Alexandros Korkovelos is a winner of the 2017 IHA Young Researcher of the Year award. In this article from his award submission, he discusses his research on small-scale hydropower potential in Sub-Saharan Africa.
Sub-Saharan Africa has been at the epicentre of an ongoing global dialogue around the issue of energy poverty. More than half of the world’s population without access to modern energy services lives there.
It also happens to be a sub-continent with plentiful renewable energy resource potential. Hydropower is one of them, and to a large extent it remains untapped. This study focuses on the technical assessment of small-scale hydropower (0.01–10 MW) in Sub-Saharan Africa.
The underlying methodology was based on open-source geospatial datasets, whose combination allowed a consistent evaluation of 712,615 km of river network, spanning over 44 countries. Environmental, topological and social constraints were included in the form of constraints in the optimisation algorithm.
The methodology followed in this study can be divided into four main steps. The first, considers the acquisition and calibration of all the input GIS datasets so as to retrieve essential information that can be used in the assessment.
The second step considers the calculation of the hydropower potential in each location, whereas the third step involves the selection process of suitable sites based on technical and topological criteria.
Finally, the forth step considers analysis of the results and visualisation. Figure 1 visually schematically represents these steps:
Figure 1: small-scale hydropower assessment methodology flowchart.
In total, 15,599 potential sites were identified across the sub-continent, aggregating to a total technical potential of 25,221 MW. The results are mapped in Figure 2 below.
Figure 2: map illustrating the hydropower potential sites identified for capacities between 0.1 and 10 MW in Sub-Saharan Africa.
Graph 1 presents a categorisation of the potential small/mini hydropower results per African power pool. The Southern African Power Pool shows the highest value, with an estimated potential capacity of approx. 9.9 GW, followed by the Central and Eastern African Power Pools showing approx. 5.7 and 5.6 GW respectively. The Western Africa Power Pool shows the lowest potential, with approx. 3.9 GW.
Graph 1: small-scale hydropower potential per African power pool.
These results are primarily explained by the difference in the available land for hydropower deployment in each power pool. As Table 1 indicates, both the actual and suitable area that the Southern Africa Power Pool offers for mini and small hydropower is higher than the one identified in the other power pools.
On the contrary, the restricted areas identified in the Western Africa Power Pool, a densely populated area with intense agriculture activities, excluded as much as 64.6 per cent of its area. This indicates that the results are quite sensitive to the selection of restriction zones, which need to be selected appropriately so that they reflect the existing social, economic, technical and environmental limitations in the studied area.
Table 1: identified small scale hydro power density per African power pool.
|Power pool||M/S hydropower sites||M/S hydropower power potential||Total area||Restrictions||Suitable||Small scale hydropower availability index|
In order to get an alternative look on the results, a hydropower availability index was introduced, indicating the potential power in terms of kW per km² of identified suitable land. The southern part of the sub-continent seems to offer higher availability index for small scale hydropower deployment with the western, eastern and central parts to follow respectively (Table 1).
Mini hydropower potential
The total mini hydropower potential (0.1–1 MW) in Sub-Saharan Africa was estimated at 3,421 MW. Most of the 10,216 sites identified were located in the central part of the sub-continent, with the Democratic Republic of the Congo (DRC) and Angola showing the highest potential, reaching 975 MW.
On the contrary, no potential site was identified in Djibouti, while Burundi, Rwanda, Gambia and Swaziland show very little mini hydropower potential. The main reason behind that is the small size of these countries, with short, low stream-order river networks, which in combination with the restriction zones applied did not allow the identification of any potential site.
This does not imply that there is no small-scale hydropower potential in these countries, but rather points out on of the limitations of the suggested approach. Take for example the case of Rwanda, where approximately 662 km of river network has been identified. The assessment yielded about 28.4 MW of small-scale hydropower potential in 29 sites across the country, which, however, were characterised as un-suitable, as they were located within restricted areas.
Small hydropower potential
For small hydropower (1–10 MW), there were 5383 sites identified across the studied countries, with the total estimated potential reaching 21,800 MW.
The highest potential is evident in the central corridor of the sub-continent with South Africa, DRC and Sudan accounting for approximately one-third of the total potential identified. No potential sites were identified in Burundi, Djibuti, and Rwanda for the same reasons explained in the previous paragraph.