Energy remaining

[Dantius]

Since someone recently brought up the surprisingly large numbers of people on this site with scientific background, I just thought I'd pop in and share this (pdf) fascinating (albeit somewhat dated) study I recently found on energy sources, and our dependency on them/the dangers of continuing their use. I especially liked the part comparing potential power generation at current consumption, with the dramatic difference between oil (50 years), coal (200 years), uranium dioxide breeder reactors (3000 years), and fusion reactors (150 billion years), which is about 100 time longer than the postulated life of the sun! All in all, it does seem to support the conclusion that deuterium/tritium reactors are the best, cheapest, and cleanest method of power generation that could ever become available. Just throwing this out there to see what you all think.

[Alorael at Large]

The enthusiasm for fusion is perpetual but not necessarily helpful. If they can be built, net-gain fusion reactors will be of immense value. But that's a big if! Fusion "holds the promise of being a safe, inexhaustible and rather clean energy production method," but there's no promise at all, just speculation and hope.

 

Breeder reactors are at least possible under current technology. Nuclear power suffers from a largely undeserved bad reputation, and I'd put money on nuclear power gaining ground rapidly as fossil fuels become more expensive if there aren't any huge breakthroughs in sustainable generation. It's a simple cost-benefit thing.

 

—Alorael, who also doesn't like tables of how long fossil fuel reserves will last. The tables you found are based on discovered, accessible reserves. More will be discovered and more will be made accessible. Of course, projected total reserves also includes things that probably won't be found or will never be accessible. How much oil there is is a matter of intense speculation, and it's rather unclear what a good estimate is.

[cfgauss]

One typically has to be very careful about the methodology of these kinds of reports to get any meaningful information out of them.

 

Like Alorael mentioned, there are large uncertainties associated with oil reserves, since there're still large parts of the earth that haven't been carefully investigated for oil, and there has really been no incentive for oil companies to go looking for new places for a very long time. Also, the exact amount listed in various reports seems to give the "economically viable" sources, which changes substantially with technology and energy prices. So I'd be willing to bet based on this that, if we were pressed, we could get enough oil to last of order hundreds of years.

 

Not so sure about coal, since I haven't looked into it.

 

Nuclear fission also depends a lot on technology. With early fission designs, the available fissionable material would not have lasted nearly as long as with fancy modern designs. But certainly we've got enough to last in the thousands of years range.

 

Fusion is basically something that can last forever, since the universe is full of hydrogen, and the solar system has got plenty in it without going too far.

 

The biggest problem with fusion reactors is related to funding. No one really wants to dump a great deal of money into them right now, since the current designs are all (of necessity) geared to doing research as much as energy production. There are several experiments going on now that IIRC will be collecting data soon, but they've had plenty of funding and political problems to delay them.

 

There also seems to be a lack of interest in the theory part of nuclear fusion, and the nuclear theory community in general doesn't seem to be what it once was, since a lot of the easy stuff has been done, and a lot of what remains is for technical reasons very difficult to do. But this problem again is largely due to funding, and the lack of funding has seemed to not attract the diversity of ideas needed to do super-clever things that allow you to solve new problems.

[keira]

I liked that idea of giant solar arrays in space, beaming down energy as microwaves to Earth. Has this been nixed? I assume it's innificient, but hey, it's not like we'll run out of room in space tor more arrays.

[cfgauss]

I think attenuation of energy in the atmosphere is a big problem with these methods, no? Not to mention building a huge, efficient enough enough laser that requires no maintenance in space would be extremely technically difficult.

 

Not to mention that people would complain that the REAL reason for building the space-lasers is for the government to use them as weapons, and to spy on your thoughts. OTOH, the government that can build space-lasers and doesn't is not a government that gets my support!

[Niemand]

Quote:

I liked that idea of giant solar arrays in space, beaming down energy as microwaves to Earth. Has this been nixed? I assume it's innificient, but hey, it's not like we'll run out of room in space tor more arrays.

I don't; think how much energy you would be spending just to lift the things up out of the gravity well. Then you have to consider the vast amount of material required to build all of the collectors. No matter how well you build them they will need some kind of regular repair or replacement.

Here's a back-of-the-envelope calculation:
Energy usage of the United States, P: 1.05e20 J/yr = 3.33e12 W (ref)
Luminosity of the Sun, L: 3.84e26 W (ref)
Distance from the Earth to the Sun, r: 1.5e11 m (ref)
Best solar cell efficiency I could find mentioned: .43

The power density of solar radiation at earth is then L/(4*pi*r^2) = 1.36e3 W/m^2. The collected power density, with an efficiency of .43 is then n = 5.85e2 W/m^2, and so the required collecting area is P/n = 5.69e9 m^2.

