Recently, I came across details about Nickel-Iron batteries. Compared with Gel Batteries, they are more expensive, a bit heavier, not easily available...
Why are they so interesting? Well, Gel (and Lead-Acid) batteries have lifetimes measured in the hundreds of charges. Nickel Iron (Ni-Fe) have lifetimes measured in the decades. Lead based batteries have their lifespans drastically cut short by overcharging, discharging too deeply, or higher than optimum temperatures; Ni-Fe don't suffer from those problems. Nickel-Iron can also be home made, which is nice, although there are a few people offering them - one large but international, one more local to me. If it concerns you, they are also not made from toxic or extremely hazardous materials
They are more expensive than ordinary Lead batteries, but have none of the disposal problems. If you want them to last, Lead based batteries don't like having more than about a quarter of their capacity drawn out of them before they are recharged. So, if you can draw three-quarters of the capacity out of a battery, the price balances out. Then take the fact that lead batteries have a maximum life of about a decade, when Ni-Fe are rated for 30-50 years... I think I know which I'd prefer to work with.
Having said that, I have a large lead battery not doing anything, and no budget at the moment for a big bank of Ni-Fe ones yet... Admittedly, I wouldn't say "No" to reviewing some, if they were offered.
What good is producing power if you can't store it?
And if you can store power, all that energy can be made to do work later.