When I was in primary school in Change, Zimbabwe, I often traveled with my school and with the AWANA club at Mutare Baptist Church. On one of the camping trips when I was in 6th grade (11 years old), we went to one of the dams around Mutare. We spent the weekend in Little Bridge Dam. It’s a small dam, but it seemed huge to me at the time as a 12-year-old. Later that year, as part of a school trip across the country, we stopped in Masvingo to see the Great National Monument of Zimbabwe and Mutirikwi Lake. At the time, Late Mutirikwi was the largest dam in Zimbabwe. When I first saw it I was just impressed as I walked over the dam wall. I couldn’t believe how big it was. It was the largest dam I had ever seen at that time. Lake Mutirikwi covers about 90 km², the height of the sheet pile is 63 meters and the length is 309 meters, according to Wikipedia. The dam has a capacity of 1,378 million cubic meters. It has since been overtaken by the Tokwe Mukosi Dam, a 1,750 million cubic meter reservoir, also in Masvingo Province, which is now the largest inland dam in the country.
Since then I have been fascinated by dams and hydropower projects. When I was in high school, in Harare, at Prince Edward School, we had to choose 2 optional subjects in addition to the compulsory subjects as part of the A Level Physics course (18 years old). One of the electives I chose was the sustainable energy course. The course had quite a bit of content on hydroelectric power plants. It brought back fond memories of my school trips to the dams around Zimbabwe. I immediately started to wonder why there were no hydroelectric power stations at these dams I had visited? Not even 5 or 10 MW installations that can feed the local environment and contribute to the national grid? I would have quite a few discussions with friends and family after this topic with the feeling that these plants would be too small, and it would be better to go for bigger centralized plants like the big 1050 MW Kariba dam. Distributed generation projects were not fashionable then, but I felt strongly about this and the potential role of distributed generation projects as part of the energy mix. I thought then that we should add turbines to every dam all over the country.
22 years later, some of Zimbabwe’s old dams are getting some turbines! According to local media reports, Lake Mutirikwi will have 2 x 2.5 MW turbines. The 5 MW project will cost $14.2 million. Power drain from the dam will be via a 25km 33 kV transmission line to the Kyle substation. The project hired 170 workers, 10% of whom were from surrounding areas, boosting employment in the local community.
The local newspapers also say that the peak demand in Masvingo province is around 22 MW. The 5 MW installed at Mutiriwki will be enough to cover about 20% of this, depending on water levels. Another 17 MW hydroelectric power plant is planned for the larger Tokwe Mukosi Dam and another 5 MW plant is planned for Manyuchi Dam. The three plants will add a total of 27 MW, which is more than enough to meet the demand in Masvingo, depending on water levels. The 3 hydroelectric projects can hopefully be combined with some utility scale solar in the near future, perhaps even through some co-location floating solar projects. Droughts caused by climate change are now more frequent, putting pressure on the grid during periods of low water levels. Adding solar PV can help manage crucial water sources.
In the third quarter of 2021, from the 2.203 GWh of the Zimbabwe Power Company Kariba Hydro Power Station contributed 64% of the total energy production. Hwange Coal Power Station contributed 33% and the small coal plants contributed 3%. The share of clean electricity will fall sharply from next year when the new units of the new 600 MW coal-fired power plant in Hwange come online.
Zimbabwe has small thermal plants in Bulawayo, Harare and Munyati that are not doing very well. These factories were built in the 1940s. Although some renovations have been done over the years to increase their production, they are all still struggling. There could be an opportunity to dismantle and reuse the ailing small coal plants in Zimbabwe. Maybe install some scaling storage in those three locations. Perhaps some 40 MW/120 MWh Megapacks or something similar at each of those locations can store power during off-peak hours and discharge if necessary to support the grid. The combination of small hydro, solar and battery storage could replace these ailing small thermals. It’s good to see that work has begun on the small hydros. I hope more locations are found across the country to add more small hydro projects.
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