All the really frightening climate change graphs have the vertical scale in tenths of a degree. The scale is from –0.6 ºC to 0.8 ºC (about 1.4 ºC). On the horizontal axis, the time is given as from 1880 to 2018, a period of 138 years.
We know that, routinely, temperatures can change from, say, 12 ºC to 30 ºC over a 24 hour period. This is a change of 18 ºC over 24 hours or an average of 0.75 ºC an hour. To plot a change of 1.4 ºC over 138 years is an average of 1.15-millionth of a degree per hour, which means that the thickness of the line of the graph is more than the change in ten years. However, before the readers reach for their smartphone twitter accounts to agree about how much they disagree with me, I am not going there. I am going to discuss the appropriate use of number scales related to quantities of things electrical.
We have progressed very rapidly from kilobytes to gigabytes. When IBM compatible computers first appeared, all storage was on 360 kb floppy disks. Now computer memory is in gigabytes. To access this sort of memory, computers had to go much faster, and so all computer electronic systems moved along at the same speed as memory capacity increased.
It is, however, mistaken to think that we can just go from megawatts to gigawatts when we discuss electrical power systems. Routinely, people pronounce on electrical power systems and write things like “power demand in ten years’ time will probably be between 10 GW and 15 GW more than today”, making it seem as if the one or the other are more or less the same number.
This is foolish, since the difference between 10 GW and 15 GW is 5 000 MW, which is a great amount of power. The difference is about the power demand of the Western Cape, it is the power demand of 100 gold mines, it is more power than the expected rating of the Medupi power station.
One should take care at such loose talk. As an electrical engineer, I know that, for example, to have a renewable- energy generation system that is rated at 100 GW means that we would have to have a power system that could transfer this power. If this system was located at the coast, you would need twenty 765 kV transmission lines to send the power inland and 680 km2 of land to accommodate the generation facility. The power lines alone cost about R30-million per kilometre. To install 20 of them at an average line length of 500 km would cost about R200-billion. This assumes that connecting a renewable-energy system to a 765 kV transmission system is feasible.
It is one thing to have computer storage ramped up rapidly to meet needs and have computers developed to be able to access the storage. It is a much more expensive thing to have power system generation increase by 100% and have the transmission and distribution systems increase in capacity to transmit and distribute the power generation increase.
I am suggesting that we should be careful with thoughts and words when discussing power generation. We really should not express power system capacity in gigawatts, since it is easily forgotten that a fraction of a gigawatt – even 5% – is still quite a large amount of power, equivalent to the consumption of a medium-sized town.
Think about it.