Stardate 20040603.1434

(On Screen): In my perusals of my referer logs, I noticed that Greg Burch had linked to an old article of mine, for which I thank him. Unfortunately, I don't agree with his post in which he did so. I started writing a letter to him explaining why, and it got longer and longer and so I decided to post it instead.

Greg comes to a conclusion which many others have also reached. It's been a pretty regular fixture in my mailbox for a long time. He explains it this way:

We've got years, perhaps decades, of violent conflict with the Islamic world ahead of us. Sooner or later we'll have to realize that the only thing that is making this necessary is our dependence on oil from the Middle East. The culture that is attempting to destroy us is on artifical life support through the money pumped into the Middle East for oil. If that stopped, our enemy would wither and die, or change.

To begin with, I don't think that this war was caused by our use of Arab petroleum. It would have happened eventually anyway.

But even if it was caused by our use of Arab oil, that doesn't mean it will end if we cease using Arab oil.

And in any case, it isn't actually possible for us to stop relying on Arab oil without drastic and painful changes in lifestyle combined with commission of economic suicide. It wouldn't be possible for us even come close to maintaining our current GDP.

This is a fundamentally difficult problem, and most of the constraints are physical, practical, and insurmountable. This is one of those problems which look really simple to solve, but only if you don't look really closely.

As I mentioned, I've gotten a lot of email over the last couple of years from people who came to the same conclusion as Greg has. In response, I've written a lot of posts about various aspects of this in the past to show how intractable it is, and I'll start with a roundup of them, along with summaries of the points they make.

The war wasn't caused by our reliance on Arab oil.

There aren't any credible alternatives to Arab oil (general discussion).

Conservation isn't the answer.

Discussions of the flaws of alternative energy sources: geothermal, solar, wind, solar satellites, tides, fission, hydrogen, biomass

There are no other alternatives, either. Most people don't understand the size of the problem. There are only four potential sources of energy which are large enough (core taps, solar satellites, fusion, direct conversion of matter to energy) and none of them are practical now.

We aren't going to replace Arab oil with turkey guts.

Ethanol doesn't make sense as a fuel.

More details on why we won't be using electric power for vehicles. (Also includes a discussion of some aspects of terrestrial solar power.)

More discussion of the inherent problems of all forms of biomass (including ethanol and "biodiesel" and conversion of turkey guts).

In that last article, I gave this list of five properties any proposed alternative energy source must have if it is to make any real difference.

1. It has to be huge (in terms of both energy and power)
2. It has to be reliable (not intermittent or unschedulable)
3. It has to be concentrated (not diffuse)
4. It has to be possible to utilize it efficiently
5. The capital investment and operating cost to utilize it has to be comparable to existing energy sources (per gigawatt, and per gigajoule).

Note: energy and power are not the same thing. Power (measured in watts) is the amount of energy (measured in joules) produced or consumed per unit time. #1 above requires both that the total energy embodied in the resource be huge and that it be possible to utilize that energy at a very high rate (i.e. at high power levels). If there are significant practical limits on the rate, then it cannot offset the rate at which we use petroleum. If the total energy is limited, it will get used up too rapidly.

We engineers have a saying: "Anything is possible for the man who doesn't have to do it himself." I can understand why Greg wants to find some sort of technological fix for the political problem we face. But there is no point in initiating something like a "Manhattan Project" for this.

This seems like a modification of a rhetorical device I heard again and again in the 1970's and 1980's: "If we can put a man on the moon, why can't we...?" e.g. "why can't we provide clean drinking water for everyone on the planet?"

For me as an engineer, the answer was always obvious: they were not the same kinds of problems.

There are three things needed in any engineering development project: will, resources, and engineering implementation, but the third can only happen after the first two. John F. Kennedy made a speech challenging the US try to put a man on the moon before 1970; after JFK was assassinated, that created the political will to embark on the Apollo project, and to spend whatever it took to make it happen. That's when the engineers started working on it.

But not all projects are engineering development projects. In the case of "clean drinking water", the engineering is pretty simple. The real problem is political: finding the will and the resources. So the honest answer to the rhetorical question is, "Because we don't care as much about it." That's not an engineering problem.

The problem of "providing clean drinking water" is fundamentally easy from an engineering point of view. The goal of putting a man on the moon was a very tough and challenging engineering problem but it was not obviously impossible to do it (though the time constraints were pretty severe). The goal of the original Manhattan Project was also tough and challenging.

But "eliminating our reliance on Arab oil" transcends "tough and challenging" and resides in the lofty realm which engineers call "nontrivial". (Translated for laymen, that means, "Forget about it. You won't live to see it happen.")

