Synchronous and Cogged Fan Belts
FINDINGS #12, March 2013
Synchronous and Cogged Fan Belts Improve Efficiency, Save Energy
Ventilation fans consume a significant portion of the electricity used in U.S. commercial buildings. In fact, ventilation accounts for approximately 12% of total commercial-building electricity use.(1) Total fan energy use is higher still, due to the presence of beltdriven fans in cooling towers and other non-ventilation applications. Inefficiencies account for some of this electricity use, specifically losses that occur during the transfer of energy between motor shafts and fans. Two innovative fan belt technologies that replace the standard V-belt address this issue. Cogged V-belts reduce the amount of material on the inner surface of the belt, and are designed to reduce the bending resistance as the belt travels around the sheave. Synchronous drive belts have teeth that integrate with slots in the sheave (much like a bicycle or motorcycle drive) and are designed to reduce both belt slippage and frictional losses. Belt manufacturers claim energy savings of up to 5% for synchronous drive belts(2) and 2% for cogged V-belts.(3) While this is a small portion of overall building electricity use (between 0.3% and 0.5%), this technology offers a simple and inexpensive way of reducing ventilation energy use. Recently, GSA’s Green Proving Ground (GPG) program, Rocky Mountain Region, put synchronous drive belts and cogged V-belts to the test on two different fans in the Byron G. Rogers Federal Building and U.S. Courthouse in Denver, Colorado. Findings included energy savings up to 20% and simple payback for synchronous drive belts of less than four years.
What We Did
RESEARCHERS COMPARED BOTH BELTS TO INCUMBENT TECHNOLOGY
The Rocky Mountain Region GPG team commissioned the National Renewable Energy Laboratory (NREL) to perform measurement and verification of cogged V-belts and synchronous drive belts on both a constant volume (CV) and a variable air volume (VAV) fan at the Byron G. Rogers Federal Building and U.S. Courthouse. These motor/fan combinations were tested with their original, standard V-belts to obtain a baseline for standard operation. The standard V-belts were then replaced with cogged V-belts, and finally with synchronous drive belts. The power consumption by the motor was normalized for both fan speed and air density changes. Energy savings and operation and maintenance (O&M) savings were compiled into an economic life-cycle cost analysis of the different belt options.
What We Measured
MONITORING ENCOMPASSED SEVERAL CRITICAL VARIABLES
Monitoring consisted of measuring real and apparent electricity consumption, fan speed, motor speed, and sound level of the two fans with their original V-belts, then repeating the measurements for the cogged V-belts and the synchronous drive belts. Electrical performance was monitored for each belt placed on the CV fan for a period of between 3 and 5 minutes, with data recorded at one-second intervals. Monitoring captured both the start-up and the steady-state operation of the CV fan. The variable frequency drive (VFD) on the VAV fan was placed into “hand mode” and the frequency was set manually in increments of 5 hertz (Hz), from 15 to 60 Hz (the maximum), to capture the performance at different fan speeds. Approximately 2 to 3 minutes of metered data were recorded at each frequency, along with fan speed, motor shaft speed, and ambient noise.
What We Concluded
SYNCHRONOUS DRIVE BELTS AND COGGED V-BELTS BOTH REDUCE ENERGY CONSUMPTION
Both synchronous drive belts and cogged V-belts reduced energy consumption when compared with the incumbent V-belt technology. Savings were greater on the VAV fan and were highest at lower fan speeds. Both types of belt demonstrated a lower life-cycle cost than the standard V-belt. For cogged V-belts, this was due solely to reduced energy usage; O&M costs stayed the same and the cost of the belts themselves was only slightly higher. For synchronous drive belts, lower life-cycle costs were a result of greater energy savings, a 75% reduction in O&M costs, and competitive belt replacement costs: one synchronous drive belt can perform the task of multiple V-belts.
CORRECT FAN CHOICE AND EXPERT INSTALLATION ARE KEY
Synchronous drive belts and cogged V-belts provide a relatively simple, low-cost way of achieving energy savings, but they must be installed correctly and applied in appropriate situations.
- For VAV fans, the synchronous drive belts performed well and showed savings at all ranges of fan operation.
- For CV fans, cogged V-belts are the best solution. Synchronous drive belts pose risks when combined with the CV fan’s high-torque starts and increased operational speed.
- With both types of belt, higher operating hours and higher electricity costs will result in shorter payback periods.
- No significant change was noted in the sound levels generated by different belt operation.
For more information, contact Kevin Powell firstname.lastname@example.org Green Proving Ground Program Manager.
2. Energy Savings from Synchronous drive belts. The Gates Corporation. http://www.gates.com/ptPartners/file_display_common.cfm?thispath=Gates%documents_module&file=Energy%20 Savings%20from%20Synchronous%20 Belt%20Drives.pdf&location_id=3427. Accessed 26 June 2012.
3.3Energy Tip Sheet #5. Motor Systems.Industrial Technologies Program. Office of Energy Efficiency and Renewable Energy. Department of Energy. September 2005. http://www1.eere.energy.gov/ manufacturing/tech_deployment/pdfs/ replace_vbelts_motor_systemts5.pdf. Accessed 26 June 2012.
Reference above to any specific commercial product, process or service does not constitute or imply its endorsement, recommendation or favoring by the United States Government or any agency thereof.