We started the visit with a very informative, short presentation by Auke on the Universe. Unfortunately he was hampered by projector problems which were the result of either overheating or an unstable power supply. After the talk the group set about building Southern Star Wheels in preparation for the evening’s viewing.
While the group went off to supper, we drove down to the viewing site on a netball court and also had our supper, courtesy of Lynnette. After supper we set up and waited. The group arrived but, for some unknown reason, the message about bringing the Star Wheels did not seem to have registered because, apart from two that I saw, there were none there. Auke did an extensive what’s-up-tonight, pointing out a wide range of interesting objects and constellations and, after that Lynnette operated Maphefu and Lorenzo while I set the Celestron on the Moon.
Not having heeded Martin’s instruction to write down the settings for various types of objects, but rather trusting my memory, I could find everything but not produce the sort of imagery the system was really capable off. Mrs Foster’s little boy really seems to have a persistent learning disability.
As for the learner who snubbed Lynnette, when she told somebody that the darker areas on the moon were lava plains, by remarking to bystanders, “Just ignore her, there is no lava on the Moon”; I would like to suggest that said person should do some reading. It might then be possible to convert a Smart-ass to a Bright-ass. Lynnette was just too polite to take you down a peg or two.
Generally all went well and I thought that the group of learners, who were more interested in catching up on cuddle-time than in astronomy, was significantly smaller than on the previous encounter. In all fairness though, it was lot warmer on the netball court than on the grass at Dassenberg Broilers, where we saw them last (go here to read about that occasion) and also a whole lot less windy. Thank you very much for the opportunity to do the presentation Carl, the learners and Elkanah House.
Into the Belly of the Beast with the Cape Centre courtesy of Richard, Vanessa and Eskom.
ESKOM is South Africa’s power utility and came into being in 1923 as the Electricity Supply Commission or ESCOM. In 1987 ESCOM became ESKOM, a name which the company has retained to the present. Eskom is currently responsible for the generation of about 95% of the electricity generated in South Africa and about 45% of the electricity used in Africa. Lynnette and I were very early so we headed for the Orchard Farm Stall outside Grabouw for a light breakfast.
Eskom laid on tea coffee and eats for our group at the Visitor’s Centre of the Palmiet Pumped Storage Power facility near Grabouw in the Elgin Valley. That was followed by a presentation from our very competent guide, Vanessa, in which she first explained the differences between Eskom’s different power generation units and gave us some general background on Eskom. She went on to give us a detailed explanation of how the Palmiet plant functioned and emphasized the difference between a conventional hydroelectric system and a pumped storage system such as Palmiet.
The latter is always situated on a waterway connecting an upper and a lower reservoir and not on a natural waterway or river. The Palmiet generator is situated between the Kogelberg Dam on the Palmiet River and the Rockview Dam higher up on the slope of the mountain. Palmiet can supply electrical power during periods of peak demand, or in an emergency, by allowing water to flow from the Rockview Dam to the Kogelberg Dam through two reversible generator- motor/pump- turbine sets. During periods of low energy demand excess generating capacity is available and the same water is pumped back up from the lower to the upper reservoir. In addition the upper reservoir is also connected, via an extensive set of pipes and channels, to the Upper Steenbras Reservoir, which is one of the dams supplying the City of Cape Town with water. The Palmiet system augments Cape Town’s water supply by around 25 million cubic metres (m3) a year. One cubic metre is 1000 litres and an Olympic swimming pool contains 2,5 million litres of water. So, the Cape town water supply receives the equivalent of 10 000 Olympic swimming pools from the Palmiet pumped storage scheme.
The Palmiet generating system can be brought on stream in about three minutes. In comparison, a coal-fired system requires eight hours or more before it can supply power from a cold start-up. Power generated here can be sent down lines to the Bacchus substation near Worcester and to the Stikland substation in Cape Town.
After more refreshments and a closer look at all the informative material on the walls of the well maintained display area, we followed Vanessa down to the power generation facility by car for a closer look at this eco-friendly setup.
The initial impression at the power plant was that of a rather inconspicuous building with an attached section that, judging by the spider web of wires, masts and pylons, clearly represented something electrical and very much hands-off. However, to parody an old television commercial for Cremora Coffee Creamer “It’s not what’s on top, it’s what’s down below” because about 60 metres below us (that is just over 18 storeys) are two pump-turbine generator-motor sets that can each turn out 200MW. When running in pump-mode these two units return water to the Rockview Dam at a combined rate of 126 m3 per second. You can check my calculations, but that converts to filling an Olympic swimming pool in less than 20 seconds!
