Energy Efficiency Assessment of Variable Speed Pump Drive in Industrial Cooling System

The energy policy of the European Union strives for lower greenhouse gas emissions by lowering the overall energy consumption, mostly by introducing more renewables and by improving energy efficiency. In coherence with the latter item, energy audits must be conducted every four years in larger companies in order to comply with the directive 2012/27/EU. In this paper, a comprehensive approach for the determination of energy efficiency indicators for drives without knowledge of electrical parameters is presented. A functional relationship between electrical and hydraulic parameters is established by means of measurements. Then an analytical procedure is developed to calculate electrical power and drive efficiency out of archived hydraulic parameters. It was found that the analyzed drives are heavily oversized and the overall efficiency is very low, not more than 34 %. In order to assess possible energy savings, a proposed method is used to generate the efficiency map of the variable frequency pump drive. It is shown that possible savings can reach up to 20 % if the drive is revitalized using a properly sized ultra premium efficiency motor and a new pump designed by modern guidelines to guarantee the best possible efficiency.