Readers will likely find some parallels here to climate science: A number of studies dispute whether cutting back on salt consumption to government-recommended levels is really healthier. Gary Taubes wrote a long opinion piece in the NY Times this Sunday highlighting evidence that eating too little salt can actually increase mortality from heart disease. Now, I don’t really have a dog in this hunt and haven’t studied the evidence either way, but I thought the reaction of the anti-salt crusaders was familiar:
Proponents of the eat-less-salt campaign tend to deal with this contradictory evidence by implying that anyone raising it is a shill for the food industry and doesn’t care about saving lives. An N.I.H. administrator told me back in 1998 that to publicly question the science on salt was to play into the hands of the industry. “As long as there are things in the media that say the salt controversy continues,” he said, “they win.”
When several agencies, including the Department of Agriculture and the Food and Drug Administration, held a hearing last November to discuss how to go about getting Americans to eat less salt (as opposed to whether or not we should eat less salt), these proponents argued that the latest reports suggesting damage from lower-salt diets should simply be ignored. Lawrence Appel, an epidemiologist and a co-author of the DASH-Sodium trial, said “there is nothing really new.” According to the cardiologist Graham MacGregor, who has been promoting low-salt diets since the 1980s, the studies were no more than “a minor irritation that causes us a bit of aggravation.”
This attitude that studies that go against prevailing beliefs should be ignored on the basis that, well, they go against prevailing beliefs, has been the norm for the anti-salt campaign for decades. Maybe now the prevailing beliefs should be changed. The British scientist and educator Thomas Huxley, known as Darwin’s bulldog for his advocacy of evolution, may have put it best back in 1860. “My business,” he wrote, “is to teach my aspirations to conform themselves to fact, not to try and make facts harmonize with my aspirations.”
‘The following approximate figures illustrate the problem.’
Ted
I don’t disagree with your numbers. I am emphatically not claiming we should switch to H2 today; I added it only as an afterthought after I mentioned electricity which is probably much more plausible as a fuel for transportation. Electrical motors are very efficient, way more efficient than internal combustion engines. The main issue here is the battery which is presently very inefficient. But if you read the history of the industrial revolution similar arguments were made against the steam engine and later the internal combustion engine. Do you have any idea of how inefficient the pre Watt steam engine was? A modern day electrical engine would pump circles around it. None of these are issues which make either electricity or even H2 unusable in principle. They are all a matter of developing the technology and this will take time.
‘As to your question “what do we do when fossil fuels runout”, our whole lifestyle will have to change.’
No it won’t. Nuclear power can easily supply all our electrical needs, more cheaply and efficiently than fossil fuels. There is at the very least an order of magnitude more easily available power in uranium reserves than in fossil fuels. Someday it will also power batteries which will run our cars. If you doubt that, look at the (admittedly poor) electric cars available even today. Bad as they are, would you rather ride a horse or drive a Chevy Volt? I have to believe that necessity will make the engines better, and more importantly improve the efficiency of their batteries.
Like I said; know nukes.
Waldo
I admit, I was somewhat surprised by your comments about nuclear energy. Over the years, I’ve spent a lot of effort arguing the merits of nuclear power to those who seem to have an irrational fear of it (even other scientists and engineers). I admit to some bias, but if there are environmentalists out there who champion it, perhaps you are right. Perhaps my view of them isn’t quite as balanced as I thought it was.
Increasing the use of nuclear power vs. practically everything else would in my opinion be a very good thing. But Ted still has a good point. Forcing change (even the right change) overnight would be catastrophic to our economy and our lifestyle.
There are reasons which go well beyond the dubious science of AGW which suggest to me that pumping large amounts of CO2 quickly into the atmosphere may not be a good thing and that gradually (but steadily) moving away from it makes a whole lot of sense.
And of course, a car powered directly by nuclear energy would be freaking awesome, especially one which drives itself. I drive a Ford Fusion so maybe the name would then make more sense…sigh…or…well maybe not. Nuclear fusion may never become economical. There is no reason in principle, though that a fission powered car couldn’t happen but I still suspect that using nuclear power to make some sort of intermediary fuel may always be the option of choice.
‘Probably the overall efficiency (best case) would be well under 10% overall efficiency’
Actually your numbers are not that horrible. Factor in how cheap nuclear power could be if the political climate was right and reasonable increases in efficiency at several points, and H2 does not seem completely implausible to me. You said this could be about twice as expensive as fossil fuel, right? So our choice in the future may be between the equivalent of $7 gas, the electric car, or riding a horse.
I agree not a good choice for today, but still a whole lot better than giving up our future.
****”I would not feel constrained to limit my discussions to those that are climate scientists, despite your frantic admonitions that I MUST.”
You are a master at engineering strawmen, Ted. Never said either of those two things, nor have I ever suggested that you refrain from posting here. You apparently need to confabulate debate points to make a point.
What I am suggesting is that, when you find a “greenie” engineering project you feel is untenable, you confront the scientists and engineers working on the project. Do us all a favor and correct those creative teams investigating wind and solar power. If you do not, it leads one to believe that you are, in fact, simply venting here and not confident enough to actually enter the engineering world with your “calcs.”
