Energy saving in operations management through variable-speed drive technology: environmental versus economic convenience

CO2 emissions are mainly due to electricity generation. The percentage of electrical energy used within industry rises up to 70% in industrialised countries and electrical motors use the greatest part. Due to the high degree of flexibility required in production systems, the classical on-off control system causes large energy losses due to mismatches between the output power of fixed-speed motors and the mechanical power demands of the electromechanical system. Variable-speed drive (VSD) systems, developed through the inverter-fed alternating current technology, are identified as the motor system technology with the most significant energy-saving potential. The purpose of this paper is to analyse and compare both the economic and the environmental benefits related to the potential retrofitting of existing production systems managed using the traditional on-off control according to different variable typologies: the flexibility requirement variables, the production system variables and the variables related to the specific country considered. As a result, the paper identifies the relation between the two economic and environmental objectives according to the analysed variables. Two company cases are reported in order to demonstrate both the economic and the environmental benefits of applying the VSD technology to existing production systems.