GE moves from steam to air cooling for 7HA and 9HA

GE is releasing air-cooled H-class gas turbines. Two versions will be available for the 50 Hz market (9HA.01 and 9HA.02), and two versions for the 60 Hz market (7HA.01 and 7HA.02). GE’s first steam-cooled H-class turbines also operate at more than 2600°F. But sales have not been as robust as expected. Vic Abate, President of GE Power and Water, indicated that a total of 6 H-class units have been sold to date, 3 in Japan, two in the U.S. and in the UK. Part of the reason for this was the cost.

“A steam-cooled H-class turbine is more costly and more complex in terms of maintenance and operations,” said Abate. “Air-cooled units, enabled by single crystal technology and ceramics, are more cost competitive and plant output is higher.” 

In simple cycle mode, the 9HA.01 is rated at 397 MW while the 9HA.02 is rated at 470 MW. Efficiency is said to be more than 41%. Operating as a 1x1 combined-cycle unit, the 9HA.01’s rating rises to 592 MW (the 9HA.02 is 701 MW), and efficiency is said to exceed 61%. A simple cycle 7HA.01 is rated 275 MW while the 7HA.02 is rated at 330 MW. In the combined-cycle configuration, the 7HA.01 manages 405 MW while the 7HA.02 is rated at 486 MW. Efficiencies for simple cycle and combined cycle are greater than 41% and greater than 61% respectively

GE is billing this release as heralding the largest and most efficient combined cycle gas turbine on the market. Abate argued that when an apples to apples comparison is done between these models and those of other OEMs, using the same ambient conditions and applications, GE’s efficiency numbers come out on top.

“The big improvement in efficiency in our HA models is primarily down to the compressor,” said Abate.

These H-class machines incorporate a 14-stage compressor with a radial diffuser (the base compressor is adapted from the F5 jet engine) as well as a Dry Low NOx (DLN) 2.6+ axial fuel staged combustor. Belfort, France was the scene for the manufacture of the first 9HA gas turbine, which has now been shipped to the U.S. where validation testing will take place at a GE test site in Greenville, S.C.

Unlike other load-testing facilities for large combined cycle turbines, the GE facility is not connected to the grid. It represents an investment of more than $200 million.

“By not being connected to a power plant, we are free to stall the machine, strain it to its limits, and test its capabilities in ways that others can’t,” said Abate.  “We can run it to limits it will never see in actual operation.”

Abate also stressed the company’s modular strategy which, he said, results in fewer man hours during construction. He cited EPC partners spending 10,000 fewer hours compared to a comparable F-class project. For example, instead of a couple of dozen valves to be welded in the field, GE takes that number down to one.

As for the turbine itself, the customer is French utility EDF and the site is currently being built. Abate estimated that the HA turbine would arrive in France in the middle of next year with commercial operation expected in mid to late 2016.