.
- Higher efficiency: 43.3% in simple cycle and up to 64% in combined cycle, representing a heat rate reduction of about 1.7% and 1%, respectively vs. the 7HA.02.
- Optional wet compression: enables up to 7% increase in power output.
Operating flexibility
- Shorter start time: full simple cycle load in 10 minutes and full combined cycle load in under 30 minutes.
- Faster gas turbine ramp rate: over 70MW per minute about 25% faster than the 7HA.02.
- Fuel diversity: can run over a wider range of fuel specifications which enable lower cost natural gas contracts.
Capital cost and installation time
- Larger combined cycle power blocks drive economies of scale to lower $/kW
- Modular packaging shortens critical path installation cycle by 8 weeks and reduce construction risk.
Compressor design evolution
The basic compressor design used in all HA gas turbines was first developed for the 7F.05 gas turbine (ca. 2009) and has accumulated over 2 million operating hours, according to GE.
While air flow (inlet annulus area) and pressure ratio have increased over time, the 7HA.03 compressor retains the same 14-stage design, airfoil counts, and material sets as the 7HA.02. To enable a roughly 10% increase in air flow for higher power output (vs. 7HA.02), the titanium row 1 compressor blade length was increased. The design retains three sets of electrical variable stator vanes, one set at the compressor inlet (the “IGVs”) and one each at stages 2, 3 and 4, that assist in startup and improve part-load efficiency.
Water injection for wet compression (approximately 1% water-to-air ratio enables up to a 7% increase in gas turbine power output, which is especially useful in hot and tropical climates such as is common at the Dania Beach location.
Advanced DLN2.6e combustor
“The 7HA.03 leverages the latest in our long history of combustion technology developments,” says GE, whose early development work on dry low NOx (DLN) technology dates to the 1970s, with first field testing of DLN-1 in 1980 and first commercial installation in a 7E gas turbine in 1991. Based on that long history, GE claims that their “DLN family” of combustors has accumulated over 150 million operating hours.
The DLN2.6e combustion system, first applied to the 9HA.02 and now standard in the 7HA.03, continues to use staged fuel combustion (axial fuel staging). It features the unique “unibody” construction concept with combined combustor liner and transition piece.
New for the DLN2.6e is an advanced multi-tube premixer, which according to GE doubles fuel flexibility compared to the 7HA.02 system. The advanced premixer design, developed with support of the US DOE National Energy Technology Laboratory (NETL), features miniaturized tube sections functioning as “fast” mixers compared to the earlier design where premixing is achieved by large “slow” mix swirler passages.
This miniaturization enables 1) premix combustion of fuel gases with higher reactivity, such as ethane, propane and hydrogen; 2) eliminating flow disturbances created by swirling; and 3) improved “spatially distributed” flow uniformity which reduces NOx production at H-class firing temperatures (>2600°F). The validated ability to operate on both rich and lean natural gas variants, says GE, enables operators to widen their fuel specification and lower fuel cost when negotiating fuel supply contracts.
Staged fuel injection allows maintaining low NOx performance while increasing firing temperature as the design achieves uniform and well-controlled heat release to avoid temperature spikes which could increase local NOx formation.
While operating at reduced firing temperature for part-load, the fuel injection split between zones can be adjusted to maintain emissions compliance (both NOx and CO) over a wide range of load settings. GE points out that axial fuel staging can limit NOx emissions from the 7HA.03 to less than 25ppm and CO to less than 9ppm, with low combustion dynamics, over a load range from 15% to 100% full-load.
Another benefit of fuel staging is the ability to reduce combustor residence time at high temperature which, along with flame temperature, is the principle determinant of NOx emission levels. This is achieved by adjusting the fuel injection split to limit the temperature rise in the primary reaction zone and by placing the secondary fuel injectors to shorten the residence time at high temperature in the secondary zone.
Overall, GE says that the DLN2.6e design provides a combustion system with higher firing temperature capability, lower emissions at both full and part-load, higher durability, lower turndown and higher fuel flexibility than predecessor designs. Turndown to 20% gas turbine load with emissions compliance also enables increased plant duty during periods of low demand.
This offers added flexibility to operators to manage their gas turbine operations, minimize fuel burn, avoid unnecessary and costly shutdown and startup cycling.
Four-stage turbine evolution
The 7HA.03 has a proven 4-stage turbine framework originally introduced in the early 2000s on the steam-cooled H design. Instead of steam, however, it uses compressor bleed air to cool stator vanes and blades in all four turbine stages. The GE design does not rely on externally cooled compressor bleed air, with its associated piping, filters, heat exchangers, etc. that other OEMs use. This enables them to reduce plant footprint and equipment costs, lower auxiliary system loads, and reduce operating and maintenance costs.
According to GE engineers, the stage 4 turbine blade (S4B) has been lengthened for the 7HA.03 to accommodate roughly 10% increase in exhaust flow and to maximize gas turbine output and efficiency. As introduced with the 7HA.02, the S4B is a two-shroud design consisting of both a tip shroud and a mid-span shroud. Both shrouds engage during acceleration and provide damping to prevent potentially damaging vibration during operation.
Constructability features
As GE puts it, “meeting plant construction milestones is critical to project success”. Based on this guideline, the 7HA.03 gas turbine enclosure design has evolved into a highly modularized configuration featuring a relatively small number of pre-assembled mechanical (valves, piping, etc.) and electrical systems packaged in stackable modules that allow for quick installation and reduced safety concerns. GE says that the improved constructability of the 7HA.03 package offers contractors a shortened critical path construction cycle by 8 weeks compared to F-class plants and a reduction in field labor by 13,000 man-hours.
