I suppose I should stop worrying about people being wrong on the internet, but when you’re invigilating an exam, you start reading Facebook, and then you end up with a long debate about renewable energy. It just came up. I’ve decided to take some of the stuff I put up on Facebook and add it to the comments I’ve been collecting in this post about energy in South Africa.
An article on IOL started it all, but this one is better. Both of the articles get very confused about the units – the IOL one talks about “GW per hour” and the Guardian one mentions electricity costing “23 cents per kW/h”. The point is that Germany set a record of 22 GW of electricity being produced at some point on Saturday, 26 May 2012.
Units
So let’s clear up the energy unit problem first, with some examples. We have to understand
the difference between energy, measured in Joule in the SI system, and
power, which is measured in Watt (Joule/second) in the SI system. Power
is energy per time, or the rate at which energy is used. In more understandable terms, energy is to distance as power is to speed.
Now let’s look at what the IOL article is saying: “22 gigawatts of
electricity per hour”. This is the same as saying “I drove to Pretoria
at 60 kilometers per hour per hour”. Note the extra “per hour” – it
doesn’t make sense. The official they quote, and the Guardian gets it right and says that
they were producing “22 GW” at their peak capacity. Remembering the
speed analogy, this is like saying you hit 160 km/h on the highway on the way to Pretoria.
Your average speed will typically be much less. For perspective the
article also mentions that this is about a third to half of their
demand, which puts their demand at between 44 GW and 66 GW. The entire world’s electricity consumption is around 119 PWh/year or 13.6 TW.
Energy from the sun
South Africa vs Germany
South Africa is well-known as a sunny country – it is clear we are in a good place solar insolation-wise from the graph above, and we have more surface area with less people than Germany. So why are the Germans supplying such a large fraction of their electricity demand with solar while we aren’t? In fact, why are we planning to build more nuclear power stations?
How much are we talking about?
We have things they don’t (coal and uranium)
Probably the best argument that I have come up with is shown in the following graph showing Energy imports as % of energy use. Note that this is bigger than just electricity.
It is clear that Germany does not have enough sources of energy inside their borders to supply their demand. South Africa does. Their investment into other sources of energy reduces their reliance on other countries. South Africa exported 67 Mt of hard coal in 2009 while Germany imported 38 Mt, our economy is largely constrained by the resources available to us. If Germany had more coal, I am pretty sure they would not have pushed nearly as hard to get rid of this import. By the way, the same source also lists Germany as one of the top importers of natural gas in 2009.
They have things we don’t (money)
Why even consider coal if it’s bad for the environment?
The allure of cheap energy is huge. Coal as a Energy Return on Energy Invested (EROEI) of over 100, nuclear in the 50s and solar closer to 10 (see table 2 of this analysis). Tom Murphy has a much better analysis of the problems of low EROEI that I could hope to do called The Energy Trap. Briefly, the problem is that it takes energy to build devices to make energy, even if the ultimate source of that energy is “Free”. This means that we have to climb into debt somewhat to build new capacity when we don’t have the really huge payback we get from coal.
Final words