Mon, 30 Nov -0001 00:00:00 +0000
In 1969, I was doing first year physics with a view of entering the school of engineering at the University of Zambia the following year when I came across a quotation from Lord Kelvin which has stayed with me to this day.
He was an Irish and British mathematical physicist and engineer who was born in Belfast in 1824 and said, “When you can measure what you are speaking about, and express it in numbers, you know something about it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts advanced to the stage of science.”
The unavailability of daily statistics from ZESCO on power production, and its imports and exports, or expression of numbers according to Lord Kelvin’s terminology, has led to “knowledge of a meager and unsatisfactory kind” on what has led to the depletion of water at Kariba Dam, which has resulted in speculations, apart from the obvious one of climate change or is it El Nino? What should have been a technical issue argued in terms of numbers has now been highly politicized and politics is a difficult subject to express in terms of numbers.
One speculation on the social media is that of the 2X180 MW Chinese machines guzzling a lot of water. “REALLY?” on the Lusaka Times blog had this to say: “These guys at ZESCO need to tell the nation the truth. Water level on the Zambezi river which feeds the Kariba Dam is not the major problem. If it were then Mozambique would be facing the same problems since they also get water from the Zambezi river to run their turbines. And if indeed lack of water in the Kariba Dam is the reason for low power supply then ZESCO should tell people not to expect any improvement soon because it takes three years of good rainfall to fill the Kariba dam. The reason for load-shedding is that ZESCO decided to replace the original turbines with some low capacity turbines they bought from China.
Let the truth be told!!!” Another blogger says “These lies by the PF govt is alarming. They sold the old genuine machines that produced electricity even when the water is low and pocketed the money, further, they replaced them with counterfeit machines that requires more water to generate electricity.
Now these are the repercussions of failing to use qualified engineers.” Others are speculating that ZESCO is exporting power to meet contractual obligations.
Let me now explain the depletion of water at Kariba Dam in terms of numbers. There were 4 machines (turbines/generators) installed at Kariba North Bank each with an installed capacity of 150 MW bringing the total to 600 MW in the 1970’s.
During the Power Rehabilitation Project ZESCO decided to include repowering of the generation plants at Kariba North Bank and Kafue Gorge power stations to increase the power generating capacity by 120 MW and 90 MW respectively, at the same time as the rehabilitation, to avoid having to shut down the units a second time for repowering.
Rather than invest in new hydropower stations the least cost solution was repowering which was estimated to cost at about US$200,000 per MW, compared to new hydropower projects in Zambia which were estimated to cost US$800,000 to US$1,000,000 per MW. The total installed capacity at Kariba North Bank Power Station is 720 MW after repowering before the installation of the 2×180 MW Chinese machines in the extended machine hall. With the Kariba North Bank Power Station Extension Project the total installed capacity now is 1080 MW from the original 600 MW.
There has been a rapid demand for electricity in Zambia as new customers have been connected to the grid and, according to Mr. Henry Kapata, there was a backlog of new connections as high as 25,000 which have since been reduced to some 15,000.
These have included residential, commercial, agricultural, industrial, and mining customers. Demand has increased from around 1,600MW in 2008 to about 2,200MW in 2015.
This should be viewed as a good thing because in the final analysis IT REPRESENTS ECONOMIC GROWTH AND PROGRESS FOR THE COUNTRY unlike in the 1980s and 1990s when we used to boast about Zambia’s surplus energy an indication of a stagnant economy, most of which was being exported to Zimbabwe whose economy at that time was booming after its attainment of independence in 1980.
New generation projects have been on the drawing board for a long time stretching as far back as the 1970’s but the challenge has been bringing them in on time to keep up with the growing demand. Long before the current shortages, ZESCO recognised the growing electricity demand and began to contract for new generation.
For example, feasibility studies for a dam in the Middle Zambezi’s Batoka Gorge below Victoria Falls were conducted by the Batoka Joint Venture Consultants on behalf of the Zambezi River Authority and completed in 1993. I was a member of the Batoka Gorge Joint Technical Committee which comprised staff from Zesa and ZESCO charged with overseeing the preparation of the Batoka Gorge hydropower project feasibility study. One of the issues that was of concern to us was the height of the dam for a roller compacted concrete dam (RCC).
