Boron availability

[jamesr]

KeithPickering wrote:

Now I can see how the electrons and ions produced might be captured with nearly 100% efficiency (although this too needs to be demonstrated). But 40% of the energy produced is in the form of x-rays, which are supposed to be captured by the layered foil shell. How efficient is that shell? If it’s only 20% efficient (which is comparable to solar PV cells), the device itself will only capture 68% of produced energy. And that would mean that the effective breakeven point is 47% higher than the theoretical breakeven point.

It may turn out that you can get to theoretical breakeven, but not quite to practical breakeven … or just barely over the line, which would mean that the excess salable energy would be a lot more expensive than assumed.

X-rays are not produced by the fusion directly, so it might be a little missleading to say 40% of the energy is produced in the form of x-rays. They are the result of electrons being deflected by ions and emiting Bremsstrahlung radiation.

The key point for Focus Fusion yet to be shown, as I see it, is whether bremsstralung x-rays will cool the plasma too fast and stop enough of the boron fusing in the plasmoid to release more energy than it took to make it. The plasmoid needs to confine the Helium ions and recycle their energy to keep the Hydrogen-Boron plasma hot for over 50ns (a very long time for an ion with a few MeV of energy). The He 2+ and B 5+ (and any other impurity) ions emit huge amounts of x-rays as they interact with the electrons. According to conventional physics this makes ignition of a pB11 plasma impossible as it will always radiate away the energy faster then the fusion reactions can heat it.

Only if the magnetic field in the plasmoid (assuming the plasmoid does exist in the form postulated) is strong enough for the ‘magnetic field effect’ to restrict the energies of the electrons and so result in a lower electron temperature than the ion temperature can there be any hope of it working. It is this that the ongoing experiments need to demonstrate. If the boron bremsstralung rate is only reduced to say 10 times higher than for hydrogen (rather than the normal 5^2=25 times), then the whole effort is still futile. It is needed to get down to only a few times higher that hydrogen for the plasma.

Only after this burning of a pB11 fusion mix has been demonstrated, I think will engineering the capture of the x-rays to recover their energy to get to the breakeven be worth pursuing.

[Tulse]

The element produced is He3. It could be used for dirigibles

Fusion-powered zeppelins that never need refilling — awesome!

[HermannH]

KeithPickering wrote:
It may turn out that you can get to theoretical breakeven, but not quite to practical breakeven … or just barely over the line, which would mean that the excess salable energy would be a lot more expensive than assumed.

That is the worry I have as well. According to Eric’s simulation results in the Technical Paper 1 the maximum reasonably achievable ratio of (Xray + Beam) / Input is 1.57.

If you assume a conversion efficiency of 80% for both and no other losses inside the system the net gain on each shot is 25%. This is certainly better than unity but not very comfortably so. Also, if you have low overall gain the waste heat that is generated is going to be very large compared to the net electrical output.

Of course several approximations and assumptions were used in the simulation. So the final result could turn out to be quite different.

[Tulse]

If you assume a conversion efficiency of 80% for both and no other losses inside the system the net gain on each shot is 25%. This is certainly better than unity but not very comfortably so.

I’m not clear on the economics of this — why would 25% over unity not be “comfortable”?

What are the hypothesized maximums for other fusion approaches? I have to believe that a process involving direct electrical generation from the fusion reaction will be much more efficient and economical than the MCF and ICF approaches of creating suns to boil water to drive a turbine to turn a generator.

Also, if you have low overall gain the waste heat that is generated is going to be very large compared to the net electrical output.

Of course, the “waste” heat itself can be used either to generate further electricity, or for heating and industrial applications, making the system more economical than figures for just direct electricity generation might suggest.

[HermannH]

Tulse wrote:

Also, if you have low overall gain the waste heat that is generated is going to be very large compared to the net electrical output.

Of course, the “waste” heat itself can be used either to generate further electricity, or for heating and industrial applications, making the system more economical than figures for just direct electricity generation might suggest.

That is theoretically true, but the coolant temperature must be significantly lower than the maximum operating temperature of the part that needs to be cooled. Therefore the waste heat is probably at a relatively low temperature unlike in a coal power plant where the boiler temperature is pushed as high as possible. The higher the ‘steam’ temperature the more useful things you can do with it. It’s like a car, the waste heat from the engine is good for heating the car in the winter, but otherwise it is just a problem.

