If you are concerned about energy efficiency, fans should be an integral part of your home cooling system. They use less energy than air conditioners, cooling only the skin instead of all the air in the house. Some fans cool single rooms, and others move air through the whole house. Before you decide on purchasing a particular kind of fan, learn what makes fans more or less efficient. This includes understanding the difference between a high-capacity and high-velocity fan.
The efficiency of a fan is determined by how much air it is able to move, how fast it moves that air and how much power it consumed to move it. A fan's capacity, or the amount of air that it can move, is determined by the shape and size of the blades, number of blades, shape of the case, speed of the blades and power of the fan's motor.
A high-velocity fan rotates very quickly. This certainly will help it to have a higher capacity. This may even help it operate at a higher efficiency. However, this does not guarantee that the fan is a high-efficiency fan. Poor blade design can still keep the overall capacity low. A bad motor can waste power, keeping the overall efficiency low.
Energy and Velocity
Additionally, increasing the velocity of a fan is a very bad way of increasing its efficiency. The energy required to turn the fan increases much faster than the speed. Doubling the speed requires four times as much energy. Tripling the speed requires nine times as much energy. Additionally, motors themselves work less efficiently when they heat up, making high-speed fan motors less efficient.
A fan that has a good blade design will have a higher capacity at all speeds than one that doesn't. This method of increasing air capacity requires no extra energy. Purchasing a fan rated as a high capacity fan is always going to be the best option for energy efficiency. You can run a high-capacity fan at a lower speed than a low-capacity fan and still get the same degree of cooling for much less energy. As an additional bonus, high-capacity fans at low speeds also make less noise than low-capacity fans running fast.
- University of Central Florida: Measured Ceiling Fan Performance; Sonne and Parker; 1998
- Georgia State University Hyperphysics: Kinetic Energy
- Iowa Energy Center: A Fantastic Alternative
- U. S. Department of Energy: Cooling Using a Whole House Fan
- U. S. Department of Energy: Estimating Appliance and Home Electronic Energy Use
Jason Thompson has been self-employed as a freelance writer since 2007. He has written advertisements, book and video game reviews, technical articles and thesis papers. He started working with Mechanical Turk and then started contracting with individuals and companies directly via the Web.