Recently I attended parts of a series of lectures hosted by the Andlinger Center for Energy and the Environment.
The most recent lecture was by Dr. David Eaglesham (formerly) Chief Technology officer of First Solar, another basketcase in the "solar will save us" industry that according to Amory Lovins, writing in 1976, was supposed to save our asses by the year 2000 except that it now seems to be 2012 and our asses, um, aren't saved by solar energy or anything else.
A small matter, one supposes.
Dr. Eaglesham's lecture was entitled Challenges for the Photovoltaic Industry.
Here is the sum total of what Dr Eaglesham's lecture - according to me at least, although I admittedly hold a jaunticed view of such things - about the problems of the solar industry came down to: "Not enough subsidies."
If you ask me, one of the problems of the photovoltaic industry is that its products don't work very well, but, again, no matter. I may remark below on some more substance about Dr. Eaglesham's lecture, and some of the questions I posed, and also questions that were not asked by anyone in the audience, which may well have consisted of a set of people 100% of whom may have been much smarter than I am.
(A good goal in life is to try, as often as is possible to be in rooms where one is the dumbest person in the room.)
However this diary is not about "problems of the solar photovoltaic industry." This is about the technology that is - whether you believe it or not - far more critical to the issue of climate change than, in my opinion, than solar PV energy will ever be. This is a diary about turbines.
In any case, I was just speaking of people who are much smarter than I am. To that point, the director of the Andlinger Center is Dr. Emily A. Carter. The paper I will discuss in this diary was written by her on the occassion of her election to the National Academy of Science and was published in the Proceedings of that Academy, PNAS April 5, 2011 vol. 108 no. 14 5480-5487.
Here is the title of the paper: "Atomic-scale insight and design principles for turbine engine thermal barrier coatings from theory."
It's a paper about refractory materials and superalloys, a topic in which I am very interested and about which I commented, albeit peripherally, in my last diary about the radioactive metal Technetium, a diary which, upon review, seems to have contained one statement that may have been misleading.
NNadir is a liar.
Superalloys are alloys - they almost always contain a large amount of nickel - that can withstand high temperatures as well as corrosive environments without losing their mechanical strength.
Examples of superalloys include Hastelloy®, Inconel as well as others, some of which are actually proprietary. Superalloys are widely used in turbines for jet aircraft as well as turbines in powerplants as well as in other applications such as spacecraft.
Doctor Carter is one of the world's leading authorities on - and developers of - what is called "Orbital Free Density Functional Theory."
Orbitals, as many people know - unless one has joined Greenpeace and has thus remained blissfully unaware of the contents of science books - may be thought of as three dimensional distributions of the probability of "seeing" an electron in a particular area of space - this definition is somewhat chemist centric inasmuch other particles, which are not fermions (as electrons are) also can have 'orbitals' which do not obey (as electrons do) what is known as the "Pauli Exclusion Principle." (Particles that do not obey the "Pauli Exclusion Principle" are called bosons.)
One often sees electronic atomic orbitals depicted as a set of shapes, but in the larger sense, these representations are often for heuristic value: The real value of this constructs is to utilize the mathematical forms of these orbitals (which are considered as waves) in constructing more physically meaningful mathematics. In practice, in molecules, the situation is very much more difficult to handle. One may use the conception of atomic orbitals and "mix" them in various ways - for instance one approach has been to use linear combinations of wave functions to make "molecular orbitals" - but the calculations can and do become very complex.
