By Steve Blankinship,
Two years ago, Houston-based Reliant Energy had little hydroelectric generation. Today, it has more than 700 MW of hydropower.
Last year, Reliant acquired 71 hydro facilities in New York State to go along with the two facilities already owned in Pennsylvania and Maryland. Sixty-nine of those facilities came by way of Reliant’s merger with Orion Power Holdings. The upstate New York plants had been previously owned by Niagara Mohawk Power Corp. and were sold to Orion as part of New York’s electricity deregulation, which required utilities to divest of generation assets.
“Although still only 4 percent of Reliant’s production capacity, acquisition of the New York State hydro facilities helped us diversify our energy portfolio at a time of strong incentives to provide ‘green’ energy in New York,” said David Youlen, managing director-hydros.
Tailrace at Reliant Energy’s Oswegatchie Power Plant in Edwards, N.Y. Photo courtesy of Reliant Energy.
The New York plants are spread across three drainage basins in the upper part of the state – Lake Ontario, the St. Lawrence River, and the Hudson River. The average age at Reliant’s New York plants is 72 years, and range from 0.3 MW to 56 MW with an average plant size of 4.2 MW. All of the New York hydro generating plants operate without staff and function by pond level control or through a centralized control center at Reliant’s hydro operations headquarters in Syracuse. Reliant’s roving operators and maintenance crews, dispatched from 15 locations throughout the state, maintain the plants.
Early this year, Reliant completed its first major hydro plant redevelopment – a new facility that cost $3.3 million and replaced the existing Oswegatchie hydro facility which had been out of service for the last 10 years. The reconstruction included the addition of fish-friendly trashracks, two hydro turbines and generators, penstocks and a new powerhouse.
“Oswegatchie was selected to be our first major hydro upgrade in New York State in more than 20 years because it was out of service and licensing hurdles at the site were considered to be very manageable,” Youlen stated. Built in 1913 with a capacity of 0.8 MW, it was a unique site, with an old wooden powerhouse, an elevated wooden flume and in more recent years, only one unit of two operational. The site was to be retired in 1975, but through the perseverance of many employees of then-plant owner Niagara Mohawk, the plant continued operation and even the decommissioned unit was soon brought back into service. The plant continued to produce energy until a flume wall collapsed in 1992.
“The design consultant, Kleinschmidt Associates (Pittsfield, Maine), incorporated cost-saving suggestions from the contractors into the final design,” said Joseph Viau, Reliant project manager. “The site design used the original site excavation to the maximum extent possible to minimize the quantity of rock excavation.”
The intake design accommodated the need to increase the intake opening relative to the penstock sizing in order to minimize the approach velocity and the head differential across the trashracks. In addition, the Oswegatchie site is in a cold region of the state and high approach velocities tend to increase the occurrence of frazil ice. Since the site already had an access road, only minor widening and improvements were required to get to the plant.
“Numerous aspects of the project addressed environmental issues. The new one-inch clear trashrack spacing helps prevent fish entrainment, and there is a minimum 40-cubic-feet-per-second environmental flow release through the bypass reach of the Oswegatchie River,” stated Viau.
The new equipment includes two hydroelectric turbines built by Canadian Hydro Components at its manufacturing facility in Almonte, Ontario, Canada. Each turbine is rated at 1,280 horsepower at 35 feet of net head. Potencia of Mexico City, Mexico manufactured the generators, each rated at 1 MW. The new penstocks are 6.5 feet diameter steel structures. North American Hydro of Neshkoro, Wisconsin supplied the electric switchgear and generator controls.
The new powerhouse measures 42 feet long by 28.5 feet wide by 19 feet tall, and features a single ply membrane roof with stone ballast. The turbines are located in the center of the building, and are below the tail water. Therefore both the draft tubes are fitted with stop log-type gates to enable dewatering.
The upgrade has boosted capacity to 2 MW. Anticipated average annual power production is 9,555 MWh compared to original annual power production of 5,700 MWh.
Another factor crucial to the success of the plant upgrade was that it took only 13 months to complete the Federal Energy Regulatory Commission (FERC) license amendment process and construction from the initial submittal of the amendment application to commissioning of the new units. Most hydro projects of this nature can be years in the making.
The Oswegatchie plant also faced very little opposition from local and county officials. That’s because Reliant ensured that the new machines enhanced the flow regime of the river. This provided improvements in downstream river stability while producing additional electricity.
Reliant is currently more than one-quarter of the way through construction on another redevelopment at the Higley Hydro plant on the Raquette River in Colton, New York. Reliant hopes to begin another capacity addition project at its School Street site in Cohoes, New York in 2004.