Helms Pumped Storage Plant

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Helms Pumped Storage Plant
Courtright Reservoir 2.jpg
Courtright, the upper reservoir
CountryUnited States
LocationFresno County
Coordinates37°02′13″N 118°57′53″W / 37.03694°N 118.96472°W / 37.03694; -118.96472Coordinates: 37°02′13″N 118°57′53″W / 37.03694°N 118.96472°W / 37.03694; -118.96472
Construction began1977
Opening date1984
Owner(s)Pacific Gas and Electric Company
Upper reservoir
CreatesCourtright Reservoir
Total capacity123,000 acre⋅ft (151,718,266 m3)
Lower reservoir
CreatesWishon Reservoir
Total capacity129,000 acre⋅ft (159,119,157 m3)
Power Station
Hydraulic head1,625 ft (495 m)
Turbines3 x 404 MW Francis pump turbines
Installed capacity1,212 MW

The Helms Pumped Storage Plant is located 50 mi (80 km) east of Fresno, California in the Sierra Nevada Mountain Range's Sierra National Forest. It is a power station that uses Helms Creek canyon on the North Fork of the Kings River for off-river water storage[1] and the pumped-storage hydroelectric method to generate electricity. After being planned in the early 1970s, construction on the plant began in June 1977 and commercial operations began on 30 June 1984. It has an installed capacity of 1,212 MW and is owned by Pacific Gas and Electric Company.[2]

Design and operation[edit]

The power plant operates by moving water between an upper and lower reservoir. When energy demand is high, water is released from the upper reservoir to the generating plant and the water is discharged into the lower reservoir. When demand is low (such as at night), water is pumped into the upper reservoir to be used as stored energy at a later time. This is accomplished by pump-generators which serve a dual role: the pumps can reverse for use as generators. The plant can go from a stand still to operational in eight minutes which allows it to meet peak energy demand. It consumes more electricity pumping than generating electricity but pumping occurs during periods of low demand with unused surplus energy available at lower costs from the electric grid.[2][3][4]

The upper reservoir, Courtright Reservoir, has a storage capacity of 123,000 acre⋅ft (151,718,266 m3) is at altitude of 8,184 ft (2,494 m). Wishon Reservoir, the lower reservoir, has a storage capacity of 129,000 acre⋅ft (159,119,157 m3). It is at an altitude of 6,550 ft (1,996 m). Connecting the reservoirs, from upper to lower, is first a 10,511 ft (3,204 m) long head-race tunnel which turns into a 2,248 ft (685 m) long steel penstock which drops in elevation and splits into three individual penstocks, which each feed a separate pump-generator. After the water has passed through the generating turbines, it is discharged into the lower reservoir via a 3,797 ft (1,157 m) long tail-race tunnel. The difference in elevation between the reservoirs has an effective hydraulic head (drop of the water) of 1,625 ft (495 m). The underground power station is near Wishon Reservoir and houses three 404 MW Francis pump turbine-generators.[3][4]

The Helms Pumped Storage project was designed to be used with the Diablo Canyon Nuclear Power Plant, also owned by PG&E, in the 1970s, when Diablo Canyon was being designed and permitted. It is connected to that power plant by a dedicated high-tension power line. [5]

See also[edit]


  1. ^ The Dam Truth About Reservoirs "There are 2 broad categories of reservoirs, the valley reservoir [or on-river storage,] and the off-river storage reservoir"
  2. ^ a b "By the Numbers: Helms Pumped Storage Facility". Pacific Gas and Electric Company. 17 October 2011. Retrieved 15 January 2012.
  3. ^ a b Kermit Jr., Paul (March 1989). "Design Features of The Helms Pumped Storage Project". IEEE Transactions on Energy Conversion. Institute of Electrical and Electronics Engineers. 4 (1): 24–25. Bibcode:1989ITEnC...4....9P. doi:10.1109/MPER.1989.4310531.
  4. ^ a b Yeung, Manho (17 October 2008). "Helms Pumped Storage Plant" (PDF). Pacific Gas and Electric Company. Archived from the original (PDF) on 2 January 2012. Retrieved 15 January 2012.
  5. ^ "Diablo Canyon's odd cousin in the mountains", October 12, 2015, San Luis Obispo Tribune

External links[edit]