And please—occasionally you attempt the dignity posture (as above), but you are every bit as rude and obnoxious as I am. I am happy to discuss, and I am equally happy to be as big a jackass as the person I’m posting to. And please don’t try the “logic” posture either while slinging hyperbole and hidebound opinions. You have repeatedly insulted and challenged climate science, but that is beside the point. You want a respectful dialogue? Fine with me. You need to be an adult also, however.
Steve, you and I actually think a lot alike on these issues. More importantly, I often work with and around engineers, sometimes scientists, and a great many of them are very pro-nuke. Many have faith in the advancements of solar and wind power also, but we it would seem we have much better control over nuclear technology which does not blight the landscape or kill raptors. Honestly, I’m all for nuclear power now as we continue to investigate other sources to compliment it.
I like your point to Ted above about the steam engine—just a word of warning, Ted is intent on damning virtually all new power technology; he is unconvinced by the pace of advances in the last century and a half and convinced that, if we do not have all the technical problems solved today, right now, then he seems to think said technology is doomed to failure, forcing economic hardship on the rest of us.
****”What do you favor garbage or gold ?”
I favor vetted scientific opinion.
To wit, the scientists involved are convinced of the models’ viability.
If you know more than they do, prove it. Prove them wrong.
Otherwise you are faking it here.
My one issue with your comments above, Steve, is the idea that AGW (if it exists) is necessarily ot most likely beneficial. Perhaps it is, but we actually don’t know what the effects of AGW (if it exists) will be; it is an essentially unprecedented phenomenon. If the science is correct and the predictions of the scientists studying the Earth’s climate are correct, we are playing a dangerous game.
I am one of the people in the world, and absolutely the only one who frequents these boards, willing to admit that I do not know if CAGW is real or not, nor am I in a position to judge. Pauld called me “agnostic” regarding the climate, and that is a great term—I am an AGW agnostic.
However, in the same way that I believe the scientific consensus that smoking is bad for me, I see no reason to doubt the experts—those most qualified professionals who are the best informed—and I worry that the amateur / political commentary at places such as this have unnecessarily poisoned the information and public opinion.
In other words, it is significant that the last decade was the warmest on record because that would seem to bolster the overall scientific opinion—more importantly, in the same way that engineers who have faith in nukes are important, the climate science community believes the hottest decade on record is important (a simple Google search confirms this). Peeps like netdr would rather simply dismiss or ignore this fact and argue that, because temps have been more or less steady in the hottest decade on record, we should dismiss AGW out of hand. That simply is not smart or sane.
The good peeps here will denigrate any poster, scientist, or scientific institution which suggests the above and flock, virtually without question, to any scientist (Lindzen and the Pielkes—Tim Ball or Willie Soon) or any institution (the Heartland) who challenges AGW.
SteveD:
The question is: are the problems with a proposed scheme fundamental or are they subject to improvement (better design).
In the case of a steam engine, the power output and efficiency are limited by thermodynamics. In turn, how close one can come to 100% thermodynamic efficiency depends on the design of the machine. For example, if the early steam engines had a thermodynamic efficiency of 10%, then obviously improvements can be made. If the thermodynamic efficiency is quite high, additional improvements can only be very small. Power plants, for example, have an efficiency of about 37%. This is mainly due to thermodynamics, and hence little improvement is possible. (the heat of vaporization is lost to the condenser).
In the case of energy storage (for example, hydraulic), it can easily be shown that, for fundamental reasons, about ten times the wind energy rated capacity must be installed if we want ALL our energy from wind. This is mainly fundamental, not due to lousy equipment which could be improved. One must differentiate between the two. We CAN improve equipment design, but we cannot repeal the laws of physics. To persist in an endeavor that depends on violating physical laws for its success is incompetent and irresponsible.
In the case of solar panels, there is a fixed amount of energy reaching a square meter of land surface. No matter how efficient the solar panel is, this cannot be exceeded.
I have attempted to limit my criticism of energy schemes to theoretical limitations, not design limitations. If you believe I have erred in this regard, please tell me where and I will review my studies.
As regards electric cars and batteries, there are fundamental limitations. The power plant where the electricity originates has an efficiency of about 37%. Charging a battery requires that the applied voltage be substantially greater than the battery potential, so as to have a driving force for the charging current. Same situation for th battery discharge. The overall eff. of the battery charge/discharge will be about 80%. There is also the electricity transmission and distribution loss. I explained all this earlier. Having a perfect battery would not alter these facts, although the range and weight could no doubt be improved over time. The above numbers are not capable of substantial improvement. The battery design is. These are the sort of distinctions that must be born in mind when evaluating various schemes. Having faith inscience and technology is great, provided one does not expect to violate the laws of physics.
SteveD:
You are certainly correct that all our electricity needs can be met with nuclear. The other problems are how to make steel, aluminum, cement, etc. that use large amounts of coke or coal. How about transportation fuels? How do we manufacture ag chemicals, plastics, etc. withut petroleum? etc. etc. Unless these questions can be answered, our lirestyle will have to change, no doubt with a diminution in our standard of living.
There is an error in mmy previous post. Where it says “ten times the wind energy capacity”, it should be “ten times the total electrical equipment capacity”.
You are right that an electric motor is much more efficient than a steam engine. But where does the electricity come fro? A steam engine! So we are right back to the original problem re efficiency, as I pointed out earlier.
