How can solar energy be used when the sun is NOT shinning?

Answer 1

In the long run, ALL energy is solar energy. When the Sun is shining down on us, we can use photovoltaic solar panels to directly convert the light into electricity.

When the Sun is not shining on us (because it is cloudy or at night) we continue to use stored energy, in several forms.

First, we might have set up batteries to store electricity from our solar panels; today's solar power stored for tonight.

Or, we could use a fuel like alcohol, sometimes produced from grain, corn or other plants. The plants grew in the sunlight, we fermented the grain into alcohol and we're using last YEAR'S solar energy today.

We make our campfires out of wood. The trees grew in the sunlight over the course of years, so when we cut down the trees and burn the wood, we're using solar energy stored up 50 or 100 years ago.

Coal, oil, and natural gas; solar energy stored in plants that died millions of years ago, trapped in the dirt and converted to petroleum by pressure, heat and time.