Certainly the GPS navigation equipment on board a vessel could fail in the event GPS signals are jammed or otherwise inoperable. As for the navigation aids the

Certainly the GPS navigation equipment on board a vessel could fail in the event GPS signals are jammed or otherwise inoperable. As for the navigation aids themselves, as of a decade ago there were no GPS devices in the aids (though a GPS receiver is used for precise placement of buoys). The navigation lights in (or near) the lighthouse structures use large lead-acid batteries for energy storage, and a large solar array for charging. When I left, we were in the process of converting many of the aids to LED lamps, which use far less energy (thus reducing the size requirements of the batteries and solar arrays). For the larger lamps, we had a pretty complex box with the electrical equipment to manage charging, flash patterns, backup lights, etc. (the old "SACIII" aka Solar Aid Controller). The electrical systems are all pretty neat but really don't need the "shelter" of a lighthouse, and many lights are on simple towers.