"According to our calculations, with specific frequency converters and motor investments, energy savings at the review locations would equal up to 20–30 percent, depending on the conditions. The investments should provide payback in one to four years," says Veikko Ruohonen ABB Sales Manager.
The appraisal inspired action. Two new 800 kW, 6kV motors for the district heating pumps were installed, along with two new medium voltage drives for control purposes. In addition, eight air fans were replaced. The new ones have 132 kW, 400V motors and low voltage drives instead of throttling control.
Helsingin Energia says that the energy saving goals have been met. It is difficult to provide detailed measurement results, because heating period conditions do vary annually. However, the calculation and retrospective measurement did not account for the fact that most of the throttle control's thermal energy returns to the process (i.e., the district heating water).
"The preliminary review is useful for investment decisions, and it is likely that we will perform similar calculations in other locations of ours, too. Energy saving opportunities are not always as clearly visible as in the case of the Hanasaari district heat pumps," says Ossi Liukko, Group Manager at HelenEngineering.
Measurements on district heat pump energy consumption have been performed prior to and after the installation. Researcher Juha Viholainen of Lappeenranta University of Technology has reviewed the calculations and compared them. Data of actual pumping, compiled by Helsingin Energia, has also been available.
According to the calculations, the energy consumption of the reviewed pump in comparison to the pumped volume has clearly decreased when shifting from valve control to rotation speed control with frequency converters.
"The appraisal showed that this location in particular is very suitable for rotation speed control with frequency converters and that the solution's benefits compared to valve control are clearly seen," says Viholainen.
|Energy appraisal focuses on what is essential|
ABB's energy appraisal service is a simplified energy efficiency assessment service with no costs, provided for major industrial and power plants.
The ideal appraisal location is up to three to five large motors, where the introduction of a frequency converter and possible motor replacement would save energy.
ABB's offering also has more extensive energy efficiency assessment services.