The ground floor machine hall, with its huge crane that can lift a whopping 360 tonnes from a depth of 65 metres, looks like an aircraft hangar at first glance until you notice the two circular walled areas. Approach them with caution if you have even the slightest tendency to vertigo, because when you look over the waist-high wall into the 23 metre wide pits, the first stop for your gaze is 18 storeys down where you can see the giant blue inlet valve. Bear in mind that these shafts actually extend a further 20 metres below that level to the drainage pumps. For comparison the Media-24 building on the Foreshore in Cape Town is 93 meters high so, if you knock the top four storeys off that building, you have the total depth of each of the two machine shafts at the Palmiet pumped storage facility.
Vanessa led us down into the belly of this beast, divulging the one fascinating fact after the other as we dropped lower and lower. On the floor of the machine hall it was quiet and there was no detectable vibration, but as we went deeper and deeper into the concrete and steel entrails of the beast, the noise levels rose, earplugs were issued and the vibrations in the walls and floors increased: the beast was not asleep and I was feeling distinctly like Bilbo Baggins creeping up on Smaug. In the lower passages watertight doors appeared on which the signage clearly warned that they shut automatically and without warning in the case of an emergency. Vanessa reassuringly pointed out flights of steel staircases vanishing upward into the glare of fluorescent lights. I could not but wonder exactly how fast one could run up those stairs with the water hard on one’s heels.
The huge rotor of the pump-turbine generator-motor spinning at 300 rpm a few meters away from one’s face as it churned out its 200MW, was very, very impressive, even for the less mechanical minded members of the group. I, however, could hardly take my eyes off the giant inlet valve. It just sat there, big, blue and quite ugly but that silent immobile monstrosity was all that stood between us and a very sudden, very watery grave. Just bear with me while I bore you with some more figures. At the Rockview inlet high above our heads, water is admitted at a rate of 185 m3 per second into a tunnel 6.2 metre wide. The tunnel diameter is reduced in steps: first to 5.4 metres, then to 3.9 metres and finally to 2.6 meters where it enters the generating complex. Now consider the vertical drop from the Rockview Dam to the generating complex and the reduction in conduit diameter as well as the fact that, according to Vanessa, the water is travelling at 60 km per hour when it reaches the valve. All of these factors must add up to an enormous pressure and definite case of German engineering when one needs it most. Perhaps you also now understand why I found the valve so fascinating and also why I wondered how fast Lynnette and I could negotiate those steel steps.
To deal with flow variations and pressure fluctuations, there is a surge tank positioned shortly after the start of the downhill watercourse. This structure is a cylindrical free standing structure 61 m high and 21 m in diameter which instantly relieves any variations in the pressure of the downstream system. The tower and the northern aspect of the Rockview Dam are both clearly visible from the N2.
On a final note, the Palmiet pumped storage scheme has an impressive safety record and an even more impressive conservation record. The plant is situated in the Kogelberg Biosphere Reserve, designated as such by UNESCO’s Man and the Biosphere Programme in December 1998. The Reserve comprises the Kogelberg Nature reserve, the entire coastal area from Gordon’s Bay to the Bot River vlei and inland to the Groenland Mountain and Grabouw, a total area of some 92 000 ha. Palmiet is the recipient of several prestigious awards.
In 1987 Palmiet was presented with the award for the Most Outstanding Civil Engineering Achievement by the South African Institute of Civil Engineers.
On completion in 1988, Palmiet won the Environmental Planning Professions Interdisciplinary Committee Award for integrated environmental planning and management.
In 1997 Palmiet was presented with the Conserve Award for outstanding achievement in effective conservation and sustainable utilization of the environment to ensure a better quality of living for all South Africans by the South African Minister of Environmental Affairs and Tourism.
In 2003 Palmiet was awarded the Blue Planet Prize by the International Hydropower Association.
Palmiet has consistently been rated a five star performer in industrial safety by the National Occupational and Safety Association (NOSA) and is the holder of the NOSCAR, NOSA’s most prestigious annual achievement award.
With all these fine achievements it is inexcusable that ESKOM has slipped to the levels of inefficiency we experience at present. Read these two documents clearly displayed in the Visitor’s Centre and compare them with the actual situation as we South Africans experience them. It is totally farcical.