Akosombo dam, Ghana (1020MW)

Akosombo dam is located on the Volta River in Ghana. The rockfill embankment dam has a crest length of about 700m and a height of 134m, and involved 12Mm3 of surface excavation. It was constructed from 1961 to 1966 primarily for the purpose of electricity generation, but also provides a livelihood for about 300,000 people through fisheries in the lake.

The project’s original electrical output was 912MW, which was upgraded to 1020MW in a retrofit project that was completed in 2006.
In January this year Zoetic Global, a US-based project developer, executed a 20-year power purchase agreement with the Electricity Company of Ghana (ECG) for 100MW of additional power at the dam site.

The project will involve an array of modular hydrokinetic turbines to be deployed in the post-dam wash of the Akosombo Dam. The In-Stream Auger Turbine (IAT) technology being used is designed for high efficiency power generation from flowing water and will leverage existing infrastructure at the dam site including grid connections, access roads, and on-site maintenance buildings.

Zoetic is working with strategic partners including Natural Power Concepts, International Coil Ltd, and JWF Industries on turbine production and preparations for the project implementation. The manufacturing of the hydrokinetic devices and components is scheduled throughout 2016 via partnerships in Pennsylvania and India, with final assembly taking place in Ghana.

John Pitre, inventor of the IAT and founder of Natural Power Concepts, says that "The IAT was designed with developing countries in mind. With traditional hydroelectric plants taking several years to complete and requiring extensive site construction with heavy environmental impacts," he says, "I believed that an alternative solution was needed that could be lower maintenance and more quickly deployed."

In addition to agreements in Ghana, Zoetic is actively negotiating Power Purchase Agreements in other nations in Sub-Saharan Africa as interest in renewables increases across the region. "With recent drivers such as the Obama Administration’s Power Africa initiative and the Paris Climate Pact," Mr. Ringo says, "renewable energy promoters have an immense opportunity to deliver real impact to the developing world."

Aswan High Dam, Eqypt (2100MW)

With an installed capacity of 2100MW through 12 turbines, Aswan High Dam is the largest hydropower project in Eqypt.

The project features a rock-fill dam which impounds the River Nile creating Lake Nasser, which has a water storage capacity of 132 billion cubic metres.

The project was constructed from 1960 to 1968 with an investment of approximately $1 billion.

The multipurpose dam serves the irrigation needs of both Egypt and Sudan, controls flooding, generates power, and helps in improving navigation across the Nile. It is 111m in height, 3830m in length, and has a base width of 980m. Its single spillway has a water discharge capacity of 11,000 cubic metres a second.

Companies involved in the project included ABB and Power Machines.

Cahora Bassa Dam, Mozambique (2075MW)

The Cahora Bassa system is the largest hydroelectric scheme in southern Africa with the powerhouse containing five 415 megawatts (557,000 hp) turbines. Most of the power generated is exported to South Africa through a HVDC system.

The dam, located about 80 miles (125 km) northwest of Tete, is 560 feet (171 m) high and 994 feet (303 m) wide at the crest. It has a volume of 667,000,000 cubic yards (510,000,000 cubic m).

The dam impounds Lake Cahora Bassa, which is 150 miles (240 km) long and 19 miles (31 km) wide at its widest point. The lake has a capacity of 51,075,000 acre-feet (63,000,000,000 cubic m) and extends to the Zambia-Mozambique border. The dam was built by a consortium of Portuguese, German, British, and South African companies; construction of the dam began in 1969 and was completed in 1974.

Mozambique took over control of the Cahora Bassa project from Portugal in November 2007. The project had been under the majority control of Portugal as an overhang from the colonial era, despite Mozambique having gained independence the same year.
There have long been plans to increase output at the plant by at least 300MW, but as yet no expansion work has been undertaken.

Gibe III dam , Ethiopia (1870MW)

Ethiopia’s Gibe III hydro project will have a total capacity of 1870MW once fully operational, with the project having started initial operations with the first of its 10 x 187MW turbines generating electricity in October 2015.

The Gibe III dam and associated hydroelectric project is located on the Omo River in Southern Ethiopia in a very remote region. The project features a roller compacted concrete (RCC) dam, which was completed to early impoundent in 2015.

The project overcame some very challenging conditions from a design standpoint as well as a construction standpoint. Its size alone makes the project implementation very difficult in itself. Adding to the difficulties is the natural terrain, steep abutments (in some places 45 degrees or steeper), and extreme hot weather conditions.

