atomic_fungus (atomic_fungus) wrote,

Salient Quote

Burying Our Carbon Dioxide At Sea

The first sentence of the penultimate paragraph is the telling point:

"...all of these data are based on computer models, and cannot possibly account for every possible variable, so one cannot have complete confidence in the results."

The article is a discussion of why sequestering CO2 in the oceans may not be a good idea. It uncritically accepts the proposition that anthropogenic global warming is taking place and that some reduction of human emissions of CO2 must be undertaken to prevent a man-made global ecological catastrophe.

The irony is that the case for anthropogenic global warming itself is based on computer models, which (as the author of the article correctly notes) "cannot possibly account for every possible variable".

If you read the comments following the article, they are the same-old-same-old arguments one always sees in energy discussions: the pro-nuclear person; the pro-hydrogen person; the pro-solar person; the anti-nuclear-pro-environment person; and so on. None of them understands either the economics of energy or the laws of thermodynamics.

The pro-hydrogen folks don't understand that hydrgen is an energy storage medium, not an energy source.

The pro-solar people don't seem to comprehend the primary limiting factor of solar power: the sun is only in the sky for part of the 24-hour day.

Both solar and hydrogen power suffer from conversion inefficiency: any time you convert power from one sort to another, you suffer losses in the conversion; and with current technology those losses are egregiously large.

While it is true that the sun bakes every square meter of the Earth with a kilowatt of light energy, the best solar panels we can make only convert 20-30% of that energy into electricty--so at best you get 300 watts per square meter. At the eqinoxes in the temperate latitudes, that means each square meter of solar panel will net you around 3600 watt-hours of electricity (3.6 kilowatt-hours) per square meter of array, per day. Best case (at summer solstice) would be 4.8 kilowatt-hours, and worst case (at winter solstice) would be 2.4 kilowatt-hours. This assumes that it's sunny all day, of course, which does not happen every day.

If you wish to store some energy for use at night, you must charge batteries. When you charge an electrochemical battery, around 10-20% of the electricity used to charge the battery ends up being stored. The rest is used up.

This means, in the best possible case, you'll store 0.96 kilowatt-hour per square meter of solar array in batteries, in your basement. That's 0.96 kilowatt-hour, out of the 16 kilowatt-hours, total, of sunlight which struck your solar panel on the day of June 20. That's assuming that you're storing 20% of the 30% of light which struck the solar panel, which is itself an optimum case. In practice, the efficiency of the system wouldn't be that high.

The same goes for using electricity--regardless of source--to liberate hydrogen from whatever compound you choose to liberate it. It takes much more energy to electrolyze hydrogen from water (say) than you will realize by burning it. If you use the hydrogen to fuel an internal combustion engine, to power a generator, you are just compounding the conversion loss. Fuel cells are much more efficient in this regard, but they still cannot extract all the energy from hydrogen which was put into its liberation.

You can't just drill for hydrogen; the reactive nature which makes it desirable as an energy storage medium means it cannot be found pure in nature. It also keeps hydrogen from being an energy source.

Fossil fuels are sources because the energy has already been put into the chemicals by nature. Whatever theory you ascribe the formation of fossil fuels to, it's certainly not man-made; in the case of coal we can burn it straight from the ground. In the case of petroleum, it requires some processing before use, but the energy budget still shows more energy coming out of the various fuels than went into processing the crude oil. (MUCH more.)

The anti-nuclear-pro-environment person spouted the usual guff about the dangers of nuclear waste. (I dealt with that particular straw man in an earlier entry: Just Recycle! which itself was prompted by a article.)

And finally the "tipping point" shibboleth was raised: the notion that the miniscule amount of CO2 contributed to the atmosphere by human activities might will upset the "delicate balance of nature".

CO2 is recycled naturally. It comprises about 0.75% of the Earth's atmosphere. Plants need it; they inhale it and exhale oxygen. (The actual process is known as "transpiration" since plants don't have lungs. But you get the idea.)

About 206 billion tons of CO2 is contributed to the atmosphere on a yearly basis. Out of this 206 billion tons, about 6 billion--around 3%--comes from human activity.

Let's therefore assume that 3% of the CO2 in the atmosphere came from man-made sources--that without civilization, 3% of the CO2 that is now there would not be. (This is a HUGE assumption; it assumes that we contributed 3% of the annual contribution for all of human history, which "just ain't so".)

Any system which can be driven out of a stable condition by a forcing of only 0.0225% (ie 3% of 0.75%) is not stable. We are only just beginning to learn how stable the climate of the Earth actually is; in general it has been demonstrated that very large forcings are required to get large changes in climate. As a climate forcing, 0.0225% is vanishingly miniscule.

The largest volcanic eruption on record--that of Mount Tambora in 1815--caused "The Year Without a Summer". That eruption dispersed 100 cubic kilometers of dust and ash into the atmosphere; that would be a cube 4.65 kilometers on a side weighing about 319 billion tons. Yes: one volcano, in one eruption, blew 319 billion tons of rock into the atomosphere and it caused one year's worth of climate change.

Those who worry about man-made CO2 causing global warming also ignore the fact that water vapor is a much more potent "greenhouse gas" than CO2 or methane, their other worry. By itself water vapor comprises between 2.5% and 5% of the Earth's atmosphere, and its contribution to warming vastly dwarfs CO2 and methane due not only to its much greater concentration (on the order of 100 times as much!) but also due to its much greater specific heat capacity...and its tendency to form clouds. Opaque clouds, which absorb light (the entire kilowatt per square meter) and keep it from striking the surface, thus warming the atmosphere. And the climate computer models don't do a good job of modeling the behavior of water vapor.

So you see, much of the commentary at the end of the linked article is just the same old dreck which inevitably comes up when such matters are raised...and very little of it has to do with science or economics.

  • Post a new comment


    default userpic

    Your reply will be screened

    Your IP address will be recorded 

    When you submit the form an invisible reCAPTCHA check will be performed.
    You must follow the Privacy Policy and Google Terms of use.