Hi, my name is Puck, and I'm a dwarf fortress addict, who, let's face it, fails hard at maintaining any noticeable military force.
I can keep the little buggers happy and drunk (one probably implies the other anyway) but for the life of me, I can't get them to fight properly.
Tantrum spirals might be only one unlucky accident at the construction site away, at certain times at least, I don't even want to begin thinking about what would happen if they actually had to do some stuff that's, in comparison, really dangerous. So I came up with what I call the "Lazy ass Puckster automated double bridge defense 2000 ™".
I tried to build a defense system that uses the pathfinding AI of the goblins to trap as many as possible in one go. It could probably be built differently with a higher kill rate, but I found the workload for building/efficiency rating rather perfect. 1 Bridge was not enough, 2 was just fine. I could think of different combinations that would catch more, but I think it's just not worth the resources.
First you dig two holes, three tiles wide and as long as the maximum bridge length (10 squares?). The depth is up to you. Depends on what you want to do with possible intruders. Between the pits you need 2 spaces solid floor (on the ground level, the pit below can be one piece, 22 tiles long). Then you add six pressure plates, (hostile creature triggered, full weight range) at certain spots. Link EVERY plate to BOTH _retractable_ bridges. Looks like this, assuming your fortress entrance is to the left
(P=Plate, X=Bridge, #=Floor):
PXXXXXXXXXXP#XXXXXXXXXX
PXXXXXXXXXXP#XXXXXXXXXX <-- add gobos from here
PXXXXXXXXXXP#XXXXXXXXXX
Make sure the LOS from the entrance of your fort to the bridges is blocked. That's because it helps your retreating dwarves as well as the occasional inside/outside dancers from getting shot. (I'm lazy, remember? "Stay inside" is about as much micromanagment as I can handle) I like to accomplish this with some walls that create narrow paths. Those are perfect for setting up some failsafe weapon traps as well, which you need, because if two full sieges come along, one or two lone runners WILL make it across. Then make sure the bridges are the only way to your entrance/weapon trap area, by walling the whole thing off in an according manner.
Since the bridges are 3 tiles wide you can set up the trade depot somewhere in the "inner courtyard" area, if you want.
Some things to remember:
you probably need an access shaft to the pits below the bridges. For one, to properly and nicely dig it, and maybe because you want to loot the corpses. I suggest walling off the entrance and removing that wall as needed as well as some lockable doors; you don'T want to get screwed over by a single troll that survives the dive.
Also consider an "emergency escape shaft" from your entrance bypassing the bridge setup, just in case something destroys the bridges for one reason or another. Wall that one off til you need it, too
Flying creatures obviously will bypass that setup. I think you can get rid of them by building ceilings over the weapon trap area. (The only dragon attack I had so far ran into a goblin siege or two, because the dragon got stuck somewhere. They duked it out. I think I had some manticores or chimeras or wotstheirname, that died from the weapon traps with ceilings)
I hope I explained it properly. Just had my first coffee...
Oh and about the windmill: couldn't you just build one, just for testing, select it with "q" or summat and then see if it creates power? I don't think you can check wind properties otherwise. You can always dissassemble the thing afterwards.
That being said: WATER POWER IS SUPERIOR (because it has a higher potential to kill everybody in a spectacular manner)