Performance assessment of the National Energy Efficiency Motor Retrofit Programme

Standard efficiency motors were replaced with energy efficient motors in various applications as part of the National Energy Efficiency Motor Retrofit Programme. The aim of the programme was to reduce the total electricity consumed by these motors. However, concerns have started to surface that the promised savings of the energy efficient motors were not always realised. In this paper an overview of the programme is given together with some explanations on why the promised savings were not realised. Some of the key findings of this paper are that: Replacing a standard motor with an energy efficient motor will not necessarily result in energy savings, since energy efficient motors runs faster than standard motors. This is especially true for centrifugal fan and pump applications that are governed by the affinity laws; i.e. where the power consumed is directly related to the cube of the flow. The whole motor driven system therefore has to be considered to make sure that the whole system is optimised. Energy efficient motors will only achieve reduction with the optimised control. In constant load systems, an energy efficient motor will need to be slowed down to achieve the full energy reduction benefits of the motor. Three scenarios of speed increases were chosen to calculate the impacts of the programme. The scenarios were for a 1%, 2%, and 3% speed increases. It was calculated that, taking the specific application of the motor into consideration, the annual electricity consumption would have increased by 333 MWh 1,731 MWh, and 3,154 MWh for the 1%, 2%, and 3% speed increase scenarios respectively.