That's more than 5000 square kilometers of solar cells to collect enough power for the U.S. alone, ignoring the efficiency of transmitting (from the collector) and receiving (on the ground), and assuming that the equipment used is at least as good as the best available today, not in mass production, but as prototypes or at best small scale production. Anybody want to try to estimate how long it would take to manufacture those solar cells?

[Alorael at Large]

The more telling problem is launching 5000 square kilometers of solar cells into space and positioning them. Not happening.

 

—Alorael, who hopes fusion pans out. Abundant, cheap energy would make the world a very different place, and almost certainly it would do so for the better.

[cfgauss]

Yeah, off the top of my head, those order of magnitude estimates look okay. But you don't need to replace 100% of energy production with solar energy. And I think part of the advantage is that you can get power to locations that you couldn't put normal powerplants, and running lines to would be too lossy.

 

But in general, solar definitely isn't such a great solution for anything.

[Kelandon]

I just want to slap a few people around and yell at them that fission isn't actually dangerous anymore. Yes, it produces some harmful radioactive stuff, but compared to what oil and coal do, it's not a big deal, and the risk of meltdown is virtually nil with modern technology.

 

I was under the impression that we still can't do much more than build bombs with nuclear fusion. Have we actually gotten to the point where we can get useful energy out of it?

 

Also, isn't the primary issue with solar that it's expensive overall? If we got enough resources together, couldn't that become a significant part of the solution?

[cfgauss]

Fission was never really dangerous. It's only dangerous when you're horrifyingly stupid with it (like with anything else). That's really what happened with Chernobyl, horrible incompetence, terrible design, combined with a collapsing economy.

 

With fusion, we are at the stage where we do not get more energy out of the reaction than we put into it. Partly due to technology, and partly due to a lack of understanding of the details of how we should engineer this reaction to be self-sustaining. The new research reactors, e.g., ITER, and the other big one whose name I can't remember, I believe will be able to produce sustained power for short lengths of time. They should tell us how to design commercial reactors well enough that the next stage could be prototyping real commercial reactors.

 

Solar is expensive to produce, and cannot produce nearly enough energy to be more than marginally helpful. It can be helpful in, very hot sunny areas where you can get constant extra bonus power, and on individual buildings where it can reduce the load on the grid on hot days due to air conditioning, which otherwise might cause brownouts.

[Student of Trinity]

I know a guy who works on fusion (for a big US lab, not in his basement), and he's not optimistic about any kind of hydrogen fusion, because the reactions all release lots of neutrons. In fact most of the energy they release is carried by the neutrons. So a hydrogen fusion plant would seemingly inevitably become more and more radioactive over time — not the fuel, but the reactor, as all its pieces captured neutrons and became unstable.

 

This guy considers that the long-term solution is hydrogen-boron fusion, which produces hardly any neutrons. The problem is that H-B fusion needs much higher temperatures, and we've been having enough trouble just getting temperatures high enough for hydrogen fusion. So it's a fairly distant goal. Long-term, though, nuclear reactors seem to be pretty obviously the way to go. Nuclear fusion is, after all, God's own solution for powering most of the universe, since it's what makes stars shine.

 

Up to that point, it's clear that we will eventually run low on fossil fuels, but the last drop of oil will probably stay in the ground until the sun eats the earth. That's because the way oil runs out is not that the last Saudi well makes a sucking noise and the tank is now empty. It's that the cheap and easy oil gets used up, and the oil that's harder to extract becomes economically viable. Eventually oil ceases to be economically competitive with alternatives, and people stop extracting oil. Having the price of oil go way up may be no joke, but at least we're not going to suddenly have no oil at all left, and be stuck with a planetful of generators and engines that will never run again. That's not the scenario.

[cfgauss]

Yeah, radioactivation of other materials, and losing energy are problems, but I believe the radioactivated materials aren't nearly as radioactive as in a fission plant, and aren't active for nearly as long. So it's really a matter of just replacing parts that can't be too contaminated. So it's still better than a fission plant.

 

But part of the science being done at these places is to determine how to construct materials that don't become contaminated, and if we can do fancy things like get energy back from the neutrons.

 

From the people in ITER I've heard from, and from the experimental physics people I know who've talked about this, they are hardly not optimistic... They all seem to be very excited about it. And, really, we know very little about the engineering challenges we'd have to face anyway, which is the whole point of these science reactors. This is a regime where it's very difficult to do good theoretical calculations, and our collider experiments haven't necessarily dealt with.

 

But it will certainly be a while before we can even think of making a commercial one... They've really just recently agreed on where to build ITER, and it won't be finished until ~2020, and there's at least a good 20 years of work that can be done there before moving on to the next generation of design.

