DIY Renewable Energy for Home

I hear that the new solar panel systems will be affordable and aimed at the DIY crowd so I like to know if my home is properly orientated.
I am located near Napa CA, my home has no roof slant facing the south.

The ones that have solar panels and and when night time comes they automatically turn on. How do they work? This is for a DIY project I want to try. Also how much power to solar panels generate? What size do solar panels come in? Do they come in the small size that are on solar lights? Also can you buy those solar panels and where?
I’m asking about solar lights it because I want to build a greenhouse for a science project. I need lights shining on the plants 24/7. I saw the solar lights and thought that might be a good concept for lights always shining.
I live in a very sunny part of California so whether there is sun or not is not a problem.

DIY, Cleaner ENERGY- Solar construction