500 lumens does not sound very bright for a large property. If you want dusk/dawn always on, you are looking at a big system, with a big panel, and a big battery. You are better off just trenching a 24V wire and get a reasonable sized light.
Good point, 500 lumens is not much more than a 40W incandescent puts out. LEDs can do much
better power-efficiency wise of course.
If running low-voltage power cable is accepted, I can't help but think that some of this 12/24vdc
automotive LED "auxiliary" lighting product might provide a solution. It is meant for trucks, farm
equipment, and offroad vehicles but also for fixed use. Most that I've seen are rugged and very
well sealed, and runs from 10-30vdc at constant power/brightness (or nearly so) at very high efficiency.
One issue is that "spot" style lights tend to have narrow beams, but others such as some "light-bars"
may be more like directional floods, possibly having broad enough coverage.
The whole arrangement could be switched from one location either by a timer, photoelectric or even
manual switch.
If power-fail operation is required, arrangement with local battery with charging over power cable is
possible but of course adds cost; and batteries require proper care and be maintained.
Just throwing out a bunch of ideas.
Dave