In one of her papers, Dr. Carter gives a feel for this level of complexity. She writes, in a paper about a new software tool she has helped to develop called PROFESS:
In general, in order to solve for the electronic structure and properties of matter, one must solve the time-independent Schrödinger equation ℋΨ = EΨ, (1)where ℋ is the Hamiltonian operator, E is the total energy, and Ψ is the many-body electronic wavefunction under the Born– Oppenheimer approximation. The Ψ that corresponds to the lowest E then contains all information about the ground state of the system. However, Ψ contains 3N degrees of freedom (N is the number of electrons), and is expensive both to compute and to store. For example, accurate ab initio electron correlation methods that directly use this approach (e.g., configuration interaction and coupled cluster theories) generally tend to be too expensive for studying more than tens of atoms, even with linear scaling versions, which have been used to handle up to ∼130 atoms [1,2].Carter, et al, Computer Physics Comm. Volume 179, Issue 11, 1 December 2008, Pages 839–854
An alternative scheme to solve for ground state properties is put forth in the Hohenberg–Kohn theorems . The first theorem states that the ground state electron density ρ contains everything necessary to recover all information about the electronic ground state, including, e.g., the electronic wavefunction, the total energy, the associated forces on the nuclei and the stress in the unit cell. In theory, using the density entirely obviates the need to compute or store a full N-body electronic wavefunction. Since the electron density only has three coordinates associated with it, this theorem formally reduces the number of degrees of freedom from 3N to 3, an enormous simplification. The second theorem is a variational principle that provides a way to find this ground state electron density by minimizing the electronic total energy with respect to variations in the electron density.
If the Schroedinger equation above looks deceptively simple, one should certainly magnify the word "deceptively" considerably, perhaps not as much as the scientifically illiterate anti-nuke community magnifies the possibility that any death in a nuclear related system in a period of half a century is worthy of infinitely more attention than the 3.3 million deaths that occur each year, every, from air pollution, but close to that much.
The Schroedinger equation for a many body system - and even the simplest molecules are such systems - is very, very, very, very complex, because all of the electrons in a system of atoms push each other around, and in fact, pull the atomic nuclei around, and moreover do so in a way in which the ordinary laws of macroscopic physics do not apply, but are instead subject to the laws of quantum mechanics.
Some simplifying assumptions are made, the most famous of which is the Born-Oppenheimer approximation (yes, that Oppenheimer) - to which Dr. Carter refers - that ignores, essentially, the movements of nuclei and focuses instead on electrons. This simplifying assumption has proved very useful although it is well known that nuclei do, in fact, move in the kinds of electric fields that comprise all matter, and in fact, the entire point of approximating the solutions to the Schroedinger equation is to show how atomic nuclei are pulled into specific geometries by electrons.
But no matter.
Now, if I carried on for a long time about these energy minimization modeling schemes of Dr. Carter's, I would be in the position of rote dogmatic anti-nuke - and there are no other kinds of anti-nuke - that is, I would be speaking on a subject I know nothing about, so that's all I'll say about PROFESS, except to note that the quantum mechanical concepts with which Dr. Carter works are relevant to what I will now discuss.
I said this diary is about Dr. Carter's paper on turbines and it is.
Almost all of the electricity produced on earth is generated using turbines. Turbines are involved in nuclear plants, gas plants, coal plants and in fact in hydroelectric plants. (There are some powerplants that are diesel powered and these represent only a small fraction of the world's power supply.)
The turbines in those plants that are heat engines (which excludes hydroelectricity) operate on two different kinds of cycles, one of which is the Rankin (steam) cycle and somewhat less common, Brayton cycles. There are a small number of plants - largely gas plants - that operate on both cycles, and predictably enough, these are called "combined cycle" plants.
Combined cycle plants can have very high thermal efficiency, as high as 60%, whereas plants that operate on only one cycle have thermal efficiency that is typically on the order of low thirties percent efficiency.
One way of increasing the energy efficiency - the amount of useful work - that one can get out of a system is to operate it at high temperatures. The thermal efficiency of a Brayton system is typically written as follows:
η = 1 - T1/T2Here η is a dimensionless number defined as the "efficiency" (often written in percentage terms, and thus multiplied by 100) and T1 and T2 are the temperature of the surroundings (generally determined by the weather) and the temperature of in the hottest part of the plant, which is generally right before the gas (be it steam or fuel exhaust) hits the turbine. Thus the hotter the engine is run, the higher the efficiency. (Note too that power plants are more efficient in winter than in summer.)
In a Brayton cycle plant, very high temperatures are involved. In a gas plant (or in a special - and rare - type of coal plant that is sold as "lipstick on the pig" by the coal industry, an IGCC plant) the gas hitting the turbine is extremely hot.
