Kafue Gorge Hydro Power Station, Zambia
Monday 30 August
ZESCO Head Office
Denis Banda picked me up at 8am this morning, and we set off for the ZESCO head office, to pay our respects to Mr Musonda Chibulu, the director of generation projects.
As we drove Denis gave me some background on the company. ZESCO has around 4000 employees, and has a hydro capacity of around 1700 MW. When I asked how Zambia could support all the hydro, he explained that almost the whole country is the catchment of the mighty Zambesi river, and consequently, drought is uncommon.
At the offices, I met up with Bonje Muyunda and Robam Musonda of the environmental team, and they too hammered that fact home. Apparently 40 % of all water in Southern Africa is within the Zambian area, and consequently their team is more concerned about flood management than drought prevention.
The key sites that ZESCO manage include:
Kafue gorge – 990 MW
Kafue Lower (still under development) – 750 MW
Kariba North – 690 MW
Victoria Falls – 108 MW.
Bonje explained that an independent Zambezi river authority manages abstraction limits with the Kariba basin (to minimise political unpleasantness between the two neighbours, Zimbabwe and Zambia). Recently a Zambezi river basin commission has been drawn up to look at all the water within the Zambezi, and while its neighbouring countries have signed, Zambia has stalled, as there is a much greater impact on the country. With virtually all its inland rivers flowing into the Zambezi, the impact could be much more serious.
We talked about Cleaner Development Mechanisms (CDM) and whether ZESCO was using this as a source of funding for any of its projects. Apparently it is in the process of doing so for Itezhitezhi (ITT) power station, which is a site being developed on the upper Kafue. The sites do not need ISO 14000 to qualify.
Kafue Gorge Regional Training Centre
Dennis and I left Lusaka around 11am, and headed down to Kafue Gorge power station (around an hour’s drive). We popped into the training centre, which has become a centre of excellence for hydropower training in the southern African region. With input from NorAid (Norwegian Aid), the centre has flourished, and it really impressed me. I took away the course schedule, and noted some of them, to inspire Scottish Water perhaps to add some similar courses to their schedule:
High voltage regulations (duration dependant)
Power plant operation and control (3 week course)
Operation and Maintenance (2 week course)
Turbine Dynamics and Operations (2 week course)
If Scottish Water is serious about adding another 30 odd sites to its hydro portfolio, I firmly believe that it needs to adapt its training courses to reflect this shift. I suspect it is a bit far to send the delegates to Zambia, but it was certainly a world-class facility.
After lunch we met with Samuel Sindesi, the head of operations at Kafue Gorge. Samuel explained that ITT (Itezhitezhi) header dam was built much further up the Kafue river, to control release of flow down to the plant’s intake dam, Kafue dam. Although the two sites are 400 km apart, Kafue dam is only 6m lower in height than Kafue! As you can imagine, the land in between is extremely flat, and is appropriately called the Kafue flats, and is an internationally recognised wetland. It takes water between three and four months to get from ITT dam down to the Kafue dam!
As a result silt is no issue at all in the Kafue dam, as the water moves so slowly, that it has settled out any sediment. However, what is a major problem is the build-up of water weed (hyacinth) on the slow moving Kafue dam. This is exacerbated by the presence of a fertilizer factory (Nitrogen Chemical Zambia) and Zambia sugar refinery, both located in the Kafue flats, and discharging eutrophic effluent into the river.
The hyacinth clogs the intake screens to the headrace tunnel. In 2009, the situation got so bad, that no water got through at all, and the plant was shut down three times. The situation is now managed by manually dredging the dam, and there are mini-mountains of hyacinth drying out all around the dam, waiting until they are sterile enough to be used for fertilizer. The plant controls the Kafue dam, and is currently releasing a 7.2 m3/s compensation flow (although from what I gather, this can be reduced in dryer periods). The dam is currently releasing at 130 m3/s to provide capacity with the impending rainy season (November – March).
We inspected the manual inlet valve. Samuel explained that the plant has never operated this, for fear that it may jam shut, and he said it was more than his job was worth, to explain that why there was no power coming from Zambia’s biggest power plant! Fortunately, the inlet tunnel has never had any maintenance requirements, and it is possible to shut off the turbines separately.
There is an effective conservation area in the 14 km zone between the plant and the dam, with the whole area being managed by ZESCO, in conjunction with the department of forestry. The mopane woodland is pristine and I saw no exotics as we drove around. It’s a pity that they don’t stock it with game, as the high site security would help protect the game from poaching!
Water goes through a 10km headrace tunnel and then drops 500m into six 165 MW Francis turbines. We drove down to the inlet tunnel and Samuel pointed out the location of a mudslide that occurred in 2005, when heavy rains induced a mud slide down the steep mountain sides. The mud used the access road and tunnel as a conduit, and went straight into the plant, and got into the turbines, damaging them. I was impressed with the simple channels that had been built to prevent this re-occurring.
There are four people per shift, operating underground. The site was opened in 1977 (interestingly, by President Tito of Yugoslavia, who was chummy with Zambian President Kaunda.
Water and Drainage
The site has no oil separators for the water drainage sump. Furthermore, one of the BHEL Indian transformers recently blew a valve, and the housing room is covered in oil. When we went in, workers (with no breathing apparatus) were using paraffin and peat to clean up the oil, and the smell of hydrocarbons was overpowering. To be 500 m underground, with poor ventilation and then dealing with hydrocarbons- I was nearly gagging just walking in and out.
The turbine cooling water is fresh water from the intake tunnel and is discharged at around 34oC via the tail race.
I wouldn’t normally mention the journey, however this one was exceptional. We left Kafue dam at around 5.15pm, and the sun was already low in the sky. We still had a 2 hour journey to make to get to Siyavonga, which is the town on the Zambian side of the Kariba dam (the dam wall providing the border between Zambia and Zimbabwe).
As we drove from Kafue, the road got worse and worse. We went down a serious mountain pass (losing all the altitude that had made Kafue such a perfect location for a hydropower plant). The pass was like a lorry graveyard, and we passed two recent serious lorry crashes, one very fresh, with the trailer spread across the whole road. We even passed an arest-a-bed (with sand pits, in theory to stop lorries with failed brakes). Dangling at the end of the sand pit was the burned out carcass of a lorry, which had obviously used the bed in earnest, unsuccessfully. As well as this, we passed through numerous police road blocks. But driving with ZESCO was like having a royal escort. I felt invincible, and we sailed on, finally arriving well after dark at the ZESCO guest house in Siyavonga, high on the hill looking down over the twinkling lights of the capenta fishing boats on the mass of black water below.
We had village chicken (i.e. traditional African chicken) with nshimna (corn meal) for dinner. The guest house is very traditional, and so I have been using my hands to eat, and pushing the nshimna around the spinach to try and get it into my mouth. I have to say this has been a challenge, and my plate and hands look messy by the end, but Denis, my ZESCO colleague has an immaculate shining bowl by the end of his meals. I obviously have things to learn about traditional eating!