At 181m high, it was going to be one of the highest RCC dam in the world. It was feared that Zambia and Zimbabwe were being used as guinea pigs for a technology not yet proven at such heights. A roller compacted concrete dam is rolled and compacted in horizontal layers using earthmoving techniques and equipment resulting in a dense strong material constructed at a fast rate cheaply.
At this height it was feared that the horizontal joints might become a source of leakages. The construction of so many high dams, since then, has proved this fear to be unfounded.
Misunderstandings over the ownership of the Kariba hydroelectric power plant, which the two countries share, prompted the Zambian government to develop cold feet over Batoka in 1994. “Such a background does not give us a firm foundation to enter into yet another costly project like the Batoka one,” former Zambian energy minister, Edith Nawakwi, told The Financial Gazette in 1994. Both countries decided to pursue “go-it-alone” policies with Zambia initiating a second stage dam on the lower Kafue and Itezhitezhi power station and Zimbabwe developing a large-scale Hwange coal-fired power station.
Notable recent additions to the country’s generation capacity have included 50MW from a new Ndola-based fuel oil generation plant, and the 360MW (2x180MW) Kariba North Bank Extension to meet peak evening demand but was used, allegedly, continuously to end load shedding.
Zesco has also completed the 120MW Hydropower Station at Itezhi-Tezhi and 300MW of coal-fired power from Maamba Collieries. Delays to these two projects have exacerbated the current energy shortages in Zambia. Both were planned to be online in 2014, but have been delayed due to financing issues and the slow completion of power lines to connect these projects to the national grid. If Itezhi-Tezhi and Maamba had been finished on time, load shedding would not have been as severe.
Zambia’s total installed generation capacity is currently just over 2,200W and has grown to over 2,600MW upon completion of these two new schemes, i.e, Itezhi-Tezhi and Maamba. Other new projects are at various pre-development stages, but timeframes continue to drift and financing requirements cast uncertainty over further projects. For instance the 750MW Kafue Gorge lower hydro project would greatly increase power supply availability in Zambia in perhaps the 2020 timeframe, but financing for this $2-billion project is not yet secured. It is now not even clear whether this project will be implemented at all in view of the presidential announcement that it is cheaper to import electricity from countries like South Africa with surplus energy. This year, there has been talk about constructing the 600MW solar power project although this is, according to the US Energy Administration, an expensive (and inconsistent) option, especially for a country with an abundance of hydro and coal.
The former Vice President Dr Guy Scott cut the ribbon when he commissioned the Kariba North Bank Power Station Extension Project in August 2014, which he said would lead to a significant reduction in the load shedding in the country and better the lives of Zambians in both rural and urban areas and was a step in the right direction towards the government desire to have all Zambians have access to electricity.
To Be Continued next week
He continued to say that this investment in the power sector would help address the lack of investment in the sector for over 30 years. He paid tribute to the China Exim Bank and the Southern African Development Bank. The Chinese Ambassador to Zambia Youming Yang said the handover of generators is a perfect gift for Zambia’s commemoration of 50 years of independence. The completion of the project saw ZESCO increase its power generation capacity from 1840 megawatts to 2200 megawatts.
In normal years the power generation capacity of 2,200 MW and now 2,600 MW with the completion of the new schemes would have put to bed load shedding but not in a year after, it is claimed, one of the strongest El Niños on record. El Niño means The Little Boy, or Christ Child in Spanish because it was originally recognized by fishermen off the coast of South America in the 1600s in the month of December, a Christmas month, with the appearance of unusually warm water in the Pacific Ocean. It, therefore, has nothing to do with climate change as this was well before the industrial revolution, although it is claimed that its intensity and regularity has increased with climate change.
The term El Niño refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific.
La Niña means The Little Girl in Spanish. La Niña is also sometimes called El Viejo, anti-El Niño, or simply “a cold event.” La Niña episodes represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. Global climate La Niña impacts tend to be opposite those of El Niño impacts. In the tropics, ocean temperature variations in La Niña also tend to be opposite those of El Niño. The current rainy season in Zambia will be influenced by it and Zambia is expected to have normal rainfall. However this is no guarantee that Zambia will have enough rains and we should continue to be frugal with our water resources.