When the American space program began in the early 1960's, they knew specifically what they wanted to accomplish, and they had a pretty good general idea of how it would be done. Likewise, in 1942 when the decision was made to begin the "Manhattan Project", there was a theoretical basis for nuclear weapons and they had a pretty good general idea of what would be needed to make them work.

In both cases the project mission was to convert the theory and general approach into detailed engineering practice. There's no doubt they were both really tough problems, but the people on those projects knew where they were trying to go and had a pretty good idea before they began about how to get there.

However, a hypothetical "eliminate reliance on Arab oil" project would not have any theoretical basis for a solution. There are no alternative energy source which satisfy those five requirements which we have or could readily develop the technology to utilize.

Greg is looking for a miracle. He wants the people on such a project to come up with some surprising answer. He doesn't have any hints for them about where they should look for it; he merely tasks them with finding it.

Unfortunately, this is a bit like the people who say we should "win without war". I wish it were possible, but what's missing is any idea of how we would actually do that. I don't think it can be done.

And I don't think we can substantially reduce our reliance on Arab petroleum. There is no "tough but achievable" solution. All alternatives are either well understood and easy (and already being used) or are intolerably difficult, and there are no as-yet-undiscovered alternatives which would satisfy those five criteria.

This, too, ultimately isn't an engineering problem.

Fusion won't solve the problem. Fusion has been "on the brink of success" all my life, and there's no telling when they'll actually make it work, or if they ever will. But if they did, I think it virtually certain that commercial fusion power generation will fail #5. The kind and amount of equipment which will be needed even for a moderate sized generation facility would make the capital cost and maintenance expense unacceptably high.

Solar satellites won't solve it, either. Solar Satellite power technology will fail #5 even more badly than fusion. It will also badly fail #4.

When it comes to power generation, the job's not done until the energy reaches the end user. The challenge of energy delivery is particularly severe for solar satellite technology.

Generally speaking, every time energy is converted from one form to another a lot of it will be lost (because of the Second Law of Thermodynamics). All technologies which generate power and deliver it to end users involve such conversions. A coal-fired electrical generation plant burns coal to produce heat, converts heat to pressure by applying a lot of that heat to a boiler to produce steam, converts pressure into mechanical motion (with a turbine), converts mechanical motion into electricity (with a dynamo), and then delivers the electricity with long distance power lines, which usually requires multiple voltage/current conversions using transformers or motor-generators. Many of those conversions are very efficient but some of them involve pretty significant losses.

The efficiencies of every step have to be multiplied together to calculate the overall system efficiency. If you have five steps and each one wastes 20%, then each step has an efficiency of 0.8, and the overall system efficiency will be 0.8*0.8*0.8*0.8*0.8 == 0.328, meaning about 33% of the original energy would be delivered to end users, with the remaining 67% being lost. But if each of those five steps wasted 30% instead of 20%, the overall system would only deliver 17% of the original energy. The more conversions required, and the worse the efficiency on those conversions, then the lower the efficiency of the overall system.

Solar satellite power generation is particularly poor in this regard. Sunlight is concentrated using mirrors (with some losses) onto a boiler (with some of the light reflecting instead of being converted to heat, and some of the heat radiating away via black-box radiation). The next few steps are the same as for a coal plant: steam drives a turbine, which drives a dynamo, which generates electricity. At that point, all you have to do is to deliver it, but that is not easy with solar satellites.

The electric power would have to be converted to microwaves (with a lot of losses). That would be beamed down to earth (with losses from atmospheric reflection, scattering and absorption). Most of the beam would strike the receiver but some would not because of beam spreading. (Also, there beam would tend to wander a bit because of atmospheric refraction, which also makes stars "twinkle".) The receiver would have to capture the microwaves that struck it and somehow convert back into electricity, and every way I know to do this has dreadfully poor yields.

Microwaves are not the only approach to the downlink, but every approach I know of for the downlink either cannot handle the power levels involved, or is terribly inefficient. Compared to terrestrial electrical power generation technologies, solar satellites inherently require more conversions, many of which have poor efficiency, and the overall system efficiency will necessarily be far worse. I would be surprised if the system had a yield as high as 5%. I would tend to think it would be even lower.

On the other hand, the energy which would have to be expended to create a solar power satellite would be huge compared to the energy needed to build a terrestrial power generation facility. Would it break even before it reached the end of its operating life? Would it actually produce more energy than it cost? I'm not so sure it would.

The capital cost to create a solar satellite would also dwarf the cost of terrestrial power plants which delivered comparable amounts of power, but the satellites and terrestrial power generators would sell their power on the same market at the same price. Could a solar satellite produce enough revenue during its operational life to repay its capital cost? It seems unlikely.

