Thursday, January 10, 2008

Anaximenes' way

Anaximenes thought that the fundamental element was Air. He argued that rarefaction of Air produced Fire and condensation produced Water and eventually Earth. He was a predecessor of Democritus whose atomic theory of matter made possible the insights of Lavoisier and the understanding that the elements were more than four but still finite in the number of kinds.

Democritus is sometimes called the ultimate materialist but a Jungian who examined the structure of myth tagged him for including the spiritual in his theory related to his spherical and slippery soul particles. Almost, these soul atoms seem like the Chi of Lau Tzu or the breath of life of Genesis. Almost, they seem to be what Anaximenes took Air to be.

The direction of density in Anaximenes theory makes sense. Earth will silt out of a pool of Water, Air bubbles in Water and Fire rises in Air. In some ways we see Air becoming Fire as flame fills the Air. Rain also shows Air becoming Water. But what of Air becoming Earth? I'm not sure how he came to this though he is essentially correct about the formation of the Earth from a cloud of gas which at some point was entirely gas though it had already condensed out dust when the solar system formed. And, felt-like dust did play a role. One path he might have taken would be to observe a rotting log becoming soil and further observing that trees, no matter how large they grow, do not leave a depression in the soil around them. Where did the wood come from? Not from Earth. Perhaps from Water which came from Air? As we know now it comes from both water and air, but we need Lavoisier's division of air into its own elements to be clear about how.

Behind all of these ideas is the concept of conservation of matter which Democritus used to arrive at the ideas that there must be irreducible unchanging units, and which Lavoisier began to demonstrate quantitatively. A century after his false conviction and execution in the Terror of the French Revolution, we learned that there is a means of transmutation that ushered in the horrors of the nuclear age. But, even then, the core concept of conservation held but was shifted to baryons rather than elements and we were back to protons, which exist as Air as the basic unit. So, in a large sense, Anaximenes had it right to begin with.

The myth of the formation of Mankind from mud leads to the Ash Wednesday admonition: "Remember that you are dust and to dust you shall return." This is extremely helpful to set a penitent tone, and it is true that we are partly dust. But, by number, if not by mass, we are mostly hydrogen and so to Air we shall return as well whence we came for the most part. It seems fitting then that the conclusion of penitence is resurrection and ascension into Anaximenes' beloved Air.

I had originally thought to title this post Air Mining but decided to give it its present title because I think we'll be fulfilling Anaximenes' quest.

We've become troglodyte during the Stone, Bronze, Iron, Coal and Nuclear Ages, relying more and more on grubbing under the Earth for things that we use. When once the branches of trees and bones of animals were enough, we must have ever harder and hotter substitutes for our tools. But, we have not completely forsaken the air. We still get our water from it, and this, after all is the main constituent of our bodies. We get oxygen from it both to breath and to burn the coal and oil and gas that we drag up from the Earth. This is becoming a problem as last year was the second warmest on record. We get carbon from the air rather than the earth for our food at least, and to do this we also take nitrogen from the air to grow our plants, not being satisfied with the efforts of clover, beans and alder. We fill windows with argon to help with insulation. In bulk, we gather energy from its flow and rely on its mix of transparency and opacity to regulate our global temperature and let in the low entropy power of the Sun. We use its convective properties to carry away heat by constructing ugly cooling towers where even the much higher heat capacity and steady flow of a majestic river are not sufficient to deal with our wasteful methods of producing electricity. We have not forsaken the Air completely, but our deeper and deeper delving in the Earth is abusing it and unbalancing out ecosystem. The brimstone and quicksilver we dig out of the earth with our fuel spreads death through the air across our forests and waterways while the carbon itself accumulates in the atmosphere adding opacity to it, raising temperatures faster than the ecosystem can adapt.

In our discussions of Real Energy we have seen that there is no need to mine the Earth for energy; it is counter productive. And we have seen that if we do need fuel, we can make it directly from the air without burdening the ecosystem. Thus, real energy does away with the Coal and Nuclear ages. But what of the Stone, Bronze and Iron Ages? Can we similarly pull ourselves out of our shadow haunted Cave and return to the open Air? The Coal and Nuclear Ages were about the hubris of out doing the Titan Prometheus but to overcome the Bronze and Iron Ages we must propitiate the Olympian Hephaestus, because while Prometheus' stolen goods are about the means, Hephaestus' art is about the ends, the making of harder substances than wood or bones or stones. And, that is what gave us mines in the first place.

It turns out that an insight of Lavoisier's allows us to break away from Bronze and Iron. He learned that diamond is actually crystallized carbon. Diamond is harder by far than bronze or iron but it is rarely formed in nature, requiring very high temperature and pressure deep in the Earth. Associated with volcanoes, it is perhaps Hephaestus' highest art. But, the feedstock, the concentrated carbon, often ultimately comes from Air unlike copper, tin or iron. Diamond is very permanently sequestered carbon dioxide, though, at a pinch, if we run low on carbon dioxide, it is possible to burn diamond in air. Diamond is also formed industrially using vapor deposition, a direct Anaximenesian approach, but here we will consider an unusual form of diamond, Lonsdaleite, which forms as meteors fall through the atmosphere, because Lavoisier's art seems to provide a simple approach to its production that might allow it to be used in structural applications. There are other forms of carbon that show promise in structural applications including nanotubes and buckyballs, but we want a direct comparison to steel for our demonstration so we'll stick with diamond.

When we looked at mining the air for fuel, we needed to obtain water and carbon dioxide. In this case we will need a supply of carbon dioxide only. The hydrogen and bromine we'll be using will be recycled in the process.

Our project is to construct a transmission line from a wind farm for lower energy cost than using steel by mining the air for our building material. We will build a GW capacity line, similar to current high voltage transmission lines. A difference though is that we will support our conductor using our building material rather than metal cable. This will allow us to change the conductor configuration, use a higher voltage and thus lower line loss.

We'll start with our conductor. High voltage transmission lines are often a composite. A strong cable is used to support the conducting material. This is because the better conductors like aluminum and copper are less strong than steel but the amount of conductor needed is not so great that it would be thick enough to hold up against its own weight and wind forces. You could space pylons more closely, but that would increase the overall use of steel. As we already saw, a conductor 6 cm in diameter (say aluminum) can be used to carry 30 GW of power at three times the voltage currently used High Voltage Direct Current transmission because the larger radius increases the limit set by corona discharge compared to a smaller radius used for the Pacific Intertie which carries 3 GW. We can retain the larger radius by making the conductor hollow. The cross sectional area of the conductor can be reduced by a factor of 30 to meet our 1 GW goal. So, the thickness of our cylindrical conductor will be about 0.5 cm. Diamond has a high tensile strength (about 95 GPa) compared to prestressed steel strands (about 1.6 GPa) so that the cross sectional area we will need will be (proportionally) less than the ratio of the radii of the hollow-to-non-hollow conductor (about a factor of three) times the ratio of steel-to-diamond tensile strengths (about 1/59). So we need about 20 times less cross sectional area compared to steel. By mass, this comes to about a factor of 44 less mass. We'll arrange this in the form of a sheath around the conductor which will need to be in the form of a woven cloth because the coefficient of thermal expansion of metals is a factor of ten or so larger than for diamond. We'll also include a few atmospheres of carbon dioxide within the supportive sheath so that in case it gets heated to 800 C, a breach of the sheath will cause any combustion to be extinguished. We'll also provide for an external conductor to avoid this situation arising from lightning.

We can largely ignore the improvements in weight that diamond conveys in the construction of our conductor because most of the weight is in the conductor itself. Also, we needn't really have gone to the trouble to improve our conductor since our wind farm may only need to build out a transmission line that is 100 miles or so long and conventional conductors using high voltage alternating current would do the job. So, this portion is mostly for fun. Much more of the embodied energy in out transmission line is in the pylons and we turn to this now.

Steel used in construction has a lower tensile strength than prestressed strands by a factor of 2 so that we can reduce the cross section of our structural members by a factor of 124 using diamond as opposed to steel and ignoring the reduced mass of the pylon itself. The amount of mass is thus a factor of 276 less. The embodied energy of steel is 32 MJ/kg so all we need to do is figure out how much energy we need to make 3.6 gm of diamond and we will be able estimate our energy savings.

We already calculated that to condense carbon dioxide from the air we need 0.77 MJ/kg so things are looking pretty good. We'll take a supply of hydrogen and form methane using the exothermic Sabatier reaction which means that we will need to recycle the water produced at this point. The energy input is about 14 MJ/kg. After these energy inputs we are basically doing room temperature chemistry (Lavoisier's specialty) producing bromoform from methane and then producing poly(hydridocarbyne) from the bromoform. We'll input about 2 MJ/kg of carbon using free radical halogenation to make the bromoform. The polymer is then painted in solution on our growing structural element and warmed using argon gas. The waste heat from the methane formation can be used for this step. To be safe, lets add another 14 MJ/kg to be sure the bromine, argon solvent and remaining hydrogen all get properly recycled. This assumes we use oxidation of hydrogen to separate our reactants but the hydrogen bromine can probably be handled with less energy input. So, in all we need about 31 MJ/kg to produce our structural element, similar to the value for steel. But, to replace the steel we need much less so we need a factor of 280 less energy to build a pylon.

Take a deep refreshing breath. Anaximenes would say "I told you so."

Now, world steel production is only 1.3 billion metric tons per year and to replace that we would need only 4.7 million metric tons of diamond compared to about 3 billion metric tons of carbon in our fossil fuel pollution. But, there are probably other materials that could be replaced as well. Concrete production comes to around 12 billion metric tons and wood is harvested at 3 billion metric tons per year. So, we might begin to sequester a few percent of our carbon emissions by mining the air for carbon. Leaving the trees alone might have the largest effect, since this would both take up carbon in forests and help to bring our estuaries back into balance.

