Source: ZESA’s stronger management shows power stability is possible – herald
The Zimbabwe Electricity Supply Authority’s efficiency and output have been rising rapidly over the last few months as it manages its core generating capacity more tightly.
It managed to get through the last two months, December and January, with only minimal power disruption, including the remarkable achievement of going for 41 days, from shortly before the festive season to the end of last month, with no load-shedding at all.
The huge cuts in inflation rates and the greater availability of foreign currency meant that ZESA could pay for imports through the Southern African Power Pool, probably mainly from Mozambique, which has the largest regional generating surplus these days, and that its tariffs would cover the cost of a modest percentage of imports.
ZESA should be able to maintain the progress as it brings all available capacity at Kariba South into use once the main floodwaters start arriving from Angola during next month.
But the small rise in inflows into the lake from Zimbabwean and closer Zambian rainfall at least wound back the need to tighten water rations and started a process of very modest higher rations while the Upper Zambezi flows are being assessed.
ZESA now needs to accelerate its refurbishment, replacement and maintenance of the older units at both Kariba South and Hwange Thermal, work that finally has been budgeted for.
At Kariba South, two of the original six 125MW turbine and generator units are down.
The very low and tightly rationed supplies of lake water for generation over several years perhaps allowed some drift. While even an excellent season and very strong flows down from Angola will not need the two units for total generation output, having all six older units plus the two larger units of Kariba South Extension will give ZESA flexibility.
Although the station is rated at 1 050MW, total output will almost certainly have to be at or below the historical high point of 750MW, and the six functioning units can supply that.
Because of the huge storage capacity, ZESA, and ZESCO on the Zambian side of the dam, with a similar maximum output, have an inbuilt capacity to handle the large surges in demand at peak periods.
It is easy with all units functioning to take output to over 1 000MW for a few hours, and then cut right back in the early hours of the morning to well below the average in order to meet the average set by the Zambezi River Authority.
Peak power is always the most costly on a national or regional grid and even if Zimbabwe must import for some years to come, there is no need to concentrate those imports into the most costly part of the day.
Hydropower is exceptionally useful for surge supplies as it takes only a few minutes to open the valve to a turbine, bring the generating unit up to speed and then connect to the grid. A thermal unit needs to see the boiler heat up to convert to steam, perhaps up to an hour, before the generator can be brought online.
The other major refurbishment and replacement involves all the older six units at Hwange, commissioned during the 1980s. On a good day, the six can generate perhaps half their design output, and ZESA engineers can take a bow for getting that much out of equipment up to 40 years old, but a full-scale overhaul is now needed.
Since the civil engineering works are still sound, along with infrastructure such as the road network, staff housing and a wide range of peripherals, it is far cheaper and quicker to replace the units if that radical step is fully needed, rather than start a new station from scratch.
ZESA has moved promptly and has already selected an Indian contractor to do the work, with the financing arrangements at both ends sorted out.
Again, the very low inflation and tighter management mean that what is collected in tariffs is not going to suddenly melt away. It can be held until the work set for the next progress payment has been certified as being done properly. It will take around five years to get Hwange up to just over 1 500MW, the station’s required output.
Meanwhile, ZESA, and so Zimbabwe, are very reliant on the total of 600MW that can be produced by the new Hwange Units 7 and 8.
While these are now running smoothly, they will always need maintenance.
It would be useful if imports could be arranged in advance to cover gaps in output as ZESA shows its new determination.
The retreat from load-shedding has meant that miners, industrialists and farmers can push ahead in expanding production and productivity.
Energy conservation is now far more a way of controlling costs, so a factory needs to be efficient to make money, rather than a survival tactic.
This major effort by ZESA does not mean that Zimbabwe needs to cut back on solar and other sources.
For a start, there can be faults, but secondly, the more power generated the better. The smart metering ZESA offers needs to be more extensively used.
Under the Second Republic, we have been getting things fixed up and working. ZESA is just one on the list and is now producing returns for the expansion investment that has been made.
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