Potential of alternative energy sources?

[Billy T]

...You do have a point, I've never seen Bassard's work either but Lenard's is available. Also bassard's work has been cacluated by others a feasible:
http://scitation.aip.org/getabs/ser...00007000011004547000001&idtype=cvips&gifs=yes

That is a calculation of the ratio of fusion power output to electron injection power imput, which by assumption ingores all the radiative losses ("no electron ion interactions" assumed is clearly stated) and I am almost sure any radiation losses associated with the scattering of ion on ions or the cyclotron losses as well have been ignored. The question about the out put being greater than the input I assummed was no problem. The real question is:

Is there any plama condition (assume you can achieve any you want) in which the output fusion power is greater than the rate of all losses? The radiatve losses are especially a concern when some of the ions have more than one unit of atomic charge (i.e. Bussard plans 50% of the ions to be B+++++)

In the DT reaction both the D and the T are only with one atomic charge - this makes reaction at much lower temperatures possible and the loss much less. Also compared to the DT reaction, the PB the energy per fusion is about 5 times higher AND the reaction cross-sestion or rate is much better, as I recall.

SUMMARY: that reference does not even address the important question.

 

[kevinalm]

Billy,
Been busy so I couldn't get back to you sooner. Your post #47 reads like a list of the objections raised by detractors. Bussard seems to have been confident that he had answers to them. Bearing in mind that my understanding is likely heavily flawed, here are a couple of aspects that may apply.

Since the ions (I'll refer to the fuel nuclei as ions if that's ok.) are in a 'quasi' harmonic well, they spend most of their time at max r, cool and slow. This has the effect that it is at this r that ion/ion thermalization occurs and surprisingly helps to maintain athermal distribution as the ions pass through the core. Bussard calls this 'annealing'. Electrons also have speed profiles that depend on radius, only they are slowest at min r. How these two profiles intersect is not a straight forward matter, in terms of scattering and thermalization. To me, it would not be all that surprizing if the normal calculation methods used for "thermal" systems like the tokomak were very far off from reality.

Another thing that Bussard talked about was the "wiffle ball effect". (That's where the WB designations come from.) As electrons are injected into the interior, the field lines distort, something like a magnetic balloon being inflated. The interior field becomes very sperical and the cusps pinch off, effectively becoming very small. As far as what that means for the behavoir of internal electrons, or the plasma as a whole, I have no idea, except that accurate modeling isn't going to be a trivial matter.

I think (and I am by no means certain) that the polywell is intended to run at drastically lower plasma density than say a tokomak. It would seem reasonable that if you are trying to run on a largely athermal ions instead of the 1% thermal 'tail' that density requirements are much lower.

I suspect the only way to really find out if it works is to build a steady state machine and see what happens. Trouble is to do that requires cooled copper or superconducors and that sets the minimum size at R=1 meter or there abouts. Bussard's model says that 1.5 meter is the scale for a 100 Mw D-D reactor.

Hopefully, Nebel and Park (the LANL guys) can clarify the situation with the WB-7 experiments. Rumor has it that the Navy pubication embargo has been permanently lifted, so there should be a peer reveiwed paper sometime in the future.

 

[Billy T]

....Electrons also have speed profiles that depend on radius, only they are slowest at min r. How these two profiles intersect is not a straight forward matter, in terms of scattering and thermalization. To me, it would not be all that surprizing if the normal calculation methods used for "thermal" systems like the tokomak were very far off from reality....

I agree that yields and losses etc cannot be even guessed at from Tokomak (or old Stellarator) experience; however, given (or with assumed) local density of electrons and ions only one can do a lot with confidence.

For example, calculate the electric potential everywhere. From this and the nature of the electrons injected (current and energy) one can then get good idea of the energy density everywhere. How this energy is distributed among the particles is a little more speculative but not much unknown if you work hard at the calculations. One can be confident that the electrons do have a local temperature (I.e. a Maxwellian distribution) everywhere, except for the few that have just been injected into that local volume. - They will very rapidly also take their place in the distribution.
For example if some of those injected do make it into the center and turn around they will not make it back even once to the edge of the well but the stopping them is a "pressure" that can build the well.

By design, we know that there is an excess of electrons everywhere (if there were more ions in some small delta r spherical shell then the electric potential would be going up, not down as you pass from R greater thru that net positive shell. (actually as some if not all, of the Boron is multiply ionized there could even be less that 20% the ion density as the electron density everywhere.

