Potential energy savings through legislative development : A closer look at EU Ecodesign requirements for electric motors

Abstract:

One of the legislative regulations aiming at reduced energy consumption in the European Union, is (EC) 640/2009 that imposes requirements of the efficiency of electric motors sold in the Union. This study aimed at examining the effectiveness of these legislative requirements.

To illustrate the opportunities of reducing energy consumption by the introduction of more efficient motors, an efficiency measurement of electric motors that drive the fuel feed system in a cogeneration plant in Nybro was intended to be carried out.

This was to enable a comparison between the efficiency of existing motors with motors which comply with the efficiency levels in (EC) 640/2009 and to calculate how much the energy consumption would decrease in this energy system if more efficient motors were introduced.

The planed measurements could not be carried out to give a reliable result because the plant suffer from the same problem as many other industries in the EU, which is that the motors in this energy system are oversized and operate at low loads.

Oversized motors do not operate at their rated efficiency and therefore a comparison of existing motors and motors that comply with the efficiency requirements in (EC) 640/2009 fails to give a correct result, since they would not operate at their rated efficiency if they were installed in this energy system due to the efficiency drop at low loads.

Instead the load factor was determined with the Input Power Estimation Method that showed that all motors were operated far below their rated power, thus making this an inefficient energy system. This is a common problem, and an impediment for the directive to achieve its full potential energy savings because the efficiency of motors drops substantially if they are operated below their rated power. The results show that guidelines to avoid motor misapplications is just as important as raising the efficiency of electric motors.

In the studied case higher energy savings can be achieved by replacing the tested motors to smaller motors instead of introducing new motors of the same size with a higher efficiency.