04 November 2009

Devastating Takedown of Super Freakonomics

Click for full size

Not really such a big patch of territory.

You don't have to go far for help
I think that the book is an exercise in muddy headed contrarianism: The idea here is if you come to conclusions that are counter intuitive, particularly if they are favor conservatives, you get air time and book sales, and thus academic integrity be damned.

In any case, Professor Raymond T. Pierrehumbert takes a look at the chapter on Superfreakonomics where the authors claim that solar panels will contribute to global warming, and shows that anyone who can add 2 and 2 should never have put out this tripe.

First, he Googles world electric consumption, 16.83 trillion KWH, and figures back to wattage, which gives about 2 trillion (1.921T actually) watts.

Well, with 200w/m for an average area (he used 250 W on the assumption that you place solar cells in sunnier climes), and the current commercial efficiency of 15% that means that one would need about an area equal to 2x1012/(.15 X 250)=5.333x1010 m2=53,000 square kilometers, or a square about 231 kilometers to a side. (top picture).

Wiki has Earth's surface area as 510,072,000 km2, so this is 0.0105% of the earth's surface.

Now, you actually have to double this, since you need to account for the fact that at any given moment, half the earth's surface is in darkness, so it rises to a whopping 0.0210% of the Earth's surface area.

This is a worst case scenario, particularly since the albedo (reflectivity) of a solar cell is frequently the same as the roof that they are placed on (yes, this is an argument for white roofs in warm climates), but let's ignore that, and go to his numbers:
So, let’s say that sand has a 50% albedo. [note the albedo of the earth is 0.39, I learned that from the Greek composer Vangelis] That means that each square meter of black solar cell absorbs an extra 125 Watts that otherwise would have been reflected by the sand (i.e. 50% of the 250 Watts per square meter of sunlight). Multiplying by the area of solar cell, we get 6.66 trillion Watts

That 6.66 trillion Watts is the “waste heat” that is a byproduct of generating electricity by using solar cells. All means of generating electricity involve waste heat, and fossil fuels are not an exception. A typical coal-fired power plant only is around 33% efficient, so you would need to release 6 trillion Watts of heat to burn the coal to make our 2 trillion Watts of electricity. That makes the waste heat of solar cells vs. coal basically a wash, and we could stop right there, but let’s continue our exercise in thinking with numbers anyway.
Of course, the problem is not the heat produced by coal production, it's a trivial part of the equation, it's the heat trapped by the emissions that are the concern, and it is (go to article) at least two orders of magnitude greater than waste heat.

His conclusion:
A more substantive (though in the end almost equally trivial) issue is the carbon emitted in the course of manufacturing solar cells, but that is not the matter at hand here. The point here is that really simple arithmetic, which you could not be bothered to do, would have been enough to tell you that the claim that the blackness of solar cells makes solar energy pointless is complete and utter nonsense. I don’t think you would have accepted such laziness and sloppiness in a term paper from one of your students, so why do you accept it from yourself? What does the failure to do such basic thinking with numbers say about the extent to which anything you write can be trusted? How do you think it reflects on the profession of economics when a member of that profession — somebody who that profession seems to esteem highly — publicly and noisily shows that he cannot be bothered to do simple arithmetic and elementary background reading? Not even for a subject of such paramount importance as global warming.
(emphasis mine)

He then finishes with a Google map (bottom pic) showing that it is a ½ mile walk to the Hinds Geophysical Laboratory on his own campus in order to confirm these numbers.

It would be even shorter if he cut through campus and the Administration building, though considering that the ethics office is likely located there, he probably wants to take the long way.

(on edit)
I updated the pictures to go with the popup format that I now use.

Given Michael Kinsley's most recent exercise in mindless contrarianism, where he came out against journalism, I feel compelled to note that this behavior (Michael Kinsley disease) becomes even more toxic and has less intellectual integrity when juxtaposed with Chicago School economic delusions.


Susan said...

That last line of yours was so very, very funny Matthew, first laugh all day!

Truly, what a flash of brilliant wit!

Of course, isn't "ethics" departments on college campuses an oxymoron of some sort?


Post a Comment