One must look at the whole picture, not just part of it. The step one is considering may look great, but the TOTAL pictue, from A to Z, may be terrible.
SteveD:
While all our electricity needs could be met with nuclear, it remains to be seen how that will play out. In the aftermath of the Japaneses tsunami disaster, many (the Germans for example) are planning to get out of nuclear energy entirely. In the US we have not built a nuclear plant since Three Mile Island. Any change in this attitude is bound to be delayed by the Japanese disaster. In a few hundred years, if the choice is between nuclear and sitting in the dark, I am sure nuclear will reappear.
Almost anything is theoretically possible. It has been proposed to make gasoline out of CO2. Make H2 with nuclear energy, react it with CO2 to make syn gas (CO and H2), and via German WWII technology (Fischer-Tropsch process), make it into gasoline. (The Germans stareted with coal to make CO). I ran some back-or-the-envelope calcs and it would take about 35 nuclear plants worth of electricity to make one nuclear plant’s equivalent of gasoline. A chemistry professor many decades ago wrote that one could make gasoline out of limestone. Heat the limestone to drive off CO2 and proceed as above.
The question is not what is possible (almost everything is) but what is feasible. We could, for example, fill the great plains with windmills, flood the Rocky Mts with storage lakes, and have plenty of power. If we were willing to have a several thousand dollars per month electric bill, this could surely be done. Using CO2 to make gasoline would work if wwe were willing to pay hundreds of dollars per gallon for the product.
If left alone, the ecnomic system would sort it all out. As energy gets more expensive, the cheapest alternative would come into play. Then the next, etc. On the consumer side, we have the option to change our lifestyle rather than pay more for energy. For example, neighborhood grocery stores would spring up and folks would walk to the store. Housing developments near places of employment would reappear, as was the case 80 years ago. It is possible (if not extremely likely) that this approach would be better than the idiots in ahington picking winners.
Ted:
You’ve put a lot of words down on paper so I am not sure where to start. Not all of it is related to my point. I really don’t care about solar or wind power, that’s just silliness on the part of those who advocate them. I only care about nuclear power. So, I’ll start with this statement:
‘many (the Germans for example) are planning to get out of nuclear energy entirely’
This action tells us a lot more about the Germans than it does about nuclear energy. If they plan to get out of nuclear what are they going to replace it with? Magic fairy dust? (Please note that my sarcasm is directed at them, not you) They’ve run out of rivers, which means the only thing left is…you guessed it; something made from fixed carbon, me thinks which might cause AGW.
‘In a few hundred years, if the choice is between nuclear and sitting in the dark, I am sure nuclear will reappear.’
That’s sad, but probably correct. And if that does happen then our standard of living will decrease, at least for a while. But the blame will not lie with science or the laws of physics.
I am not arguing against the theoretical limits for either batteries or hydrogen fuel – I’m an enzymologist; I know all about thermodynamics and limits. I deal with that every day – I’m only surprised that you consider these limits horrible. An overall efficiency of 10% isn’t great, but it is something we can work with, especially given that there is at least an order of magnitude (and probably two orders of magnitude) more energy stored in uranium in the earth’s crust than all the fossil fuels combined. (100 x 0.1 = 10 which means that in the long run electric cars using a nuclear source can do 10 X as much work as our gasoline cars) Ten percent is about the efficiency of photosynthesis and plants do pretty well. Why? Well, because 10% of a whole lot is still a whole lot.
In any event, the battery technology of today is already efficient enough that given the proper energy source (nuclear), it would spare us any major reductions to our lifestyle. Electric cars are plausible and they do a sight bit better than golf carts. They exist today. They will always be considerably less efficient than those fueled by fossils but so what? We drive a small vehicle, reduce our speeds and switch out batteries every 50 or 100 miles or so. That’s an inconvenience not a drop in lifestyle and I’ll bet engineers could come up with a convenient way switch the batteries.
I am also not arguing that we should convert to nuclear so much as I’m arguing that we will switch; eventually, when we have no choice.
‘Unless these questions can be answered, our lifestyle will have to change, no doubt with a diminution in our standard of living.’
Many of these questions have already been answered. We’ve already discussed transportation. Steel, once made doesn’t vanish and it is reusable. In the future we will probably ‘mine’ old junkyards for metal, or simply recycle it better. Plastics will be made from transgenic plants. Plants will make other materials as well, like fertilizer and ag chemicals.
‘If left alone, the economic system would sort it all out.’
Hmm…now you’ve got me worried. That might be a problem. When in world history has the economic system ever been left alone?
Ted:
I have a question for you. You stated that power plants have an efficiency of about 37% and that this is mainly due to thermodynamics and so little improvement is possible.
My understanding is that a great deal of the energy is lost as heat up the stack. However, this energy is still, at least in theory usable, though no one has yet come up with a good way to do this. In that case though, an ingenious design might still harness it.
Waldo:
‘Perhaps it is, but we actually don’t know what the effects of AGW (if it exists) will be; it is an essentially unprecedented phenomenon.’