I now return to Dr. Carter's work, in which she describes something about these conditions, in the PNAS paper referenced at the outset. She writes:
To maximize energy efficiency, gas turbine engines used in airplanes and for power generation operate at very high temperatures, even above the melting point of the metal alloys from which they are comprised. This feat is accomplished in part via the deposition of a multilayer, multicomponent thermal barrier coating (TBC), which lasts up to approximately 40,000 h before failing. Understanding failure mechanisms can aid in designing circumvention strategies. We review results of quantum mechanics calculations used to test hypotheses about impurities that harm TBCs and transition metal (TM) additives that render TBCs more robust. In particular, we discovered a number of roles that Pt and early TMs such as Hf and Y additives play in extending the lifetime of TBCs.The bold is mine.
Hf and Y refer to the elements hafnium and yttrium. By the way both of these elements are byproducts of the nuclear industry. Yttrium is a fission product produced in about 4% of nuclear fissions and the element has no long lived radisotopes. Thus it can be isolated from used nuclear fuel and used essentially in any application for the element.
Hafnium is always found in zirconium ores. Because it is a very efficient neutron absorber, and because nuclear fuel rods and other constituents of reactor cores need to be transparent to neutrons, hafnium must be removed from zirconium before the zirconium can be used. Historically this was a very difficult challenge, because the chemistry of hafnium and zirconium are very close, particularly because the former element occurs in the periodic table after the so called "lanthanide contraction." However obviously this challenge has been met on an industrial scale. Hafnium free zirconium can also be obtained from used nuclear fuel because it is a fission product and hafnium is not. Yttrium is also a fission product, and is, in fact one of the most common fission products.
Both hafnium and yttrium are relatively rare elements, although supplies of the latter are higher. Hafnium is used in the control rods of nuclear reactors because its physical properties with respect to things like corrosion are very similar to zirconium and, as said, it absorbs neutrons.
Interestingly, when used in control rods, small amounts of hafnium are transmuted into the element tantalum. Tantalum - if you are familiar with it - is obtained from the mineral "Coltan" the mining of which has caused great tragedy in parts of Africa, where people are enslaved or even killed - particularly in the war ravaged region of the Congo - in efforts to obtain it. However this matter is certainly understandable since tantalum is used to make very high efficiency capacitors, which are important to the electronics industry that makes cell phones and computers using them, the latter being very useful for smug and superior westerners to disseminate information about how wonderful Greenpeace is, for instance, and about how the world will be saved by efficiency and stuff like that.
The author of this diary, who recently had the privilege of being the dumbest person in the room also makes use of these capacitors, just to be clear. The author of this diary is hardly an innocent, since he knows what's involved in his lifestyle, something he has cheerfully confessed in this space for many years, here for instance:
NNadir is a liar, and more recently was the dumbest person in the room.
Anyway, to return to the point of turbines.
Dr. Carter writes in the PNAS paper:
Turbine engines operate via the Brayton cycle, which offers lower carbon dioxide emissions and lower cost for power generation than other possible alternatives. Their efficiency can be increased by increasing the inlet temperature, which allows more expansion of gas that creates more pressure to drive the turbine. However, high-temperature operation, under oxidizing conditions, poses serious demands on the materials used to construct jet engine components. Materials must be found that are robust under such harsh operating conditions. Engineers over the past few decades have improved greatly the thermomechanical properties of the metal alloy comprising, e.g., the turbine blades, and have created a multilayer coating for the blades that protects against both heat and corrosion, referred to as a thermal barrier coating (TBC).This - along with her more sophisticated and elegant way of saying what I said above - is the crux of her paper, in which she gives a solid theoretical footing to the empirical development of thermal barrier coatings. And the development of said coatings has been, up to now, empirical.
