An underground power station is a type of hydroelectric power station constructed by excavating the major components (e.g. machine hall, penstocks, and tailrace) from rock, rather than the more common surface-based construction methods.
One or more conditions impact whether a power station is constructed underground. The terrain or geology around a dam is taken into consideration, as gorges or steep valleys may not accommodate a surface power station. A power station within bedrock may be less expensive to construct than a surface power station on loose soil. Avalanche-prone valleys often make a surface station unfeasible as well. [1] After World War II, large hydroelectric power stations were placed underground more often in order to protect them from airstrikes. [2]
Often underground power stations form part of pumped storage hydroelectricity schemes, whose basic function is to level load: they use cheap or surplus off-peak power to pump water from a lower lake to an upper lake. During peak periods (when electricity prices are often high), the power station generates power from the water held in the upper lake.
Some notable underground power stations are:
Mica Dam is a hydroelectric embankment dam spanning the Columbia River 135 kilometres north of Revelstoke, British Columbia, Canada. It was built as one of three Canadian projects under the terms of the 1964 Columbia River Treaty and is operated by BC Hydro. Completed in 1973, the Mica powerhouse had an original generating capacity of 1,805 megawatts (MW). Mica Dam, named after the nearby settlement of Mica Creek and its associated stream, in turn named after the abundance of mica minerals in the area, is one of the largest earthfill dams in the world. The reservoir created by the dam is Kinbasket Lake. Water from the dam flows south directly into Revelstoke Lake, the reservoir for the Revelstoke Dam. Mica Dam is the tallest dam in Canada and second tallest in North America after the Chicoasén Dam in Mexico and it is the farthest upstream dam on the Columbia River. The dam's underground powerhouse was the second largest in the world at the time of its construction, and was the first 500 kV installation of sulphur hexafluoride (SF6) insulated switchgear in the world.
The Wivenhoe Power Station is situated between the Splityard Creek Dam and Lake Wivenhoe. The Splityard Creek Dam is situated in hills adjacent to Lake Wivenhoe and is about 100 metres (330 ft) above it. The power station is the only pumped storage hydroelectric plant in Queensland.
Lake Chelan Dam officially known as the Lake Chelan Hydroelectric Project is located approximately 32 miles (51 km) north of the city of Wenatchee in Chelan County. The dam is located at the lower or southeasterly end of 50.4 miles long Lake Chelan, and is within the limits of the city of Chelan. The powerhouse is located near the community of Chelan Falls. The reservoir has 677,400 acre-feet (835,600,000 m3) of usable water storage. The 10-year average generation for the Project is 365,000 megawatt hours.
Raccoon Mountain Pumped-Storage Plant is a pumped-storage hydroelectric underground power station in Marion County, just west of Chattanooga in the U.S. state of Tennessee. Owned and operated by the Tennessee Valley Authority (TVA), the plant can generate a maximum of 1,652 megawatts of electricity. The reservoir at the top of the mountain covers 528 acres (214 ha), with a dam that is 230 feet (70 m) high and 5,800 feet (1,800 m) long, the largest rock-fill dam ever built by TVA. The plant serves as an important element for peak power generation and grid balancing in the TVA system.
The Robert Moses Niagara Hydroelectric Power Station is a hydroelectric power station in Lewiston, New York, near Niagara Falls. Owned and operated by the New York Power Authority (NYPA), the plant diverts water from the Niagara River above Niagara Falls and returns the water into the lower portion of the river near Lake Ontario. It uses 13 generators at an installed capacity of 2,525 MW (3,386,000 hp) with an average annual net generation of 15,897,000 MWh between 2014 and 2023, and a capacity factor of 71.9%.
The Srisailam Dam is constructed across the Krishna River in Nandyal district, Andhra Pradesh and Nagarkurnool district, Telangana near Srisailam temple town and is the 2nd largest capacity working hydroelectric station in India.
The Ingula Pumped Storage Scheme is a pumped-storage power station in the escarpment of the Little Drakensberg range straddling the border of the KwaZulu-Natal and Free State provinces, South Africa. It is about 22 km (14 mi) North-East of Van Reenen.
Caliraya Dam is an embankment dam located in the town of Lumban province of Laguna, in the Sierra Madre Mountain Range of the Philippines. The reservoir created by the dam, Lake Caliraya, initially supplied one of the oldest hydroelectric plants in the Philippines, and later became a popular recreational area for numerous water sports and fishing. The dam's construction was started in 1939 under the supervision of the architecture firm of Pedro Siochi and Company and a small hydroelectric plant was operated in 1942.
Richard B. Russell Dam is a concrete-gravity and embankment dam located on the Savannah River at the border of South Carolina and Georgia, creating Richard B. Russell Lake. The dam was built by the U.S. Army Corps of Engineers between 1974 and 1985 for the purposes of flood control, hydroelectricity, recreation, additional stream flow regulation, water supply, and fish and wildlife management. The concrete structure of the dam spans 1,904 feet (580 m) and rises 210 feet (64 m) above the riverbed, housing a hydro-power plant with an installed 600 megawatts (800,000 hp) capacity. The Richard B. Russell Dam is the final large dam completed by the U.S. Army Corps in the Savannah River Basin and lies 30 miles downstream from the Hartwell Dam (1962) and 37 miles (60 km) upstream from the J. Strom Thurmond Dam (1954).