[Frozen Feet]

The amount of solar radiation earth receives contains enough energy to supply whole of human civilization many times over. By placing solar panels everywhere we can, we wouldn't need any other fusion reactor besides our beloved sun.

 

Of course, coating f.ex. Sahara with solar panels takes resources and time, quite a lot in fact to make it even viable. But this is true with any form of energy. Otimistic evaluations of fusion reactors I've seen claim that in ten years, we'd have reactors producing 15 giga wats of energy - but even currently, mankind's consumption is measured in tera wats. For fusion to really solve energy problems, we'd need to build hundreds, if not thousands of reactors all over the world.

 

Obviously, that is not trivial. Even after the technology is safe and sound, building a reactor can take years - that many would take decades. In the interim, all problems caused by dwindling supplies of easily accessible fuels would continue, and likely worsen.

 

I'm not going to bother opening other cans of worms related to the issue, such as overpopulation, increasing energy consumption all around, logistics and environmental issues concerning rapid large-scale construction projects. Suffice to say that all around, reducing amount of people consuming energy, and making their energy-consumption more effective have as good or better chances of working than any novel energy sources we might access.

[cfgauss]

This is definitely false. As mentioned above, we'd need ~5000km^2 for just the US's current energy requirements. The world's energy consumption is ~10^22 J / year, which is two orders of magnitude larger than the US's. So we'd expect to need 5000x100=500,000 km^2 to do this. Sure, the earth is ~500,000,000 km^2, but a half million square kilometers is just stupidly huge. We simply could not reasonably produce that many solar cells.

 

Not to mention that if you distribute this evenly around the Earth, you need at least twice as much, since it's always half dark and all... Not to mention that higher latitudes become less efficient as ~sin(latitude), too. Not to mention weather. So you'd really need to cover at least ~1% of the earth in solar cells, to meet TODAY'S energy needs.

 

So this is well outside of the range of conceivable things to do, even in the fairly idealized case I gave above.

 

edit:

I should note, the effective things to produce are (roughly) the ones with highest energy density per dollar. J/(area*$). Solar clearly fails here since both the area and $ values here are quite large. This is why nuclear always wins.

 

edit2:

Also note, if you want to do something more exciting like building a Dyson sphere, you run into other problems of your sphere coming into thermal equilibrium with the radiation, and no longer being able to extract energy from the star!

[Frozen Feet]

What efficiency are you attributing to our hypothetical panels? Currently, their somewhat pathetic, capable of conversing only a few percents of incoming radiation into electricity; I don't recall excact figues anymore, but multiplying their efficiency with ten is within realms of possibility. Just today I read an article about one scientist or another claiming we could theoretically get all our energy from the sun by 2050.

 

I'll see if I can dig the figures out from my archives. You are right that trying to get all our energy by solar panels would be very impractical - my main point was that it's true of all other options as well.

[cfgauss]

Well, physics disagrees with the idea that we can get all of our energy from the sun . The assumptions above used ~40% efficiency so even if you could increase efficiency to 100% that's simply not a large decrease in area.

 

The best solar can do is provide surplus power. Particularly, meeting power needs that increase with sunniness, like air-conditioning, as I mentioned before, or in areas with lower needs for power and poor access to other sources (desserts, etc), or in areas where you need something to run autonomously (weather stations, possibly street lights, satellites, etc).

 

But as a general solution, it simply doesn't work. With current technology, in fact, no single technology can hope to meet current energy needs except nuclear fission.

 

edit:

Not to mention the technical problems with solar that've been ignored. E.g., efficiency decreases with time, so if a panel lasts ~10 years, you need to replace your entire system every 10 years, so your massive multi trillion dollar cover the earth in solar panels project has a 100s of billion / year maintenance attached to it.

[Frozen Feet]

NEEEEEE... wrong. Nuclear fission isn't anymore the magic solution than others mentioned. Currently, mankind uses ~14 TW of energy yearly; in 30 years, this is estimated to rise to 40 TW. To get that additional 25 TW, we'd need to build 25 000 new plants each producing 1 GW of energy; that's 833 per year, or 2.3 plants build per day. Not happening. There might not even be enough easily attainable fissible material.

 

I found the article; sorry it's in Finnish, I'll get to translating relevant portions when I have time. According to it, earth receives 172 500 TW worth of energy per year from the sun. So there's a very big reason why we should look forward to harnessing as much of it as we can.

[Student of Trinity]

Lowering the temperature of any amount of water by just one degree Celsius releases enough energy to raise that same amount of water higher than the Eiffel tower. If that water were steam, condensing into liquid water would release enough energy to lift it into space.

 

Burning a kilogram of gasoline will let you heat up about 10,000 kilograms of water by one degree, or boil about 20 kilograms into steam.