This, they claim, relates to the greatly reduced number of required field operations: 98% fewer valve installations, 64% reduction in electrical terminal points, 63% less connections and 55% fewer field welds.
Testing and validation
GE points especially to their factory-based testing and validation capabilities as playing a vital role in the evolution of their gas turbine technology to reach the level of the 7HA.03. Their full-speed full-load gas turbine test facility at Greenville, SC is used to validate both 50Hz and 60Hz heavy-duty gas turbine products before first-unit commercial operation in the field.
“The level of testing and validation possible is comparable to a gas turbine operating well beyond 8,000 hours connected to the grid,” GE claims. “Being isolated from the grid facilitates off-speed operation (90%-110%) over a range of “equivalent” load conditions, and variable speed enables testing at flow conditions equivalent to ambient temperatures ranging from minus 37ºC (-35ºF) to 85ºC (185ºF).” GE says this form of testing allows them to explore the hardware boundaries and make any necessary modifications, map operating limits and identify areas with growth potential. “Our fleet leader program which starts at commercial operation, and extends through the first hot gas path inspection, is an important second step in the process.”
During the field validation period, which has now officially begun for the Dania Beach units, the program includes careful monitoring of performance, with frequent borescope inspections and mini combustor inspections. Depending on findings, GE makes adjustments, and updates the equipment, as determined by analysis of the data, during the scheduled inspection.
Service and maintenance
With the 7HA.03 now operational, GE continues to leverage the HA service philosophy using an innovative modular design that allows for short-cycle outages and repairs. The 7HA.03 features a quick-removal two piece turbine shell that facilitates removal of all static hardware in the hot gas path. All compressor blades are field replaceable without having to pull the rotor. Once they complete their initial field validation period, they will enter the established program of extended maintenance intervals, which now align the combustion and hot gas inspections. This will be done after 32,000 hours of service thus maximizing unit availability (major inspections normally conducted after 64,000 hours).
Hot gas path inspection
GE field service engineers report that refinements to the inner turbine shell roll-out design have cut hot gas path inspection time in half since the first HA outages in 2017. The purpose of an HGP inspection is to examine condition and renew combustor and turbine parts exposed to high temperature gases. For the 7HA.03 it is expected this should typically be completed in less than 22 days. HGP inspections are conducted at the equivalent of 32,000 base-load operating hours. During this outage all hot gas path components (combustor, turbine blades, turbine vane, turbine shrouds) are removed and replaced. The condition of compressor blades and vanes is examined via borescope.
Major inspection
Purpose is to examine the internal rotating and stationary components, from the inlet of the machine through the exhaust. Typically, can be completed in less than 29 days. A major inspection occurs at the equivalent of 64,000 baseload operating hours and includes previous elements of the combustion and hot gas path inspections. Requires laying open the complete flange-to-flange gas turbine casings at the horizontal joints.
Rapid Response Combined Cycle
Rapid Response (RR) combined cycle design breaks the thermal links normally existing between gas turbine startup and that of the steam cycle. Since steam always lags, RR is a way to avoid delays due to hold points usually built into the gas turbine startup procedure to protect the HRSG and steam turbine.
GE says that RR is accomplished by the addition of terminal attemperators to control steam temperature during startup independently of gas turbine exhaust temperature. Also involves the adoption of various HRSG design features and modifications to other plant equipment.
For combined cycle operation, it allows the gas turbine to start and reach full load more rapidly without the usual concern about high thermal stresses in the HRSG and steam turbine.
In this way, compared to conventional combined cycle plants, RR improves operational flexibility and enables operators to respond more quickly to dispatch signals from the system operator. Improvements include faster power delivery to the grid, more economical and profitable plant startup, and lower startup emissions.
These benefits become especially important to plant owners as combined cycle plants evolve from the role of primarily baseload power to fast, reliable, clean and efficient backup to the growing influx of intermittent renewable energy on the grid.
7HA.03 Performance Data
GE published ratings at ISO standard site conditions (59°F, sea level, 60% RH) net of inlet and exhaust losses and auxiliary power loads.
| Simple Cycle Package | |
| Net power output | 430 MW |
| Net heat rate (LHV) | 7884 Btu/kWh |
| Net heat rate (LHV) | 8318 KJ/kWh |
| Net efficiency (LHV) | 43.30% |
| 1-on-1 Combined Cycle Plant | |
| Net Power output | 640 MW |
| Net heat rate (LHV) | 5342 Btu/kWh |
| Net heat rate (LHV) | 5636 KJ/kWh |
| Net efficiency (LHV) | 63.9% |
| Plant turndown (minimum load) | 33% |
| Ramp Rate (per minute) | 75 MW |
| RR to hot restart* | <30 minutes |
| 2-on-1 Combined Cycle Plant | |
| Net Power output | 1282 MW |
| Net heat rate (LHV) | 5331 Btu/kWh |
| Net heat rate (LHV) | 5624 KJ/kWh |
| Net efficiency (LHV) | >64.0% |
| Plant turndown (minimum load) | 15% |
| Ramp Rate (per minute) | 150 MW |
| RR to hot restart* | <30 minutes |
*denotes rapid response design and hot restart, typically after over-night shutdown where steam turbine is still warm and HRSG drum pressure is about 500 psi or higher.
