James A Besha, president of Albany Engineering Corporation in the US, gives an historical insight into the rehabilitation of the Stuyvesant Falls hydro project in New York State
In the field of hydropower, sometimes what is old becomes new again. Such is the case with the historical hydroelectric plant at Stuyvesant Falls, New York in the US. It was built at the turn of the 20th century to supply power to a 60km long electric railroad that opened for business in November 1900. The third-rail line was considered the longest road of its type and stretched between Hudson and Albany, New York, deriving its 600V direct current power from the dam and power station on Kinderhook Creek.
The hydroelectric power facility, owned by the Albany and Hudson Railway and Power Company, included a dam, water conveyances, powerhouse and generating equipment. The dam, abutted by the creek’s natural rock walls, was constructed of coursed ashlar limestone with Portland cement mortar and stood 4.1m high and 79.3m wide. At the east end of the dam, a water intake of cut stone with concrete overlays guided water into two riveted steel penstocks. The intake, which was 3m wide and 13m high, included two steel head gates and a steel taintor gate and trash sluice. The penstocks measured 2.2m in diameter, with thicknesses ranging from 3/16 to a ½-inch, and extended 871m downstream of the dam to the powerhouse. Built with local brick, the powerhouse had gable-end construction, measured 24.9m x 43.2m in plan and stood 10.6m high. On the south side of the powerhouse, the downstream bay stood three stories high and ran the full length of the building. The lowest level of the south bay enclosed the turbine cases, the second level housed the low-voltage switchboards and transformers, and the third level held the high-voltage switchboards.
The power station housed ten Francis-type turbines in horizontal pressure cases. The turbines ranged from 0.38m diameter, single runner turbines to 0.84m double runner turbines. Three 0.84m diameter turbines operating at 375rpm drove 750kW, 12,000V, three-phase 25Hz generators. Power from these units was transmitted to remote substations where it was converted to direct current for traction power for the railway.
Three 0.53m turbines, operating at 600rpm, drove both 125kW and 50kW generators operating at 2200V, single-phase, 60-cycle for lighting circuits and transmission to communities along the railway system. Local traction supply for the rail line was furnished by two 0.76m turbines operating at 450 rpm, which drove generators of 200 kW capacity, each operating at 600 V direct current. Excitation for all generators was produced by two 0.38m turbines operating at 975rpm that powered two 45kW, 60V direct current generators.
Lombard hydraulic governors controlled all the turbines. The 25Hz alternating current generation was stepped up at the powerhouse to either 11,000V or 22,000V for transmission to three remote substations. At the remote substations the alternating current was stepped down to 380V, then commutated to 600V direct current by rotary converters that powered the third rail of the railway.
Understanding its obligation to provide reliable service even during times of low water or other disruption, the railroad company integrated a steam plant with the hydro plant to generate supplemental electric power. The steam plant comprised two triple drum water boilers of 1750HP each. Steam was generated in 150 psig and supplied to marine-type condensing engines, the largest of which had 1.22m diameter cylinders. The engines were belted to each of the 750kW alternating current generators and to the 250kW lighting generators. The steam plant ran on heavy fuel oil transported to the plant through a 0.15m diameter pipe supply line running over the Kinderhook Creek from an oil storage depot adjacent to the rail line.
The combined hydro and steam plant’s highest production was in 1937 when it generated 15,952MWh. The railroad shut down in 1929, and over the years the plant underwent changes in ownership, use and configuration. This included substantial changes to the hydroelectric generating equipment and abandonment of the steam generation system.
In 1942, under the demands of a rapidly accelerated war effort and the need for more power, a turbine-generator set from the Spiers Falls hydroelectric plant (located nearby on the Hudson River) was relocated to the Stuyvesant Falls facility to replace the original generating equipment. The turbine, manufactured by Allis-Chalmers Manufacturing Company in 1917, was a 1.10m diameter double runner Francis turbine housed in a horizontal, double spiral case. At Spiers Falls it had operated at 22.86m of head, but at Stuyvesant Falls it would operate at closer to 30.48m. The generator, built in 1904, was a General Electric Model ATB, which produced 3500kVA, at 2400V, three-phase, 0.8 power factor. It was originally a 40Hz unit operating at 240rpm but was rebuilt in 1942 to withstand the higher speed of 360rpm, which allowed for 60Hz operation. However, its 3500kVA capacity was significantly less than the output of the turbine now operating at a much higher head.
Though all the hydraulic turbines and generation equipment were replaced, the 1942 plant modifications retained the civil features including the dam, intake and penstocks. In order to generate more power, a substantial increase in hydraulic capacity for the penstocks resulted in increasing the velocity of the conveyed water. This had the effect of inducing considerable head loss; while the design was not optimal, it was done under war-effort pressure to increase generation requirements. The year 1945 was one of the best generation years on record when the plant produced 19,544.4MWh. The lowest generation on record was 49MWh in 1979.
