Fans are used in boilers, furnaces, cooling towers, and many other applications. As in other motor applications, considerable opportunities exist to upgrade the performance and improve the energy efficiency of fan systems. Efficiencies of fan systems vary considerably across impeller types. However, the cost-effectiveness of energy efficiency opportunities depends strongly on the characteristics of the individual system.
Fans | Energy Conservation In Plants
Fan over Sizing
Most of the fans are oversized for the particular application, which can result in efficiency losses of 1-5%. However, it may often be more cost-effective to control the speed with adjustable speed drives (see below) than to replace the fan system.
Adjustable Speed Drive (ASD)
Significant energy savings can be achieved by installing adjustable speed drives on fans. Savings may vary between 14 and 49% when retrofitting fans with ASDs.
For instance in an identified the opportunity to install ASDs on six motors in the cooling tower (ranging from 40 hp to 125 hp) where the motors are operated manually, and are oversized for operation in the winter, ASDs installation for all the six motors to maintain the cold-water temperature set point can result in about electricity savings of 1.2 million kWh/year. However, it is important to note here that the payback period would be relatively high due to the size of the motors for an annual savings of about $46,000.
High Efficiency Belts (Cog Belts)
Belts make up a variable, but significant portion of the fan system in many plants. It is estimated that about half of the fan systems use standard V-belts, and about two-thirds of these could be replaced by more efficient cog belts. Standard V-belts tend to stretch, slip, bend and compress, which lead to a loss of efficiency. Replacing standard V-belts with cog belts can save energy and money, even as a retrofit. Cog belts run cooler, last longer, require less maintenance and have an efficiency that is about 2% higher than standard V-belts. Typical payback periods vary from less than one year to three years.
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