So are you woried about imcompatible power or having no access to power at all? The chargers that are desgined for the Nook work from 120 to 240 V, so you only need a travel adapter to make it fit in the power socket of where you are going.
On the other hand if you are looking for a way to charge it where there is no power you can get both solar usb chargers as swell as hand crank radios (http://www.amazon.com/FR160B-Microlink-Self-Powered-Weather-Flashlight/dp/B001QTXKB0/ref=dp_cp_ob_e_title_3 that have usb chargers.
Also there are hand crank power adapters that have a cigarette lighter adapter
that you can generate power from and charge your Nook The 12 cigarette adapter would require a simple usb adapter that plugs into the cigarette lighter socket. So you really have plenty of alternatives.