Variable speed drives work by controlling the waveform of the current and voltage supplying the motor, ensuring that it runs no faster than is necessary. |
Fiskeby is a major user of energy, and at the same time very conscious about energy conservation. ABB’s industrial drive, the wall-mounted ACS880-01, was installed on a dilution water pump resulting in an immediate 80 percent reduction in the energy needed for that operation. Each year this amounts to around 120 MWh and approximately 7,000 euros, which translates into a payback time of less than two years. More of these drives have since been installed, with excellent results.
Only Running at the Speed Required
Previous to the installation of the drive, flow control was achieved by running the pump full speed against a valve that was nearly closed 80 percent of the time. This was like driving a car and pushing both the accelerator and the brake at the same time. It was an outdated control system, typical of applications with large potential for energy savings. With the drive, the pump now runs at a speed depending on the level of the tank it is feeding. This means it is running slower for much of the time, hence the energy savings.
Where to Start
In order for a water company to reduce energy costs, it is a good idea to first evaluate how energy is being used. An energy appraisal is a systematic examination of key pump applications. It helps define where and how much energy could be saved with the installation of VSDs. Seeing the potential savings in black and white can help operators to make informed decisions that ultimately deliver improved profitability.
About the Author: Jukka Tolvanen is a program manager responsible for energy-efficiency-related R&D programs at ABB Drives. He holds a master’s degree in electrical engineering from the University of Technology in Helsinki, Finland.