The Addition Of Small Hydroelectric Power Plants To Some of Zimbabwe’s Old Dams Finally Underway

When I was in primary school in Mutare, Zimbabwe, I used to go on quite a few trips with my school as well as with the AWANA club at Mutare Baptist Church. On one of the camping trips when I was in Grade 6 (11 years old), we went to one of the dams around Mutare. We spent the weekend at Small Bridge Dam. It’s a small dam, but it looked huge to me back then as a 12-year-old. Later that year, as part of a country-wide school trip, we stopped in Masvingo to see the Great Zimbabwe National Monument and Lake Mutirikwi. At the time, Late Mutirikwi was the largest dam in Zimbabwe. When I first saw it, I was just in awe as I walked across the dam wall. I could not believe how big it was. It was the largest dam I had ever seen at that time. Lake Mutirikwi covers about 90 km², the dam wall’s height is 63 meters, and its length is 309 meters, according to Wikipedia. The dam has a capacity of 1,378 million cubic metres. 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 country’s largest inland dam.

Since then I have been fascinated with dams and hydropower projects. When I was in high school, in Harare, at Prince Edward School, we had to choose 2 optional topics in addition to the compulsory subjects as part of the A Level Physics course (18 years old). One of the elective courses I chose was the renewable energy course. The course had quite a lot of content on hydroelectric plants. It brought back fond memories of my junior school trips to the dams around Zimbabwe. I immediately started to wonder why there weren’t any hydroelectric plants at these dams I had visited? Not even 5 or 10 MW plants that could feed the local area and contribute to the national grid? I would have quite a few debates about this with friends and family after on this topic with some feeling that these plants would be too small, and it would be better to go for larger centralized plants like the big 1,050 MW Kariba dam. Distributed generation projects weren’t fashionable back then, but I strongly felt about this and the potential role of distributed generation projects as part of the energy mix. I thought back then we needed to add some turbines to every dam everywhere around the country.

22 years later, a few of Zimbabwe’s old dams are getting some turbines! According to local media reports, Lake Mutirikwi is getting 2 x 2.5 MW turbines. The 5 MW project will cost $14.2 million. Power evacuation from the dam will be via a 25 km 33 kV transmission line to the Kyle substation. The project has seen 170 workers being hired, 10% of them being from the surrounding areas, boosting employment in the local community.

The local papers also say that the peak power demand in Masvingo province is around 22 MW. The 5 MW being installed at Mutiriwki will be enough to meet approximately 20% of this, depending on the water levels. Another 17 MW hydropower plant is planned for the larger Tokwe Mukosi Dam and another 5 MW plant is planned for Manyuchi Dam. The three plants will add 27 MW in total, which is more than enough to meet the demand in Masvingo, depending on the water levels. The 3 hydroelectric projects could hopefully be paired with some utility-scale solar in the near future, maybe even through some co-located floating solar projects. Climate change-induced droughts are now more frequent, which puts a strain on the grid during the periods when water levels are low. Adding solar PV could help manage crucial water resources.

In Q3 of 2021, of the 2,203 GWh from the Zimbabwe Power Company Kariba Hydro Power Station contributed 64% of the total energy production. Hwange Coal Power Station supplied 33%, and the small coal power plants contributed 3%. The share of clean electricity will go down quite a bit from next year once the new units at the new 600 MW coal power plant in Hwange come online.

Zimbabwe has small thermal power plants in Bulawayo, Harare, and Munyati that are not doing too well. These plants were built in the 1940s. Although some refurbishments have been carried out over the years to try and boost their output, they are all still struggling. There could be an opportunity to decommission Zimbabwe’s ailing small coal power plants and repurpose them. Perhaps install some utility scale storage at those three sites. Maybe some 40 MW/ 120 MWh Megapacks or something at each of those sites could store power during the off-peak times and discharge as needed 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 started on the small hydros. I hope more sites are identified around the country to add more small hydro projects.


 

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