I'm currently designing solar powered control system using Yuasa batteries  and PV panels. The system currently under test seems to work well, even with the overcast northern skies.

It is interesting using 12 instead of 24 volts, most sensors work quite happily down to 10v, and the increase in current is not a big issue.

Started design work on control system for Heat Exchanger units.  These self contained units recover heat from effluent and are controlled using Siemens S7-200 PLCs  with Germaine Systems' GSM Plantmonitor system.