Dr. Carter writes:
Despite these advances, more robust TBCs are desired, either to extend TBC service lifetime under present-day operating conditions or to operate at even higher temperatures to achieve more efficient energy conversion. As a result, characterization and optimization of TBC properties have continued to be active areas of research. As is the case for most materials development, the usual path to improve TBCs relies on trial and error. Many materials compositions are fabricated, characterized, and tested. Unfortunately, characterization typically is performed postmortem, as virtually no instruments exist to characterize a TBC in situ during operation.She gives us a little basic tutorial on what thermal barrier coatings are and how they work and what the current state of the art is:
Turbine engine components are made of nickel (Ni)-based superalloys, the microstructure and composition of which has been tailored to minimize deleterious changes at high temperature (e.g., creep). The idea of coating the metal parts with a material with low thermal conductivity has been around since the late 1950s, and TBCs have been used since the 1980s, but it has been an ever-present challenge to make these coatings durable and prevent them from spalling (chipping off) after some time in operation (1). The structure of a state-of-the-art TBC consists of three layers (Fig. 1). The topmost layer is a ceramic material that constitutes the actual heat shield. The material of choice is yttria-stabilized zirconia (YSZ), because it possesses a unique combination of properties. First, doping ZrO2 with 6–8 wt%Y2O3 ensures that the resulting YSZ adopts the tetragonal phase at all temperatures of interest, so that thermal-cycling-induced phase transitions—which otherwise would occur in pure zirconia, causing stress buildup—are avoided. Second, YSZ has one of the lowest thermal conductivities of all ceramics, because it possesses an unusual defect structure that scatters phonons, thereby hindering heat transport. Third, despite being a ceramic, its coefficient of thermal expansion is well matched to that of the metal superalloy so that stress buildup due to thermal expansion mismatch is minimized. Finally, YSZ has a low density, which minimizes weight, and it is very hard and therefore quite resistant toward foreign-body physical damage (2, 3).A word about the mechanism of "foreign body physical damage" to turbines involves steam itself. When you hear someone using the term "clouds of steam" you are in fact listening to an oxymoron. Steam is clear and colorless; it is like air, invisible. Any "clouds" one sees associated with the presence of steam involves the condensation of steam to form small suspended drops of liquid water. The momentum of water can be quite abrasive, which is clear on a little reflection when one has been in a driving rain, where the water can collide with one's face in a way that is, if not painful, is at least uncomfortable. The commercial and consumer use of devices like power washers also shows that liquid water can be reasonably abrasive. In a large steam turbine system, where the steam and any liquid water that condenses in it can be traveling at very high velocities, it is possible to actually abrade the surfaces of turbines. This is a non-trivial point. I mention it because it is important to note that mechanical strength and resistance is also an issue. (In order to prevent this kind of damage, many steam type plants include a device called a "steam separator" in the line before the turbines.)
One tries to minimize the presence of condensate my manipulating via engineering and heat flow via operating conditions the presence of condensates, of course, since almost by definition they will reduce turbine efficiency.
Now for the interesting part which I will paraphrase rather than produce via quotes from the PNAS paper, which in any case requires no special access restrictions as it is freely available on the internet. Also this diary is becoming too long.
One of the issues that Dr. Carter addresses is the relationship between the thermal barrier, which is generally yttrium stabilized zirconia, and the alumina layer - alumina, sometimes rendered as synthetic sapphire is a powerful refractory (heat resistant) material -and the superalloy itself. The superalloy, it turns out will begin to degrade when oxygen atoms migrate into it, as compounds like NiO form. Another effect of some importance is the effects that oxygen will have on the bonding layer between the thermal barrier coating and the superalloy, itself a specialized alloy containing cobalt, yttrium, aluminum and chromium, or alternatively (although almost certainly at higher cost) a platinum aluminide.
It is interesting to note - although it is not discussed in Dr. Carter's paper directly but perhaps indirectly alludes to it - that oxygen deficient perovskites (also tetragonal) that are in effect oxygen conductors, although those that are YSZ type are often doped with elements with multiple oxidation states. A paper in the journal Solid State Ionics refers to the use of cerium doped yttrium stabilized zirconia as an oxygen permeable substance in, as an example, a solid oxide fuel cell. (cf. Solid State Ionics 180 (2009) 314–319)
Moreover, according to Dr. Carter, the integrity of the bonding layers can be degraded by the presence of sulfur, often a constituent of dangerous fossil fuels - including dangerous natural gas as well as gasified biomass.
