The 1,870MW Gilgel Gibe III (Gibe III) hydroelectric power project is being constructed on the Omo River in Ethiopia’s Southern Nations, Nationalities, and People’s Region State (SNNPRS).
It is expected to be the largest hydroelectric power plant in Ethiopia and will produce an estimated 6,500GWh of energy a year.
The project will include a 243m roller compacted concrete dam, the first of its kind in Ethiopia and one of the tallest in the world.
Gibe III was launched in July 2006, with the first unit starting its trial-running generation in September 2013. It is expected to be fully commissioned by 2016.
State-owned public utility enterprise Ethiopian Electric Power Corporation (EEPCo) is the developer of the project, which is expected to cost €1.47bn (approximately $1.83bn).
The first two units are expected to come online in June 2015.
Gibe III hydroelectric power project details
The Gibe III project is located within the Omo Gibe River Basin, approximately 450km south of Addis Ababa. It will be used for flood water regulation and maintenance, as well as power generation.
Once commissioned, Gibe III will enable Ethiopia to become self-sufficient in power generation and help it export power to neighbouring countries through a regional interconnection transmission system.
The 243m-high Gibe III dam will have a crest length of 610m and will be constructed at an altitude ranging between 650m and 1,650m above sea level. Its reservoir will have a total storage capacity of 14.7 billion m³.
The surface powerhouse will be located on the left side of the river and will contain 1ten vertical-axis Francis turbines with a nominal power output of 187MW each. It will also include two power tunnels of 11m diameter each. Each tunnel will be connected to five generator units using two penstocks and manifolds.
A switchyard will be installed with ten step-up transformers of 200MVA to convert the voltage from 15kV to 400kV. It will include a double bus-bar scheme linking five three-phase 400kV transmission lines.
Gibe III hydroelectric project construction
Major works at the project include the construction of the dam, powerhouse and two diversion tunnels, as well as the excavation of temporary access tunnels.
Other works will include the construction of twin pumping tunnels, coffer dam, intake structures, horizontal tunnels, and four vertical wells and two distributors.
The Ethiopian Government is providing approximately €448m through the EEPCo.
EEPCo and Tebian Electric Apparatus (TBEA) signed a contract worth $34m for the construction of the transmission lines in July 2009. Chinese EXIM bank will provide 85% financing.
Power transmission from Gibe III
Power will be transmitted to the national grid by two 400kV transmission lines. The first line of the double circuit will be 50.3km long, while the 51km-long single circuit second line will transfer electricity from the Gibe III switchyard to Wolaita Sodo substation.
Contractors for construction and engineering services
EEPCo awarded a $1.7bn engineering, procurement and construction (EPC) contract to Salini Costruttori, an Italian company. Salini also signed an agreement for the construction of a 66kV electrical power line from the Sodo-Wolayta substation to the plant site.
Studio Pietrangeli was contracted by Salini to provide engineering services for the feasibility study, basic design, final design and technical supervision during construction.
A joint venture of ELC Electrocosult and Coyne Et Bellier will act as EEPCo’s representative for the quality control of the design and construction phases.
EEPCO hired Tractebel Engineering and ELC to review the design and assist in the EPC tendering, acting as the owner’s engineer for the project.
Shanghai Electric Group was awarded a contract for the design, manufacture and commissioning of two 400kV substations at Wolayta Sodo and Akaki. This also included the extension work at the existing Gilgel Gibe-II and Sebeta-II 400kV substations.
TBEA, a Chinese company, signed a deal to install power transmission lines running from Gibe III to the Wolayta substation.