Technical feasibility studies

  • Access to hydropower site and Sombwe Camp
  • Topography
  • Hydrology
  • Geophysics
  • Characteristics of the layout
  • Geotechnics
  • Power purchase agreement (PPA)
  • Transmission line (Separate study)

Access to the site and Camp Sombwe

Access to a hydroelectric site is the first step and it makes technical feasibility studies and field work possible. In 2015 the hydroelectric site was identified by helicopter due to no excising road or path leading there. KIPAY has constructed a 50 km road to make the site accessible by vehicles and to supply equipment for the technical feasibility studies.

The nearest village Kalera is located 50 km from the site. To save time and be efficient KIPAY established  Camp Sombew in September 2016.  The camp has hosted KIPAY representatives, local workers from the Kalera village and KIPAY contractors (Rubaco, Ingérop, Knight Piésold)

The feasibility studies is completed and at the moment the camp is guarded by a KIPAY team consisting of workers from the Kalera village.

The camp is provided with water (submersible pump ) and electricity (3kva Generator).

OVERVIEW OF THE SOMBWE SITE

 

b. Topography

The Sombwe hydroelectric site was identified through comprehensive surveys using the existing cartography as well as the map made by the Royal Museum for Central Africa in Belgium anno 1952. To improve the topography of the site KIPAY has created a LIDAR cartography covering an area of 209km2 (from Sombwe to Kiubo: 45 km in linear distance)

  • LIDAR point X, Y, Z.
  • High resolution images (10 cm)
  • CAD files

c. Hydrology in Sombwe

A hydrological study must be based on actual chronologically quantities of water (general daily instant flows) and in particular hydrological conditions like: pluviometry (the measurement of rainfall), evaporation, sedimentation, flood, baseflow, etc.

Upstream of the Sombwe hydroelectric site you find Mwadingusha and Koni Hydroelectric Dams ( around 160 km in linear distanse). The hydrological studies were based on historical hydrometric data of the said power stations (the Lufira river watershed), implementation of some measurements of the flows made to the Kiubo-Sombwe section and the satellite rainfall data covering a period of 100 years (1915 to 2014) of the study area. This show that:

  • The average flow: 105.7 m3 / s
  • Total supply capacity (Tank capacity): 320 Mm3
  • Average annual flow: 3,332 Mm3
  • Flood safety assessment: 6 391 Mm3
  • Loss of supply due to sedimentation after 50 years: 5% month
  • Total surface area of ​​the reservoir: 20 km2

NB: The hydrological studies have been completed and revision is in progress.

On  the 12-September-2017 a 5m scale was installed at the Sombwe site for measuring the water level. A trained operator does the daily readings. But on the 07-April-2018 there was a ten-year flood (according to regional data) that buried the scale until the 14-May-2018.The readings were then resumed but the flood deformed the scale and tore of the second one-meter pattern. The scale was repaired in July 2018. (see before and after photos of the flood) All readings done after the flooding up to 20-July 2018 are now corrected by the cosine of the deformation angle.

During the flood the team based in Sombwe marked the water level on the tree at the left bank of the Lufira River and after the flood, compared to the mark, the height of 7.59 m was measured. This height corresponds to a flow rate of 1003 m3 / s measured at Kiubo by the ADCP.

In addition, since 04-December-2017, an automatic climatological station has been installed in the Congo Safari garage (Kiubo Lodge). It mainly measures the values of the following quantities:

  • Rainfall
  • Sunshine
  • Wind speed
  • Temperatures (indoor and outdoor)
  • Atmospheric pressure
  • Illumination

Also in December 2017 a 2-meter scale was installed in Kiubo for water level readings and a trained operator does readings twice a day.

When this work is completed it will create: daily flow curves, characteristic of flows (nominal, maximum, minimum). Below the temporary curve Heights-flows based on the readings of water levels in Sombwe and the measurements of flows made.

Below, the photos illustrating the Sombwe (Hydrometric Station of Sombwe)

Geophysics

To size foundations or ensure the stability of structures, it is essential to know the structure and nature of the soil and subsoil. The data collected feeds the technical studies, which determine the characteristics of the structures according to the mechanical capacities of the soil and subsoil and the constraints of the structures.

At the Sombwe site, two geophysical processes were uses:

  • Magnetometry (preliminary geophysical study),
  • Electric tomography (final geophysical study).

Geotechnical

The geotechnical survey for Sombwe hydroelectric site is finalized and extracted cores are sent to South Africa for laboratory analyses, the first results of which show the predominance of hard rock (quartzite).

Transmission line

The feasibility study for transmission lines is not a part of the feasibility study for production. According to the Congolese law on liberalization of the electricity sector (2014) production of hydropower is divided in three parts:

  • Concession for production
  • Concession for transport
  • Concession for distribution

Kipay has completed the production feasibility and has started to work on the feasibility studies for concession for transport.

The different concessions are indirectly connected, the concession for production also address the various possibilities for transport the power produced in Sombwe. There are two options for connecting to excising grid in Fungurume (160 km in linear distance) and Panda (200 km in linear distance).

A site visit to FUNGURUME and TENKE stations on 24.- 27. June, 2018, showed that the FUNGURUME substation will be the best interconnection option for the Sombwe line.

  • 220 kV substation adapted to the voltage level of the Sombwe line;
  • Shortest distance to other points of interconnection;
  • Good geographic location (almost no easements) and
  • Available space to implement the span from Sombwe.

The FUNGURUME substation belongs to SNEL(the National electricity company of the Democratic Republic of the Congo). Any use or modification can only be carried out with the approval of SNEL, because of this, KIPAY have to sign a memorandum of agreement with SNEL.

There are two two 220kV sections busbars at the FUNGURUME substation. One of the functions as back up. A new 220 kV span have to be installed in order to receive the new SOMBWE power line (see the site visit report).

The existing post in FUNGURUME has been extended several times the past years by different units. The crossing of the existing lines by the new SOMBWE line is likely (see figure below).

Simplified single-line diagram of the Sombwe substation and line terminating at the substation

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