This year marks the 40th anniversary of the Niagara power project. Connie M Cullen, from New York Power Authority in the US, tells the story of one of the most famous hydro plants in the world
POSSIBLY no other place on earth witnesses the wonders of nature and man existing in such proximity as Niagara Falls. Though it took nature several million years to produce what the Falls are today, it took man only three years to realise his task of producing power.
The Niagara project was constructed and is owned and operated by the New York Power Authority (NYPA) – the largest state-owned public power organisation in the US. Built between 1958 and 1961, Niagara was constructed for US$737M. No tax dollars were used in its construction as the Power Authority is a non-profit, public benefit corporation that finances projects through bond sales to private investors and repays the bonds with proceeds from operations.
To paraphrase from a famous advertising campaign, the Niagara project is ‘two generating facilities in one’. The larger Robert Moses Niagara power plant is a hydro facility that uses a gravity flow system, working alongside the Lewiston pump-generating plant, a combination pumped storage, hydro power facility. Together, they have a generating capacity of up to 2400MW. While both are located in Lewiston in Niagara County, about 8km north of Niagara Falls, the Robert Moses plant was built into the side of Niagara river gorge with the Lewiston plant located about 1km east. The two are connected by a wide power canal that serves as their forebay.
As the Niagara river is located on the international border between the US and Canada, it is shared by both countries under a treaty signed in 1950 which balances the spectacular natural beauty of the Falls with the need for electricity.
The treaty requires 2800m3/sec of the river’s water to flow over the Falls during tourist season (1 April- 15 September from 08.00-22.00hrs, 16 September-31 October from 08.00-20.00hrs). This leaves the remaining amount to be diverted equally between the US and Canada for power production.
During the rest of the year and at night, 1420m3/sec must go over the Falls with the rest diverted for power use. A study conducted between 1936 and 1957 determined the average flow over the falls to be 5716m3/sec. Today, because of low levels in the Great Lakes feeding the river, the average flow is about 5461m3/sec.
Frenchman Daniel Joncaire is generally recognised as the first to develop the power possibilities on the US side of the waterway and began the first Niagara water-powered business in 1757 – a sawmill.
Over time, a number of pioneers continued to develop the river’s generating potential for mechanical power. In 1881, local entrepreneur Jacob F Schoellkopf took this further and used the river for generating electricity. He built the first hydro station on the lower river (below the Falls) for the operation of several businesses and 16 open arc-lights on Niagara village streets.
In 1895, the first large scale hydro facility in the world, the Edward Dean Adams station, which eventually expanded into two power houses, began operating in Niagara gorge. Just a year later, Adams power-streamed 30km from Niagara Falls to Buffalo for the first long distance transmission of large quantities of electricity from a central power station.
During 1895 and 1896, the Schoellkopf company built another larger generating station, followed in 1903 by the construction of another, more efficient plant, which expanded over time to produce the largest quantities of electricity yet. By 1924, the Niagara Mohawk Power Corporation had acquired the Adams and Schoellkopf stations.
As the need for power grew, squabbles also grew between private and public development groups over who should develop the water power potential of the river. Then on 7 June 1956, a landslide destroyed two-thirds of the Schoellkopf facility, Niagara Mohawk’s largest power plant. The loss of this plant resulted in a power shortage endangering thousands of jobs.
In response to this emergency, Congress passed the Niagara Redevelopment Act in 1957, directing the Federal Power Commission (predecessor to today’s Federal Energy Regulatory Commission – FERC), to issue a licence to NYPA to fully develop the US share of the river’s hydro potential.
Under the direction of chairman Robert Moses, NYPA began this monumental job on 18 March 1958, with a construction force totalling over 11,000 at its peak, working year-round in all weathers. The Niagara project generated its first power just three years later on 28 January 1961. The first power ceremony on 10 February was presided over by chairman Moses and then-New York State Governor Nelson A Rockefeller, who symbolically switched on the project’s initial production of electricity.
During project construction, enough concrete was used to pave a two-lane highway for almost 1500km. Stacking the earth and rock excavated on an acre of land would create a column 6400m high – taller than North America’s highest peak Mount McKinley.
To benefit power production from the river’s descent of about 100m from Lake Erie to Lake Ontario, the Power Authority diverts water from the upper river (above the Falls), via two underground conduits. About 4km above the Falls, and marked by two intake gate housings, water is diverted from the river and enters the conduits on its journey to the Niagara project located 8km downstream of the Falls.
The 20m high and 14m wide conduits have 0.76m thick reinforced concrete walls and floors. Together, they transport 2.7M litres of water at 4m/sec. As the water leaves the conduits, it enters an open, 580m long and 50m deep canal (the transition section). Water then flows into the forebay feeding both the Robert Moses and Lewiston plants. The forebay is 152m wide, 1.2km long and 31m deep.
The Robert Moses plant
The Robert Moses power house is a semi-outdoor plant 590m long, 38 stories high and 177m wide. The 13 Francis turbines, which are currently being replaced, are capable of producing power at 175MW during peak periods under optimum flow conditions.