 

This is why advancing from animal power to fuel-fired heat engines is kind of where the human race grew up and got a real job, and started doing things on a completely different scale from before. Even a pretty lousy car delivers as much power as a couple of hundred horses. (According to Wikipedia, and it sounds plausible to me, an actual horse can deliver up to about 15 horsepower for a few seconds, but the power output it can sustain for hours is actually somewhat less than one horsepower. Most summers I take in a horsedraw competition, where teams of two big horses compete to drag weights across sand. The horses strain impressively. The tractor that replaces the weights for each run does so effortlessly.)

 

This is the difficulty we face in weaning ourselves from oil. There is really a LOT of energy to be had from burning oil. Looking for substitutes is a bit like planning to quit your job at the law firm and go into social work, but still somehow keep up the mortgage payments on your ten-million-dollar McMansion. It's just not easy to match that income stream. It's not easy to come within a factor of ten of matching it.

 

[waterplant]

What seems likely for the future is many sources to supply energy - solar. nuclear, wind, geothermal, hydro, burning various gases, biofuels and good old fossil fuels (tho' in a limited capacity).

 

Originally Posted By: cfgauss

With current technology, in fact, no single technology can hope to meet current energy needs except nuclear fission.

 

No single current technology will meet our current energy needs including nuclear fission. Luckily for Earthlings we won't have to rely on today's technology forever, will we? Solar panels built 5 years ago have been superseded by new designs increasing their life from 30 years to 50 years. A planned wind farm planned for southern Victoria (Aus) recently reduced the number of turbines due to increased output of newer models.

[cfgauss]

Originally Posted By: Student of Trinity

This is the difficulty we face in weaning ourselves from oil. There is really a LOT of energy to be had from burning oil. [...] It's not easy to come within a factor of ten of matching it.

Yes, exactly. That's a great analogy.

Originally Posted By: Frozen Feet

NEEEEEE... wrong. Nuclear fission isn't anymore the magic solution than others mentioned.

No one said it's a magical solution, simply the only single one that's actually physically possible.

And the calculation above by Niemand and the adding in of other factors I did later are pretty basic physical calculations. There's really no way around them. It's simply physically impossible.

edit:
And the kinds of claims like "you'd have to build x number per day" are horribly misleading. For example, you hear the UFO conspiracy people claim Egyptians could not have built the pyramids because they'd have had to have laid like 10 blocks per second on average. Well, yes, they would, but that number is so large because averages don't really characterize most processes!

[Niemand]

Originally Posted By: Frozen Feet

The amount of solar radiation earth receives contains enough energy to supply whole of human civilization many times over.

True, (pi*radius_earth^2*1.36e3 W/m^2 ~ 2e17 W), but not directly useful. Collecting the energy is the real challenge. If you put your collectors on the surface you have to deal with attenuation due to the atmosphere, the earth spinning, the axial tilt, and so.

Originally Posted By: Frozen Feet

For fusion to really solve energy problems, we'd need to build hundreds, if not thousands of reactors all over the world.

Definitely true. Consider though: A reactor can assumedly be built almost anywhere, compared to a vast array of solar cells, so you can build one right next to a big city, like Paris or Berlin, rather than having to build thousands of kilometers of distribution network from Northern Africa. It can operate continuously, without regard for weather conditions or seasons. Nobody is saying that reactor technology is ready yet, what with having yet to achieve physical break-even (to say nothing of economic break-even), but our solar collection technology isn't really in all that much better a state.

Originally Posted By: Frozen Feet

Suffice to say that all around, reducing amount of people consuming energy, and making their energy-consumption more effective have as good or better chances of working than any novel energy sources we might access.

Certainly if population growth and per capita consumption grow unchecked, nothing we can do will be able to keep up, barring a crazy science fiction style free energy break-through. Controlling demand will have to be a goal just as much as finding ways to provide a supply.

Originally Posted By: cfguass

This is definitely false. As mentioned above, we'd need ~5000km^2 for just the US's current energy requirements. The world's energy consumption is ~10^22 J / year, which is two orders of magnitude larger than the US's. So we'd expect to need 5000x100=500,000 km^2 to do this. Sure, the earth is ~500,000,000 km^2, but a half million square kilometers is just stupidly huge. We simply could not reasonably produce that many solar cells.

As noted above and by you, the statement you were objecting to isn't really false at all, but its truth isn't useful as it ignores crushing levels of impracticality.

Originally Posted By: Frozen Feet

What efficiency are you attributing to our hypothetical panels?

As noted by cfguass and in my calculation, I assumed an effieicncy of .42. Such panels can be made right now, but not in large quantity.