I have a couple points to make here: 1) from the estimates I’ve seen, the world is much colder than is optimal for humans considering the crops we grow and the huge areas of the earth which are virtually uninhabitable because of the cold. That’s why I asked the question about the optimal temperature, earlier. Therefore, it’s not the increase in temperature that’s the problem; it’s the rate of increase in temperature. If this is true, gradual GW would be beneficial, rapid GW very detrimental. 2) But GW is not essentially an unprecedented phenomenon. Global temperatures have fluctuated up and down throughout earth’s history. So, the question becomes under what conditions (e.g. overall temperature plus the directional trend and the rate of the trend) in the past have humans done the best? BTW: While climatologists are experts on the climate, historians or archeologists are probably more likely to be able to answer this last question
‘However, in the same way that I believe the scientific consensus that smoking is bad for me, I see no reason to doubt the experts’
I don’t completely disagree. The opinions of the experts in any field should be taken seriously; however: 1) the smoking comparison doesn’t quite work since this is a much simpler problem and even then it took a long time (longer than most people realize) for scientists to determine conclusively that smoking leads to lung cancer and other health problems. 2) Climate science is very young and its only human nature for its proponents to exaggerate how conclusive their own field is. If you doubt that large groups of scientists can do this in apparent consensus and be in error, take a look at psychology. 3) I’m not sure the consensus is as great as you think it is. Although most climatologists believe in some degree of AGW, they do not agree on how much; and there are some who say, essentially none. 4) Physicists, probably the best group of scientists next to climatologists who have the expertise to discuss this problem are decidedly torn on this issue and many have petitioned against it.
‘because temps have been more or less steady in the hottest decade on record, we should dismiss AGW out of hand.’
I am not entirely sure he is saying that but if he is, then he is wrong. In fact, if AGW is occurring there is no reason to believe we would see a perfect uniform increase in temperature. It would surely occur in fits and starts. However; if the temperature has in fact been steady for 10-20 years (not sure exactly how long), it would seem to make the more extreme AGW scenarios less plausible, since periods of stable or cooling temperatures will statistically be shorter and less dramatic, with greater AGW.
From what I understand, all of us, Waldo, NetDr, Ted and me seem to be global warming agnostics. So then where is our actual disagreement?
SteveD:
The efficiency of modern boilers is very high (over 90%). Flue gas temperature is rather low and represents a relatively minor loss. The losses are due mainly to thermodynamic effects, as follows.
Boiler feedwater is vaporized at high pressure (around 2200 psi) and superheated. The latter means heating the steam well above the temperature at which it leaves the water’s surface (called saturation temperature). Degrees superheat is the degress above saturation temperature to which the steam is heated after it leaves the surface of the water. The superheated steam passes through the turbine and is exhausted to the condenser. The condenser operates at high vacuum where the condensing temperature is quite low, thus maximizing the pressure drop across the turbine and recovering as much energy from the steam as possible. Theoretically, the max energy that can be generated is equal to the change in enthalpy of the steam from turbine inlet temperature and pressure to turbine outlet pressure, following the line of constant entropy. This latter (no change in entropy) represents the max energy that can be theoretically recovered. In actuality, the turbine is less efficient (about 75%) so that there is an increase in entropy and the steam leaves the turbine at a higher temp than the theoretical at zero entropy change. If the turbine was 100% efficient, overall efficiency would increase from the 37% I mentioned before to 45% or so.
The main cause of loss is that the energy required to vaporize the water (about 1000 Btu/lb) is lost. Thus, if the change in enthalpy between high pressure superheated steam and condensed water is, say 1600 Btu/lb, about 1000 bteu is lost to the condenser. In a cogen situation, the turbine exhaust runs at a highr pressure (perhaps 40 psi) and the heat of condensation is used for process heating. This is a well used scheme in chemical plants and refineries. Overall efficiency thus goes from 37% to perhaps 80% because the heat of condensation is put to use. Because of the higher exhaust pressure, less electricity is generated per pound of steam. This costs nothing, as that energy is used for process heating.
Engineers have tried all sorts of things to milk the last drop of efficiency out of steam power. Super-critical boilers, extra high superheat, staged feedwater heaters,etc. have been experimented with for years. Many of them had enough problems so that the idea was abandoned. Thus, it is unlikely that steam power plant efficiency can be much improved.
An interesting point is that the old reciprocating steam engines can be more efficient than turbines, but they are not suitable for the huge power plants being built. Some of these use a million pounds/hr of steam. Only turbines can handle such huge flows (to say nothing of much less mechanical complexity).
To summarize: the loss of the heat of condensation in the steam to the condenser is the culprit. You can see the large plume of water vapor from the condenser cooling towers at the power plant. This is essentially the same amount of heat that is lost from the power cycle.
One can get out a steam Mollier diagram or pressure-enthalpy diagram and ahve all sorts of fun trying different schemes. Unfortunately, there is no way around the laws of thermo. Sort of like looking for a perpetual motion machine.
In a somewhat similr manner, all sorts of energy schemes can be worked out on paper, such as hydraulic or compressed air energy storage, tidal power, etc. One can easily determine all the energy effects and the limitations of a proposed scheme with only a small amount of engineering time. Large sums are thereby not wasted. In all cases (as above), there is a theoretical limit to the energy that can be produced. The design of the equipment merely determines how close to this figure we can come in actual practise. No matter how clever the design, we can’t exceed the theoretical number. For example, for hydro storage of power, one can easily calculate how much water to pump to a given elevation to store a prescribed amunt of energy. The actual will be substantially higher than this due to various inefficiencies. Engineers make a living getting the machine efficiencies as high as possible, but again, the theoretical limit cannot be exceeded.
