Ther are many AP/Routers available that operater on low voltage 5-12vdc and some that operate on PoE @ 48vdc. I am using Linksys devices as they can operate @ 12vdc and I just use a car battery with a solar panel.

Your issue is one of getting the signal from the PC to the hub. Not seeing the actual site, and going by your description I would guess and say you may need to run several devices to repeat the signal to get it to where you need it. Remember that that an AP/Router doesn't have to be connected to an ethernet card or WAN to operate as a repeater.

I would suggest looking at places where you can install devices in much a manner that you can get a line of site between the builds. This may mean placing a repeater somewhere in between the 2 buildings to achieve this. Then work out how you are going to get the signal to the termination points (clients). This may also mean using a repeater again to get sufficient signal strength to the clients.

Also don't think straight (wifi signals never travel in a straight line). Use devices (APs) to move the signal around obsticals (around also implies over). Also look to using "B" mode only, most if not all wireless devices give much better specs on the lower bandwidth.

I hope that some of my comments are helpfull.

Regards

Fred