Intermediate/peakload - Gas - 111 MW

Cogentrix Energy, Inc., a major independent power producer in the United States, owns several power generation assets.  Cogentrix recently acquired power generation assets including the Plains End facility from National Gas Transmission (NEGT). NEGT’s predecessor, PG&E’s National Energy Group (NEG), contracted to build a power plant near the City of Arvada, Colorado, in the United States. NEG in turn contracted with Wärtsilä North America, Inc. for a 111 MWe intermediate peaking plant. NEG built this facility in order to provide electricity and capacity under a long-term contract they have with the local utility, Public Service Company of Colorado.

When making their technology decision, the critical factor was the ability to operate at peak efficiency at high altitudes and temperatures. NEG’s overall aim was to supply dependable, low-cost power to their customer. This resulted in the construction of the largest natural gas-powered reciprocating engine plant in the United States, according to the U.S. Department of Energy.

Wärtsilä solution
The Wärtsilä peaking plant is designed as a pre-engineered, gas-fired power system allowing the users to generate their own power when electricity demand is at its highest. The Cogentrix plant is based upon 20 Wärtsilä 18V34SG natural gas engines, at 5.7 MWe per unit. This plant is permitted to operate up to 6000 hours per year.

The Plains End power plant also has excellent rapid response and load following capability thus providing reliability to the electric transmission systems. The plant is connected to Offtaker’s Generation Control (AGC) system at the Denver Dispatch Center from where the plant can be operated remotely using numerous dispatch algorithms that allow the dispatcher to decide the most responsive or economical mode of operating the plant.

Its multiple-unit arrangement enables the plant to ramp up from a warm standby to the full plant load of 111 MW in less than 10 minutes. With this feature the plant is considered as a virtual operating reserve though the plant is not running.  Further, when a specific plant dispatch mode is selected, the plant follows the AGC initiated load demand by ramping the plant load up and down  at a maximum rate of 12 MW/min between 50% and 100 % of the full rated output, thus giving Offtaker the means to absorb the load swings in the electric transmission system.

Wärtsilä’s intermediate peaking plants are delivered standard in less than 14 months, which was the right fit for the needs of this project. The plant is managed and monitored with Wärtsilä’s state-of-the-art remote control system, WECS, which enables reliable and flexible operation with a minimum of personnel. With the Wärtsilä intermediate peaking plant, Cogentrix enjoys a high level of service and at the same time reduces its risk of power shortages through a multi-unit design.