Re: Running 12v appliances off a 24v pv system
Technically, I suspect you could get away with running small loads off of an inverter or directly off of DC with no batteries if you replaced the batteries with a large supercap or bank of supercaps. You would need a voltage regulator to insure that the input voltage to the inverter or DC devices never exceeded it's max input voltage.
The advantage to the supercap is that it will last far longer (probably the rest of your life) than a battery but the downside is that it can not store much energy long term. So most of the power would need to be used as it is being made available in real time.
I suspect it will act sufficiently as a resevoir for power to be useful.
Also for long term plans you might look into NiFe ( Nickel Iron) batteries. They have been known to last for 50+ years with just a replacement of the electrolyte (typically a potassium hydroxide solution available as a powder) which can be purchased and stored.
6 SolarWorld 175 (1 KW), 14 Arco Solar 16-2000 (~1.5KW total), 15 REC 250 (3.75 KW) 2 KW 48V Whirlwind turbine, Outback 3648, 8 Dekka Solar L-16's, Outback FM80, Midnite Classic 150, Honda 2000i backup, & Generac 5KW.