Comment on the statement, "Because batteries must be replaced regularly and contain very toxic materials, the OFF-grid systems probably do more harm than good in the long run. Until battery technology catches up." Look at Thomas Alva Edison "Primary Battery" patent of 1906. It is the Alkaline battery using Nickel/Electrodes. I can provide an article that tells how to collect the pieces and build it. Some are claimed to have worked for over 80 years. Minimal emmisions. Only needs water top-up approx. each 3 weeks. Electrode replacement approx. 10 years. Made from readily available, locally purchased parts 1.5 volts DC per cell. 10 cells=12VDC. 20 cells=24VDC. 40 cells=48VDC. Will completely discharge w/no damage. Will take fast charge without damage. Each cell housed is cheap ex-chemical containers of 20 USGallons. I have complete instructions in MSWord format.