Flexible 7HA.02 gas turbines for
Colorado Bend and Wolf Hollow
Exelon has ordered four GE 7HA.02 gas turbines for its two projects at Wolf
Hollow and Colorado Bend, both in Texas, USA. These are the first US orders for what GE claims are the world’s largest and most efficient gas turbines.
The existing Wolf Hollow power station. It is currently a three-unit 704 MW plant located in Granbury, near Dallas.
Texas has a growing demand for electricity, and has need for new, affordable and clean power. Water availability can, at times, be an issue, making it important that any new power supply minimizes its use of water.
The Electric Reliability Council of Texas (ERCOT) manages the Texas energy market for about 85 per cent of the state’s electric load. ERCOT dispatches power on a cost basis, ensuring that the lowest cost units are dispatched before higher cost units. As a result, Exelon views ERCOT as a strong market for high efficiency combined cycle plants that can be dispatched more often for better long-term returns.
A significant proportion of electricity in Texas is generated by wind power, about 9 per cent in 2014. Because of the intermittent nature of wind power, it needs complementary technology to help balance power supply and demand. High-efficiency combined cycle gas turbines provide exactly that.
Texas also has concerns about the availability of skilled manpower, leading to a requirement for short installation schedules.
As a result, Exelon is building two new 1000 MW combined cycle power plants in Texas, to be located at the existing sites of Wolf Hollow, near Dallas, and Colorado Bend, near Houston. Each of these new plants will include two GE 7HA.02 gas turbines, the first US order for these units. These turbines offer high efficiency – the 7HA.02 is claimed to be the most efficient gas turbine, enabling an overall efficiency of greater than 61 per cent in a 60 Hz combined cycle plant. GE says it also has the lowest turndown in its class while maintaining emissions compliance.
In addition, the plants are configured to use air-cooled condensers, which greatly reduce water consumption.
The existing Colorado Bend facility is a six-unit 498 MW plant. Phase 1 of the plant
entered commercial operation in 2007, with phase 2 starting in 2008.
Wolf Hollow and Colorado Bend
Wolf Hollow entered commercial operation in 2003, and was purchased by Exelon
in 2011. It is currently a three unit 704 MW plant located in Granbury, near Dallas, Texas.
Colorado Bend is a six unit 498 MW plant located in Wharton County, near
Houston, Texas. Phase 1 of the plant entered commercial operation in 2007, with phase 2 starting in 2008. The plant became part of the Exelon portfolio as a result of Constellation’s merger with Exelon in 2012.
Because of the growing demand for power in Texas, Exelon decided to add a 1000 MW gas-fired combined cycle plant consisting of two 7HA.02 gas turbines and a D600 steam turbine to each site. The equipment for these is expected to ship in 2016, with commercial operation starting in summer 2017. The first unit at each plant is scheduled to start in May 2017, with the second unit starting in June 2017.
These plants were required to have high efficiency and flexibility, low water
consumption, and technology that was complementary with the high level of wind power generated in Texas. David Sikora, Senior Vice President of Engineering and Asset Management for Exelon Power, said that the decision to select the 7HA.02 was based on its performance capabilities, capital cost, the presence of a long-term service
agreement, and its constructability. He said that the deciding factors were the very high efficiency levels, combined with flexibility, giving it high levels of availability.
Because of the rapid ramping speed of the turbine, and its good turndown capability, Exelon has estimated that it will be able to save $8 million in reduced fuel costs. These two factors enable the units to be able to rapidly change output to match demand.
Another factor in Exelon selecting the 7HA.02 gas turbine for these projects was that the modular constructability enables a shorter installation schedule. This
enables Exelon and its EPC contractor to make cost savings. In addition, the less time required for construction, the fewer man-hours are needed. This is an important factor, as there are concerns about a shortage of skilled manpower in Texas. The units will be less impacted by the shortage of skilled manpower as a result of being located on sites that already have operating units, giving a pre-existing skills base in the localities. Exelon will be starting to hire additional staff at the two sites for operation of the new plants, planning to take on 17 extra staff at each site. These will be hired over time, starting in 2016, with the intention of enabling them to work on the commissioning teams to give them experience of working with the units.
Sikora said that, given that the 7HA.02 was cutting-edge technology, it was important to Exelon to have a longterm service agreement. He said that whenever new technology was being adopted, it was important to stay close with the OEM, who is the best placed to resolve any issues that may arise.
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