Originally Posted By: Frozen Feet

Just today I read an article about one scientist or another claiming we could theoretically get all our energy from the sun by 2050.

If you can find the article, please do; I'd love to know what this person thinks we could do to overcome the difficulties involved.

Quote:

With current technology, in fact, no single technology can hope to meet current energy needs except nuclear fission.

I agree with this except perhaps for the final qualification. I see fission as a transitional technology, which can hopefully be superceded. While it is pretty safe, and the fuel reserves are not small (given our capabilities for making the fuel last), it does still produce nasty waste that we aren't very good at dealing with (at least as long as people keep preventing anyone from actually doing anything to get rid of it, like, oh, burying it under a mountain), and the available fuel is still definitely finite.

There are certianly good reasons to develop other power technologies. Solar power can be great for smallish devices that need to operate in remote locations, or that you just don't want to string tons of cables to (including all sort of things from portable programmable road signs such as are used at road construction zones to mars rovers). Hydroelectric power is great if you happen to ahve a good sized river nearby and a good area to trap it in (the Colorado river works well for Nevada, Arizona, and California, but it would be hard to find any good place to put a dam on the Mississippi, which is why no one has as far as I know). Either form of nuclear power is good for taking care of an area like a city where a lot of power is needed in a small area, particularly if there's nothing else handy nearby.

As a very long term problem, I consider nuclear power likely to be critically important for human space exploration. Solar power becomes seriously useless if you try to go any significant distance away from the sun, which is why even the unmanned probes which have been sent to the outer solar system have depended on nuclear power sources, although the ones they use are very simple (crude, even). If you're going to build a space ship that doesn't just hang around near the inner planets, you absolutely have to have a compact power plant, and that plant is going to have to supply a good deal of power if you want to keep even a few humans alive on board. Fission may actually remain the best alternative here for some time, though, as it is already highly sucessful for submarines (which are, after all, very like spacecraft), and it's looking more and more like the only way to make fusion work is to build big (look at a diagram of ITER and check the scale) to make it run at all.

(I can't even keep up with the thread growing, so I'm going to stop writing now.)

[cfgauss]

Originally Posted By: Niemand

There are certianly good reasons to develop other power technologies. Solar power can be great for smallish devices that need to operate in remote locations, or that you just don't want to string tons of cables to (including all sort of things from portable programmable road signs such as are used at road construction zones to mars rovers). Hydroelectric power is great if you happen to ahve a good sized river nearby and a good area to trap it in (the Colorado river works well for Nevada, Arizona, and California, but it would be hard to find any good place to put a dam on the Mississippi, which is why no one has as far as I know). Either form of nuclear power is good for taking care of an area like a city where a lot of power is needed in a small area, particularly if there's nothing else handy nearby.

Absolutely. The best and most economical thing to do is what's convenient for your location, and that your location can bear the burdens of maintaining.

Quote:

Fission may actually remain the best alternative here for some time, though, as it is already highly sucessful for submarines (which are, after all, very like spacecraft), and it's looking more and more like the only way to make fusion work is to build big (look at a diagram of ITER and check the scale) to make it run at all.

Definitely the case. Fission can be made very small and efficient, since we've been doing it for a very long time, and thinking about it even longer! Fusion, some day, I'm sure will be made compact and efficient somehow, but it won't be portable for a very long time! (But how cool will it be when you can carry a tiny star around with you?)

[Frozen Feet]

The whole point of my previous post was that providing all of mankind's energy with fission isn't any more plausible than other means; required constructions and materials aren't any easier to come by than those need to fill Sahara with solar panels, f.ex.

 

It's still 25000 1GW plants in 30 years; even with those 15GW fusion reactors I mentioned above, we'd still need 1667 of them. Building even one nuclear reactor is a major undertaking, and will take years to complete; to get all we need would require for hundreds of construction projects to be started right now. Neither funding or workers exist for such undertaking.

 

Egyptians could lay those 10 blocks per second*) 'cause they had hundreds, if not thousands of people working on them; while averages don't tell much about how work is done, it does tell about the scope of the project. Incresing yearly capacity by 25 TW is outside the scope of any current method, fission included.

 

*) I take no responsibility if crackpots screwed their math somewhere. The point still stands.

[cfgauss]

Averages don't tell you about the scope of anything. Check out the chapter of any good stats book that covers this for examples of how averages are "misleading" (and the equivalent chapter in any advanced book to understand precisely what they do mean!)

 

And replacing our energy with fission is many orders of magnitude more plausible for the reasons we have already mentioned.

 

There were thousands of pyramid workers, but there are many more construction workers today! If you would calculate the average number of new buildings built on earth per time, you'd get many per second. Not that one could quickly replace energy with fission, but it's possible.

