Energize Inbox, April 2014

April 1st, 2014, Published in Articles: Energize

 

Re: Wind farms paid not to generate

Sir

With reference to the article published on the Energize website on 24 February 2014, titled “British wind farms paid not to generate electricity”, I would like to think that South Africa is not going to suffer a similar problem. The power output from a wind farm can vary from zero to maximum with an annual (optimistic) average of some 30%. It is tempting to use the cyclic uprating factors which are covered in IEC 60853. This standard is geared towards daily load cycles where there are power demand peaks of only a few hours. The average power demand may also only be 30% of the maximum. Notwithstanding the equal 30% load factor, the two situations are very different. The thermal inertia of a cable can handle higher loads for a few hours before the temperature exceeds its operational limit. In a wind farm, however, the higher current can last for days which is effectively a steady state as far as the cable is concerned. Cape weather watchers can confirm the south-easter can blow for two weeks solid. We, the South African cable manufacturers, are very careful to inform potential wind farm owners/contractors that cyclic rating is not applicable for wind farm cables.

Kieron Leeburn

energize-eskom-book-win-

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Published costs of coal power incorrect

Sir

In your article, “The IRP revisited: Energy modeling in our new reality”, by Johan van den Berg, published in your March edition, the author says, “The externalities of coal power are significant – these have been quantified by the University of Pretoria for Kusile at between R0,97/kWh and R1,88/kWh”. The University of Pretoria study was just plain WRONG! Nearly all the purported costs were the cost of water – yet Kusile, dry cooled, had one of the lowest water costs or various alternatives they studied. Some of the purported costs were due to climate change – and were as much of a thumb suck as anything else. Then there were some external costs due to coal mining, nearly all of which was water. The work was undertaken for Greenpeace; and the quoted costs come from the Greenpeace report. When the Pretoria report was published in the peer-reviewed literature, they had fallen by a factor of ten – and were still wrong.

Prof. Philip Lloyd

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Criticisms of the IRP 2010 update report

Sir

Wind and solar power options, attractive as they may be because the “fuel is free” (running and ownership costs, including capital interest charges are significant, however), still need to answer the questions around the base-load problem. The economy demands power on a 24/7/365 basis, not just while the sun is shining or the wind is blowing. Energy storage at a scale commensurate with this requirement is non-trivial. The use of storage-batteries on the scale needed (multiple GWh) seems totally impracticable. Even pumped-storage hydro-electric systems are both expensive and barely adequate.

I am not sure about the ongoing employment opportunities from the renewable technologies: does this mean, for example, that today’s wind turbines are so unreliable that they need a large standby repair staff for when they suffer a mechanical breakdown? Wave energy seems not yet to have escaped from the research lab – there seem to be no major-scale plants of this type running anywhere in the world. That seems to leave only coal-based and nuclear generation as economically viable options. (Recent experience seems to indicate something new: that coal becomes unreliable in wet weather!) At the moment gas-fired power (a minor improvement in environmental terms on coal) seems unreachable in South Africa.

Tony Fisher

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