Home-made Giant batteries
I am not an engineer and don't know the answers to your questions, I just figured out for myself that you cannot get cheaper power anywhere than from a utility company.
Storing energy for use can never compete with generating and simultaneously using (without storage) in price.
Don't be fooled by the common belief (the battle for your mind) that your electric bill is too high, that's crap once you try to do it your own way, as you aparently want to. You will see for yourself.