Friday, 14 March 2014

How Not To Do Infographics

The good people over at the Australian Skeptics Facebook Group pointed me in the direction of an interesting infographic, this morning:


Apparently, to power a one megawatt hospital, you'd need 100 football fields' worth of wind farms. It seems sketchy from the outset. A quick reverse Google image search takes us to the source, 'I Dig Uranium Mining', run by Andrea Jennetta, "President & Owner at International Nuclear Associates Inc". She states on her post:
"A single gram of uranium can produce roughly 1 megawatt of energy for 24 hours. To put that in perspective, it would require 56.5 million square feet of wind farms (that’s 100 football fields) to produce the same quantity of energy, assuming the wind is blowing that day"
Something's horribly wrong with the calculations on her infographic, which was re-posted by the group 'Things Worse Than Nuclear Power' - a site that seemingly exists primarily to exaggerate the environmental impacts of any technology that isn't nuclear.

Without performing a single calculation, we can say with certainty that a single 3 megawatt wind turbine, with good wind resource all day, would easily match the one megawatt demand of our hypothetical hospital. But let's dig further into their claims.

A standard American Football field has an area of 57,600 square feet. So, if you had 56.5 million square feet, you could actually fit ~998 football fields, not 100. This just seems to be a miscalculation.

So how many wind turbines could you fit into the area they've proposed on their infographic? Let's assume each wind turbine is a three megawatt machine, and given the wind is blowing, let's conservatively assume each machine is generating at 50% capacity (1.5 megawatts per turbine). Each tower is 200 metres from the other towers. That means each turbine takes up an area of 0.4 square kilometres. The Uranium Mining site's original area was 56.5 million square feet, which is 5.2 square kilometres.

So - you could fit 5.2/0.4 = 13 wind turbines, generating a total of 19.5 megawatts. Which gives us a conservative estimate of 19 hospitals. If the wind was really blowing, and the turbines were at maximum output, it's be ~39 hospitals. Calculations here:



The comparison isn't really fair. Wind energy output is variable, which means it generates a fair amount of energy over time, but you can't assume that it'll be generating at a certain capacity, if you were to randomly choose an interval.

Plug it into an energy grid, and it successfully crowds out fossil fuels, regularly. In South Australia, it's already doing it, every single day. A quick look at how energy output has changed in SA shows this quite clearly:


On a smaller timescale, here's how wind output worked in South Australia, during the week of one of Australia's most significant heatwaves:


As you can see, there were times when SA's generation formed a large percentage of South Australia's generation. But, at other times, the percentage was quite small. So, is this a problem for the market operator, who are tasked with reliably meeting electrical demand over the entire electricity market?

Well, no. They forecast the output of wind farms - here's a comparison, for the same week, of actual output to the wind forecast generated 24 hours prior, and 12 hours prior:


Basically, you don't need to worry about hospitals shutting down because of wind farms, no matter what 'I Dig Uranium Mining' tells you.

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