Talk-Polywell.org

The transition will happen only in 10 years ... There have been several major proved lithium technologies which can rapidly ramp up production for each car on the planet ...
Plus the global manifactoring of batteries will have the same characteristics as the global semiconductor industry ... vast economy of scale, constantly dropping prices, fearce competition from Asia ...
Ask some cell phone or laptop batteries manufactorers !
Even if you wouldn't add the supercapasitors ( Eestore and the others ..) in 10 years it will be faster , quiter , safer , cleaner and yes cheaper to drive all electric car .. so you would be stupid to drive a one running on chemical combustion

MSimon wrote: http://www.naval-technology.com/projects/nimitz/

The nuclear-powered carrier has two General Electric pressurised water reactors driving four turbines of 260,000hp (194MW) and four shafts. There are four emergency diesels of 10,720hp (8MW).

That is 800 MW at the shaft. Figure 2.4 GWth. For something in the Nimitz class.

Actually, I think that is 194MW gross, all four turbines together. Wikipedia states concerning the Nimitz class carriers:

Their reactor cores are expected to operate for about 23 years.[citation needed] The only ships to use these nuclear reactors are the Nimitz class supercarriers, which have two apiece, each of which generates enough steam to produce 140,000 shaft horsepower (104 MWe).[2]

So the two of them provide 280ish. Close enough.

By the way, given the low efficiencies of PWRs, this would be closing in on 400MWth, each.

Military fission nukes aboard ship ran about 30 to 35% efficient converting thermal to work (in 1966). The efficiency depending on the temperature of the cooling water intake. And of course that is at full power. The efficiency is lower at less than full power.

I'd imagine they might do a little better these days.

MSimon wrote:Military fission nukes aboard ship ran about 30 to 35% efficient converting thermal to work (in 1966). The efficiency depending on the temperature of the cooling water intake. And of course that is at full power. The efficiency is lower at less than full power.

I'd imagine they might do a little better these days.

Yeah but the carnot efficiency betweeen seawater and a reasonable water temperature is still going to be less than 40%. We haven't got that much better since the 60s.

cuddihy wrote:

MSimon wrote:Military fission nukes aboard ship ran about 30 to 35% efficient converting thermal to work (in 1966). The efficiency depending on the temperature of the cooling water intake. And of course that is at full power. The efficiency is lower at less than full power.

I'd imagine they might do a little better these days.

Yeah but the carnot efficiency betweeen seawater and a reasonable water temperature is still going to be less than 40%. We haven't got that much better since the 60s.

True. The added efficiency mostly would come from running the reactors at a higher temp. I think temps are up 25 or 50 C from when I worked on them.

MSimon wrote:Military fission nukes aboard ship ran about 30 to 35% efficient converting thermal to work (in 1966). The efficiency depending on the temperature of the cooling water intake. And of course that is at full power. The efficiency is lower at less than full power.
.

They may have been an experimental Liquid Sodium reactor that got that high, but most run 25-28% total. As the man points out, even Carnot won't give you more than about 40%, and saturated steam Rankine is no Carnot.

KitemanSA wrote:

MSimon wrote:Military fission nukes aboard ship ran about 30 to 35% efficient converting thermal to work (in 1966). The efficiency depending on the temperature of the cooling water intake. And of course that is at full power. The efficiency is lower at less than full power.
.

They may have been an experimental Liquid Sodium reactor that got that high, but most run 25-28% total. As the man points out, even Carnot won't give you more than about 40%, and saturated steam Rankine is no Carnot.

I actually operated the plants and knew the specs. Where does your information come from?

MSimon wrote: I actually operated the plants and knew the specs. Where does your information come from?

If you worked on them and knew the specs, are you not supposed to keep such infomation to yourself, even after you retire?

What I can speak about is my general knowledge of power cycles, thermodynamics and the lot. If this were a genset, optimized to put out electricity, then maybe I'd grant ~33%, but that efficiency at peak shaft HP? No.

KitemanSA wrote:

MSimon wrote: I actually operated the plants and knew the specs. Where does your information come from?

If you worked on them and knew the specs, are you not supposed to keep such infomation to yourself, even after you retire?

What I can speak about is my general knowledge of power cycles, thermodynamics and the lot. If this were a genset, optimized to put out electricity, then maybe I'd grant ~33%, but that efficiency at peak shaft HP? No.

The most closely guarded secret was how they managed to integrate all the shielding elements to keep weight and radiation levels low.

Power levels are given out in open source.

Propulsion: 8 x Westinghouse A2W nuclear reactors,
four sets Westinghouse geared steam turbines, 4 shafts
280,000 shp shp (210 MW)
Speed: 33.6 knots (62.2 km/h)

http://en.wikipedia.org/wiki/USS_Enterprise_(CVN-65)

BTW - back in the day we were only allowed to say: above 30 knots.

Also note that operating efficiency has no tactical meaning for a nuke.