The effects of El Niño differ in different parts of the world. In some parts of the world it is associated with floods whereas in Zambia it is drought. And it is the 2014/15 El Niño that has wrecked havoc on Zambia’s electricity supply.
Figure 2: In an EL Nino year the warm current moves to the west coast of the Americas
The explanation I find most plausible on the depletion of water at Kariba Dam is that following the completion of the 360MW Kariba North Bank Extension project in 2013/2014, ZESCO generated a lot more electricity at Kariba than in previous years. The new turbines were being run much more than they were originally intended to do. According to some reports these “Chinese units” were intended to operate as peaking units not to run much more than the planned three to four hours a day. They have used more water, resulting in low reservoir levels. In any case the operating of two additional turbines bringing the total to six machines would use more water than the original 4 machines, Chinese or otherwise. In addition the original machines were 150 MW each, before repowering, and the new Chinese machines are 180 MW each and would therefore use more water.
Figure 3: The two puppies drinking milk from a saucer
Although the former Vice President Dr Guy Scott commissioned the Kariba North Bank Power Station Extension in August 2014, and told the nation and the world at large that it would lead to a significant reduction in the load shedding in the country and better the lives of Zambians in both rural and urban areas and was a step in the right direction towards the government desire to have all Zambians have access to electricity he now claims that he was ill informed and he is quoted as having said in parliament “I am the one who turned it on and I said, ‘Is there enough water for this?’ It was a huge contraption and everybody said ‘yes’”. He says, “What we have now is a weak regulator sitting between two puppies drinking milk from the same saucer and each one trying to outdrink each other”.
I can only speculate that it is possible that ZESCO was following the presidential directive to end load shedding as pronounced at the commissioning of the project hoping that the impact of climate change due to El Nino would not be severe. After all, it has not been this severe in most years. The last severe one was in 1991 when I was Resident Engineer at Itezhitezhi Dam when we could not release water for power generation at Kafue Gorge using the main spillway but had to use the low level outlet. ZESCO is now being blamed for Zambia’s overuse of the world’s biggest man made reservoir to generate electricity which has depleted its water levels.
The power crisis, along with low copper prices, has caused Zambia’s GDP growth to slow to 3.4% this year from government’s initial target of more than 7%, according to Barclays Plc. That would be the most sluggish pace since 1998, when the economy contracted.
Last year the Zambezi River Authority, which regulates Kariba and is run by the two countries’ governments, allocated Zesco water to generate 1,944 gigawatt hours of electricity from April through September, according to some source. Instead, it produced 2,971 gigawatt hours, 46 percent more than it was supposed to.
In conclusion what has led to the depletion of water at Kariba Dam is not the installation of the Chinese machines (turbines) per se at the Kariba North Bank Power Station Extension but because the new turbines were being run much more than they were originally intended to be used i.e., peaking units not to run much more than the planned three to four hours a day. Had the effects of El Nino not been as severe as experienced resulting in a severe drought we would have ALL been patting ZESCO on the back for ending load shedding. Let as also not forget that the PF promised to end load shedding if voted into power, which it did, but nature conspired against it by way of El Niño. The question of how much water should be used for power generation is a juggling act. Under usage of water results in spilling of water which is a waste. It is this spilling of water in the past because not as much water could be used for power generation because the installed capacity at Kariba North Bank Power Station was only 600MW that has resulted in the scouring or erosion in more familiar language of the plunge pool to over 90m deep which is now threatening the structural integrity of the Kariba Dam wall. However, weather forecasting is still not an exact science (according to Lord Kelvin’s definition because it cannot be expressed in exact numbers), Although it has improved with the use of satellites it still uses generalities such as normal to above normal rainfall and not say 900mm of rainfall will fall. There will be, therefore, always need to spill water when unexpected floods occur.to prevent the dam wall from being overtopped resulting in dam failure.
The author is a Freelance Hydropower Consultant and can be contacted at email@example.com for comments.