We've been looking at Energy Returned on Energy Invested (EROEI) recently. How would replacing the steel in a wind turbine with diamond affect this value? The amount of steel used in 3 MW wind turbine is described in this life cycle analysis which estimates the EROEI to be 20. Assuming 10% steel by mass for the reinforced concrete foundation, the structure contains about 460 metric tons of steel/iron. Using our conversion factor of 32 MJ/kg, this is about 14 million MJ of embodied energy and about 55% of the 7405 MWh of energy used in construction of the turbine. So, replacing steel with diamond would give 3333 MWh instead. Thus the EROEI would be boosted by a factor of 2.2 to 44.

Back in our pylon, we would want to use the same method for protecting against combustion that we used in our conductor, namely, filling hollow structural elements with several atmospheres of carbon dioxide so that a combustion rupture would be self-extinguishing. This probably has fabrication advantages as well. The thermal conductivity of diamond is quite high and we need to build our tubes by painting layers which are warmed using argon gas to remove the hydrogen in the poly(hydridocarbyne) and the solvent. Thus, having heat flow down the tube once this is done will allow us to rapidly paint on the next layer. Arranging our painting and warming heads periodically around the growing mouth of the tube would essentially have us spinning the tube into existence. At a rate of tens of microns per second growth, we can grow a meter long tube in about a day. Our manufacturing facility would bear an uncanny resemblance to a uranium centrifuge enrichment facility with all that spinning going on, but would not be prone to seismic risk since the rotational frequencies would be much lower, in the neighborhood of tens of Hertz.

Lonsdaleite, our chosen form of diamond, has still not been characterized fully experimentally and the samples studied so far show a hardness somewhat lower than common diamond. Thus, we might have to use more than we have anticipated. Theoretical study suggests that the Lonsdaleite structure may be slightly stronger than regular diamond and that present samples are affected by defects and impurities. In any case, other carbon structures are even stronger. Fullerite may be twice as strong as regular diamond. The choice of what to mine the air for will likely come down to ease of fabrication and required energy. But, our passage through our troglodyte phase and our flirtation with Hephaestus would seem to be ending and drawing to a close the Ages with which we understand history. For our new Age, the name Carboniferous has already been taken and Anthropocene seems too ominous. Let's just call it the restoration of the Holocene instead.


Cyril R said...

Fascinating stuff Chris. Carbon is truely an amazing material and it's future applications can be vast.

Have you read about amorphous diamond as a semiconductor material? Could facilitate efficient heat pump designs and 50% efficient solar cells that don't deteriorate as much over time as silicon cells do:

And there's carbon foam, amazing material for exchanging/transferring heat for efficient dry cooling, heat pumps and other applications:

Is the next age going to be the carbon age?

Anonymous said...

re. thermal conductivity of diamond - yes, very high for MONOCRYSTALLINE diamond.

But lower for POLYCRYSTALLINE diamond (phonons smacking into crystal boundaries drop thermal conductivity) and much lower yet for diamond-like carbon (DLC).

Pyrolysis of poly(hydridocarbyne) (aka 'PHC') results initially in DLC, which, as temperature increases, converts to POLYCRYSTALLINE hexagonal diamond (i.e. Lonsdaleite) - not megalithic monocrystalline form.

Polycrystalline Lonsdaleite may be sufficient for your purposes (or maybe even DLC) - but the real unsolved challenge is directly forming bulk monocrystalline diamond from pyrolysis of PHC.

Cyril R said...

Monocrystaline diamonds? Why bother with that expensive stuff, just use amorphous (real not DLC) diamond. Thermal conductivity may not be as good as monocrystalline but it's still pretty damn good (much higher than copper for example).

Cyril R said...

Also, the carbon foam has extremely high surface area which is a big variable in heat transfer rates for HX.

Chris Dudley said...

Thanks for the comments.

I think there are many applications for carbon in various forms and the electric properties are quite interesting.

Also, at this point I think it is unclear what carbon material will be used to replace steel, concrete, wood and other structural materials. What seems clear now it that there is a pathway that requires substantially less energy than steel so that steel will be replaced.

I think that the thermal conductivity comes into how quickly structural elements may be grown through a an ink jet-like method, but reduced conductivity can be compensated with more capital equipment. So long as the energy savings still provides a cost savings, then the we should see a conversion.

The existence of fullerite, when considered as a 3-d polymer, suggests there might be other low energy routes to replacing steel. Which form is dominant does not seem to me to be all that important compared with the idea that we don't really need to grub in the Earth for materials. At this point, just about every single mining death has no excuse. What is already above the surface is more than adequate for all future needs.

There is the problem of developing the technology rapidly. But we have faced that for some time in replacing coal as a fuel and we may be seeing new models now for speeding things up.

Steel Fabricators Wolverhampton said...

nice article. I like it very much. thanks for sharing it.