Saving Money with Ceiling Fans
The Purpose of Ceiling Fans
Ceiling fans convert electrical energy into mechanical rotation which drives fan blades. The fan blades displace air as they move creating a front that propagates toward the inhabitant, who experiences the effects of a gently breeze.
Why Fans are Desirable
So fans produce wind, that's basically all they do. Why do people like this? Everyone knows that a breeze feels good, but what causes this phenomenon? Here's the solution. As the wind passes over the human's skin, heat from their body is conducted into the relatively higher air pressure (caused by the fan) surrounding them. As the flowing air continues on it's path, it carries this heat, from their bodies, with it, dispersing it elsewhere, causing a local temperature drop. However, since the air typically lands (stops moving) in the same room, or at least in the same home, there is no overall temperature drop. There is only a relocation. Additionally, if water is on the user's skin, like sweat for example, the blowing air acts to help cause evaporation of this fluid by increasing its surface area, by flattening it out. As the water evaporate, it carries a proportionally larger amount of heat off with it, which depending on the exact composition of the fluid, can actually cause temperature drops into the negative degrees.
If No One is Around Does a Fan Help?
Some people incorrectly assume that ceiling fans somehow act to lower the temperature of the room. They believe that since ceiling fans are cheaper to operate than the air conditioner (which is true) that turning off the air conditioner and turning on all of the ceiling fans in the house will save money, while providing the same amount of comfort. This is wrong! An unoccupied room, with a ceiling fan on, is only wasting money. It's an example of someone paying money to provide the electricity to move air around in a room, with no net result. Sure there will be wind in that room, but with no one in there to enjoy it, it's only blowing the air around. The average temperature in the room remains exactly the same.
Saving Money with Multiple Fans
An interesting effect of motor efficiencies is that often motors use less power than should be expected at lower speeds. For example, a motor run at half speed might use one quarter the amount of power. This is counter intuitive, but in fact case, due to the specific efficiencies of the motor. I noticed a few months ago, when purchasing new ceiling fans for my home, that two fans placed side by side in the living room on the LOW setting, would produce more wind that a single fan on HIGH, but use half the power. For this reason I highly recommend installing two ceiling fans anywhere where the high mode is used in your home. This will allow you to use your air conditioning less often, and will pay for itself faster, and save more money in the long run.
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