Coo-Trois-Ponts Hydroelectric Power Station

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Coo-Trois-Ponts Hydroelectric Power Station
The upper reservoir, Coo I
LocationTrois-Ponts, Stavelot
Coordinates50°23′12″N 05°51′26″E / 50.38667°N 5.85722°E / 50.38667; 5.85722Coordinates: 50°23′12″N 05°51′26″E / 50.38667°N 5.85722°E / 50.38667; 5.85722
Opening date1969-1978
Upper reservoir
CreatesCoo-Trois-Ponts Upper
Total capacityCoo I & II: 8,450,000 m3 (6,851 acre⋅ft) (active)
Lower reservoir
CreatesCoo-Trois-Ponts Lower
Total capacity8,450,000 m3 (6,851 acre⋅ft) (active)
Power Station
Hydraulic head275 m (902 ft) (effective)
Pump-generatorsCoo I: 3 x 158 MW Francis pump turbines
Coo II: 3 x 230 MW Francis pump turbines[1]
Installed capacity1,164 MW

The Coo-Trois-Ponts Hydroelectric Power Station is a pumped-storage hydroelectric power station located in Trois-Ponts, Province of Liege, Belgium. Located next to the Amblève River, the power station uses its water to support a power scheme where water is pumped from a lower reservoir to one of two upper reservoirs known as Coo I and Coo II. When energy demand is high, water can be released from these reservoirs for power generation. The water then returns to the lower reservoir and the process repeats as needed. The same machines that pump the water to the upper reservoirs at a higher elevation are also used as generators. The plant was commissioned in two stages, Coo I (1969) and Coo II (1978). It is owned by Electrabel and has an installed capacity of 1,164 MW.[2]

Design and operation[edit]

The lower reservoir for the power station has an elbow shape and was formed with two embankment dams, one 10 m (33 ft) high and the other 30 m (98 ft). The maximum reservoir elevation of this reservoir is 248 m (814 ft). Nestled in the hills above and west of the lower reservoir are the upper reservoirs, Coo I and Coo II. Each reservoir was formed with an earth-fill dike. Coo I and Coo II have maximum reservoir elevations of 509 m (1,670 ft) and 507 m (1,663 ft), respectively. The active (or usable) storage of the combined upper Coo reservoirs is 8,450,000 m3 (6,851 acre⋅ft). The lower reservoir has the same active capacity as well. Water is transferred between the reservoirs by means of two penstocks, Coo I's being 748 m (2,454 ft) long and Coo II's at 830 m (2,723 ft) in length. The power station is located underground and contains the plant's six generators. The Coo I reservoir powers three 158 MW Francis pump turbines (FPT) with Coo II consisting of three 230 MW FPTs. The change in elevation between the two reservoirs affords a hydraulic head that varies between 230 m (755 ft) and 275 m (902 ft), the effective head is 245 m (804 ft).[3][4]

The plant can go from a standstill to full operation in two and half minutes and switch to pumping mode in about seven minutes. It generates about 1 million MWh annually and consumes about 20 percent more in pumping mode. The plant usually pumps during periods of low demand, such as night time, when energy is cheap which makes it profitable. Its ability to quickly adjust to power demand makes it a peaking power plant.[3]

A panorama of the lower Coo reservoir

See also[edit]


  1. ^ "COO I and II Pumped Storage Hydroelectric Power Project Belgium". Global Energy Observatory. Retrieved 14 January 2012.
  2. ^ "Coo hydroelectric plant". Walo. Retrieved 14 January 2012.
  3. ^ a b Engineers, prepared by Task Committee on Pumped Storage of the Committee on Hydropower of the Energy Division of the American Society of Civil (1996). Hydroelectric pumped storage technology : international experience. New York, NY: American Soc. of Civil Engineers. pp. 3.2 2–4. ISBN 0-7844-0144-6.
  4. ^ ed. by Bjørn Honningsv°ag; Grethe Holm Midttømme; Kjell Repp (2001). Hydropower in the new millennium : proceedings of the 4th International Conference on Hydropower Development, Hydropower '01, Bergen, Norway, 20 - 22 June 2001. Lisse, Netherlands [u.a.]: Balkema. pp. 123–124. ISBN 90-5809-195-3.CS1 maint: Multiple names: authors list (link) CS1 maint: Extra text: authors list (link)

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