I hope this rather lengthy explanation answers your question.
SteveD:
We seem to pretty much on the same page re nuclear energy, electric cars, etc. There is no doubt that we can use electric cars, albeit at a penalty in cost and convenience. There is no doubt that we can generate all our electricity via nuclear. No doubt, alternative processes for recovering iron from ore (electrolysis pehaps?) and alternative ways of accomlishing other things can be found.
My concerns have been as follows: Because of the hysteria caused by the AGW hyposhesis (the world will burn to a crisp ASAP), all sorts of schemes are going forward at huge expense which can easily be shown to be nonsense. We are being stampeded into doing stupid things. A calm systematic study of future possibilities is needed. Many schemes can be checked out on paper and waste avoided. For example, there is no viable way to back up or store wind/solar energy. Thus, only a small amount can be generated and then only with huge subsidies. Something resembling the tried and true procedures used in the technical industries to evaluate ideas is needed. That is my main point. Stampeding evryone into dumb moves will ruin us.
I am all for new ideas (I have about 15 patents). I merely want to check things out before we blow “charge”
on the bugle.
I am sure you are well familiar with the mess the Germans, Spaniards, and others have got themselves into by charging into the wind and solar thing. Now they want to shut down their nuclear plants. What a mess.
As we have both noted, in due course events will force us to go to nuclear and make other changes to accomodate to a fossil fuel-free environment. A little planning and less hysteria would go a long way toward getting there more smoothly. As my father used to say, it’s easier to stay out of trouble than get out of trouble.
I enjoy our discussion.
Ted:
I appreciate your detailed explanation of how the generator works. I learned something. It makes sense that the main loss of energy would be the phase state change because that requires an enormous amount of energy. What would happen if you superheated the steam and kept it in a superheated state, so that it never condensed back to a liquid? Skip the reheating water until it becomes gas stage. It would have to be recycled back somehow; I’m not sure how that would work. Is the additional energy in the superheated steam enough to power a turbine? Is there any way to build a generator in which the steam never condenses, just continues to cycle and power the turbine or a series of turbines? Would that even provide any advantage? What about using a gas other than steam?
It’s interesting to me how much more efficient modern engines are than the living organisms I work with. Like I said photosynthetic efficiency runs about 10%, compared to the 37% you stated for electricity generation. Now, if photosynthesis could be improved, that would definitely remake our world.
I agree with your concern about the hysteria over AGW and the silly schemes it engenders (solar power, really?). Actually in my opinion, even if AGW is real, the best solution would be to release the productive forces of the free market so that when AGW does come about, we have the maximum amount of resources and the strongest economy to help us adapt to it. So you could say perhaps that an answer to global warming might be ironically to burn more fossil fuels. Spending money on inadequate solutions wastes money and actually makes the entire problem worse in the long run. I also have this distinct feeling, based on admittedly not a whole lot of evidence, that CAGW is either a non-problem (so why bother worrying about it) or catastrophic and inevitable (so again why bother; we can’t change it and we’re all going to die, anyway no matter what we do)
Also, putting an end to the silly antipathy toward nuclear power would also help us out, no matter what the problem is. As I told Waldo, a real environmentalist would push for more nuclear power because it is the only green source of power other than hydroelectric that works.
‘Engineers make a living getting the machine efficiencies as high as possible, but again, the theoretical limit cannot be exceeded.’
If they could then (by definition) they wouldn’t be theoretical limits.:)
The real challenge for human survival will be someday far in the future when the uranium finally runs out.
‘To summarize: the loss of the heat of condensation in the steam to the condenser is the culprit.’
More simply the main issue is that you put a whole lot of energy into making steam but you do not recover all of it into electricity. It condenses to hot water, but there is no way to make that hot water produce more electricity. The best you can do with it is heat stuff. But if that puts you up to 80%; then there is not a whole lot of room for improvements. I suppose you might say that the 80% figure is a little misleading – the hot water can only be used for process heating – it does not have the multiple uses electricity has. It would be nicer if you could just make that all into electricity.
To clarify the point I was trying to make – instead of exhausting the steam into a condenser, resuperheat (assuming resuperheat is actually a real word) it and pass it across a series of alternating heaters and turbines, perhaps in some sort of cycle so that it never becomes liquid or if the pressure drop from the condensation is essential, then at place multiple heaters and turbines in sequence before the condenser. Get the maximum amount of work out of the steam before you lose it.
SteveD:
There are all sorts of ideas around for heat engines. The current high ptessure steam boiler-generator arrangement has been arrived at as the most practical on a large scale.
The boiler serves, in effect as a compressor to make high pressure steam out of low pressure water. It seems to be the most efficient and easy way to restore the condensate to its high pressure and high energy state.
In all power plants, as the steam passes through the turbine, it cools and nears saturation temperature. It is removed from the turbine (part way through) and reheated (resuperheated if you will) and returned to the lower stages of the turbine. This increase the efficiency and avoids liquid water forming in the turbine which would erode the turbine blades.