I think it is likely that any ion sort of at rest at the edge of the well will fall quite far into the well and not strongly collided with others but will be scattering (accelerating, producing radiation) the electrons as it does so without transfer of much energy to the electrons because of the mass difference. Thus it is reasonable to think that in the outer parts of the well the ions may not be thermal and even if they are, may not have the same temperature as the electrons at least the first time they enter the plasma region. (I am not clear on how the ions are introduced - perhaps boiled out of a tiny tub into vacuum?)

If the device is to have significant fusion making collision there will be plenty of non-fusion collisions among the ions to make most of them have a temperature, but for reasons stated, even in the center of the well they will not quite make neutral plasma. There will be a lot of recombination occurring and this is a loss of energy via UV and soft X-rays which with the assumed densities and temperatures can be computed. (True these assumed values, which are a function of radial location, may not be the ones actually present, but with them one can also compute the fusion rate, along the lines I suggested with consideration of the impact parameters these distributions imply.)

Thus for many assumed distributions, including some obviously too favorable, one can compare the radiative loss rate to the fusion energy production rate. That is what needs to be done. Perhaps there is some distribution for which the losses do not exceed the energy production rate, but I doubt it as with large number of multiple charged ions the radiation is intense. -I initially told how this blocked the old Stellarator form achieving even the much lower temperature for the DT reaction until the diverters were added (to "skim off" the influx of out gassing molecules, which were quenching the plasma via this radiation.) but the fact that highly charged ions in a hot plasma radiate like crazy is not device dependent.

It is a simple fact, always true, built on the well understood binary interactions taking place. It will be true in Bussards device as it is in all others - even the shock tube plasma I used for my Ph.D. which only had neutral and one stage of ionization Argon gas in it. Ions do recombine with electron in plasmas and radiate. X-rays or at least harsh UV if they have 4 or 5 electrons missing as is Bussard's hope with B+++++ ions.

 

[Diode-Man]

We had better find a new energy source, from what I recall, we supposedly came to the half-way point on our crude oil supply?

 

[joepistole]

Use gravity and friction to generate electricity, similar to a gravity plane. Use lighter than air gases to raise and object and then capture the energy from the fall (gravity and air friction).

 

[Billy T]

...Use lighter than air gases to raise and object and then capture the energy from the fall (gravity and air friction).

A nice paradox, but it will not work because you are not considering the whole story.

The lighter than air balloon with cable tied to generator's pulley wheel slowly gets energy for itself and the brick it is lifting by allowing a equal volume of heavier air to fall down to where it was on the surface. If you could pull the balloon, still holding the brick, back to the surface with 100% efficiency at least you would not lose anything. (If you let the balloon freely rise, you cannot even "break even" as there will be friction with the air as it slips thru and also some kinetic energy transferred to the turbulence it would generate by quickly rising.)

If, as you suggest you drop the brick when high in the air (Let's neglect fact it too is making turbulences etc as it falls as we could let it down slowly and have it turn the pulley of a balloon born generator, charging a battery for us.)

Now the balloon (without the brick) is even lighter so it will take more energy to pull it down than the energy it gave us when rising. (By exactly the energy we got out of lowering the brick, of course.)

But it is a nice paradox that will fool some.

 

[joepistole]

A nice paradox, but it will not work because you are not considering the whole story.

The lighter than air balloon with cable tied to generator's pulley wheel slowly gets energy for itself and the brick it is lifting by allowing a equal volume of heavier air to fall down to where it was on the surface. If you could pull the balloon, still holding the brick, back to the surface with 100% efficiency at least you would not lose anything. (If you let the balloon freely rise, you cannot even "break even" as there will be friction with the air as it slips thru and also some kinetic energy transferred to the turbulence it would generate by quickly rising.)

If, as you suggest you drop the brick when high in the air (Let's neglect fact it too is making turbulences etc as it falls as we could let it down slowly and have it turn the pulley of a balloon born generator, charging a battery for us.)

Now the balloon (without the brick) is even lighter so it will take more energy to pull it down than the energy it gave us when rising. (By exactly the energy we got out of lowering the brick, of course.)

But it is a nice paradox that will fool some.

Billy T, I did not say it would be pretty. The gas needs to change density as it moves to higher altitudes...eg. hot air.

