The race is on, Polywell vs Focus Fusion

[D Tibbets]

And yet Polywell is getting funds and FF is begging.

It's worth pointing out that Polywell was begging for a long time too. And this despite the fact that they had promising data from their final experiments to present.

The thing is DPF work has never stopped. Just Lerner's experiments. The same is not true of the Polywell design.

In theory FF work to net power should be a table top affair. People have been studying these gizmos in lots of labs around the world for 20 years. You would think that it wouldn't take 20 years for a net power design with so many folks studying the device.

And they are making the device out of Beryllium to avoid heat loading from x-rays. Obviously they are not getting a trivial amount. The electrodes have to be cooled. More lost power. All this from a 5 MW (net power? total power?) device. Peak power per fusion pulse on the order of 5 GW for 3 usec. assuming 100% conversion efficiency - about 15 KJ per pulse. And yet he is driving his devices with a 1 MJ pulse. The numbers don't add up. What that means if true is a bigger fusion pulse with most of the energy going into the drive pulse.

I'm not saying don't spend the money. He may have found something. The density he is working with (4 torr) is good. And he may have found a gas mixture that will work. But Decaborane is going to run up his experimental costs and require a safety engineer. And I'd still be concerned with electrode erosion.

I didn't chew on you numbers much, but it sounds consistant with the hearsay that DPF and FRG (?) machines are capable of only small positive Q's, at least with aneutronic fuels. Presumably they would do much better with D-T due to the lower electron temperatures (Bremsstrulung x-ray losses) possibly making them a better aproach than Tokamaks for economical D-T fusion (if that is as far as they can go).

This may be a key advantage for the Polywell which is advertised as having electron temperatures significantly lower than the ion temperatures (kinetic energy) in the core resulting in much less Bremsstrulung losses and correspondingly higher Q's.

Dan Tibbets

[Brian H]

The FF 5MW is projected output current, representing the X-ray portion of the pulsed power, about 40% above unity, converted by a patented design of foils in a shell to current. The current directly derived from the alpha beam is to be returned to the capacitor bank for the next pulse, while the electron counter-beam reheats the plasma. Bremsstrahlung is kept down to that manageable level by exploiting a band gap in the electron/ion interactions.

Have you gone through the patent?

[TallDave]

My understanding is that brem is reduced in DPF by the influence of gigagauss B fields in the plasmoid.

I think it's fair to say this is a bit exotic. Not impossible, but... exotic.

[MSimon]

My understanding is that brem is reduced in DPF by the influence of gigagauss B fields in the plasmoid.

I think it's fair to say this is a bit exotic. Not impossible, but... exotic.

The confounding thing is that the plasma in a DPF machines is similar (+/- 10%) across a wide range of machine sizes.

[Stoney3K]

Personally, I'd like to see them *both* hit the grid.

Even if DPF weren't able to produce 100MW in a single unit, I'd be more than happy if they were to build a 1MW one. Hell, I'll buy a 100kW generator and chuck it under the hood of my car!

If DPF even works on smaller scale power devices, it certainly has its uses as well. Think of mobile gensets used at concerts (1-5MW in a container-sized package) or for powering vehicles, where Polywell units would be too big.

The Polywells could occupy transformer buildings and power your neighbourhood, where DPF's would be more useful on the road.

The same concept works in electricity generation these days: You hardly see multi-GW diesel generators, just as much as you would see thermal (steam) power plants which output just a few hundred kW.

[Brian H]

Personally, I'd like to see them *both* hit the grid.

Even if DPF weren't able to produce 100MW in a single unit, I'd be more than happy if they were to build a 1MW one. Hell, I'll buy a 100kW generator and chuck it under the hood of my car!

If DPF even works on smaller scale power devices, it certainly has its uses as well. Think of mobile gensets used at concerts (1-5MW in a container-sized package) or for powering vehicles, where Polywell units would be too big.

The Polywells could occupy transformer buildings and power your neighbourhood, where DPF's would be more useful on the road.

