Reply To: Military Effects

[asymmetric_implosion]

@Zapkitty: I have no problem with science for the sake of science. I support the astrophysics and nuclear physics folks. I think they do amazing work. My problem is hiding behind some practical application in the near term. Inside and outside the gov’t folks invest in science for the sake of science. They seem to hate being lied to. If you tell me that you are interested in exploring the feasibility of a gain reaction from a PF, I don’t have a problem with it. If I reviewed a reasonable proposal I would probably green light it. Don’t write a proposal that says in five years I will have working reactor regardless of the fusion reaction. It is unrealistic. I take the LPP project as an example. They are two years in and there are problems with arcing and pulse power. Every project has these glitches. Some take days to resolve, some take years. ITER, NIF and all the alternative confinement concepts will suffer these problems before they can answer the question of whether they work or not. It is these unknowns that make estimating the economics very difficult. You speak of turbines which I agree are costly, but the economics are well known and cost effective as we currently use them and electricity cost are not obscene.

If you believe that aneutronic fusion is so economically viable I give you this economic calculation for consideration. FoFu reactor in production must run at 200 Hz. The only switch that exists that has a hope of operating in the regime is a thyratron which carries 11 kA per switch at voltages of interest (<100 kV). For a 3 MA PF, you need 273 units for this device rounding up for decimal places. A typical thyratron costs $3500. Imagine you can buy them in bulk for $500, so you need $136.5K per burn out. Each switch lasts 5E7 shots. At 200 Hz each switch lasts 69 hours so at 5 MW, the energy generation is 347 MW-hrs. Using the US average cost paid by the consumer of $0.133 per kW-hr ($133 per MW-hr from http://www.bls.gov/ro9/cpilosa_energy.htm), the plant makes $46151 while it costs $136.5K. Hmmmm. Even if you double the money made by selling the heat from the reactor you are still coming up short. I would argue this is a blue sky calculation so the real system would cost more per 69 days. This neglects any people to work on the plant, ES&H, other parts that might fail like electrodes or capacitors, etc. This is a doomed business proposition on micro-economics alone. If you want to argue about the cost of carbon in the atmosphere and long term effects, it is all good and well but sell the technology as necessary to save us from global flooding and wars. People might consider paying 50% more for electricity if they know it's going to save lives, provide energy independence, etc. And yes, I do consider a gov't subsidy a cost to the people.

If the next argument is that next gen switches need to be developed, I agree. Those are 10-15 years away at the current pace. The Army is driving the development pretty hard for their applications but that darn physics keeps cropping up in a disagreeable ways. Even with the next amazing step, the cost of solid state which offers 1E10 shots per cycle costs ~$1000/J. FoFu power plant will requires something like 100kJ stored to produce 3 MA reliably so a capital investment of $100M in the pulse power alone. It runs at 200 Hz for 1E10 shots or 13888 hrs. Again, a 5 MW power plants so you make, $1.9M using $133 per MW-hr. This assumes the replaceable materials cost, people, ES&H ,etc less than 2% of the initial capital investment in the pulse power to make money. You might have a leg to stand on with economies of scale if you can amortize the cost of the plant over many years. The cost of solid state pulse power is not going to drop below $100 per J in the near future so you will be right on the edge of economically viable in 10-15 years with some gov’t subsidy to hide the cost.

This neglects all the really complicated issues like source reproducibility over the long run, beryllium chemistry with hydrogen and boron, electrode erosion, neutron production, etc. It really doesn’t matter which subsystem is the cost driver, it is the total cost that matters or return on investment. Fusion might have better efficiency of conversion, more compact geometry, no carbon, but as an energy source it costs more than anything we have now even in the most promising case. When all is said and done, it will cost more than this simple calculation while the cost of energy will only increase by 10-20%.

Should we pursue fusion science? Sure. Fusion energy comes after fusion science is proven and proper cost modeling is possible with all the factors considered. Is economics the only reasonable driver? No, but those decisions are above my pay grade.