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Feb 03, 2012

The CSIR blunders on

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Aviation|Cape Town|Construction|DURBAN|Gold|Johannesburg|Pretoria|Africa|Generator|Industrial|Projects|System|Turbines|Africa|China|South Africa|United States|Chevon Refinery|Building|Energy|Equipment|Steel|Mossel Bay|Weastern Cape|Environmental|Power|Turbines
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In last week’s instalment of this column, I made a mistake.

Referring to the Council for Scientific and Industrial Research environmental- impact assessment (EIA) for 70 wind turbines in the Weastern Cape, I wrote: “These turbines have a hub height of approximately 60 m to 100 m, a blade diameter of between 70 m and 112 m . . . [the distance] from the ground to the top of the blade will be between 130 m and 212 m. For the 130 m turbines, each turbine, plus blades, will be taller than all but 15 buildings in the whole of South Africa. The 212 m turbines will only be topped by the Carlton Centre, in Johannesburg, and will be way taller than any building in Cape Town, Pretoria or Durban.”

This is not correct. It should read: “. . . [the distance] from the ground to the top of the blade will be between 95 m and 156 m. For the 95 m turbines, each turbine, plus blades, will be taller than all but 35 buildings in the whole of South Africa. The 156 m turbines will only be topped by the Carlton Centre and Ponte, in Johannesburg, and will be way taller than any building in Cape Town, Pretoria or Durban.”

The EIA discusses visual impact, impact on bats, impact on birds, noise impact, paleon- tological heritage, archaeological heritage and economic impact, but nowhere does it discuss the impact of adding generation to the power system, specifically in the case of Mossel Bay (42 MW). This is no mean amount of power. A medium-sized gold mine draws 42 MW. The whole of Mossel Bay draws about 42 MW (if we exclude the refinery). The Chevon refinery, in Cape Town, uses about 20 MW. If this power is to be shipped out, it has to be collected from the turbines and transported through power lines to the power system.

So, apart from the forest of 42 wind turbines, there will be a whole lot of power lines, a fact which the EIA does not mention. Then again, if you have a 42 MW generator operat- ing at an intermittent load, this becomes something of a factor in the effect on the local power system. A problem called ‘VAR imbalance’ occurs and this can lead to voltage flickers on the existing power system.

There is also another phenomenon called ‘voltage slide’, which causes the system voltage to collapse slowly. Now many people I have spoken to about this topic just brush it aside with comments like: “There are wind turbines all over the world and this doesn’t happen.” All over the world, right, but not where the main source of generation is 500 km away. It is a real consideration. But, hello! Ignored in the EIA.

Other matters left out are the effect on radar equipment in the area (both civil and military) and the general effect on aviation. Stringing a whole lot of 156 m structures around the place just has to affect flying patterns. Also not addressed is whether a wind turbine ever produces the amount of energy used to construct it. In other words, if X kWh is used in construction, does the turbine ever produce more than X kWh? It is hard to get the figures accurate but it takes about 40 GJ to produce a ton of steel from ore and 25 GJ if it is produced from scrap steel.

A big wind turbine (Vesta 152) weighs 267 t, so, if it is all steel (which it is not), it must produce at least 4 200 000 000 000 kJ over its life time. If it is a 2 500 kW turbine, then, over 2 000 windy hours in a year, it will produce 180 000 000 000 kJ. Thus, many years will pass before it actually produces more power than it generates. And, on a production basis, a wind turbine has negative energy consumption. So, why, oh, why, are these projects going ahead? Or even being contemplated?

There is a reason for this, but it is often screened behind the emotion of global warming and saving the planet. The reason is allowing the US and China to continue polluting unabated. Watch this space and more next week.

Edited by: Martin Zhuwakinyu
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