The same concept works in electricity generation these days: You hardly see multi-GW diesel generators, just as much as you would see thermal (steam) power plants which output just a few hundred kW.

Side reactions producing slow neutrons mandate some shielding, about a meter of water shell plus an inch or so of boron10, which would bring the size and weight up beyond automobile capacity. A large truck, or ship or plane could manage it. But battery tech is likely to trump on-board generators for small vehicles for quite some time to come. As for your 100kW under the hood, the Tesla electric 125 mph cars draw about 15kW at 60mph, so you'd be over-powered unless you were driving a bullet-proof limo or something.

For concerts, etc, I guess a few megawatts might be called for, but that's a lot of power, still. Maybe in a tractor trailer, used also to charge up electric vehicles for the tour convoy it could make sense. At $¼million a crack, it might be a while paying for itself on such limited duty. Same for any private or commercial road vehicle.

In neighborhoods, 1 5MW DPF unit would handle around 500 homes, which is a pretty decent-sized neighborhood! It's looking like the cost per watt to install and sell of DPF will be a fraction of PolyWell, so if they were competing, a cluster of DPFs would economically out-perform PolyWell in any size range.

[D Tibbets]

A mobile 1-2 MW power source would be handy. But with, I presume. low Q's just above breakeven you may need to have a 10 MW radiation and heat source in order to get 1 MW of useful power. You may actually need a 1 MW net power source (~ 1300 horsepower) to power a car that carries the weight of the massive radiaters needed.

On the otherhand, a DPF power cell at an Antartic or Martian base would be handy both due to it's assumed small size and it's toasty warmth. Conversely, a space craft would need alot of extra radiators to handle the waste heat.

Dan Tibbets

[Brian H]

The proposed 5MW FF DPF unit is rated on electrical output. Net thermal efficiency is estimated at 40-50%; since it is not a heat engine that's about the measure of heat needing to be vented or otherwise disposed of. It is very difficult to imagine, btw, a recovery system for that heat other than simple stuff like building heating which wouldn't cost more than just adding more FF capacity and using resistance coils to provide the heat (much more conveniently).

[Stoney3K]

Side reactions producing slow neutrons mitigate some shielding, about a meter of water shell plus an inch or so of boron10, which would bring the size and weight up beyond automobile capacity. A large truck, or ship or plane could manage it. But battery tech is likely to trump on-board generators for small vehicles for quite some time to come. As for your 100kW under the hood, the Tesla electric 125 mph cars draw about 15kW at 60mph, so you'd be over-powered unless you were driving a bullet-proof limo or something.

We're driving SUV's and family estates which have 100's of horsepower of engine grunt under the hood, where in daily traffic you only need a few dozen. Does anyone complain here?

100kW is about 136bhp, which is a reasonable amount for any car. Performance sports cars often carry a lot more punch.

As for concerts, etc, I guess a few megawatts might be called for, but that's a lot of power, still. Maybe in a tractor trailer, used also to charge
up electric vehicles for the tour convoy it could make sense.

Concert stages often rely on (fixed-base, but movable) diesel gensets these days to power their equipment (PA, light, video, laser), which can gobble up a few hundred kW if you have a decent sized show. Having one or two MW to work with never hurts.

At $¼million a crack, it might be a while paying for itself on such limited duty, tho'. Same for any private or commercial road vehicle.

For neighborhoods, 1 5MW DPF unit would handle around 500 homes, which is a pretty decent-sized neighborhood! It's looking like the cost per watt to install and sell of DPF will be a fraction of PolyWell, so if they were competing, a cluster of DPFs would economically out-perform PolyWell in any size range.

Polywells might be very useful if you need a lot more MW's in less volume, e.g. for large urban areas or future arcology projects. Polywells are a lot harder to shuffle around when they're completely built than DPF units, as I said, a complete DPF generator would probably fit in a 20-foot shipping container (or railway locomotive, or normal-sized ship's engine room).

Both units may be on the big heavy side for regular road traffic and aerospace applications, though, but when you've got plenty of power, you can pretty much create hydrocarbons from scratch and run any modern engine from that.

