1,020MW Akosombo Hydro Electric Power Plant
Dam Name | Akosombo Dam |
Location | Akosombo |
District | Asuogyaman District |
Region | Eastern Region |
Type of Dam | Rock fill Embankment Dam |
Reservoir | Storage Reservoir |
Water Course | Volta River |
Length of main Dam at crest | 660m (2,165.33ft) |
Length of Saddle Dam | 355m (1, 164.68ft) |
Axis from Bedrock | 111m (364. 17ft) |
Net Generation | 6, 502, 784,456 kwh |
Height at axis from bedrock | 111m (364.17ft) |
Area of Lake | 8,502sq.km |
Capacity of Lake | 148 x 10 12 litres |
Shoreline | 7,250km |
Length of Lake | 400km |
Original Constructions | 1961 – 1965 |
Structural Height | 375ft |
Hydraulic Height (Normal operating Depth at Dam) | 68.8 metres (226 ft.) |
Top parapet (Elevation) | 290ft |
Spillway Crest Elevation | 236ft |
Crest Elevation | 236ft |
Crest Length | 640m (2,100ft) |
Crest Width | 40ft |
Base Width | 366 meters (1,201 ft) |
Volume of Dam Construction Materials | 7,943,520m3 (26,061,100.42ft) |
Main Dam Axis | N 89° 05″ 18″ E |
Saddle Dam Axis | S 54: 30″ 04″ E |
Top of Exclusive Flood control Pool (Elevation) | 278ft |
Reservoir Capacity | 120,000,000 acre feet |
Hydraulics
The Akosombo Dam has 640m crest length and 141m high. Two spillway structures are constructed in concrete and founded on rock. The two gated structures include in total 12 identical gates (6 gates at each spillway, dimensions W x H= 11.73m x 12.19m). The two spillways are adjacent to each other but the spillway chutes are pointing in slightly different directions. The gates are operated by one single moveable hoist (same hoist used on both spillways). The 335m crest length and 37m high Saddle Dam located about 1km east of the main Dam is constructed as a rock fill embankment Dam with central core of clayey materials. The Saddle Dam is founded on rock and the foundation level is well above the tail water level.
Total water Storage at Elevation | 84.73 metres (278.0 ft.) |
Maximum Water Surface Elevation | Concrete lined, Rock founded, Six twin |
Spillway Type | Gated Spillway Structure |
Spillway Capacity at Elevation Drainage Area | 34,000 m3/s (1,200,000 cu ft/s) |
Drainage Area | 6500 sq km |
Probable Maximum Flood (PMF) (Inflow) | 32,042 m3/s |
Probable Maximum Flood (PMF) (Outflow) | 23,010 m3/s |
Maximum Operating Level | 84.73m (278ft) |
Minimum Operating Level | 73.15m (240ft) |
Maximum Water Level ever recorded | 84.59m (277.54ft) on 8th November, 2010 |
Minimum Water Level ever recorded | 71.62m (234.96ft) on 21st July, 2007 |
Maximum Annual Inflow ever recorded | 62.09 MAF in 1968 |
Minimum Annual Inflow ever recorded | 6.20 MAF in 1983 |
Turbine
- Unit output -173.1MW (222000hp) (Retrotted Units)
- Head (Max) -68.88m (226ft)
- Synchronous speed – 115.4 Rev/Min
- Type of Turbine -Francis, Vertical shaft
- Manufacturer -VA Tech, Voest Alpine, Austria
Generator
Rating -179.5MVA at 14.4KV, 0.95PF Manufacturer -General Electric, Canada
Exciter
Type – Static (SILCO-5) Manufacturer -General Electric, Canada
Unit Transformer
Type – Outdoor 3phase Rating -200/MVA, 14.4/161KV Cooling -OFAF Manufacturer -Areva, Turkey
Governor
Type -Digital/Hydraulic Manufacturer -Andritz Hydro, Austria
Penstock
Type -Steel, one per unit Diameter | 7.2m (24ft) |
Maximum Water Surface Elevation | Concrete lined, Rock founded, Six twin |
Funding
Financial Support:
|
$ 47,000,000 |
|
$ 14,000,000 |
|
$ 10,000,000 |
|
$ 27,000,000 |
|
$ 98,000,000 |
Total Cost of Project (at the time of project completion) | $196,000,000 |