eBusiness Weekly
The present vicious load-shedding by Zesa exposes a quarter century plus of short-term management, poor national energy planning with a lot of debate but no action, an operational model that goes against all professional advice, and an over-reliance on imports in a region that is now has a generation deficit thanks to growth in our neighbours.
The drought that hit the Zambezi watershed in 2018-2019 rain season just adds to Zesa’s woes: it is not the cause. If Zesa had been run properly for the last 30 years and if Zimbabwe had been prepared to invest, whether through public funds or through private enterprise, the drought-induced cut back in Kariba generation would be a minor nuisance, not a near national disaster.
Zesa for all practical purposes has two power stations: Kariba South Hydro Power Station and Hwange Thermal Station. There rest, even if maintained and refurbished, would not be adding more than 10 percent to total output. They are really small.
The two big stations are quite different and need to be operated in tandem for optimum performance. Hwange has six boiler-turbine-generator sets: Four with a design output of 110MW each and two with a design output of 210MW each. That gives the station a rated capacity of 860MW, although a deficient design for the cooling system reduces this to something nearer 750MW on warmer days. But assuming that five of the units were fully operational at any one time, with one down for routine maintenance, refurbishment or replacement, then Hwange could and should be generating 650MW to 750MW continuously, 24 hours a day. That would cope with the bulk of Zimbabwe’s base load, what we need to keep all the lights on at say 1am.
Kariba South has always been different, and with the recently commissioned extensions that difference has grown. The station has six turbine-generator sets of 125MW each, upgraded from the original 110MW by some intelligent modification of the tail races, plus the recently-commissioned pair of 150MW turbine-generator units. But the station was never been able, except in exceptional years, of generating even 750MW continuously for 24 hours a day and certainly could not, even in the best year, generate 1050MW every hour of every day. There simply is not enough water coming down the Zambezi. We know this because since Zambia commissioned the north bank station the Zambezi River Authority has never had to open a flood gate. Every drop of water entering the lake exits through a power station.
But that does not matter. It takes a couple of minutes to bring a hydro generator up from rest to full output. If Kariba South and Hwange had been operated properly as a pair, then Hwange would take the base load and Kariba South’s ranks of generators would be switched on and off as needed to provide the extra power with the station perhaps going flat out in the evening peak but perhaps having just one turbine slowly spinning at 1am to help balance the grid. Lake Kariba’s storage capacity is huge, so this variation in output would not matter in the least. The daily water ration, or for that matter the weekly or even monthly ration of the ZRA, could be used when needed.
But since the commissioning of Hwange, Zesa has used that station badly, switching units on and off continuously and relying on Kariba South for base load. Operationally Kariba power is very cheap; the water is free, and once capital costs are paid off, and the wall was paid for decades ago, there are only maintenance costs to cope with, and those tend to be lower in a hydro scheme. Unfortunately, this generating regime wears out a thermal faster, requiring more maintenance and more frequent refurbishment. And Zesa has always had an inadequate maintenance budget for Hwange. So right now it is only on a good day that we get even half of what we should. Hence the vicious load shedding.
In the late 1980s there was a great deal of debate on how Zimbabwe should meet growing demand for power and energy. A notorious paper by British consultants suggested expanding Kariba South, although Zimbabwean experts noted that the consultants were using river flow measurements from a freak decade and Zambezi flows were lower than what was assumed. They correctly wanted the base load increased first, with a further pair of large units at Hwange, before Kariba South was extended to allow Zesa to cope with growing peak demand by using most of its water ration in just a few hours a day. Some even wanted the proposed Sengwa station built before the extension.
The debate droned on for years, with extra input for a second hydro scheme first at Mutapa Gorge, shot down on environmental grounds, and then Batoka. In fact nothing was done except doubling the floor space for Zesa head office by commissioning a second high-rise office block in Samora Machel Avenue, partly to cope with the exponential growth in management following a split of Zesa into multiple units. At the same time Hwange was degenerating. Zimbabwe did not crash because there was, at that time, a generation surplus in Southern Africa. Eskom of South Africa had recently commissioned a pair of very large air-cooled thermals and its old thermals were still operational; Zambia fixed up its Kariba North and Kafue stations; the end of the Renamo revolt in Mozambique allowed Cahora Bassa to be used fully. So Zimbabwe could import at a higher price than its own operational generation costs but without the need for investment. This was recognised as a temporary expedient, extended with the destruction of primary industry in the hyperinflation era. Now all chickens are coming home to roost.
But Zesa’s more competent professionals were not inactive. They noticed that solar generation was becoming cheaper and wanted solar added along with a Kariba extension. Solar has a capital cost, but operationally is cheap since sunlight is free. Its problem is that energy needs to be stored for nights and in any case the biggest demand peaks, are in the early morning and evening when sunlight is diminished and in winter is just not there.
But with Kariba South over-engineered the lake suddenly becomes the largest and most efficient storage battery on the planet. Those suffering now might like to imagine a Zimbabwe with 250MW installed solar generation. During these sunny winter days that extra power allows a couple of Kariba generators to be switched off. The saved water can now be used as the sun starts to set and everyone wants to cook and Kariba can go flat out for a couple of hours. With a properly maintained Hwange taking base load, at worse the regional drought would mean residential areas switched off in daylight working hours, not intolerable, and in a normal rain season no switch off at all.
Imports are still possible, but in off-peak hours. But again with extended Kariba this is no problem. Switch the station off in off-peak and live on imports while keeping the water for peak periods. Even under present rationing Zesa could run Kariba South flat out for eight hours plus a day. The problem is what to do in the other 16. Imports are way down because Zesa owes Eskom and Cahora Bassa a lot of money. But Zimbabwean consumers owe Zesa close on RTGS$1 billion. That, even at interbank rates, could pay off the debts and leave Zesa with some useful change.
Obviously we have reached the stage where Zesa rates are too low, especially if imports have to take a more prominent role. But regulators have always been suspicious of Zesa requests because of the high administrative costs and lack of debt collection. That can be fixed quickly.
The new Government is already draining the swamp inhabited by Zesa’s top management. Zesa has some competent people who know what they doing and do not steal. It should be possible to assemble a top managerial team, much smaller than at present, who can run an efficient utility and a debt-collection system that works.
The proper rates can then be calculated. After the black-outs consumers will go along with a proper rise, but only if assured that Zesa is being run honestly and efficiently.
In the very short term debt collections must be channelled to restoring imports. The correct decision to spend US$5 million on fixing one of Hwange’s large units will help, in August. While the first, and unbuilt, solar station is bogged down in legal disputes, a proper process of getting another one built must be pursued. This can be commissioned in months.
In the medium term the Government has given the go-ahead for the expensive refurbishment and extension of Hwange, which also means that the owners of the coal field need to be jacked up to cope. Rio Tinto are back in the picture to build and run the Sengwa thermal.
And long-term planning needs sensible decisions now so as Zimbabwe’s economy starts growing there is energy to keep it growing. At least a quarter century has been wasted. We now need to fix the mess and then keep it fixed.
