How do places with wind and solar energy sustain their power?

Some places rely on solar and wind energy right? To power their homes and such. How do they use energy in the night or when there is no wind? Do they have something that stores the energy like a big battery or something?

I have to “make” a green city and it will use renewable energy source including solar and wind energy. How would I make the wind and solar energy sustainable and not have shortages of power?

Small places, like a remote house or an island, might have batteries. A large place, like a city, would be connected to a "Grid", or electrical energy transmission system. If the wind stopped blowing, deep in the night, they would pull energy off the grid, from a nuclear plant, or coal-burning generation station, or hydroelectric project many miles away. A town on an island might have a large diesel generator.

I came accross a new, proven and tested home made wind power system and solar power system which eliminates our electricity bills. It was written by a Renewable energy enthusiasts Michael Harvey the diy called Earth4Energy. You can get your copy to save energy and help environment while eliminating your power bills. Get it from here: http://homemadeenergyreviews.blogspot.com/