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Special Report | March 2014

Powering lives in Ghana

The $622 million Bui Dam project, when completed this year, will have an installed capacity of 400 MW and an estimated average annual generation of 980 GWh. PROJECTS INFO reports on this project.  

The Bui Dam is a 400 MW hydroelectric project in Ghana, Africa. The dam can define many of the positive aspects that are associated with the construction of dams. It is built on the Black Volta river at the Bui Gorge, at the southern end of Bui National Park. The project is a collaboration between the government of Ghana and Sinohydro Corporation Ltd, a Chinese construction company. Once completed, the proposed 400 MW hydropower project will be the second largest hydroelectric generating plant in the country after the Akosombo Dam.

 

Its design includes the development of an irrigation scheme for agricultural purpose and it also presents an opportunity for enhanced eco-tourism and fisheries.

 

Construction on the main dam began in December 2009, and the first generator produced power for the grid on 3 May 2013, with completion expected in 2014.

 

Finance plan
 The total cost of the project was estimated at $622 million. The Government of Ghana provided $60 million while the Exim Bank of China provided a loan of $562 million. The $562 million was made up of a concessionary loan of $268.5 million and a buyer's credit loan of $293.5 million.

 

The Bui Project experienced a shortfall in project funding arising primarily from the unanticipated effects of the 2008 global financial upheavals as well as unforeseen essential works and the inadequacy of the budget provided for some line items in the EPC contract, totalling $168 million. The Government of Ghana secured the additional funding in December, 2013 bringing the total project cost to $790 million.

 

Transmission system
 Power produced from the Bui Generating Plant is evacuated from the newly constructed Bui Switchyard through 161 kV transmission facilities which will be operated as part of the National Interconnected Transmission System.

 

A total of 240 km of transmission lines were built under the project. These were two 17 km and 18 km lines which broke into the existing Sawla-Techiman line to form Bui-Sawla and Bui-Techiman lines respectively.

 

Other facilities constructed were:

 
     
  • 67 km Bui-Kintampo line
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  • 138 km Bui-Sunyani line
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  • Expansion of the Sunyani substation to accommodate the new Bui-Sunyani line
 

Design
 The Bui Dam is a gravity roller-compacted concrete-type with a height of 108 m (354 ft) above foundation and 90 m (295 ft) above the riverbed. The crest of the dam is 492 m (1,614 ft) m long and sits at an elevation of 185 m (607 ft) above sea level (ASL). The main dam's structural volume is 1,000,000 m3 (35,000,000 cu ft). Southwest of the dam two saddle (or auxiliary) dams maintain pool levels and prevent spillage into other areas of the basin. The first and closest to the main dam is Saddle Dam 1. It is 500 m (1,640 ft) southwest of the main dam and is a rock-fill embankment dam. The dam rises 37 m (121 ft) above ground level and has a crest length of 300 m (984 ft). 1 km (1 mi) southwest of the main dam is Saddle Dam 2. This dam is a zoned earth-fill type with a height of 7 m (23 ft) ASL and a crest length of 580 m (1,903 ft). Both saddle dams have a crest elevation of 187 m (614 ft) ASL.

 

The reservoir that the main and saddle dams create will have a maximum capacity of 12,570,000,000 m3 (10,190,665 acre ft) of which 7,720,000,000 m3 (6,258,706 acre ft) is useful for power generation and irrigation. The reservoir's maximum operating level will be 185 m (607 ft) ASL and the minimum 167 m (548 ft) ASL. At the maximum level, the reservoir will have a surface area of 440 km2 (170 sq m) while at minimum it will be 288 km2 (111 sq m). The reservoir's volume at minimum level is 6,600,000,000 m3 (5,350,707 acre ft). The average length of the reservoir will be 40 km (25 mi) with an average depth of 29 m (95 ft) and a maximum 88 m (289 ft).

 

Just downstream of the dam on the left bank is the dam's powerhouse. The intake at the reservoir will feed water through three penstocks to the three separate 133 MW Francis turbine-generators. Each turbine-generator has a step-up transformer to increase the voltage to transmission level. A fourth unit, with a penstock on the spillway, will provide four megawatts for station service and black start power, and will provide minimum flow to maintain river levels if the main units should be shut down. The power station will have an installed capacity of 400 MW and an estimated average annual generation of 980 GWh. The power station's switchyard is located 300 m (984 ft) downstream. Four 161 kV transmission lines connect the substation to the Ghana grid.