New century, renewed plant
Age, deterioration and changing times forced the plant into obsolescence toward the end of the 20th century. The owner at that time, Niagara Mohawk Power Company, terminated operation and surrendered the licence in 1996. In 2002 the Town of Stuyvesant (where the plant is located) contacted Albany Engineering Corporation for assistance in developing the plant.
Albany Engineering, based in Albany, New York, specialises in hydroelectric design and development and has a diverse portfolio of projects ranging from 1.5MW under-river powerhouses to a 260MW pumped storage scheme using an abandoned mine. But the firm also has a demonstrated interest in historic plants, having restored its own 1897 plant in Mechanicville and the 1921 Henry Ford plant at Green Island, both located in New York on the Hudson River. The Mechanicville plant, still running on its original 40-cycle equipment, is considered the oldest continuously operating hydro plant in the US.
Founded in 1924, Albany Engineering Corporation prides itself on its innovative approach to hydropower projects while working within the environmental context and historic integrity of each project. As an example, the renewed plant at Stuyvesant Falls will incorporate extensive environmental protection measures to safeguard resident and migratory fish species. Albany Engineering will install an intake system of its own design that offers extensive protection for fish, preventing their entrainment and impingement.
This fish passage and protection system comprises a state-of-the-art, positive exclusion inclined screen system constructed of a water-ballasted-steel space frame that supports injection-moulded polycarbonate screen panels. The system uses a high ratio of sweeping velocity to through velocity that facilitates the passing of fish and debris to the apex of the screen system where it is then passed downstream via a pipe conveyance.
The 1942 Spiers Falls turbine will not be used in the new plant due to a penstock configuration that results in significant head loss and limited turbine output. Its accompanying generator is also undersized for the turbine. They will be replaced by two identical vertical Francis turbines, manufactured by Allis-Chalmers, with runner diameters of 1.12m with concrete spiral cases and elbow draft tubes. The turbines will be directly connected to vertical generators manufactured by Westinghouse Electric Company. These two turbines and generators, originally installed at the Osage hydro plant at Lake of the Ozarks, Missouri, are a perfect fit.
The vertically configured units will permit installation of the generators above flood level, correcting a deficiency existing in both the original 1899 and 1942 configurations. The new units have a generating capacity of approximately 3000kW each, operating at 4160V, 60Hz alternating current at 1.0 power factor. The units, which operated until they were removed from Osage in 2009, are undergoing complete refurbishment.
The new facility will use the existing 1899 dam and intake (rehabilitated in 1979). Leaks, erosion, corrosion and other factors of time have affected the original penstocks. The two original steel penstocks will be cleaned using high pressure water-jet blasting; some sections will be replaced, and the interior throughout will be relined with a modern polyurea coating system. After refurbishment, the penstocks will make their transition to the turbines with their new hydraulically optimised terminal portions positioned safely beneath floor level and encased in concrete. The deteriorated, original 1900 surge relief towers will be replaced by synchronised bypass valves, hydraulically connected to the turbine wicket gates, to assist in minimising pressure surges during turbine operation.
Rehabilitation plans include installation of new unit breakers and switchgear, station service, transformer, fused disconnect switches, and lighting and surge arrestors. New turbine and generator controls and protective devices will be installed in accordance with the requirements of the local transmission provider, National Grid. New solid-state exciters, lubrication and cooling systems, and hydraulic pressure units will also be installed. New drive motors, hoist chain/cables, remote controls and safety devices will update the powerhouse crane. A programmable logic controller will operate the new equipment automatically with digital protective relaying and digital synchronisers.
The new plant equipment will use approximately 21.24m3/sec, operating with a gross head of 30.48m and a net head of approximately 29.8m. The new generation facilities will be connected to the National Grid transmission system through an adjacent 34,500V switchyard. The newly expanded facility will generate approximately 20,000MWh annually.
The project is currently being relicensed under the Federal Energy Regulatory Commission regulations. Plans to install minimum flow turbines and generators at both the intake and powerhouse are included in the relicensing. The combined capacity of these units will be 900kW.
Because the plant is in the Stuyvesant Falls Historic District, the powerhouse exterior will be restored carefully, including refurbishment of windows and doors. The exquisitely detailed brickwork will be re-pointed and repaired. Other updates include a potable water supply, sanitary waste disposal facilities, lighting, security systems and communications systems.
Construction work began in January 2010 and should be completed by June 2011. Testing and commissioning will take place through the fall of 2011. The planned rehabilitation of the hydroelectric station, generating approximately 7.9MW, is scheduled for completion in late 2011. And thus, Albany Engineering Corporation will bring this century-old plant to life once again, supplying electricity to the region as an historic beacon of renewable green energy.
The author is James A Besha, president, Albany Engineering Corporation, 5 Washington Square, Albany NY 12205, US. Contact: Info@albanyengineering.com