The purpose of the paper is to discover the theory behind the empirical properties of bond coatings and thermal barrier coatings on superalloys that are currently employed, and succeeds at explaining through bonding theory, why hafnium in particular is particularly valuable in the coating systems of turbine blades: It has excellent bonding properties to alumina formed in the thermally grown alumina oxide layers that form during the preparation and use of coatings of these types.
She has less success explaining the role of platinum.
She also suggests that her results suggest that early d transition elements, including the light and strong elements scandium and titanium might have fair properties in these types of systems, albeit not as good as those of zirconium and hafnium - but maybe compensated by their lower weight.
The considerations involved in this program are mostly relevant to the use of dangerous fossil fuels, since in effect - this is especially true in the case of gas turbines - the operation of these kinds of facilities can be tantamount to focusing a blow torch on a turbine.
By the way, if you have heard that gas is "clean energy" you are engaged - in my opinion - in self delusion. Gas is not clean. It accounts for more than 20% of the 30 billion metric tons of dangerous fossil fuel waste (as carbon dioxide) dumped into the earth's atmosphere. Even if we manage to shatter every cap rock in North America to get the last gasp of it, it will not prove sustainable.
If you have any familiarity with my writings, you will know that I oppose all dangerous fossil fuels, coal, gas and oil and want them all phased out. However this does not mean that I am indifferent to turbines, in particular turbines involved in direct chemical reactions. And let's be clear, combustion is a chemical reaction. So are chemical reactions that can kind of be thought of as anti-combustion reactions, including some that are in fact, mildly exothermic. I can imagine the need to place turbines in lines involving these, if for no other purpose than to increase efficiency.
The kinds of systems I would imagine would involve very different chemistries than the type depicted here. Indeed there would be excellent reasons for avoiding nickel (and thus superalloys) entirely. Nickel is not, for instance, really compatable with carbon monoxide.
An example of the kinds of systems I think about is the supercritical carbon dioxide brayton loop being developed at Sandia National labs. It is said to offer a giant leap in thermal efficiency in power plants. This type of system is not really all that applicable to dangerous natural gas systems - although one could imagine it in a type of combined cycle dangerous natural gas plant, but it would be applicable to dangerous coal plants - albeit without limiting the enormous environmental costs of coal - and to nuclear plants.
(My oft stated contention is that the latter type of plants - nuclear plants - are the only environmentally acceptable form of energy production for a planet with 7 billion people on it. Nuclear energy is not risk free, but it is certainly risk minimized. There are no other energy alternatives that can match it for sustainability, environmental impact and yes, safety.)
But for now, the ideas surrounding things like supercritical carbon dioxide brayton cycle systems or other types of working fluids are still (regrettably maybe) exotica.
The point is that Dr. Carter's work - she claims her PROFESS type programs can now model millions of atoms, whereas other types of approaches were capable of modeling accurately less than 100 atoms (at best) - is that she has provided new tools for materials scientists to use in designing and engineering energy systems. The current work is really applicable to dangerous natural gas fueled systems, but could be applied to other types of systems with other materials science demands.
Dr. Carter is the author of hundreds of scientific papers - she's a leader in her field - and her work suggests that science and engineering in the United States are not quite dead yet.
The reflection on gas brings me back to the ex-chief technical officer of First Solar, Dr. Eaglesham, who, as I stated at the beginning, gave a well attended talk recently at the Andlinger Center Lecture Series.
Dr. Eaglesham is a very, very, very, very nice guy and very smart too and was very gracious during the Q&A session during which I kind of felt guilty for being such a pain in the ass, even though it is hardly my fault that no asses were saved by solar energy in 2000, as predicted by Amory Lovins in 1976, earning him "genius" status.
His reasons, again, for the failures of solar companies around the world was "not enough subsidies." Although I didn't argue the point, I'm somewhat incredulous about that statement, since 100's of billions of euros, dollars, yen, yaun and other currencies, historical and current have been thrown at solar energy schemes, much of it public money.
