Changing from variable pitch in motion to variable-speed takes 70% off fan energy use
Energy usage for a series of fans in air-handling units and cooling towers at the European Bank for Reconstruction & Development has been reduced by nearly 70% following the installation of variable-speed drives on 23 variable-air-volume fans for the AHUs and four cooling-tower fans by Flakt Woods using ABB drives.
The VAV fans in the AHUs range from 30 to 60 kW and previously used variable pitch in motion to regulate airflow. They were not performing to their original specification because of factors such as age and higher cooling requirements. Flakt Woods’ approach to improving their performance was to fix their pitch and control the airflow delivered using variable-frequency drives on the fans.
The cooling-tower fans had 30 kW motors.
Work was carried out over weekends so as not to affect the bank’s operations during the week. The project included integration with the existing Trend BMS, so engineers from Flakt Woods and Trend worked together to ensure the change from variable pitch to 0 to 10 V control via the BMS was seamless. The project took four months to complete.
Before the work was started, operational data for a 30 kW fan was gathered over seven weeks so that a before-and-after comparison could be made.
Before the installation of the variable-speed drive the average power consumption of that 30 kW fan was 22 kW, which fell to 7 kW — a 68% reduction or over 56 MWh a year based on 252 working days.
For the project as a whole, the annual savings are estimated at 1300 MWh, representing 690 t of CO2.
