Таум-Сок: Гидроаккумулирующая электростанция в Миссури

The Taum Sauk pumped storage plant is a power station in the St. Francois mountain region of Missouri, United States about 90 mile (145 km) south of St. Louis near Lesterville, Missouri, in Reynolds County. It is operated by Ameren Missouri. The pumped storage hydroelectric plant was constructed from 1960–1962 and was designed to help meet daytime peak electric power demand. It began operation in 1963. Electrical generators are turned by water flowing from a reservoir on top of Proffit Mountain into a lower reservoir on the East Fork of the Black River. At night, excess electricity on the power grid is used to pump water back to the mountaintop. The Taum Sauk plant is an open loop pure pumped operation: unlike some other pumped storage sites, there is no natural primary flow into the upper reservoir available for generation. It is therefore a net consumer of electricity; the laws of thermodynamics dictate that more power is used to pump the water up the mountain than is generated when it comes down. However, the plant is still economical to operate because the upper reservoir is refilled at night, when the electrical generation system is running at low cost baseline capacity. This ability to store huge amounts of energy led its operator to call Taum Sauk "the biggest battery that we have". An unusual feature is the upper reservoir which is constructed on a flat surface, requiring a dam around the entire perimeter. On December 14, 2005, a catastrophic failure in the upper reservoir dam put the plant out of operation until it was rebuilt, recertified, and reopened on April 21, 2010. The new upper reservoir dam, rebuilt from the ground up, is the largest roller compacted concrete dam in North America.

The upper reservoir can hold about of water behind a wall nearly 100 feet (30 m) tall. It sits 760 feet (232 m) above the 450 MW hydroelectric plant, which gives it a greater head than that of Hoover Dam. The two are connected by a 7000 feet (2134 m) tunnel bored through the mountain. The Taum Sauk upper reservoir sits on ridge just below the summit of Proffit Mountain, not Taum Sauk Mountain, which is about 5 mile (8 km) to the east. It is visible from Route 21 north of Centerville and from Route N approaching Johnson's Shut ins State Park from the south. Before the failure of the upper reservoir, visitors could drive to the top of Proffit Mountain and walk to an observation deck above the reservoir. Ameren operated a museum at the entrance gate highlighting the geologic and natural history of Missouri. The power plant was frequently visited by geology students because of a striking example of Precambrian/Cambrian unconformity in the rock layers exposed by the plant's construction.

In 1953, the Union Electric Company began to look for a site on which to build a new pumped storage plant. By 1958, company officials had decided to focus on sites with at least 300 feet (91 m) of vertical head, which would allow them to use a smaller storage reservoir. Union Electric hired Sverdrup Parcel & Associates to evaluate potential sites in the St. Francois Mountains, which were chosen for their relative proximity to St. Louis (where Union Electric was based) and the favorably large elevation differentials (some approaching 1000 feet (305 m)). Sverdrup Parcel & Associates intended to recommend Taum Sauk Mountain as the site, in part because it was the highest point in Missouri at 1752 feet (534 m), but strong political opposition to development of the scenic mountain (which was later incorporated into a state park) ruled it out. The nearby Proffit Mountain ended up being an excellent alternative thanks to its comparable elevation (1720 feet (524 m), the 6th highest point in Missouri), its close proximity to the East Fork of the Black River, and the reasonably short distance (27 mile (43 km)) to the existing power transmission grid. At its completion, the Taum Sauk plant was by far the largest pumped storage plant in North America in a number of measures, and was considered a major milestone in the development of pumped storage technology. Its pump turbines were the largest ever produced at the time of construction, it had an unusually high head (the highest in the US at the time, far surpassing all previous US pumped storage projects), a large storage capacity (it has been described as "the first of the large capacity pumped storage stations to begin operation in the United States"), black start capability, and had the unique ability to be operated either remotely by remote human operators in off site facilities located 90–120 miles away (at St. Louis or Osage Power Plant/Bagnell Dam) or even fully automatically with zero human intervention. From 1998–1999, the turbine runners for both units were upgraded, resulting in improved flow rates and another power uprate to 225 MW per unit (450 MW total). The plant was named an IEEE Milestone in October 2005, just months before the upper reservoir failed. It was subsequently rededicated as an IEEE Milestone in 2010 after the new upper reservoir dam was completed.

Water was pumped into the rebuilt reservoir for the first time on February 27, 2010, and engineers monitored the response of the new structure as the water level was repeatedly raised and lowered. The final approval required from the FERC for "return to normal project operations" was received on April 1, 2010. The utility met the Missouri Public Service Commission’s in service criteria for operations on April 15, and electricity was first generated from the new structure on April 21, 2010.