I think you misundersood my commentes re cogen. Here, the LP (low pressure) steam is used in a heat exchanger where the heat of condensation is fully utilized. You don’t just recover the sensible heat in the condensed water. Thus one gets power out of some of the steam and heat of condensation out of the rest of the enthalpy. Presto! 80& total energy efficiency.
In steam locomotives, the exhaust steam from the engine is simply blown out into the atmosphere. The energy from expanding it further into high vacuum, as is the case in a power plant, is lost (as is obviously the water). The result is much lower efficiency. All this can be readily seen on a steam Mollier diagram (Enthalpy-entropy diagram) which is used by engineers for this sort of study.
The purpose of the condenser in a power plant is to enable turbine exhaust to be at high vacuum, increasing efficiency The water is also saved for recycle to the boiler. Treating boiler feedwater is expensive. Again, the easiest way to generate high pressure vapor is with a boiler.
Any high pressure gas can be used for power generation. Compressed air storage has been proposed for use with wind/solar (energy storage). This is certainly thermodynamically possible, but quite inefficient.
The whole subject of thermal power generation is very interesting. I have written computer simulation programs for power plants and played with the variables. If you are familiar with heat engine thermo and are interested in studying the subject further, I suggest that you get a steam Mollier diagram and play with it. A very interesting exercise. Needless to say, engineers have been doing just that for generations, which is why our power plants are as good as they are.
I fully agree with you that competitive free enterprise will arrive at the best way to deal with the energy situation over time. I am sure in a hundred years or so virtually all our electric power will be nuclear. I am somewhat uncerain what we will do for transportation energy and organic raw materials. Perhaps we will radically modify our lifestyle to suit. As you point out, free enterprise will find the best solution. I imagine it will be substantially more expensive than the present low cost fossil fuel situation allows.
Many climate scientists have pointed out that the advent of the next ice age a much more serious threat than AGW. You can’t grow food in freezing weather. I imagine the world population will go way down and be concentrated at the equator.
I am an environmentalist in that I was a backpacker for forty years and much value clean air and water and a pristine wilderness. The enviroloonies seem to be against all human activity: mining, manufacturing, energy, forestry, nuclear, etc. etc. This is no way to constructively contribute to the discussion or to solve the world’s problems. Marching around with a “down with everything” sign is just stupid. Interestingly, the greenies are dead set against nuclear energy, but they offer no valid alternatives.
As to your last point, I imagine when current energy sources run out, population will shrink to where a primitive economy can support it. We seem to be fixated on the idea that mankind will continue to have increased population and an ever-increasing standard of living in perpetuity. This might well be a false assumption. Perhaps we are living in the golden age of homo sapiens. Lots of resources and a managable population.
As to your point re recycling the steam without condensing, there is no way to get it back to its original high energy state without putting that energy back in. You would need a steam compressor that used as much energy as was generated in the turbine (at 100% efficiency). Unfortunately, there is no way to circumvent thermodynamics in power generation. The maximum amount of work one can get from steam is the isentropic expansion from high pressure steam to exhaust pressure. No way around this.
The whole discussion depends upon Nuclear power being worth a premium which it isn’t.
Global warming is mild and beneficial so far.
Ok, I think I understand the cogen process now; the high pressure steam generates the electricity, the low pressure steam is used in a heat exchanger, so you can approach 100% efficiency. If you used the low pressure steam to drive a turbine it wouldn’t do much and the condensation would create a problem. The energy left over in the hot water, I imagine is only a tiny amount by comparison. (Since the latent heat of vaporization is so much greater than the energy needed to heat water). I suppose you could use it to make soup for the workers or sell it as pure water. Well you said it was expensive to treat, so I assume it has to be pure to begin with?
‘It is removed from the turbine (part way through) and reheated (resuperheated if you will) and returned to the lower stages of the turbine.’
Actually, this is exactly what I meant about recycling the steam, except for some reason, I was envisioning sending it to a second turbine. It doesn’t violate the laws of thermodynamics. In fact sending it back to the lower stages of the same turbine makes a lot of sense.
‘I imagine it will be substantially more expensive than the present low cost fossil fuel situation allows.
We will probably have to allocate a greater percentage of our pay to transportation. On the other hand other costs (like food) may drop effectively balancing this out. But all of this does assume we will let the free market sort it out. The human race doesn’t have a great track record on that.
‘As to your last point, I imagine when current energy sources run out, population will shrink to where a primitive economy can support it.’
Not really a very inspiring vision but at least this could explain why we haven’t heard signals or received visits from any other intelligent life forms, assuming they exist in the first place. They all ran out of power and are now huddled around their little water mills in small villages. More seriously, it is also possible we could get lucky and there are still some possibilities to explore. We will always have hydroelectric power which can produce a substantial amount of energy capable of running an advanced civilization containing perhaps somewhat fewer people than today. Perhaps someone will figure out how to make nuclear fusion work, or we find uranium in the asteroid belt. Plants can be engineered to produce hydrocarbons although this really is not an efficient way to use solar power. An unexpected discovery from particle physics could lead to a new way to convert matter into energy.
NetDR
‘The whole discussion depends upon nuclear power being worth a premium which it isn’t.’
I am not sure I understand what you mean. Power is power, right? Why would electricity made from nuclear power sell for less than that made from other sources?
