Hello Kent,
We just got a new solar panel with battery back up built-in. It can be used with a single camera and a wireless access point to shoot the image back to your main location, or it can also be paired with our 4G capable camera and another camera and accessed via cell service.
https://www.securitycameraking.com/product/120w-solar-panel-w-controller-45whr-battery/
This solution is fairly straightforth and easy to set up and use, or you could go with calculating the average amount of sun in the location, how much voltage you will need based on the cameras you go with, source a NEMA enclosure for the batteries and inverters, source solar panels, wireless bridges, and then put the entire package together.
If you are savvy, you could put together a fairly complex system and it would work well. Otherwise, the solution we just brought in is fairly straightforward and easy to deploy. Let me know if you would like more information.