One of the greatest challenges that was overcome by the contractor Salini-Impregilo S.p.A was the amount of RCC that had to be placed in the dam body to meet the demanding "fast tracked" schedule. On December 11th through December 12th 2014 the Salini-Impregilo team placed 18,519m3 in a single 24 hour period breaking the world record for the most RCC placed in a single 24 hr period for any RCC dam structure worldwide to date.

Experts from 26 countries took part in the project. Companies involved included Harsco, Tractebel Coyne et Bellier, Sandvik, Sicoma and RCC Conveyors USA LLC

Grand Ethiopia Renaissance Dam (6000MW)

The multi-billion dollar Grand Ethiopian Renaissance dam is being constructed on the Blue Nile, about 20km from the Sudanese border. With a capacity of 74 billion cubic meters, the project is expected to generate electrical power of up to 6000MW.

The project has however provoked some controversy, with Egypt concerned that the dam could reduce its water share, while the Ethiopian side maintains that the dam is primarily built to produce electricity and will not harm Sudan and Egypt.

On September 22, 2014, the panel of experts in the three countries proposed the conduction of two additional studies on the dam project, the first one on the effect of the dam on the water quota of Sudan and Egypt and the second one to examine the dam’s ecological, economic and social impacts on Sudan and Egypt.

On 10th February, the tripartite national committee on the Grand Ethiopian Renaissance Dam agreed on a joint stance toward the technical proposal submitted by the French consultancy firms that were assigned to study the impact of the dam on Sudan and Egypt.

The French companies Artelia and BRL were selected to undertake the dam impact studies.

On the side-lines of the recent Africa 2016 Forum, Egyptian President Abdel Fattah el-Sisi met with Sudanese Presidents Omar Hassan Al-Bashir and Ethiopian Prime Minister Hailemariam Dessalegn to discuss the technical progress made on the Grand Ethiopian Renaissance Dam, to review the progress of the Declaration of Principles signed in March 2015, and the progress of the tripartite meetings between the three countries’ ministers of foreign affairs and water resources.

Sudanese ambassador to Egypt Abdel Mahmoud Abdel Halim said the meeting had boosted progress between the three countries in terms of the technical aspects of the GERD.

Companies involved in the project so far include: Tratos Cavi Spa, Studio Pietrangeli, Salini Impregilo

Inga-II dam, DRC (1424MW)

Completed in 1982, Inga II has a total capacity of 1424MW. The project is the second dam after Inga I (351MW) to be connected to one of the largest waterfalls in the world, Inga Falls, with plans to build a third (Inga III) and fourth (Grand Inga), both of which are detailed below.

Both dams have faced problems and fell into disrepair, operating far below capacity. Canadian company MagEnergy signed an agreement with operater SNEL to rehabilitate some of Inga’s II turbines, with work starting in 2006 to fix one 168MW turbine together with other emergency work. A second phase was expected but since then there been issues with the validity of the contract with MagEnergy.

In 2014, Cegelec Belgique Export (VINCI Energies GSS), in a joint venture with Siemens, was awarded a €90m contract for work on modernizing two turbines at the project. For Cegelec Belgique Export, the project involves, on the one hand, reinforcing the two substations enabling power to be transmitted from Inga to Kolwezi (a distance of 2,200 km);and, on the other, replacing the power transformers, and various works at the substations (section switches, circuit breakers, etc.). Other companies involved in the project include Idreco (International Dredger Constructions) of the Netherlands and Andritz.

Inga 3 (4800MW) and Grand Inga (40,000MW+)

The proposed 4800MW Inga 3 project is the first part of the 40,000MW Grand Inga project on the Congo River. The Inga 3 development would divert about one sixth of the flow of the Congo River into the Bundi Valley. A dam on the Bundi River would create a 15.5km2 reservoir. Inga 3 does not include a dam on the Congo River itself. A preliminary environmental and social assessment concluded that the Inga 3 development has a smaller footprint compared to hydropower projects of the same capacity. The land area to be flooded per megawatt of electricity generated will be among the smallest in the world, said the Bank. A feasibility study on the project was completed by AECOM and EDF.

As part of the project, 1000MW of electricity produced would be sold to the national utility SNEL, which in turn would sell it to households and small businesses in greater Kinshasa. A further 1300MW is expected to be sold to mining companies in DRC’s Katanga Province and an additional 2500MW would be sold to South Africa. At the same time, the mid-size hydropower projects would help to increase energy access for people living in the rest of DRC.

In early December 2015, DRC Prime Minister Matata Ponyo said the country intends to begin construction Inga 3 as early as the end of 2016, or the start of 2017, depending on the selection of principal partners for the project.