Nuclear is actually the cheapest way to make a lot of electricity in a hurry. It is only the political and insurance costs which keep it from being our main source of electricity generation. As coal dries up and becomes scarcer, np will become relatively even cheaper by comparison.
The fact that nuclear power exists at all even as it is burdened with huge insurance and regulatory costs is proof positive of how cost efficient it is. I read recently that Ameren is planning on building another one in the near future. Why would they do that if it would lose money?
A funny thing is that when there is no UN agency to define a global consensus, such things are local phenomena. In my native sweden we continue to eat enormous amounts of salt (in comparison to america). We live long and healthy and no-one worries about salt. Works fine for us 🙂
Steve
Nuclear power deserves no premium if it is available and cheaper use it. The “Global Warming” excuse is nonsense in that the warming is 1/2 degree per century and since 2001 has been global cooling.
If the insurance and regulatory costs of nuclear power can be reduced and it is cheaper use it, but don’t blame “Global Warming” which is actually “Global Cooling ” since 2001.
cooling 2001 to present
Least squares trend line; slope = 0.00450811 per year
http://www.woodfortrees.org/plot/hadcrut3vgl/from:2001/to/plot/hadcrut3vgl/from:2001/to/trend
http://tiny.cc/ga7d9
The amount of coal is virtually limitless [400 year supplies ] and peak oil seems to never happen. There is more proven oil now than there was in the 40’s.
NetDr
Like I said earlier, the present trend whether cooling or warming is essentially meaningless and the proper scientific comparison is against what would have happened, not how the earth was in 2001. An eleven year trend proves nothing either way. We simply do NOT know how to predict climate or what sort of effect (if any) we are having on it. AGW could be real…or not. I simply don’t know and neither do you. The theory is plausible but unproven. For all we know, we could be heading into another ice age. Even if the levels of CO2 presently projected for 2100 CE are not enough to initiate AGW, what about at 2200 CE or 2300 CE? What will the CO2 levels be then? We have enough coal for at least 400 years, right?
Actually, 400 years of supplies is a tiny amount of energy compared to what can be found in uranium – in it we have enough to supply ourselves for thousands of years with present day deposits and I’m guessing we’ll find a lot more of that as well when we start using more of it. There exists at least 10 x the energy stored in known uranium deposits than in the known fossil fuel deposits. Mankind is very lucky to live in a universe where nuclear power is possible and uranium easily available. Like I said, know nukes.
And, there are other issues around using fossil fuels (e.g. political, safety, cost) and releasing CO2 into the atmosphere which have nothing to do with the climate, especially if we continue this for another 400 years. (E.g. CO2 inhibits mitochondrial respiration which keeps us all alive – high CO2/O2 favors an increased ratio of plant biomass/animal biomass etc.)
The government effectively subsidies fossil fuels vs. nuclear and has been doing this for a long time by forcing massive insurance and regulatory costs on the nuclear power industry which do not exist for other forms of power generation. It is the fossil fuel industry which essentially has been given the premium in reverse. Take away these restrictions away from np and let the market make the decision and you will see a mostly nuclear powered world. The countries which have fewer restrictions (e.g. France) use proportionally more np. (I’m not sure if this would be the case for the US since we have a lot of coal but most other countries don’t – in that case I would not suggest that the US switch – I’m guessing it would still be cheaper in the US though). In a recent conversation I had with some scientists at Ameren, I was told their company would much prefer to build nuclear plants in the future but the regulatory costs are enormous.
Ted has said that he doesn’t favor trashing our economy on the off chance that AGW is real. I agree with that. Now I’m not generally in favor of using the precautionary principle but if we can use a better and cheaper form of energy generation and at the same time eliminate any possibility of AGW however small and shut the AGW alarmists up so I don’t have to listen to them anymore and save on the cost of mining and transporting coal and use a form of power generation with a cooler moniker, and have fewer miners killed in mine cave ins AND do all of this by eliminating government regulations and thus promoting the free market (which BTW is my real hidden agenda) – well that just seems like a no brainer to me.
I appreciate Steve’s very balanced commentary and I apologize to you, Steve, for coming back so late and for responding so briefly—I am in the beautiful Sawtooth mountains on a semi-vacation and only have the Net occasionally. The only thing I can say, my friend, is that I hope your evaluation of the benefits of AGW (if it exists) is correct. The forests here are blighted by a bark beetle which, among other factors, thrive when there is drought; then I spent part of the morning talking to a resident of Hawaii about the drought her island has been experience for the last five years and how this is affecting cattle farming, the ecology, and the economy—are ether of these a direct result of climate change? Is the fact that my brain immediately made this connection a result of pop-media and self-serving enviro-science? I don’t know and I did not broach the subject. But these seem to be the sort of effects scientists have been warning us about. I withhold judgment without looking into either of these further, and then I would still defer to the experts on ecology and climate.
Go Nukes!!
Waldo: Enjoy your partial vacation. No need to worry about responding quickly or in any great detail. I do have a couple comments, though.
‘are either of these a direct result of climate change?’
Here is what I think. At least some of the stuff you listed is going to happen whether or not climate change is really occurring, just by normal year-to-year variation in the climate. Our history books are filled to the brim with harsh winters, hot summers, droughts, tornados, floods; all manner of disasters and extremes. They surely will occur more often and to a much greater extent if GW is occurring. So how do you tell when these weather anomalies reach the point beyond that which we should deem natural?