 

Remember, your claim was

Quote:

Currently, mankind uses ~14 TW of energy yearly; in 30 years, this is estimated to rise to 40 TW. To get that additional 25 TW, we'd need to build 25 000 new plants each producing 1 GW of energy; that's 833 per year, or 2.3 plants build per day. Not happening.

How is building enough coal, wind, solar, or hydroelectric plants more possible than this, considering you have to build many more of them to get the same energy as a nuclear reactor? Your argument of increasing energy being "too hard" to meet used to easiest way to meet those requirements, then claimed it's impossible!

 

It has to be done one way or another! And building the most cost effective power plants (which in many regions is nuclear) is, in fact, the most cost effective way to meet power demands! It's so easy it's almost tautological!

[Student of Trinity]

I have saved this New Yorker article for several years because it's the first thing that really made me appreciate the enormous scale of modern human industrial activity. It's mainly about concrete in New York City — how it's made, how it gets into the city, how it's poured, and so on. On the last page, it segues into the author's trip to a concrete convention in Las Vegas, and digresses for a while before coming back to its theme with a bang.

Originally Posted By: David Owen, in The New Yorker, Nov 10 2003

On my second afternoon in Las Vegas ... I made a concrete pilgrimage to the Hoover Dam, which is about thirty miles southeast of the Strip and was once the largest concrete structure in the world. (Upon its completion, in 2009, the record-holder will be another dam, Three Gorges, in China.) The Hoover Dam was built between 1931 and 1936 by the U.S. Bureau of Reclamation, and it spans a deep canyon carved by the Colorado River. It is more than seven hundred feet tall, more than twelve hundred feet wide at the top, and roughly six hundred and sixty feet thick at the base, and is made almost entirely of concrete-approximately 3.25 million cubic yards of it, or roughly six million tons, with an additional million cubic yards in various appurtenant structures. A two-lane highway runs across the top, connecting Nevada and Arizona.

I got to the dam in time to take one of the day's last tours. From the guide I learned that the dam was cast in interlocking rectangular columns measuring between twenty-five and forty feet on a side. New concrete was added to the tops of the columns in five-foot-tall sections, and in a staggered pattern, so that each new section could harden before more concrete was added on top or to any side. Workers known as puddlers stood inside the forms as each load was dumped, then spread the new concrete with shovels and (mainly) their feet. Buried within each new section were two separate networks of pipes: one that would later be used to inject portland-cement grout into cracks, joints, and gaps between columns; and one that would be used to cool the concrete as it cured, by circulating water through it. The dam's designers had realized that a dam-sized mass of concrete, during hydration, would generate and trap so much heat that without artificial cooling the structure would require a century and a quarter to cool down, and would develop spectacular cracks as it did. As each section of the dam reached and maintained the desired internal temperature, measured by thermometers also buried in the concrete, the cooling pipes serving it were disconnected, drained, and filled with grout.

After my tour ended, I walked onto the top of the dam, toward Arizona, and leaned over the belly-high parapet on the downstream side. The face of the dam plunges down and away, and it must engender dark yearnings in the minds of certain kinds of skateboarders. Despite everything I had heard and seen and read about the dam until that moment, it was only as I stood on its rim and gazed down toward the river far below that I gained a full, vertiginous sense of the extraordinary pile of concrete at my feet-the "callous, cruel lump," in the words of a visitor in the thirties. I felt the same sense of mild unease I felt once as I floated on my back in the deepest part of a deep lake and imagined the unsettling volume beneath me.

Anyway, here's the point I want to make: New York City adds concrete to itself at the rate of approximately one Hoover Dam every eighteen months.

[Frozen Feet]

I'm not arguing nuclear fission is bad way of producing energy; just that it to cover all our future needs isn't necessarily more feasible than any other way. Notice the wording, as it also goes the other way around; other forms of energy aren't necessarily more feasible than fission. Many are less.

 

I also don't get why you insist averages don't tell anything. Before complaining about the numbers, consider what they're attached to. Look what it takes to make a safe fission reactor, what it takes to safely deposit the waste and how many are being build right now; we simply aren't going to build enough reactor for it to be the sole solution.

 

There's a good reason why I brought up cutting the amount of energy used. That 40 TW per year estimate? It's based on every human using as much energy as we Finnish people use. With current technologies, not feasible.

 

EDIT: A related link. Note the amount of reactors around, and being build. Compare that to those 25 000 we'd need. Laugh.

[Dikiyoba]

Originally Posted By: Niemand

Hydroelectric power is great if you happen to ahve a good sized river nearby and a good area to trap it in (the Colorado river works well for Nevada, Arizona, and California, but it would be hard to find any good place to put a dam on the Mississippi, which is why no one has as far as I know).