 

The dam's spillway near the right bank consists of five radial gates, each 15 m (49 ft) wide. The spillway sits at an elevation of 169 m (554 ft) and has a maximum discharge of 10,450 m3/s (369,038 cu ft/s) which correlates to a 1-in-10,000 year flood. The dam's outlet works consist of a single outlet on the right bank converted from one of the diversion tunnels.

 

Benefits
 Hydropower generation and water supply

 
     
  • The country's generation capacity will be increased thus enhancing power supply in the country in general and in particular the reliability and security of power supply to the Northern Sector of the country
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  • The Bui hydropower plant will increase the installed electricity generation capacity in Ghana by 22 per cent, up from 1920 MW in 2008 to 2360 MW
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  • Reinforcement of the transmission network in the three northern regions
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  • The irrigation of high-yield crops on 30,000 hectares of fertile land in an "Economic Free Zone"
 

Socio-economic

 
     
  • Job creation
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  • Improvement of educational, health and social facilities
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  • Development of transportation networks (access to markets for farm produce) Irrigation scheme
 

As the country moves to develop its oil and gas resources, the government is keen not to push agriculture to the backstage but to continue to improve inputs for sustainable agriculture growth, food availability and food security for the people of Ghana.

 

The government is therefore taking advantage of the reservoir to be created by the Bui hydroelectric project to promote the irrigation of over 30,000 hectares of lands. The proposed area is located about 32 km northeast of the dam site.

 

Royal Haskoning BV a consulting firm from Netherlands has been engaged to conduct feasibility studies of the proposed area and also provide detailed designs for the development of 5,000 hectares as the first phase of development.

 

The Bui area has large tracts of fertile and irrigable lands second only to the Afram Plains and it is the intention of government to utilise the land to augment efforts at opening Northern Ghana for economic growth and development.

 

Environmental impact
 The Bui National Park will be significantly affected by the Bui Dam. Around 21 per cent of the park will be submerged. This will affect the only two populations of black hippopotamus in Ghana, whose population is estimated at between 250 and 350 in the park. The dam could also have other serious environmental impacts, such as changing the flow regime of the river which could harm downstream habitats.

 

Social impact
 The Bui Dam project required the forced relocation of 1,216 people, of which 217 have been resettled as of June 2010. In order not to slow down the construction of the dam, the Bui Power Authority had opted for a quick resettlement process. Thus, all affected people are expected to be moved to a new locality called Bui City. However, as of 2010 the city does not exist and there is not even a schedule for its construction. Instead, the first 217 relocated people have been moved to a temporary settlement called Gyama Resettlement Township, which has dilapidated infrastructure. Fishers were resettled on dry land and lost their livelihoods. Although the study had recommended to establish an independent body to monitor the resettlement, no such body has been set up.

 

Highlights
 Project:
Bui hydropower project
 Cost: $622 million
 Owner(s): Bui Power Authority
 Contractor: Sinohydro Corporation of China
 Other contractors: Consultant: Coyne Et Bellier
 Consulting Engineers: Tractabel Engineering, France
 Generation capacity: About 400 MW and a net average annual energy production of 1,000 GWh/yr
 Volume: 1,000,000 m3 (35,314,667 cu ft)
 Location: On the border of the Bole (Northern Region) and Banda (Brong-Ahafo Region)
 Country: Ghana
 Closest towns: Bamboi (31.5 km), Wenchi (86 km)
 River: Black Volta River
 Workers employed: 6,000 people
 Turbines: 3x133 MW Francis turbines
 Crest elevation: 185 masl (metres above sea level) Full supply level (F.S.L): 183 masl
 Height: 108 m
 Length: 492.5 m (1,616 ft)
 Max. water depth: 88 m (289 ft)
 Construction began: January 2008 (Preparatory), December 2009 (Main dam)
 Opening date: 2013
 Status: Operational

 

Project Schedule

 
     
  • Commencement of preliminary stage: May 2007
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  • Commencement of preparatory stage: August 2007
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  • Construction of basic infrastructure, e.g. roads, camps, etc.: November 2007
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  • River closure: December 2008
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  • Impoundment of river: June 2011
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  • Completion and Commissioning: December 2013
 

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