Power development must be faster

15 Dec, 2023 - 00:12 0 Views
Power development must be faster Hwange Power Station

eBusiness Weekly

The latest review of the Zimbabwean economy by the World Bank produced the good news that it is growing year-in and year-out, that the economic and fiscal policies of the Government are largely the right ones, and that in the context of Southern Africa our growth is number one.

But, amid all the congratulations, there was one unpleasant statistic, that electricity shortages mean that our Gross Domestic Product is around 6,1 percent lower than it would otherwise be. That is a lot and it is likely to get worse as growth slows because new mines, factories and other productive development is limited by power shortages.

Already we are close on 18 months behind where we should be at present rates of growth and that gap is likely to widen unless we start moving quickly.

At present we have three inputs to the shortage. First Kariba South cannot operate at anything like its historic capacity, let alone its present upgraded capacity, simply because Zambezi flows into the lake are well below the historic averages.

While Zimbabwe and Zambia had above average rainfall last season, they between them provide little over 20 percent of Kariba inflows; the rest comes from Angola and that country had below average rainfall. This season will see less rain in all probability and so lower inflows, and so small rations of water for the two power stations.

Secondly the six units at Hwange Thermal commissioned during the 1980s were never fully maintained and in any case have large chunks of equipment way past their expiry date.

There is a perfectly decent plan to rehabilitate each of the six units, which involves in some cases the complete replacement of large chunks of machinery, but this is at best a two-year programme to what will effectively double output.

The third problem is easily the most temporary, the time it is taking to bring the two new 300MW units at Hwange Thermal into continuous operation. Both Units 7 and 8 have been switched on, and have spent times feeding the grid. The final stage of commissioning was to bring them down and check everything out. Sometime next month both should be back on grid and staying there.

But even with these two units, and the more gradual return to full output of the earlier units at Hwange, we are going to be short of power so we need to be getting ready to build the net power stations. And we need to know what to build.

The late 1980s and early 1990s saw a great deal of planning on what was needed to maintain the self-sufficiency in electricity achieved with the commissioning of the original six Hwange units.

There was a heated battle over whether Kariba South should be extended, with British consultants recommending this while Zimbabwean engineers were far more dubious since data from the 1980s showed lower Zambezi flows. All a Kariba extension would do was to help manage peak demand, not add to the energy production.

There was general agreement for two more units at Hwange, now finally implemented, and for a second coal station.

A second major hydro-station was proposed, with the optimum site for energy being at Mupata Gorge, downstream of Kariba and downstream of the Kafue confluence, so reusing the regular flows from the existing hydro schemes without floods or low-water periods.

This, after a major public campaign, was rejected on environmental grounds, with Batoka recommended instead. This is not nearly so good.

It is upstream and has a far smaller storage than Kariba, so it is not possible to catch the floods and space the water our over the year. This results in major output for two or three months and then that coming down sharply.

It is possible to operate Batoka and the Kariba stations together, allowing Batoka to take the main load in the floods, while almost shutting Kariba stations down and so letting the lake level rise sharply, and then run the Kariba stations with higher output in the low water times. But the gain to the energy grid will be less dramatic than just adding numbers.

With the growing number of drier seasons and the reduced Zambezi flows, this Batoka scheme must be recalculated for cost effectiveness. It will produce some power all year round, as the Zambezi does not run dry, but the capital cost per new megawatt might be very high, with better alternatives available.

Those could include a revamped Mutapa Gorge, with a far lower wall, smaller lake and so lower environmental impact. The flow would come from the Kariba and Kafue stations.

There is now an international commitment to phase out use of fossil fuels so we have to be careful. This includes a major effort not to commission a second coal station.

The Muzarabani-Mbire gas field now confirmed can supply a gas station that can be built a great deal more quickly than a coal station, with the carbon footprint from gas being half that from coal. This is still a fossil fuel station, but one that is less damaging so could possibly survive the phase-out period during its lifetime.

There has been a little excitement over the small hydro-stations on some major irrigation dams, and we are talking about small. The problem is that the irrigation dams hold water that is needed for farming, and for Bulawayo, not for power.

The small stations cannot therefore be in continuous operation, but they would be usable when water is released for irrigation, in fact that release generating the power to run the pumps. But much more than that does not look practicable.

The one major green energy source Zimbabwe enjoys is solar. We do not have much wind, and while we can make better use of the Zambezi system the amounts generated are lower than previous estimates.

But solar is there. We are in the tropics and even in the rainy season do not have many totally cloudy days.

The major problem with solar is the capital cost, although since sunlight is free operating costs are low, largely maintenance and regular replacement of worn panels and other parts. And the sun does not shine at all or at least not much for at least half of each day. So storage is needed if this becomes a big-time source of electricity.

For the first 500MW to 1 000MW, Kariba can provide storage. This would require shutting down Kariba generation during the sunny part of the day, using the solar to fill the needs and leaving the generation water in the lake, As the sun started going down, right at the start of the evening surge, Kariba could take over with a far larger output, adding the water saved during the day to the water allocated for the night.

This is because the power station is now oversized for normal flows.

But once that modest use was made of Kariba, we would need other storage, These could be battery parks, or they could be a sort of hydro-scheme, that is a pair of lakes at the top and base of a mountain connected by a pipeline running through a pump and generator station.

During the day, when the sun shines, water is pumped to the top lake and at night is released back down to run the generators, The pump motors and the generators would be the same equipment, just having rotors that spin in opposite direction on change of use. This is technology already in use.

It should be possible to work out which sort of storage, once the free operational storage of the oversized Kariba south station is used up, will be the most cost effective. As those using solar already know, the storage batteries are more expensive than the panels, so this is a major factor.

There should be some extra money available through the climate agreements to help developing countries find the extra money for renewable energy rather than use fossil fuels. But when that cash becomes available is a critical factor.

Some short term relief in Zimbabwe could be obtained by making it a lot easier for ordinary people to fit solar to their homes. This would have to involve cheap loans and duty free batteries as well as duty free panels. Local companies could make the water heaters, remembering that using solar panels to run a geyser is very expensive and direct sun is better.

In any case there is now general agreement that the expansion of electric power to the bulk of the rural population will require individual solar units, and expanding this to urban areas so urban households use little grid power makes sense.

But we need to be moving fast. We have economic plans that require at least 4,5 percent growth a year, and that will mean more demand for power, however carefully businesses work for maximum efficiency.

New investors will be coming in with some good ideas, and will need power to implement them. We cannot cut growth and we cannot reject investors simply because we do not have enough power stations. So we need to move.

Solar stations can be built quickly, so it makes sense to start adding these to the grid. The gas station at Muzarabani can go live if all the preliminary work has been done, within a year of the order being placed as the gas wellhead is set.

Solar can fill the gap as that is planned and built. Zimbabwe and Zambia need to examine the latest data to see how the most cost-effective additions to hydro can be implemented.

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