There's not much more hydroelectric power that can be added in the US. All the good sites already have a dam on them, and power-generation has to complete with the other bajillion things people want to use water for.

Globally, there are plenty of sites, and China's more than happy to finance dams, so the amount of hydroelectricity will go up, but the ecological and social consequences of it tend to be ugly.

Dikiyoba.

[Lilith]

Well, we can always revive the plan to dam the Yukon River. Sure, it'd create an enormous inland sea in the Arctic Circle with unpredictable effects on global climate, and the power generated would be in a frigid, marshy wasteland thousands of kilometres from where it would actually be needed, but...

[cfgauss]

Originally Posted By: Frozen Feet

I'm not arguing nuclear fission is bad way of producing energy; just that it to cover all our future needs isn't necessarily more feasible than any other way. Notice the wording, as it also goes the other way around; other forms of energy aren't necessarily more feasible than fission. Many are less.

But the point is that fission is like an order of magnitude better at least than most other sources. No other known technology is better than fission, and none except fusion are expected to be able to more efficient based on fundamental physics (unless you want to include exciting stuff like accretion of matter into black holes which can be very efficient!)

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I also don't get why you insist averages don't tell anything.

Because of my years of training as a physicist, where I see averages used correctly and wrongly all the time . Plus my background in math where I had these things beaten into my be various mathematicians.

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Compare that to those 25 000 we'd need. Laugh.

And compare that to the number of other power plants that are being built, the rate they're built at, and the cost-effectiveness of building them vs. power plant type, and laugh again, this time, realizing how wrong your other arguments have been.

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Originally Posted By: Lilith

Well, we can always revive the plan to dam the Yukon River. Sure, it'd create an enormous inland sea in the Arctic Circle with unpredictable effects on global climate, and the power generated would be in a frigid, marshy wasteland thousands of kilometres from where it would actually be needed, but...

If I've learned anything from years of sci-fi, it's that science requires needless, unpredictable risks for progress (and results in needless, nonsense results). So let's do it! We'll awaken a huge, ancient sea creature in the process, but hey, we'll grow, learn, and the main character will inexplicably end up with the hot only-other-girl-in-the-story!

What better ending could you ask for?

[Dantius]

Originally Posted By: Lilith

Well, we can always revive the plan to dam the Yukon River. Sure, it'd create an enormous inland sea in the Arctic Circle with unpredictable effects on global climate, and the power generated would be in a frigid, marshy wasteland thousands of kilometres from where it would actually be needed, but...

Nooo, that's just the Army Corps of Engineers being cooler than you ever will be. They've come up with plans to drain the Mediterranean Sea, just for the hell of it.

[Alorael at Large]

Let me see if I've got this right. We need a lot of power. Producing that power by new methods requires building a tremendous number of buildings. So many, in fact, that that many fission reactors is basically inconceivably. (I can conceive of it, actually, but let's move along.) Building anything else, though, means lower energy efficiency and even more monumental buildings projects, which means these means are even more inconceivable.

 

So, what? We're doomed? We need to start massive reactor projects right now? No, not really. Oil will become more and more expensive, and we will build the reactors gradually to defray costs. Eventually, oil will cost too much to use on any meaningful scale and we will have built those many, many reactors. Expect some painful fuel prices on the way, but don't expect them to be permanent.

 

—Alorael, who doesn't see what's wrong with the averages here except implication. There's no need to build multiple plants in a day. There's just the need to build a whole lot of plants in parallel, which is the sort of thing that happens constantly at all construction sites worldwide. How many buildings do you think are built per day?

[cfgauss]

Originally Posted By: Vituperation Free Albemuth

—Alorael, who doesn't see what's wrong with the averages here except implication. There's no need to build multiple plants in a day. There's just the need to build a whole lot of plants in parallel, which is the sort of thing that happens constantly at all construction sites worldwide. How many buildings do you think are built per day?

Yeah, the biggest problem is the implication, but the averages are a problem too because by themselves they aren't very meaningful. The whole point of an average is to remove information, which is useful when the information is, e.g., random error, less useful when you really should be keeping this information, like in the above case, when you really need a whole multidimensional distribution (so you really should be keeping infinitely more numbers than just the one average ).

[Student of Trinity]

Originally Posted By: Vituperation Free Albemuth

How many buildings do you think are built per day?

This was actually the point of my little interjection about the Hoover Dam and NYC's concrete intake. When we're talking about the power needs of the human race, we're also talking about a group whose construction capacity is pretty immense. Even if we somehow had to build 25,000 reactors in a crash program over a few years, that's really not inconceivable at all. It doesn't normally happen, because it doesn't have to happen; we build shopping malls and skyscrapers and apartment complexes and underground parking garages and a zillion other structures instead. And it actually won't have to happen, for the reasons Alorael and I have given. But if it did have to happen, I expect it could.