The Siah Bisheh Pumped Storage Power Plant, also spelled Siyāhbisheh and Siah Bishe, is located in the Alborz Mountain range near the village of Siah Bisheh and 48 km (30 mi) south of Chalus in Mazandaran Province, Iran. The power plant uses the pumped-storage hydroelectric method to generate electricity during periods of high energy demand, making it a peaking power plant, intended to fulfill peak electricity demand in Tehran 60 km (37 mi) to the south. When complete it will have an installed generating capacity of 1,040 megawatts (1,390,000 hp) and a pumping capacity of 940 megawatts (1,260,000 hp). Planning for the project began in the 1970s and construction began in 1985. It was delayed from 1992 until 2001 and the first generator went online in May 2013. The remaining generators were commissioned by 1 September 2015. The power plant is the first pumped-storage type in Iran and will also use the country's first concrete-face rock-fill dam – two of them.
The Koyna Hydroelectric Project is the second largest hydroelectric power plant in India, just after the Tehri Dam Project. It is a complex project with four dams including the largest dam on the Koyna River, Maharashtra, hence the name Koyna Hydroelectric Project. The project site is in Satara district.
Stave Falls Dam is a dual-dam power complex on the Stave River in Stave Falls, British Columbia, Canada. The dam was completed in 1912 for the primary purpose of hydroelectric power production. To increase the capacity of Stave Lake, the dam was raised in 1925 and the Blind Slough Dam constructed in an adjacent watercourse 500 m (1,600 ft) to the north, which was the site of the eponymous Stave Falls. In 2000, the dam's powerhouse was replaced after a four-year upgrade. The original Stave Falls powerhouse was once British Columbia's largest hydroelectric power source, and is a National Historic Site of Canada.
Castaic Power Plant, also known as the Castaic Pumped-Storage Plant, is a seven unit pumped-storage hydroelectric plant, operated by the Los Angeles Department of Water and Power, which provides peak load power from the falling water on the West Branch of the California State Aqueduct. It is a cooperative venture between the LADWP and the Department of Water Resources of the State of California. An agreement between the two organizations was signed on September 2, 1966, for construction of the project.
The Kazunogawa Pumped Storage Power Station is a pumped-storage hydroelectric power station near Kōshū in Yamanashi Prefecture, Japan. The station is designed to have an installed capacity of 1,600 megawatts (2,100,000 hp) and three of the four 400 megawatts (540,000 hp) generators are currently operational, for a total operational capacity of 1200 MW. Construction on the power station began in 1993 and the first generator was commissioned on 3 December 1999. The second was commissioned on 8 June 2000. The third one became operational on 9 June 2014, six year early due to post-power demand from the Great East Japan earthquake. The fourth and final generator is slated to be commissioned by 2024. It is owned by TEPCO and was constructed at a cost of US$2.2 billion.
The Okutadami Dam (奥只見ダム) is a concrete gravity dam on the Tadami River, 26 km (16 mi) east of Uonuma on the border of Niigata and Fukushima Prefectures, Japan. The primary purpose of the dam is hydroelectric power generation and it supports a 560 MW power station which is the largest conventional hydroelectric power station in Japan. The dam also forms the second largest reservoir in Japan, next to that of the Tokuyama Dam.
The Upper Cisokan Pumped Storage Plant is a proposed pumped-storage hydropower facility in Indonesia, due for completion by 2025.
The Vianden Pumped Storage Plant is located just north of Vianden in Diekirch District, Luxembourg. The power plant uses the pumped-storage hydroelectric method to generate electricity and serves as a peaking power plant. Its lower reservoir is located on the Our River, bordering Germany, and the upper is elevated above on the nearby Saint Nicholas Mountain. Construction on the plant began in 1959 and the first pump-generators were commissioned in 1962. A tenth pump-generator was installed in 1976 bringing the plant's installed generating capacity to 1,096 megawatts (1,470,000 hp). The plant generates an average of 1,650 gigawatt-hours (5,900 TJ) annually but of course consumes even more. Generally the efficiency of this energy storage method is around 70–80%. The plant is owned by Société électrique de l'Our and RWE. Construction on an eleventh pump-generator began in 2010 and it is expected to be commissioned in 2013, which will bring the plant's installed capacity to 1,296 megawatts (1,738,000 hp).
Northfield Mountain is a pumped-storage hydroelectric plant and reservoir located on and under the similarly named Northfield Mountain in Erving and Northfield, Massachusetts. It is currently owned by FirstLight Power Resources, which purchased the facility from Northeast Utilities in 2006.
The Snoqualmie Falls Hydroelectric Plant is located just north of Snoqualmie in King County, Washington state, US. It is situated about 22 mi (35 km) east of Seattle. Located just below the Snoqualmie Falls, the power plant consists of two power houses, Plant 1 and Plant 2. Plant 1 was completed in 1899 and is located underground. It is the first completely underground hydroelectric power plant ever built in the world. Plant 2 was built in 1910 and is located along the right bank of the Snoqualmie River. Both plants receive water from a small reservoir created by a weir atop the falls. Plant 1 has an installed capacity of 13.7 MW and Plant 2 a capacity of 40.2 MW for a total installed capacity of 53.9 MW, enough to power 40,000 homes.
Wreck Cove is the largest hydroelectric system in Nova Scotia with a generating capacity of 215.8 MW. Constructed from 1975 to 1978, south of the Cape Breton Highlands National Park, Wreck Cove collects drainage water from 216 square kilometres (83 sq mi) of the Cape Breton Highlands plateau to generate renewable electricity. It consists of two generating stations: the Gisborne Generating Station, with an installed capacity of 3.5 MW, and the Wreck Cove Generating Station, with an installed capacity of 212 MW, producing on average 318 GWh annually—enough energy to power about 30,000 homes.
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