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ANGOLA – NEW CACULO CABAÇA HYDROPOWER PROJECT IN THE KWANZA RIVER – CONSTRUCTION ABOUT TO BEGIN

In 2014, under the scope of a contract signed with the Ministry of Energy and Water of the Republic of Angola, COBA prepared the Final Design and Technical Specifications for the construction of the Caculo Cabaça hydropower project in the Kwanza River. This was the baseline project used for the undertaking’s construction, under an EPC context.

This undertaking is located in the middle section of the Kwanza River, upstream from Caculo Cabaça falls, with the dam located about 19 km upstream the Laúca Hydropower Project, currently under construction.

The studies and designs undertaken by the COBA group began with an assessment of the conceptual solutions chosen in the previous feasibility design phase, which ended in 2012. A careful technical and economic analysis resulted in the change of the dam type: roller-compacted concrete dam (RCC) instead of the previously chosen solution, a rockfill dam with concrete facing.

The Caculo Cabaça Hydropower Project essentially consists of a concrete dam with maximum height of 103 m and 553 m crest length, with storage capacity of about 440 million m3. The hydraulic structures comprise a controlled frontal spillway, provided with five radial gates, designed for a flow of 10.020 m3/s, and bottom outlet formed by two lined tunnels with Ø 6,0 m. In addition to the central body of the dam there are two small saddle dams, both on the left river bank, which are closed by concrete weirs with lengths of 525 m and 192 m and widths of 36 m and 4 m, respectively.

This undertaking, that takes advantage of the 215 m head between the reservoir and the outlet works, downstream from the natural waterfalls of Caculo Cabaça, includes a powerplant and a water circuit designed for a 1100 m3/s flow distributed among four pumping units with a rated capacity of 530 MW each. The water circuit flowing into pumps consists of a reservoir intake, located 2,4 km upstream of the dam’s left abutment of the dam, four 300 m-long concrete lined headrace tunnels with 9 m inner diameter, a cavern powerplant with dimensions 221 m x 26,5 m (Lxh) and 68 m maximum height, as well as two concrete lined tailrace tunnels with 16 m diameter and 5150 m length.

The undertaking includes a second powerplant, adjacent to the dam, designed to pump a 60 m3/s environmental flow.

Two substations are envisaged: a 400 kV main substation and a 200 kV ancillary substation.

The scheduled construction period is 75 months, and construction works are expected to begin shortly.

The annual mean energy generation is 8123 GWh in the main powerplant and 443 GWh in the environmental flow powerplant.

 

Lx, 31 Aug 2015