A variable-frequency drive (VFD) is a device that controls the rotation speed of an alternating current (AC) electric motor by modulating the frequency of the electrical power flowing into the motor. When used in conjunction with the ventilation and cooling system of a refrigerator or freezer, a VFD can save energy by decreasing the speed of the compressor when the target temperature has been reached, cycling it on and off as needed.
Air economizers help cool indoor air temperature by drawing air from outside a building when the air outside is cooler than the air inside. The cool air induction reduces the workload of an air conditioning unit, thereby saving energy.
Utilizing air economizers and variable frequency drives saves energy by reducing the workload and operating time of a compressor motor. This in turn extends the life of the compressor and decreases utility bills. Depending on the climate and season, energy savings can potentially be very large. In winter months, the compressor may not have to go on for long periods.
Read more about the benefits of air economizers.
Challenge Participants Currently Adopting This Practice
- Boston Copley Marriott Hotel (project story)
Financing Options, Incentives, And Rebates
- Mass Save Variable Speed Drive Incentives
- Utility Rebates – MMCIIP | Columbia Gas | WME
- Local Rebate – Cape Light Compact
- Mass Save – Technical Assistance and Engineering Services
- Rise Engineering Small Business incentive
Examples of Boston Area Businesses Using VFDs or Outside-Air Economizers:
- National Resource Management | Commercial Refrigeration Case Studies
- Green Boston building
- Boston College
- Boston University Case Center
In The News
- “Empire State Building Receives Energy Efficient Makeover” Daily Tech, October 2010
- “Integrating lighting and HVAC retrofits” Engineer, October 2010
- “Walk-In Coolers Part of C-Store Savings” The News, July 2006