Been some solar panel discussion on posts.
Mainly because a year of batteries for 24/7 Pi turns out to be car sized.
As big as a car
Not a car battery.
Basic you are looking at 100W for 24/7 but that is outside.
With lights on 24/7 maybe 20W, except the power you get from lights is 1000 times less.
I've done some tests with special low light panel 40mm sq, it will give 40uA inside, outside it is 40mA.
Maybe panels really close to light, thin film ones are best for the low light levels.
Swapping batteries weekly may be a way to do it.
Model Zero - 80ma 5V battery 1.92Amphr/day - 13.44Ahr/week, so a standard 12V 9Ahr gel cell should work.
Bigger Pi's = bigger battery
You can now get 12V/9Ahr LiFePO4 equivalents, much lighter and probably you will get more cycles from them.
Seen them for as low as $70, you can get them up to about 20Ahr, getting common for motor cycles etc.
If you can duty cycle then, much longer battery life,
Turn Pi on 1 minute every 5 minutes and you now have a monthly battery swap.
Turn it on for 10seconds every 10 minutes and the same 12V9Ahr battery is now a yearly swap.
10 second boot? Well that's one reason I use Ultibo, 2 sec boot
Add solar to this and maybe no swapping.
As they are in Network closets then you have cables you can do POE with.
You just inject power at the other end, at the PC/terminal/wall socket end.
You just need a power splitter in the closet to get the power off the cable.
Just make sure the cleaners don't unplug your power injector so they can use their vacuums
Only need access to just one cable per closet to get POE into it.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges