I am hoping to start installation of my own solar array this summer (northern hemisphere) and planned to also use an arduino to control the system.
My plans are larger scale, I plan on 8 or so 4x8 panels collecting and a 1200-1500 gallon tank. I had planned to use the one wire sensors as well, but connected on a bus. I had planned on monitoring each panel individually, both in and out ports.
I'm curious why you specified the DS18B20 part and warn not to substitute?
I'd also like to contribute back to this project as I go along, if that were acceptable to you.