Ingula, South Africa (1332MW)

Ingula pumped storage scheme will have a production capacity of up to 1332MW when it goes into operation in the second half of 2016.

Built by the CMI Joint-Venture with Italy’s Salini Impregilo as one of its partners,

The Eskom owned project is located between Ladysmith and Harrismith in the Little Drakensberg. The pumped storage scheme consists of an upper and a lower dam, each capable of holding approximately 22 million cubic metres of water. The dams, 4.6km apart, are connected by underground waterways passing through a subterranean powerhouse with four 333 MW generators.

The upper dam, named Bedford Dam, is located in the secondary of Wilge River that flows into the Vaal River system. The dam is 810m long and 40.9m high. It also has a 100m-long emergency spillway, a dam crest with elevation of 1740.6m and 8m crest width.
The roller lower dam, named Braamhoek Dam, is situated in the secondary of Klip River that flows into the Thukela River. The length and crest width of the dam are 331m and 5m. The dam is 38.6m high and has a 40m long crest. The 0.5m dam wall height holds flood inflows to avoid 1:200-year flood dam spill.

Originally expected to start coming online in 2013, the project suffered delays following a fatal incident in October 2013 which led to the death of six construction workers.

Companies involved in the project include CMI Joint-Venture with Italy’s Salini Impregilo. Others include GIBB, Royal HaskoningDHV, Knight Piésold, Murray Roberts, Voith and ABB.

Kariba Dam, Zambia/Zimbabwe (1830MW)

The Kariba Dam is the largest man-made reservoir in the world. At a height of 128m and with a crest length of 617m, the dam has the capacity of holding 181Bm3 of water. Designed as a double curvature concrete arch dam, the Kariba Dam was constructed across the Zambezi River between 1956 and 1959. Commissioned in 1960, the Dam has been central to regional energy security and economic development ever since.

The Kariba Reservoir supplies water to two underground hydropower stations with a total capacity of 1830MW generating more than 10,035GWh of electricity annually. The North Bank Power Station is operated by ZESCO in Zambia and has an installed capacity of 1080MW. The South Bank Power Station is operated by ZPC in Zimbabwe and currently has an installed capacity of 750MW, with projects underway to increase this to 1050MW.

After more than 50 years of providing power for the Southern African Region, the Kariba Dam now requires a series of rehabilitation works for its continued safe operation. The program is to be implemented over the next ten years, taking into account the need to continue operating the dam safely with minimal interruptions to power generation.

The works will include 1. reshaping of the plunge pool to limit scouring and erosion that could potentially undermine the dam foundations; and, 2. refurbishment of the spillway and associated infrastructure to improve the dam’s stability and operations.

The bi-national Zambezi River Authority (ZRA) is undertaking the necessary Environmental and Social Impact Assessment, preparing an integrated Environmental and Social Management Plan, along with the associated instruments to ensure the sustainability of project through appropriate preventive, mitigation and monitoring interventions.

The total cost of works of works is estimated at US$294 million. The Governments of Zambia and Zimbabwe have mobilized financing from the African Development Bank, the European Union, the Government of Sweden, and the World Bank to support the ZRA in implementation of the project.

Merowe Dam, Sudan (1250MW)

The Merowe Dam is a 1250MW project located on the river Nile in northern Sudan.

Construction of the project began in 2003 and was inaugurated in 2009. It is designed to provide electricity, irrigation, flood protection and sediment management. The project features concrete-faced rockfill dams – the right bank dam is the largest part of the project, 4.3km long and 53m high; the left bank is 1590m long and 50 metres high). It also features a a 883m-long 67m high earth-core rockfill dam (the main dam) in the left river channel, and a live water section in the right river channel (sluices, spillway and a 300m power intake dam with turbine housings).

The main contractors on the project were China International Water & Electric Corp., China National Water Resources and Hydropower Engineering Corp., Lahmeyer International and Alstom (now GE).

DSI was also involved in the project in anchoring the trunnion girders to the radial gates. It delivered a total of 4 x 27 = 108 pieces of 32mm St930/1080 DYWIDAG Post- Tensioning Bars in lengths between 6.0m and 11.20m with bilateral plate anchorages. All in all, the spillway dam contains 12 lower and 2 upper flood spillways where the water level can be regulated by means of the radial gates in times of critical flooding.

In addition to the supply of material, DSI assisted the client by supervising the installation, tensioning and grouting of the DYWIDAG bar tendons.