admin
At present, Zesa Holdings cannot meet peak power demand without load-shedding during severe droughts, although normally it can cope with the off-peak demand.
The power utility needs to expand both its generation and methods used to spread output, so both rising peak and rising ordinary demand are met as Zimbabwe industrialises.
Industrialisation relies on rapidly growing and ever more secure power supplies, and this is why Zesa is moving from planning to implementation.
At the moment, Zesa has a peak demand of 1850MW and a drought-year generating capacity of 1310MW without much scope, thanks to low Upper Zambezi flows during the severe regional drought and need to be more flexible in how it generates power to meet peak demand.
From its two main power stations Zesa can normally at present expect around 1085MW from Hwange Thermal, but just an average of 272MW from the 1050 Kariba South station.
That was because of the tight rationing imposed on Zambia and Zimbabwe as a result of the severe regional drought last season, with the previous season being below normal as well, especially in southeast Angola where up to 80 percent of Kariba water comes from.
With normal flows of the Zambezi, Kariba South should be able to average between 600MW and 700MW, and because of the very large extended station, that would allow Zesa to go over 1000MW at peak periods but cut back at the low demand times, like the middle of the night. But the very low permitted average does not give Zesa much flexibility to do this, almost removing its main practical ability to store power via storing water in the slack hours and releasing it in the peak hours.
Zesa is now finalising plans for a huge battery park that will allow it to add 600MW an hour of stored power for three hours every morning and every evening, the power for the storage coming from running stations flat out in slack periods to charge the batteries, with solar probably being an ever more important contributor, that being a source that produces the highest output at noon.
Besides the poor river flows, Zesa has also had for much of the past week a fault at its newest Hwange Unit 8, cutting 300MW from the grid. This, as Zesa explains, is not totally unexpected, especially in new equipment, but shows the danger as we build up our generating capacity of having 23 percent of the total in just one unit — when it goes down the effect is severe. As more units are added, this sort of fault becomes ever less critical.
Limited short-term supplies could be obtained from neighbours, mainly Mozambique but with Zambia chipping in, although we need to recognise that with their growing economies those two countries will be using more of their own power and have less to export and both are hit by Zambezi catchment drought.
Zesa’s problem is liquid cash with consumers, this time basically the large consumers since households are on prepaid meters, owe ZiG5,7 billion.
However, Zesa is pushing ahead on several fronts, and has retreated on others as a result of experience, for upgrades in generation and peak supply from early next year onwards.
The easiest and quickest source of major 24/7 upgrade right now is the rebuild of the first six units of Hwange Thermal, all commissioned in the 1980s, and so increase output of that station from 485MW back to its effective maximum of 840MW, a bit below the theory owing to an original small design fault.
Zesa is already working on the rebuild of Unit 5, one of the larger 220MW units, and expects this back on line in April next year.
That will shove its Hwange capacity up to above 1 300MW, although there will be an almost immediate decrease by around 100MW as the next unit is pulled down for rebuild, probably Unit 6 as that offers the largest return.
But Hwange should have all six older units joining the two latest ones within 36 months, to have a station comfortably generating over 1 400MW.
More importantly Zesa is finalising negotiations with an Indian company to extend Hwange with another four 300MW units, to add 1 200MW, although such construction is not instant.
While the completed Hwange will then be theoretically capable of well over 2 600MW, with a dozen units and proper maintenance schedules there will often be one down for routine work, but even if that is the largest, it will still only amount to around 11 percent of the station’s output, something that will be fed into operations routinely, rather than as crisis management.
Announcing the planned upgrade and further extension of Hwange, ZESA executive chairman Dr Sydney Gata did not bring up extensions to the hydroelectric systems.
The Batoka Gorge project has tended to headline the plans of both Zesa and Zesco of Zambia.
The same climate change and more wildly fluctuating rainfall has clearly moved that plan off central stage. We need secure power supplies for rapid industrialisation.
If Batoka had been built some years ago it would not be producing 1200MW for each utility right now, but something close to the present Kariba rations of 272MW.
The huge investment can be better and more reliably spent to produce actual power, hence presumably the proposed 1 200MW phase four at Hwange.
We can no longer rely on Zambezi power year in and year out to expand our economies, it becoming an extra useful source, rather than the central source it was in late colonial Rhodesia.
A more immediate addition to power supplies is coming from the ferro-chrome producers.
They are already building a 300MW station at Hwange for their very large consumption, with the first 100MW coming on line before the middle of next year, and work will be extended next year so eventually the station will be 750MW.
That will allow continued rapid expansion of that processing heavy industry without adding to Zesa’s burdens.
Solar is now making progress, after years when there was more talk than large arrays of panels, and this will be providing ever more useful power to the grid.
The flexibility at Kariba allows some storage, and the new battery parks will allow more so noon power can be used in the evening peak as daylight fades. We still need to push solar, but it does need to be backed by storage and by 24-hour generation.
Peter Tanyanyiwa
Online Reporter