When one considers an energy audit, one “rounds up the usual suspects”, as they said in the movie Casablanca: lighting, envelope, HVAC. However, there are other major users of energy not always considered during an audit. One that can result in significant electricity savings is replacing a constant speed fan or drive with a variable speed unit.

A study has found that upgrading fans to include fan speed controls in an intense area of electricity usage, such as a data center, can reduce both the facility’s electricity usage and average and peak electric power demand by 40 to 70%. Since many buildings’ electricity costs are due to both total and peak usage, this is important. A joint study of a 135,000 square foot data center in California by Digital Realty Trust (the owner), Vigilent Corporation, and Lawrence Berkeley National Laboratory focused on replacing constant speed scroll fans with electronically commutated motor variable speed fans of a more efficient design and deploying an energy management system to control fan speeds and computer room air handler output.

Variable speed fans using energy management software led to a 66% reduction in electricity usage for cooling compared to using a constant speed fan, on at all times. Additional energy savings were also achieved by improved temperature distribution. In all, power usage effectiveness (PUE) was improved by 8% and 2.9 million kWh were saved annually.

Variable frequency drives (VFDs) for motors can also reduce wasted electricity. In starting a motor, a VFD initially applies a low frequency and voltage, thus avoiding high inrush current. After the start, the VFD can increase frequency and voltage at a controlled rate. A motor using a VFD can develop 150% of its rated torque while the VFD is drawing in less than half of its rated current. The stopping sequence is just the opposite of the starting one. The frequency and voltage applied to the motor are ramped down at a controlled rate. When the frequency approaches zero, the motor is shut off.

According to the IEEE, there are over 40 million motors operated in the U.S., using up to 60% of total national electricity. IEEE believes that VFDs can cumulatively reduce electricity consumption by about 18% for all such motors.

Another cost-saving approach to consider is an energy management system to provide a graphical view of the heat profile in a room, such as a data center, allowing operation of an HVAC to be more efficient while ensuring equitable cooling to protect equipment.

CCES has the experts to assess whether and by how much your facility can benefit by switching to VFDs and variable speed fans, can provide you with other ways to reduce your energy usage, and maximize your financial return. Contact us today at karell@CCESworld.com or at 914-584-6720.