My expectation is that the steam temperature is going to be barely high enough to make it worthwhile to generate electricity from it. Also, keep in mind that having to attach a conventional steam based power plant to a FF reactor negates many of the cost advantages.

Imagine a reactor where you have only 10% gain over unity. That means if you feed 1 Mega Joule of energy from the capacitors into the device the electrical energy harvested is 1.1 Mega Joule. 1 Mega Joule of that is needed to charge the capacitors for the next shot, so you are left with a net output of 100 kilo Joules. But you also just generated close to 1 Mega Joule of heat that needs to be disposed. Your ratio of waste heat to useful electrical power is 10 to 1. If your gain is 5% over unity that ratio goes up to 20 to 1 and you will use up all the generated electricity just to power the cooling pumps.

So it is critically important that the gain is significantly higher than unity.

[Tulse]

All the above points are indeed true, but I’m still not clear how far over unity one needs to be for economic viability, nor where other fusion approaches would sit on that curve. (For that matter, I’m not sure what the relative “mine to outlet” energy gain is for coal-fired or nuclear powerplants — does anyone have estimates on that?)

[HermannH]

Tulse wrote: All the above points are indeed true, but I’m still not clear how far over unity one needs to be for economic viability, nor where other fusion approaches would sit on that curve. (For that matter, I’m not sure what the relative “mine to outlet” energy gain is for coal-fired or nuclear powerplants — does anyone have estimates on that?)

As far as I know FF is closer to unity (or above) than any of the other approaches. The big question is: can it get high enough above unity? Many of the other systems need to be physically scaled up (very expensive) to achieve unity or above. Even then there is no guarantee that they will be economical.

[Aeronaut]

HermannH wrote:

All the above points are indeed true, but I’m still not clear how far over unity one needs to be for economic viability, nor where other fusion approaches would sit on that curve. (For that matter, I’m not sure what the relative “mine to outlet” energy gain is for coal-fired or nuclear powerplants — does anyone have estimates on that?)

As far as I know FF is closer to unity (or above) than any of the other approaches. The big question is: can it get high enough above unity? Many of the other systems need to be physically scaled up (very expensive) to achieve unity or above. Even then there is no guarantee that they will be economical.

We need to play the ball where it lays. Once the bandwagon begins rolling, a lot of fresh capital and talent will come out of the woodwork to figure out how to improve the various efficiencies. Until then, we have a machine that is more than adequate for making the steam to heat buildings and melt plastics and many metals. It’s going to do this with or without breaking even electrically. The electrical output is the icing on the cake.

[Brian H]

Aeronaut wrote:

All the above points are indeed true, but I’m still not clear how far over unity one needs to be for economic viability, nor where other fusion approaches would sit on that curve. (For that matter, I’m not sure what the relative “mine to outlet” energy gain is for coal-fired or nuclear powerplants — does anyone have estimates on that?)

As far as I know FF is closer to unity (or above) than any of the other approaches. The big question is: can it get high enough above unity? Many of the other systems need to be physically scaled up (very expensive) to achieve unity or above. Even then there is no guarantee that they will be economical.

We need to play the ball where it lays. Once the bandwagon begins rolling, a lot of fresh capital and talent will come out of the woodwork to figure out how to improve the various efficiencies. Until then, we have a machine that is more than adequate for making the steam to heat buildings and melt plastics and many metals. It’s going to do this with or without breaking even electrically. The electrical output is the icing on the cake.

I disagree, of course. The fundamental design of FF is to generate electricity; the heat is either icing on the cake or urine in the punch. ;-P
In general, ANYTHING above unity would do, I think. The Tokamak and similar designs project numbers in the low single digits, IIRC. They’re just heat engines, of course. Once FF attains/exceeds unity, it will attract more than money; there will be brainpower and ingenuity applied en masse to refine and maximize its output.

[Brian H]

Tulse wrote:

The element produced is He3. It could be used for dirigibles

Fusion-powered zeppelins that never need refilling — awesome!

Yes, but it’s He4. He3 is very rare, and would be another aneutronic fuel candidate. http://en.wikipedia.org/wiki/Aneutronic_fusion
But

The pure 3He reaction suffers from a fuel-availability problem. 3He occurs naturally on the Earth in only minuscule amounts, so it would either have to be bred from reactions involving neutrons (counteracting the potential advantage of aneutronic fusion), or mined from extraterrestrial bodies. The top several meters of the surface of the Moon is relatively rich in 3He, on the order of 0.01 parts per million by weight[1], but mining this resource and returning it to Earth would be very difficult and expensive. 3He could in principle be recovered from the atmospheres of the gas giant planets, but this would be even more challenging.

