Fan and pump motors typically waste over 30% of the electricity they use.
About 40% of all electricity used by industry is used to power fans and pumps. The vast majority of these fans and pumps are driven by across-the-line motors, and any necessary variation in system output is generally achieved by throttling or dampening the system with a control valve or damper.
Figure that cooling fans and pumps are sized for the worst case operating conditions (i.e. the hottest day, or the highest demanded flow). However, most of the time, actual operating conditions require less than full design flow. Consequently, significant amounts of energy are expended unnecessarily and the operating cost of the system is as much as 50% higher than it needs to be. There are also indirect cost savings associated with extending motor and/or impeller life, reduced maintenance, and a reduction in noise levels.
In the case of fans, the affinity laws demonstrate that the power consumed is the cube root of the fan speed. In other words, at 50% flow, the energy consumed is only 12.5% of the same fan running at full speed. This is shown in the graph below. Even at a modest 15% reduction in fan speed, the energy savings is an incredible 40%!
The energy savings priciples in centrifugal pumps is a little different than in fans. When using a centrifugal pump, throttling the output with a flow control valve increases the system impedance, effectively increasing the total dynamic head in the system. This increased pressure wastes energy in the pump. A variable speed drive used to reduce flow saves energy by reducing the head pressure and thus the total power required by the system. This potential savings is demonstrated in the graph above.
Other advantages of reducing the pump speed via a variable speed AC drive include reduced wear and tear on pump impellers, less maintenance on impellers, and bearings, as well as reduced operating noise levels.
Please contact us to discuss your energy savings opportunities. With a typical payback of 6 to 12 months, you’ll soon be realizing lower operating costs and higher profits. In today’s high energy cost environment, this should be a top priority for every company trying to remain competitive in this tough economy.