In other words, solar satellites are possible but are not feasible. We'd be much better off spending our money to build more coal-fired generation plants. We could produce much more power while spending much less money.

But they wouldn't be as romantic.

I suppose there's a place for romance. I suppose there's a place for trophy projects. I understand why the French and Brits created the Chunnel. It was an amazing technological achievement – but it's never going to pay off the investment needed to produce it. It's clear now that they'd probably have been better off considering some other approach.

I think core taps (described in this post) could ultimately satisfy all five criteria, but there are essential technological precursors for core taps which don't exist yet. The most important problem is that current drilling technology is subject to scaling problems which mean it can never reach the necessary depths. As drill shafts get longer, the total mass of the shaft rises and turning resistance increases (from friction on a greater surface). The strength of the metal used in the shaft can't really be increased. So as the shaft gets longer, one of three things will eventually happen: either the drill will seize up because too much force is needed to overcome shaft friction and too little force will be transmitted to the drill bit to keep cutting, or the drill shaft will start to twist, or the drill shaft will actually break outright.

One of the things which is needed is an entirely new drilling technology which can reach the depths required, but it's not obvious what it might be. My best guess is that it will be based on a high powered laser, but there's more to the problem than that. (When you drill, you not only need to cut, you need to remove. How does a laser remove?) Whatever the solution might turn out to be, it's likely to bear about as much resemblance to current drilling as transistors bear to vacuum tubes.

In 1942, the people on the original Manhattan Project had a definite destination in mind and a pretty good idea of how to get there.

But people assigned to Greg's new Manhattan Project would have no such destination. All they'd have would be a nebulous goal. That's not the same thing. What's worse, they'd have every reason to believe there was no way to achieve that goal.

Greg continued:

I'll say it as clearly as I can: If we're at war -- and we are -- where is the "Manhattan Project"? Where are our leaders? Why isn't developing technologies that will free us from dependence on oil our number one priority as a civilization?

There is no such project because it would be a waste of time and money. I'm sorry, but it's really that simple.

Or rather, it can be stated that simply, but the actual reason is very complicated.

Update: In fact, if we actually became bound and determined to drastically reduce consumption of Arab petroleum, and didn't want to destroy our economy doing so, then there are two quite obvious solutions. First would be to start using Canadian oil sands. The other would be for us to start building coal gasification plants (to utilize America's vast deposits of black or brown coal). The technologies involved in both of those are well understood; neither would require a "Manhattan Project". Right now, the main reason we aren't doing either is that they're not cost-competitive with petroleum.

When I referred to the problem as "nontrivial" above, I was responding to it in the terms Greg was thinking about: development of some brand new energy source which would miraculously make it so we no longer needed much petroleum. That remains nontrivial.

Update 20040604: TMLutas thinks I'm too pessimistic.

He thinks he's totally discredited this article by pointing out that solar satellites would use solar cells instead of mirrors and boilers. Actually, in high-power designs, boilers and turbines have surprisingly good efficiency, much better than the 15% he quotes for solar cells, which waste the majority of the light which strikes them because the frequency is wrong. That's not where I think the efficiency problem lies, anyway. The problem is the power downlink to the ground, especially the conversion to RF and back to electricity in the receiver. They'll both be terrible.

He thinks he's found a citation for 90% efficiency in conversion of DC to microwave RF. Unfortunately, what he has found isn't relevant to this problem. It's easy to do that if you're only talking about a few watts. It is not at all easy if you're talking a gigawatt. No one is going to get 90% conversion of electric power to microwave transmission at gigawatt power levels. No one is going to come remotely close.

This is one of the few remaining applications where semiconductors have not yet displaced vacuum tubes. In a modern TV transmitter rated for 500 KW or 1 MW, everything is transistorized right up to the very last amplification stage, which uses vacuum tubes the size of garbage cans.

The satellite downlink will have to generate and transmit as much RF as a thousand such TV stations. Doing that is difficult. Doing that with 90% efficiency is "nontrivial".

Doing it at microwave frequencies merely adds to the fun, because extremely high frequency applications are also extremely unforgiving. I'm not really sure just how you'd generate microwave RF at gigawatt power levels, quite frankly, but whatever approach gets used, it ain't gonna achieve 90% conversion. Not gonna happen.

Lutas concludes, SDB took on an almost impossible task, proving that something cannot be done feasibly. No, I'm afraid not. I don't contend that these things are and will always remain infeasible (though the ones I discussed are definitely infeasible right now). What I contend that they cannot be done soon enough, large enough, to have any political effect on this war.

Update: More here.