GENERATION capacity at Kariba South Hydroelectric Power Station, Zimbabwe’s main source of electricity, will go up by 70,17 percent, after the Zambezi River Authority (ZRA) reviewed upwards the amount of water it allocates to the plant for power generation.
The plant will be generating 485 megawatts (MW) on average this year from 285MW in the prior year, in what will significantly improve the electricity supply situation in Zimbabwe.
This is for the first time in two years that ZRA, which manages the Zambezi River waters and the use of Lake Kariba on behalf of the governments of Zimbabwe and Zambia, has adjusted upwards the power station’s electricity generation capacity.
ZRA was established in 1987 as a successor to the Central African Power Corporation (CAPCO).
“ZRA has increased our electricity generation capacity from 285MW to 485MW. Of that amount, we are exporting about 80MW to NamPower, Namibia,” said Zimbabwe Power Company (ZPC) acting managing director, Joshua Chirikutsi, confirming the development.
ZPC is a unit of ZESA Holdings, responsible for power generation.
In November last year, ZRA increased water usage for hydropower generation at the dam, from 20 billion cubic meters to 30 billion cubic metres, which ZPC and the Zambia Electricity Supply Authority (ZESCO)’s Kariba North Bank Power Station must share equally.
This means that they would utilise 15 billion cubic metres of water each for power generation during the current year.
At full capacity, Kariba Dam stores about 65 billion cubic metres of water.
ZRA first reduced water allocation to the two power utilities in May 2015, from 45 billion cubic metres to 33 billion cubic metres, citing low water inflows into Kariba Dam during the 2014/15 rain season.
The move resulted in increased load shedding across Zimbabwe and Zambia.
In January 2016, ZRA further cut down water usage to 20 billion cubic metres to ensure that water would be conserved so that generation of electricity could continue to the next rainy season.
This resulted in Kariba South Power Station generating as little as 285MW of electricity, a move which worsened the power supply situation in the country at a time Zimbabwe was battling machine breakdowns at its four thermal power stations.
The current dam water levels is 478,56 metres above sea level compared to 477 metres recorded last year in January. This, however, is still far from the normal.
The Financial Gazette can report that live water storage, which can go up to 10 metres, is currently at about three metres.
Dead water storage is at about 475 metres.
This means that only three metres of water can be used to turn the six turbines at the power station to generate electricity.
Live water storage is used for generating power. When the lake is 100 full, live water should be 35 percent while dead water should be 65 percent.
ZRA, through the rule curve, determines water levels — that is the highest and lowest tolerable level — to which the Kariba dam reservoir may provide firm loads of water for power generation to ZPC and ZESCO, two power utilities which share the water resource for power generation.
The Kariba South Power Station has a capacity to produce 750MW, but has been producing 285MW due to low water levels.
Kariba Power Station was constructed between 1956 and 1960 with an initial generation capacity of about 666MW. But after refurbishment undertaken in 1997 and an up-rating process in 2003, the plant increased its generation capacity to 750MW.
The plant’s general manager, Kenneth Maswera, said: “The station is carrying out several plant refurbishments to maintain generation reliability. The major capital projects are driven by residual life assessments — to prioritise the more critical plant areas ahead of others.”
About US$48 million was set aside for the general refurbishment of the project. New transformers have been installed at the existing plant and governor modernisation has also been completed.
Expansion work at the power station, which is being undertaken by a Chinese contractor Sino Hydro, will result in the construction of two additional units expected to add 150MW of electricity each into the national grid.
The first unit is expected to be completed by December this year and the remaining unit would be commissioned by March next year. This will reduce the need to import expensive power. Zimbabwe is currently importing a combined 400MW of electricity from South Africa’s Eskom and Hydro Cahora Bassa of Mozambique.
The estimated cost of the project is US$533 million. The Export Import Bank of China provided US$319 million towards the project while the balance will be provided by ZPC.
The overall project progress is 71 percent complete. Onsite civil infrastructure which includes the powerhouse is 85 percent complete.
The project also encompasses major underground works requiring excavations. These are access tunnels, headrace and tailrace tunnels and penstocks covering about 3,1 kilometres and the power house and surge chamber covering about 110 000 cubic metres.
There are also surface excavations that include the intake, outfall and transformer platform covering 400 000 cubic metres. Last week Members of Parliament had a tour of the plant.
Daniel Shumba, chairman of the Mines and Energy Parliamentary Portfolio Committee, told the Financial Gazette: “As Parliamentarians, we are now enlightened after this tour of the plant. We are excited about the commitment and professionalism exhibited by ZPC and the contractor, Sino Hydro Corporation.”
It is understood that after completion of the expansion project, the power utility is expected to save about US$78 million annually because Kariba Power Station has been producing the cheapest electricity at US$0,02 per kilowatt hour (kWh). Thermal power stations at Hwange, Bulawayo, Munyati and Harare are producing electricity at between US$0,06 and US$0,08 kWh.
The country is importing electricity from Eskom at a cost of US$0,14 kWh and procuring electricity from HCB and Dema Diesel Power Plant, an independent power producer owned by Sakunda Holdings at US$0,13 kWh and US$0,15 kWh respectively. Expensive imports result in higher blended tariff.
Zimbabwe’s total peak demand is about 1 600Mw but is producing about 1000MW of electricity.