Today's joke is based on the double-meaning of fan.
The big objects you can see in the picture are wind turbines. They look like large fans - the machines you use to keep you cool.
We also use fan to describe someone who likes and admires someone or something:
"I'm a big football fan."
"She's Justin Bieber's biggest fan!"
Renewable energy is energy that comes from resources which never run out such as sunlight, wind and water. Oil is not a renewable energy.