The wind does indeed always blow and the Sun does always shine. Sometimes the wind isn't blowing in some places rather than others, sometimes the clouds or the Earth get in beweeen us and the Sun. That's a matter or organising ourselves a bit better.

There are lots of ways of storing up energy so it can be available as and when we need it. Using it to punp up water to a higher resservoir is just one low-tech example, and there are plenty more. "Bio-mass" - using solar energy to grow stuff you can burn later - is another.