 

[Rick]

My question is :

What are the chief hurdles in controlling a fusion reaction? Is it do-able or its like barkin' up the wrong tree ?

Rick

 

[Billy T]

My question is : What are the chief hurdles in controlling a fusion reaction? Is it do-able or its like barkin' up the wrong tree ? Rick

The conditions for even the easiest DT fusion reaction require a very hot plasma. Think of it as resembling jello or water, except that it has great internal pressure and "wants" to expand. You must somehow contain this very fluid mass WITHOUT allowing it to touch anything. (Except in the case of "inertial confinement" approaches, but they require huge extremely high power energy fluxes applied to tiny pellets of DT - sort of trying to make micro hydrogen bombs. It is very expensive and inefficient to make fluxes. Also by its nature, it is not a continuous process pellet after pellet must be feed in, the flux generators recharged* for the next "shot", etc.)

This means a magnetic "Bottle" is required, but it is sort of like trying to make a layer of water float on top of oil. The plasma (oil) "wants" to exchange places with the wall of the magnetic bottle (the water) and this leads to rapidly growing instabilities (Read about the "Taylor Instability" for example you can understand.) there are many different instabilities available when the walls of the magnetic bottle are pushing on the hot plasma that allow the plasma to escape. Preventing this escape is expensive as requires strong (supper conducting) magnets with very complex "twisted layers of fields" and internal currents. (Tomack field geometry is best hope, but if history is any guide, the plasma still knows a few more instabilities man does not that it can use to escape.) Even if ITER can hold the necessary plasma the system of magnets and vacuum and energy recovery for the 17MeV neutrons and the avoidance of induced radioactivity etc. seems IMHO, much too costly to compete economically with a brick furnace and chimney burning coal as a heat source for the steam turbine.
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*Typically a large room full of dozens of costly lasers as the compression of the DT pellet must be very-uniform, spherically-symmetric or you just blow it to pieces. Just the cost of the timing and intensity control circuits to make sure everyone of the lasers delivers the same flux at the same nanosecond with the same rise and fall of intensity is IMHO too much for the value of the energy released by the tiny DT pellet, which is also costly to produce and deliver in the vacuum chamber, not to mention that the 17MeV neutrons must be used for energy without inducing radioactivity in excess.

 

[iceaura]

Unless you count the gigantic swath of desert you'd need to occupy with collectors just to make a dent in the baseload while the sun is shining.

About a hundred miles square (ten thousand square miles) to replace the electrical generation of the US, about 330 miles square (100k square miles) to replace everything.

At current technology and efficiencies, etc, allowing for road and maintenance access etc. but assuming compact storage of some kind. Flywheel, maybe, or molten salt, or trainloads of recharged fuel cells for swapping out at gas stations. Probably a dedicated DC transmission line setup should be figured in there.

Wouldn't have to be all in the same place, but it would have to be in a pretty good set of locations. Los Alamos region, New Mexican desert, out by the smoked up Four Corners area - there's a lot of damaged landscape with basically suitable weather. Mexico is well suited to look into this.

Less space and damage, environmentally, than hydropower dams and associated lakes, etc.

 

[Echo3Romeo]

"Less devastating than hydro" != "environmentally benign". A Corvette is also slower than an F-15.

I agree with what you are saying, but lots of other people won't. A bunch of blasted, benighted desert wasteland might not matter to most of us, but any system with a necessarily large footprint guarantees that some NIMBY asshole is going to oppose it somewhere along the way. We already have that problem here in California.

Also, it would be nice to see your math.

 

[Diode-Man]

What if mankind figured out a way to synthesize momentum? What then?

Since all matter is made of static electric charges, wouldn't that mean that momentum is naturally electrostatic in nature?

 

[Dinosaur]

Iceaurea: Are you talking about solar cells to produce electricity? Do you have a citation or some data supporting the following? On what is the following based?

About a hundred miles square (ten thousand square miles) to replace the electrical generation of the US, about 330 miles square (100k square miles) to replace everything.

At current technology and efficiencies, etc, allowing for road and maintenance access etc. but assuming compact storage of some kind. Flywheel, maybe, or molten salt, or trainloads of recharged fuel cells for swapping out at gas stations. Probably a dedicated DC transmission line setup should be figured in there.

