A breeze across the skin gives ~ 3 degree cooling effect as it evaporates the water off your skin. Unfortunately sometimes its too hot to open the windows, or there is no breeze. That's where fans come in as a low energy alternative... but that's not all they can do.
Fans have 2 setting, usually controlled by a switch on the fan body. A summer setting for blowing air down at you to get that cooling effect with higher speed air. And a winter setting for blowing air up. During winter when you are heating your house, the hotter air will rise to the ceiling, and in raised roof area like the picture above, air temperatures can be 3-5 degrees warmer near the ceiling. Running the fan at a slow speed brings the heat down and mixes the air volume, without making a fast enough breeze to trigger the cooling effect. At the Marion house and the Solar Sollew, this was automated by MachTech with a temperature sensor at ceiling level and another at person level. When there is a 1 degree temperature differential the fan goes on, which it may do a couple of times an evening for a few minutes. A movement sensor is also integrated in the system so that it doesn't run if no-one is home. While this is a clever option, simply turning it on yourself if you are feeling a bit cool may bring enough warm air down make you comfortable.
With fans, the bigger ones with more blades are generally the biggest air movers. Look for ones with an aeroplane propeller design, or a 23 degree pitch on the blades as these tend to be the most efficient. LED Lights can also be added to check off 2 functions with the one item.