[HermannH]

Brian H wrote:
I disagree, of course. The fundamental design of FF is to generate electricity; the heat is either icing on the cake or urine in the punch. ;-P
In general, ANYTHING above unity would do, I think. The Tokamak and similar designs project numbers in the low single digits, IIRC. They’re just heat engines, of course. Once FF attains/exceeds unity, it will attract more than money; there will be brainpower and ingenuity applied en masse to refine and maximize its output.

That’s mostly correct, the point of FF is to generate electricity directly. In order for the technology to be even theoretically viable the reaction needs to generate more electrical energy than you put in. To be economically viable you need to be quite a bit above unity as explained earlier.

Of course, once you demonstrate that you can achieve even close to unity you can attract a lot of money to develop the technology further. But this development effort may take huge amounts of money and many years before we have a system that economically produces electricity. Economically, in this case, could initially mean about the same cost as coal or regular fission not necessarily ‘too cheap to meter’.

I do hope that we get well above unity quickly and this discussion is just academic.

[KeithPickering]

HermannH wrote:

It may turn out that you can get to theoretical breakeven, but not quite to practical breakeven … or just barely over the line, which would mean that the excess salable energy would be a lot more expensive than assumed.

That is the worry I have as well. According to Eric’s simulation results in the Technical Paper 1 the maximum reasonably achievable ratio of (Xray + Beam) / Input is 1.57.

Thanks for that link, and the very interesting technical paper. Apparently EL’s zero-dimensional simulation has addressed this problem pretty well, and assumes that energy recovery is 80% for both ion beam and for x-ray. As the input energy increases, the recoverable energy also increases, but the ratio of x-ray to ion beam also increases … so more and more of the fraction must be recovered by the x-ray capture shell. Since EL invented it himself, we must assume that his 80% figure is roughly correct.

A couple of final results then: at a ratio of 1.57 (energy recovered to energy input), the salable output of a reactor using 5 kg of borax per year (see my previous post for computations) would be 1111 kW. To convert ALL electric production worldwide (2.5 million megawatts) to pB11 fuel would require 12,500 tonnes or borax per year, or about 8% of current worldwide production.

[HermannH]

KeithPickering wrote:
Thanks for that link, and the very interesting technical paper.

You are welcome! There is a link to a second technical paper and a lot of other interesting stuff on the home page.

A couple of final results then: at a ratio of 1.57 (energy recovered to energy input), the salable output of a reactor using 5 kg of borax per year (see my previous post for computations) would be 1111 kW. To convert ALL electric production worldwide (2.5 million megawatts) to pB11 fuel would require 12,500 tonnes or borax per year, or about 8% of current worldwide production.

So, no matter what the efficiency, the supply of boron is not going to be an issue.

[Brian H]

KeithPickering wrote:

It may turn out that you can get to theoretical breakeven, but not quite to practical breakeven … or just barely over the line, which would mean that the excess salable energy would be a lot more expensive than assumed.

That is the worry I have as well. According to Eric’s simulation results in the Technical Paper 1 the maximum reasonably achievable ratio of (Xray + Beam) / Input is 1.57.

Thanks for that link, and the very interesting technical paper. Apparently EL’s zero-dimensional simulation has addressed this problem pretty well, and assumes that energy recovery is 80% for both ion beam and for x-ray. As the input energy increases, the recoverable energy also increases, but the ratio of x-ray to ion beam also increases … so more and more of the fraction must be recovered by the x-ray capture shell. Since EL invented it himself, we must assume that his 80% figure is roughly correct.

A couple of final results then: at a ratio of 1.57 (energy recovered to energy input), the salable output of a reactor using 5 kg of borax per year (see my previous post for computations) would be 1111 kW. To convert ALL electric production worldwide (2.5 million megawatts) to pB11 fuel would require 12,500 tonnes or borax per year, or about 8% of current worldwide production.
Borax, or boron?

[belbear42]

HermannH wrote:
That is the worry I have as well. According to Eric’s simulation results in the Technical Paper 1 the maximum reasonably achievable ratio of (Xray + Beam) / Input is 1.57.

There seems to be a little error in this paper:
On the bottom of page 5, it says “Fuel: B10H1” Shouldn’t that be B11H1?

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