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| Fig. 1: Blue Nile Falls at Tis Issat near Bahir Dar, Ethiopia. (Source: Wikimedia Commons) |
The construction of the Ethiopian Renaissance Dam across the blue Nile shown in Fig. 1 is contentious issue in the horn of Africa as the dam could potentially affect the amount of water reaching the further downstream countries, Egypt and Sudan. It is beneficial to discuss the potential amount of energy production to be able to do a holistic cost benefit analysis for all parties involved.
In 2011, Ethiopia began the construction the Grand Renaissance Dam. The Dam, which is being constructed across the Blue Nile has a planned generation capacity is 6.0 GW. However, The flow rate of the Blue Nile, shown in Fig. 2, varies significantly throughout the year. It ranges from around 200 m3/s in the fall to up to 5500 m3/s during summer season in Ethiopia. [1]
The Blue Nile's variation in flow rate is mainly caused by the increase in rainfall during the summer season in Ethiopia. For the purpose of this analysis, we shall assume that the flow rate between December and May is 200 m3/s, and that the flow rate from June till August is a constant ascent to 5500 m3/s, followed by a constant descent from August till December. This gives an average flow rate for the year of
| Φ | = | 5 12 |
× 200 m3 sec-1 + | 1 2 |
× | 7 12 |
× 5500 m3 sec-1 | = | 1688 m |
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| Fig. 2: Variation of flow rate throughout the year. (Source: T. Worku, after Nawaz et al. [1]) |
The average power generated is P = η ρΦgh, where η = 0.9 is the generation efficiency, ρ = 1000 kg m-3 is the density of water, g = 9.8 m sec-2 is the acceleration due to gravity, and h is the head of the dam. The latter ranges from 80 m to 133 m, so we will take as a typical value h = 106 m. The average power is then
| P | = | 0.9 × 1000 kg m-3 × 1688 m3 sec-1 × 9.8 m sec-2 × 106 m | = | 1.57 × 109 Watts |
This corresponds to total annual energy delivery of
| E | = | 1.57 × 109 W ×
24 h d-1 × 365 d y-1 1000 Wh kWh-1 |
= | 1.38 × 1010 kWh y-1 |
The final energy consumption of Ethiopia in 2019 came to around 10.74 × 109 KWh. [2] This would mean the dam would be able to provide 128% of electricity Ethiopia consumed on 2019. The surplus energy could either be sold to sub-saharan countries or provide power to the 44% of Ethiopia that does not have access to electricity. [3] However, further work needs to be done to see the effects of the dam on Egypt and Sudan's water supply and the effect on the area surrounding the dam.
© Temesgen Worku. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] R. Nawaz et al., "Blue Nile Runoff Sensitivity to Climate Change," Open Hydrol. J. 4, 137 (2010).
[2] "Africa Energy Outlook 2019," International Energy Agency, 2019.
[3] A. W. Yalew, "The Ethiopian Energy Sector and Its Implications For the SDGs and Modeling," Renew. Sustain. Energy Trans. 2, 1000128 (2022),
[4] A. Blakers et al., "A Review of Pumped Hydro Energy Storage," Prog. Energy 3, 022003 (2021).