As of 2010, according to the the most recent figures for solar energy production on the entire planet solar produced just 0.1 exajoules of electricity (27.918 billion kilowatt hours). For the record, humanity consumes about 520 exajoules of energy each year. The amount of electricity produced by the entire planetary effort to engage in the "solar will save us" fantasy produced the equivalent of the energy production of three average sized nuclear plants, the main caveat being that nuclear plants do not require gas plants to back them up.
Dr. Eaglesham told me and the audience by the way that it would be a bad idea to phase out natural gas, a point, again, on which he and I disagree. I favor the immediate phase out of all dangerous fossil fuels, including natural gas. He's against it.
(He was proud of the fact that most of First Solar's "big" installations are next to gas plants. No surprise there.)
Oh, yes, and then there was "China is powered by coal, and therefore they're cheating" argument that Dr. Eaglesham advanced. According to Dr. Eaglesham, China lost 15 billion dollars in the price war that has overtaken the solar industry and driven so many companies out of business around the world, fleecing the investors. This, he said, is because they can.
Actually the United States, where Dr. Eaglesham's former company covered many thousands of acres of pristine desert with cadmium telluride laced glass also burns coal.
I'm not a nice person, but even I felt uncomfortable with asking so many pointed questions about the failure of the solar industry to produce even one of the 520 exajoules now used each year by the human race, so uncomfortable that I held back - even though I did use the unpleasant words "capacity utilization" at least once - on the question of how solar energy is an alternative to coal given the well known problem of inevitable energy losses whenever a coal plant is run flat out: This question - the audience consisted of people who are generally much smarter than I am - relates to the thermal heat capacity of water and the zeroth law of thermodynamics, and incredibly, everyone let it fly. When you shut a coal boiler down by cutting off the coal supply, it is inevitable that, no matter how well the boiler is insulated, that it will cool. As anyone who has ever operated a teapot can tell you, that once a system of liquid water is allowed to cool you have to reinvest energy, the energy connected with the heat capacity of water, to bring it up to boiling again. In other words, shutting a coal plant for a few hours a day, when the sun is shining, actually costs energy rather than saves energy. This is the economic reason that coal has the second highest capacity utilization, 72%, in the United States, after nuclear, which is about 90%.
Again, these were very smart people in the room and I was the dumbest guy in the room and it was somewhat startling that no one sought to raise the point.
What gives? Maybe it was about being polite.
Oh well then.
Dr. Eaglesham is a very nice guy, and clearly a very smart guy, but even smart guys can be trapped by their "vision" and their need to believe what they want to believe.
By the way, if solar energy is an alternative to gas, it's not showing up as one, even as late as 2010, nearly 60 years after the invention of the solar PV cell, during 50 years of which the solar enterprise has received nothing but wild, blind cheering and - more recently, very expensive enthusiasm.
In 2010, according to EIA figures, the world burned 123.74 exajoules (116.753 quads) of dangerous natural gas and dumped the waste unceremoniously in humanity's favorite waste dump, the planetary atmosphere.
This was an all time record for burning dangerous natural gas and dumping the waste in the atmosphere.
As stated above, the entire solar energy industry, after 50 years of cheering and the consumption of 100's of billions of dollars, euros, yen and yuan, barely produced 0.1 exajoules. The whole damn industry was not even able to match 1% of the increase in the use of dangerous natural gas (as measured in units of energy) from 2009 to 2010.
If that faith based expenditure doesn't make you angry, it should.
Oh, and about my last diary, which was about the element technetium, I suggested that rhodium dioxide was sufficiently volatile to effect separations from used nuclear fuel via distillation or sublimation of the oxide. This idea intrigued me, but as I poked around in the literature further to check it out - in some cases looking at papers that were half a century old - it seems to me that this is at best an exaggeration and at worst simply not true. The vapor pressure of rhodium dioxide seems to be on the order of 1 torr even at 2000C. However modern analytical techniques such as vapor phase ICP-MS might be applied to the case, and seems not to have been.
NNadir is a liar.
Have a wonderful day.