I don't know how well this would work for you, but I actually have an Android app I created that I am running as my webcam for Weather Underground. I'm using an old cell phone (Android 4.4), but it works on newer phones, too. Mine is plugged in, and is sitting indoors in a window, but there are solar chargers for cell phones, as well as weatherproof enclosures. So I would think something could be rigged up.
The app can ftp to whatever server you tell it. The image can either have a name of your choice (such as "image.jpg" for WU), or a built-in name with a timestamp. It allows you to pick the picture interval, the crop settings, a scaling factor, and you can set an optional maximum file size. It adjusts the JPEG quality to meet the size. You can also tell it to ignore black images.
I have no idea how much power it is actually using, but the app isn't doing anything until the timer says it is time to capture another image.
I hope to put it on the Play store in about three weeks after I make sure it is robust.
Full disclosure: I plan on charging a dollar or two for the app, so that after a few people buy it I will be able to tell my wife all those hours I spent working on the app were clearly worth it!