[MSimon]

Personally, I'd like to see them *both* hit the grid.

Even if DPF weren't able to produce 100MW in a single unit, I'd be more than happy if they were to build a 1MW one. Hell, I'll buy a 100kW generator and chuck it under the hood of my car!

If DPF even works on smaller scale power devices, it certainly has its uses as well. Think of mobile gensets used at concerts (1-5MW in a container-sized package) or for powering vehicles, where Polywell units would be too big.

The Polywells could occupy transformer buildings and power your neighbourhood, where DPF's would be more useful on the road.

The same concept works in electricity generation these days: You hardly see multi-GW diesel generators, just as much as you would see thermal (steam) power plants which output just a few hundred kW.

Side reactions producing slow neutrons mitigate some shielding, about a meter of water shell plus an inch or so of boron10, which would bring the size and weight up beyond automobile capacity. A large truck, or ship or plane could manage it. But battery tech is likely to trump on-board generators for small vehicles for quite some time to come. As for your 100kW under the hood, the Tesla electric 125 mph cars draw about 15kW at 60mph, so you'd be over-powered unless you were driving a bullet-proof limo or something.

As for concerts, etc, I guess a few megawatts might be called for, but that's a lot of power, still. Maybe in a tractor trailer, used also to charge up electric vehicles for the tour convoy it could make sense. At $¼million a crack, it might be a while paying for itself on such limited duty, tho'. Same for any private or commercial road vehicle.

For neighborhoods, 1 5MW DPF unit would handle around 500 homes, which is a pretty decent-sized neighborhood! It's looking like the cost per watt to install and sell of DPF will be a fraction of PolyWell, so if they were competing, a cluster of DPFs would economically out-perform PolyWell in any size range.

About 6" to 8" of water and a few mm of B10 are sufficient. Plus shielding for 400 KeV X-rays.

[Brian H]

Personally, I'd like to see them *both* hit the grid.

Even if DPF weren't able to produce 100MW in a single unit, I'd be more than happy if they were to build a 1MW one. Hell, I'll buy a 100kW generator and chuck it under the hood of my car!

If DPF even works on smaller scale power devices, it certainly has its uses as well. Think of mobile gensets used at concerts (1-5MW in a container-sized package) or for powering vehicles, where Polywell units would be too big.

The Polywells could occupy transformer buildings and power your neighbourhood, where DPF's would be more useful on the road.

The same concept works in electricity generation these days: You hardly see multi-GW diesel generators, just as much as you would see thermal (steam) power plants which output just a few hundred kW.

Side reactions producing slow neutrons mitigate some shielding, about a meter of water shell plus an inch or so of boron10, which would bring the size and weight up beyond automobile capacity. A large truck, or ship or plane could manage it. But battery tech is likely to trump on-board generators for small vehicles for quite some time to come. As for your 100kW under the hood, the Tesla electric 125 mph cars draw about 15kW at 60mph, so you'd be over-powered unless you were driving a bullet-proof limo or something.

As for concerts, etc, I guess a few megawatts might be called for, but that's a lot of power, still. Maybe in a tractor trailer, used also to charge up electric vehicles for the tour convoy it could make sense. At $¼million a crack, it might be a while paying for itself on such limited duty, tho'. Same for any private or commercial road vehicle.

For neighborhoods, 1 5MW DPF unit would handle around 500 homes, which is a pretty decent-sized neighborhood! It's looking like the cost per watt to install and sell of DPF will be a fraction of PolyWell, so if they were competing, a cluster of DPFs would economically out-perform PolyWell in any size range.

About 6" to 8" of water and a few mm of B10 are sufficient. Plus shielding for 400 KeV X-rays.

The X-ray shielding is actually part of the generation package, knocking down the radiation to produce current.

[MSimon]

The X-ray shielding is actually part of the generation package, knocking down the radiation to produce current.

The X-Rays I was referring to are those from the B10 capture of a neutron.