A few years ago, I lived in a basement apartment in Winnipeg, Manitoba during the two coldest winters in over a century. I was freezing my butt off the entire winter. It was miserable. All winter long I was constantly barraged by radio and television talking heads trying to convince me that these two bitterly cold winters in a row augured global warming. (I kid you not). The rest of us though, believed we were simply unlucky. The next summer was the one of the warmest on record and the climate scientists quickly changed their tune and told us that the extremely hot summer was the result of global warming. Hot, cold or unchanging; they had arguments for everything. The words ‘not falsifiable’ came to my mind a lot those days.
I’ve heard opinions from some scientists that global warming will cause our glaciers to retreat and opposite opinions that the increased global precipitation caused by AGW should make the glaciers grow. Yet as far as I can tell, the north polar ice cap is melting and the south polar ice cap is expanding. Does this explain why almost every story I read about retreating glaciers and melting ice refers to the artic? The one story I read about Antarctica managed to discuss the ONLY glacier on the entire continent in retreat! I’ve also read lots of stories about the how the growing season is expanding in Canada and the US, but I know for a fact that at the same time it is becoming shorter in Argentina. But you don’t read about that in the newspaper, Hemispheric warming, anyone?
Another curious thing that I have noticed is that while BOTH skeptic’s and advocates agree that so far climate change has been rather moderate (one degree/century or so; they disagree only on what will happen in the future), the claims of the secondary effects of climate change seem WAY out of whack for level of climate change we know has already occurred. Some islands record huge increases in sea level which correspond to the level global warming even extreme advocates say will not occur for over fifty years. Others record no change in sea level but go unreported in the media. What gives? Even with the most extreme predictions, the polar bears should simply not be drowning yet; at least not for another twenty years or so.
Even if CAGW is the absolute truth in all respects, the majority of things blamed on it are still probably bunk. Me thinks they protest too much.
It reminds me of the response Arthur C. Clark gave once when he was asked if he believed in UFOs. He said, no, because there were too many reports of them.
‘I hope your evaluation of the benefits of AGW (if it exists) is correct.’
I really don’t know this. I can only say that I have no reason to believe that today’s temperature is the optimal temperature of human life and that any slight (or even great) cooling or warming will be a disaster.
‘I would still defer to the experts on ecology and climate.’
There seem to be plenty of experts all over the spectrum on this issue. What I would really like to see is a sound scientific debate between them. Now that would be informative.
Steve D:
An excellent summary of the situation. I would only add one thing. The CAGW advocates need to come up with an alternative, CO2-free, energy scheme. As I have pointed out many times, wind, solar, bio etc. are not viable on a large scale. Nuclear can replace fossil fuels for elrctricity, but the greenies are against that. A proper engineering report would lay out the total scene: electric power, transportation, industry, agriculture, etc. Just being against fossil fuels without addressing the whole problem is irresponsible.
Ted: I’ve seen a lot of plans floating around the internet for thorium powered cars. Not only do these seem plausible (at least in theory) but they would not ever need refueling. The chief objection again seems to be the fear of nuclear energy, safety etc. I’m no expert on this so I can’t really evaluate how well this would work.
http://wardsauto.com/ar/thorium_power_car_110811
Steve D:
I am not sure, but isn’t the need for heavy shielding a problem? Another point. What is the critical mass to get the reaction going? As I recall, a pretty large chunk is needed to accomplish this (critical mass).
On ships, weight is not such a big problem, but I don’t know about a small vehicle. There is also (as you point out) the safety problem. Nuclear waste is shipped in huge, heavy, steel containers to eliminate the possibility of rupture in case of accident. With all the idiots on the road, what are the chances of a crash with attendent radioactive contamination? Then there is the problem of disposing of the cars after they wear out.
And, of course, all these problems must be solved at nominal cost. If someone is serious about this, a complete engineering study is needed with all the “i’s” dotted and tees crossed.
‘I am not sure, but isn’t the need for heavy shielding a problem?’
Not so much with thorium. It is only very slightly radioactive which is why this would be a better fuel than uranium, so light shielding would probably work. The article suggests using aluminum foil. It also states that 1g has the energy of 7500 gallons of gas.
‘And, of course, all these problems must be solved at nominal cost.’
Well, I agree but my intended context was mostly around our previous discussion of what happens when the oil runs out. Even if the cars are more expensive and not quite as safe, they are still better than dramatically lowering our standard of living.
‘Then there is the problem of disposing of the cars after they wear out.’
The power source needs to be somehow protected like the black box in airplanes but separable after the death of the car so it can be deposed separately. Seems quite possible
‘If someone is serious about this, a complete engineering study is needed with all the “i’s” dotted and tees crossed.’
Again, I agree. I nominate Waldo. Seriously, It sounds like they’re several years away and we’re going to get self driving cars and flying cars first. However, it’s possible that someone solves the technical issues, builds and markets these things and makes them better than the cars we have today in which case the switch would occur naturally and the person who does it get’s rich. There seem to be enough serious smart people working on them. What worries me is that this effort may suffer the same fate as nuclear power generation and be judged from fear rather than on its merits.