If those numbers are correct, I find it hard to believe that it has not yet been built & functioning to stop our dependence on fossil fuels.

I suspect that it has as much credence as some of your ideas about the ancient Egyptians calculating the dimensions of the Earth from precession data.

 

[Dinosaur]

It is difficult to imagine how current fusion reactor designs can be scaled up enough to produce large amounts of usable energy in excess of what is required to maintain the reaction and confine the nuclear fuel.

Stars are wonderful fusion reactors using gravity for confinement.

A star is an example of dynamic equilibrium between a nuclear reaction trying to explode the star & gravity trying to compress it to a smaller size.

The gravitational force is spherically symmetric and presents no barrier to the escape of energy in the form of radiation. Neither the extremely high temperature of the reaction nor the escaping radiation disturb or damage the gravitational forces which contain the fuel.

Compare the above with our small scale fusion reactors. It seems to me that future technology is more likely to be capable of building a Dyson Sphere or a Ring World than being likely to build a practical fusion reactor.

Our Earth bound fusion reactor devices must be far enough away from the high temperature fuel to avoid being melted or damaged. The radiation must be able to escape without damaging the device. The confinement must be spherically symmetric. We are not close to building a small scale version of a star.

It is interesting to consider the immense amount of energy produced by Sol which is not directed toward Earth. The Earth has a circular capture area whose radius is about 4000 miles. We orbit Sol at about 93 million miles. The area of a sphere with a 93 million mile radius is outrageously larger than the radiation capture area. The sun produces over 2 billion times more radiant energy than what arrives at the Earth.

Perhaps some future technology might use mirrors orbiting Sol to reflect radiant energy to some collection system on or orbitting the Earth. I would sooner bet on some variant of this idea than bet on any of our current fusion reactior designs being scaled up or being replaced by some better design.

 

[Diode-Man]

I fear mankind is doomed to wallow in oil till the end of time

 

[iceaura]

I suspect that it has as much credence as some of your ideas about the ancient Egyptians calculating the dimensions of the Earth from precession data.

I said what! You gotta find the quote on that one - I've never been much into Egyptians, and precession is not what they'd have used.

Iceaurea: Are you talking about solar cells to produce electricity?

No. Heat engine or reflector concentrating rigs. They're much more efficient and much less expensive, and they scale up easily.

If those numbers are correct, I find it hard to believe that it has not yet been built & functioning to stop our dependence on fossil fuels.

Hell of an investment - who's gonna pay for it ?

 

[Billy T]

Solar thermal conversion has a fundamental problem:

If the absorber is hot enough (near material limits) to allow high thermal conversion efficiency, then the re-radiation losses from the absorber are also very large. US patent 4033118 (mass flow solar absorber) teaches a possible solution. My patent expired about 20 years ago. (I foresaw the end of the cheap energy long ago; solved this problem, and got patent as feared others might too.)

A brief summary of how system works to double conversion efficiency*(at much lower cost than solar cells):

Concentrated sunlight enters the open end of a glass tube, which has a reflective coating on the outer surface. As it “mirrors” along the axis deeper into the tube, a small fraction of the energy is deposited on the wall with each reflection. A second, externally-insulated, co-axial, metal tube surrounds this inner one, forming an annulus between the two tubes in which the “working fluid” flows. At the entrance end the working fluid is relatively cool, but as it too travels farther from the entrance it becomes hotter from the energy being deposited on the inner tube wall. Deep in this tubular structure the glass grades into quartz, which can resist the high temperatures better than glass.

The interior deep insides the inner tube is of course filled with intense IR radiation but little of it can escape by “mirroring” its way back to the entrance. I.e. the glass wall does not let it “see” the mirror surface but absorbs the IR for transfer to the working fluid.

Thus, a very high temperature, with very little re-radiation losses is achieved economically with approximately twice the efficiency of solar cells about one ten of their cost.
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*Patent gives ref. to two papers I published in Applied Optics that quantatively show the improved efficiency, but as patent had not yet issued, "solar energy" is not mentioned. - Papers give only the way to calculate the absorption on tube walls of "entering radiation" and the escape of "thermal radiation" from a "hot deep interior."

 

[Dinosaur]

Iceaura: Sorry. I confused you with IceAgeCivilizations or some such name of another poster with weird ideas about ancient Egyptian technology.

I still think that 100 square miles is too small an area for the amount of energy you suggest.