Variable-speed drives deliver constant savings
Energy-cost savings of £20 000 a year are being achieved in the Omnibus building in Reigate following the installation of ABB variable-speed drives on HVAC plant. The building was completed in 2001. It is based on a disused bus garage and is a multi-tenanted building with over 6000 m2 of office space. [Assuming an electricity cost of 10p/kWh suggests that a cost for CO2 permits of about £1200 a year could also be saved.]
An energy appraisal carried out by Econowise Drives & Controls found that motors driving pumps were all running at full speed, with flow controlled by mechanical throttling.
The survey also found two variable-speed drives in an air-handling unit were running at constant speed. The PID controller on the exhaust fan was reprogrammed to accept signals from a CO2 detector to run at an appropriate speed to remove the CO2. The two drives were connected so that the speed of the supply fan matched the exhaust fan.
The investment was about £14 000, giving a payback of less than nine months on energy costs alone.