Jed Rothwell wrote:
Mike Carrell wrote:
It was millions of windmills, not millions of wind towers.
That's true. A large wind turbine produces 1 or 2 MW nameplate, 0.3 to 0.6 MW actual. The wind tower being planned in Australia will produce 200 MW nameplate, and I suppose about the same actual. So it would take ~300 times more wind turbines than towers to produce an equivalent amount of energy. And 4 or 5 towers will produce as much power as one average U.S. nuclear plant. As I pointed out yesterday, it would take 2,500 towers to supply the US, or millions of wind turbines.
The big difference is land area. The wind power in takes up 10,000 ha, whereas 300 wind turbines take up for the land space, because the base of the tower is small. A nuclear plant takes up very little land area: 100 to 500 ha in the U.S.
The average nuclear plant is about 980 MW I think, and in 1999 the capacity factor was 88.5%, which is lower than I expected. In other words "actual" size is around 870 MW.
I don't understand this. I'll expose some ignorance; perhaps someone can address it:
Is 980MW the "shaft power" -- the available mechanical power which can spin generators? Or is it the actual heat output, a measurement of how many grams of water the reactor can boil?
Surely it's the former? These things run steam turbines, right? So they're heat engines. The efficiency of a heat engine is limited to something like (T(hot) - T(cold))/T(hot), so for superheated steam at, say, 1000 degrees F ~ 800 degrees K, coming down to seawater at roughly 300 degrees K, the thermodynamic efficiency should be something like 60%. Or do they push the steam up a lot hotter than 1000 degrees? At 2000 degrees it looks more like 70% maximum efficiency; at 3000 degrees the pipes start getting soft and we're still not looking at 88% (unless they've got some source of supercold water to cool the reactor).
So going with 1000 degree steam, if it's producing 980 MW of mechanical energy, the core must be putting out something between 1600 and 2000 MW of heat energy, roughly half of which gets dumped into the ocean or into the air. Yes?
So, if this is correct so far, is the 88% "capacity factor" then scaling down from there -- the efficiency of the mechanical -> electrical conversion, which is less than 100% due to inefficiencies in the dynamoes and the linkage to the grid? Or is there something else going on that I also don't understand? (Most likely...)
