When the fan is running, it causes air to move. Think about it: Air that was
not moving a few moments ago starts moving, so it must have gotten a kick
of energy from somewhere. That's the energy that started out at the power-
plant as nuclear energy in a uranium rod or chemical energy in a lump of coal,
moved from the power-generating plant to your house as electrical energy, and
made the fan spin. Finally, it ended up as 'kinetic' energy of moving air.