Power barges are expanding, both in size and market share
By Michael T. Burr
When its moorings are secured and power lines connect its 450 MW of power capacity to an onshore substation, the Port Qasim project will take barge-mounted electricity generation to a new level. The project, being developed by Karachi-based WAK Orient Power & Light Co., consists of six barges, 200 feet long. Three barges will each carry a pair of 48 MW Westinghouse combustion turbines, connected to three additional barges each holding one heat-recovery steam generator and one steam-turbine generator.
A consortium of Westinghouse Electric Corp. of Orlando, Fla., USA, and Raytheon Engineering & Construction Co. of Norcross, Ga., USA, is contracted to build the plant. Westinghouse is expected to supply the turbine islands and provide long-term operations and maintenance services, while Raytheon is responsible for plant design and construction. Raytheon has subcontracted Marine Energy Systems Corp. to build the barges at shipyards in Charleston, S.C., USA.
“We`ll build the barges in Charleston and transport them to Pakistan on heavy-lift ships,” said Bob Marshall, Raytheon Engineering & Construction senior vice president and Raytheon`s manager of the energy division.
The Port Qasim project is designed to burn liquefied petroleum gas, with distillate fuel as a backup. When development of the project began, however, the sponsors envisioned a diesel engine-driven facility. “As it grew, the developer realized it needed to be a combined-cycle project,” said Gregory J. Snyder, Westinghouse Electric Corp. Generation Systems Division manager of platform-mounted power plants.
Westinghouse initially became involved at the request of General Dynamics, which was one of the project`s original sponsors. Although General Dynamics withdrew from the project, Westinghouse remained the major equipment supplier. Also, Westinghouse has also been involved with development as a technical consultant and provided assistance in structuring the power purchase agreement with the Water & Power Development Authority.
“This is the largest power barge that we know of. We are supplying another, similar project in Pakistan–the 288 MW Wingtiek project, sponsored by Sabah Shipyard,” Snyder said. “That project is two-thirds the size of this one.” Westinghouse also has supplied combustion turbines for barge-mounted power plants operating in the Philippines and Malaysia. Further, the company is contracted to provide a 140 MW project in Ghana, which will start construction this year.
Barges provide a number of benefits for markets where power is needed urgently, but financing is difficult to obtain. “Power barges are strongly tied to financing,” Snyder said. “This is a factory-built power plant, which makes it easier to ensure standards and do testing and engineering. That equates to reduced construction risk and results in better financing.” Additionally, startup schedules of only 30 to 60 days result in less interest accruing during construction.
Another factor is the ability to relocate the project if necessary. “Because the owner can pull the project out and use it someplace else, barge-mounted plants give the financial community a sense of comfort,” Marshall said.
Nevertheless, power barges present their share of challenges, including the difficulties of arranging for cooling water at a seaport location and spacing large equipment on relatively compact barges. Siting can also be challenging. “Barges require access to mooring and protection from hurricanes. Usually the best choice is in an inland waterway,” Snyder said.
Also, mounting combustion turbines on a floating platform can be problematic. “As temperatures rise and fall during hot days and cool nights, we`ll get expansion and contraction,” Marshall said. “Keeping the machines within tolerances over a long barge can be something of a problem. We compensate with expansion joints.”
With their advantages of speedy delivery and startup, and relative ease of financing, barge-mounted power plants represent a growing segment of the power industry worldwide. “Barge-mounted power is nothing new, but it`s becoming much larger and more important for meeting power needs,” Marshall said. Of the 11,000 MW of new power capacity that Raytheon plans to begin building this year, 10 percent is barge-mounted.
Likewise, Westinghouse said barge-mounted power represents an important niche. “This will be an expanding market for Westinghouse,” Snyder said. “We`ve focused on two engines, the 251D and the 501; but now we`re moving toward barges using 701 machines for the 50 cycle market and Trent aeroderivative machines. This is a good niche in the independent power producer market.”