March 15, 2006

O&M staff keep their cool at Alaskan plant

Peter S. Jackson, PE, Tetra Engineering Group Inc. and John Kotrotsios, Chugach Electric Association Inc.

A mixed, isolated bag

More than half of Chugach Electric's thermal generation comes from gas turbines operating in simple-cycle mode. The remainder (210 MW) is produced by two combined-cycle units at the Beluga Power Plant. There, two ABB-11DM gas turbines work in concert with vintage Babcock & Wilcox heat-recovery steam generators (HRSGs) that feed a 53-MW, single-pressure steam turbine built by Brown Boveri.

The four simple-cycle gas turbines at Beluga are GE units. Two are Frame 5s installed in the late 1960s, and the others are Frame 7Bs installed in the mid-1970s and later converted to Frame 7Es.

The Beluga plant (Figures 1 and 2) is remotely located across Cook Inlet, 40 miles due west of Anchorage. To the northwest, 30 miles away, is the Alaska Range, home to an active volcano that continues to make its presence felt. So have the wildlife. Operators have long become accustomed to the occasional visit from a moose or a black or brown bear.

1. Can't get there from here. Chugach Electric Association's Beluga Power Station has six gas turbines with a total capacity of 332 MW and one 53-MW steam turbine. Courtesy: Chugach Electric Association Inc.

2. Locally fueled. The Beluga Power Plant, 40 miles west of Anchorage, was sited on top of the Beluga River Gas Field. Courtesy: Chugach Electric Association Inc.

No roads connect Beluga to any part of Alaska's major highway system, making the plant accessible only by barge or aircraft. Its gravel road parallels an airstrip on which all personnel, equipment, and supplies arrive. The privately owned airport accommodates single- and twin-engine aircraft on a regular basis as well as larger aircraft such as the Hercules C-130. Barges ship larger heavier equipment and cargo across Cook Inlet (Figure 3). With normal bay tides in excess of 30 feet, tidal damage to the barge landing must be repaired after every winter/spring thaw.

3. One if by sea. A new rotor for one of Beluga's ABB-11DM gas turbines arrives at the site's barge landing. The landing must be rebuilt each summer after the spring thaw erodes most of the roadwork. Courtesy: Chugach Electric Association Inc.