I suspect they're referring to the use of PV cells in lighthouses, Light-Buoys, Wireless Relay Stations, LORAN (pre GPS marine navigation) stations, etc.
Economics at the time restricted their limited use to mountainous areas, deserts, isolated areas, remote island outcrops, etc.
I saw PV use in the 1970s in remote Austalian rail operations to power signal boxes and repeaters .. the higher costs offset the equally high costs of maintaining a fueled generator in a remote location.
Marine shipping wasn't, to the best of my recollection, directly using PV's shipboard as they already had massive engines driving propulsion and it was trivial to bled off a little torque for a electrical generator.
Economics at the time restricted their limited use to mountainous areas, deserts, isolated areas, remote island outcrops, etc.
I saw PV use in the 1970s in remote Austalian rail operations to power signal boxes and repeaters .. the higher costs offset the equally high costs of maintaining a fueled generator in a remote location.
Marine shipping wasn't, to the best of my recollection, directly using PV's shipboard as they already had massive engines driving propulsion and it was trivial to bled off a little torque for a electrical generator.