[Frozen Feet]

Originally Posted By: cfgauss

Originally Posted By: Frozen Feet

Compare that to those 25 000 we'd need. Laugh.

And compare that to the number of other power plants that are being built, the rate they're built at, and the cost-effectiveness of building them vs. power plant type, and laugh again, this time, realizing how wrong your other arguments have been.

What arguments exactly? I already acknowledged that fission is one of our best bets for producing energy, I'm just claiming that it isn't any more sufficient to produce a certain tresshold of energy than other forms. Please don't ignore numbers I've given just because you have bad memories of someone misusing them. If you change the baseline from 25 TW to, say, 1 TW in 30 years, producing it with new fission reactors goes from impossible to manageable, but that's a very different situation from what I am proposing.

Your counterpoint is that we build a whopping lot of buildings already, but that doesn't really adress my counterpoint to it - namely, that nuclear reactors are non-trivial to make.

I acknowledge we humans build a lot of stuff. I also know from experience that most of that stuff isn't made to last for more than two or three decades; obviously that can't aply to a fission reactor. Building one is a very different proposal than building a common house or a shopping mall.

It's the same problem you brought up when we discussed solar panels. Just making enough reactors isn't enough - they also have to be maintained, placed on proper region and need to have enough fissible material available.

Now, Alorael is right that mankind isn't doomed (for a given value of doom, anyway) just because we aren't starting thousand new reactor constructions right now, or because fission alone wouldn't cut it. It's possible for us to let things roll on their own weight; however, that too has it's own implications. But as I said, I won't open that can of worms.

[Alorael at Large]

We build non-trivial buildings constantly as well. And what's the difficulty to construction ratio? If it takes twice the manpower, twice the material, and twice as long to make solid, secure buildings... we can still do that. Humanity builds a huge amount.

 

—Alorael, who has no problem with the numbers you're using. It's the numbers you have refused that are getting messy. (Admittedly, that's at least in part because a lot of those numbers aren't numbers so much as asserted orders of magnitude.)

[Frozen Feet]

Originally Posted By: Vituperation Free Albemuth

We build non-trivial buildings constantly as well. And what's the difficulty to construction ratio? If it takes twice the manpower, twice the material, and twice as long to make solid, secure buildings... we can still do that. Humanity builds a huge amount.

—Alorael, who has no problem with the numbers you're using. It's the numbers you have refused that are getting messy. (Admittedly, that's at least in part because a lot of those numbers aren't numbers so much as asserted orders of magnitude.)

One has to start somewhere to give any numbers at all. In this case, I picked an estimate from a two year old article (the link I gave first) and have used it as a baseline so far. If you, or anyone for that matter, know some more recent estimate, please share.

My skeptism of nuclear fission is based on my knowledge of nuclear powerplant construction, and the amount of reactors currently in use. To reiterate things said on World Nuclear Association's website I linked to earlier:

There are currently some 436 fission reactors in use, with combined capacity of 370 GWe. 50 more reactor are currently being build; 130 reactors with combined capacity of 150 GW are being planned, and 250 have been proposed. According to them, nuclear power is picking up again now that China and India are becoming more industrialized; a realistic estimate by them would be that between 2015 and 2025, one 1GW unit might be put up every 5 days.

The estimate I'm using is that world-wide energy consumption will increase by 25TW in the next 30 years; to cover all that with fission reactors alone, we'd need 25,000 new 1GW reactors. That averages 833 reactors per year, or 2.3 reactor per day. That's 11.5 times more than the realistic estimate.

Counting all factors that complicate building of a fission reactor, I'd posit that compared to, say, making a skyscraper, their diffuculty to construction ratio is much higher than double. And that might not even be the actual limiting factor - as I said in my first post about the issue, there might not be enough uranium for those reactors in the first place. Or copper for making sealing canisters for the waste. Or geologically stable locations to put the plant in.

Again, this is just if we tried to cover the whole increase solely with nuclear fission. Nuclear power combined with solar, wind, geothermal, and other options, probably could make it. All I'm saying is that there is no single basket we can place our fruits in, so to speak.

EDIT: Damn, I was so busy ranting wildly I forgot what I really wanted to add. I was unable to find the madman who thought all of worlds energy could be taken from sunlight, but while searching I found these. Enjoy

[Randomizer]

The problem with nuclear reactor construction isn't the building but the legal hoops needed to be jumped through before construction begins. Too many places have bad safety records so most places don't want them unless the government is strongly behind construction.

 

In the United States it looks like most new construction will be at existing locations where permits already exist to add new units to reach pre-existing laws and no new legal problems will occur.