On the upper deck of the power house a 90t gantry crane is used for upkeep of the trash rack and headgates. The lower deck’s assembly bay accommodates the power house’s 630t gantry crane, which moves along railroad-type tracks to lift and transport the main components of the turbine-generators, located under aluminum hatches, for repair and assembly. On that level there is also a 30t gantry crane to place stop logs in the draft tubes when units have to be dewatered for maintenance.
As water flows from the forebay into the Moses power house, it enters one of 13 penstocks – composed of 52 welded steel rings encased in concrete and 7.3m in average width as they taper down from 8.2m to 6.5m.
Water plummets the penstock’s 140m length and races around the inside of a scroll case. Wicket gates inside the scroll case open and close to control the water flow to the turbine so that the unit spins at 120rpm and operates a three-phase, 60 cycles (hertz) generator.
The stainless steel shafts connecting turbine and generator are 1.3m in diameter and 10m long, and are divided into two 5m sections, joined by 18x16cm bolts. The generator’s rotor has 60 electromagnets, weighs 595t and is 10m in diameter. The rotor spins inside the fixed stator frame which is 10.5m in diameter, weighs 235t and contains 396 laminated copper coils. The 2cm air gap between the rotor and stator is where an electromagnetic field is produced at 13,800V. Through the use of 13 transformers, one for each generator, this is stepped up to 115,000V by seven of the transformers, and 230,000V by six others.
Water used by the Robert Moses plant is discharged through draft tubes at over 200m3/sec at a depth of 30m dredged in front of the power house – from the river’s average depth of 7m – to reduce surface turbulence.
The Lewiston plant is known as the Niagara project’s ‘storage battery’ as it serves as both pump and generator. As pumped storage units, the 12 reversible, modified Francis pump-turbines can each produce 20MW of power. During the night when, under the treaty, more water can be diverted from the river, Lewiston’s units pump water from the forebay to the reservoir behind the facility. The 769ha reservoir holds up to 99B litres of water. In daytime peak power periods, when less water is diverted from the river, water in the reservoir is released through the Lewiston units to produce power. The water then flows into the forebay to be used again by the Robert Moses plant where it produces about four times the amount of power generated at Lewiston.
As a pump, the Lewiston plant needs 32MW and as a generator, it produces 28MW. Though using more power than it produces, the less expensive cost for power at night is more than offset by the power proceeds earned when the plant is generating in the day.
The Lewiston power house is 297m long, 73m wide and 49m high above the foundation, and below the original ground level it reaches 35m by 73m. The assembly area houses a 150t gantry crane and 65t bridge crane used for equipment maintenance.
The penstocks, which taper down from 8m to 6m in diameter, are 28m long. Twelve 13,800V motor generators are directly connected to 12 modified, reversible pump-turbines which, at 5.2m in diameter, spin at 112.5rpm. The shafts are 0.6m in diameter and weigh 70t each, with their rotors measuring 7.6m in diameter and weighing in at 140t each. Four transformers step up power from the generators to 230,000V.
The electricity travels through underground tunnels from the Robert Moses and Lewiston power houses to the 14ha switchyard, located about mid-way between them and south of the forebay. In the tunnels there are 20 underground cable circuits with a total length of 20m, which are filled with 626,520 litres of insulating oil. The 21 lines in the switchyard are divided into three voltage sections for 115kV, 230kV and 345kV lines.
Niagara electricity powers some of the largest firms in western New York with total employment of over 50,000. For economic development, certain reallocations of inexpensive Niagara power, which is strictly regulated under the federal licence, are directed to companies locating and expanding along the Niagara frontier. The NYPA also offers low-interest loans, through the Niagara Economic Development Fund, to firms looking to enlarge or start-up in Niagara County.
Under the stewardship of New York Governor George E Pataki, the NYPA is increasing the Niagara project’s ability to produce power, at times when consumers need it most, to keep pace with the state’s changing energy needs during the era of deregulation. It is conducting a 13-year US$293M upgrade programme for the turbine-generators at the Robert Moses plant, which includes the installation of 13 new turbines. The improvements are scheduled for completion in 2006, with seven units being upgraded as of spring of 2001.
When complete, these improvements will allow the Robert Moses plant to use available water more efficiently and increase power production of each unit during peak demand times, from 175MW to 200MW. The new, replacement stainless steel turbines are less subject to cavitation, making them more reliable. The new blades are configured differently, taking advantage of lessons learned during 40 years of operation on the river, to improve efficiency.
Since its construction, the Niagara project has produced close to 600TW – enough to meet New York State’s current annual requirements for more than four years. On the horizon is renewal of its 50-year FERC licence which expires in August 2007. The NYPA intends to re-apply and plans are in a very preliminary stage.
In addition to Niagara, the NYPA operates 16 generating facilities and more than 2000 circuit kilometres of transmission lines. It sells electricity to investor-owned electric utilities for resale to customers at cost and to government agencies, community electric systems and job-creating private companies. Under New York’s economic revitalisation, led by Governor Pataki, low cost Power Authority electricity is tied to almost 400,000 jobs statewide.
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