Energy Efficiency Improvement by Introducing Variable Frequency Drives for the Tea Withering Process

Abstract

Tea is a key export revenue source of Sri Lanka. It is a large energy consuming sector. The highest energy consuming operation in the tea manufacturing process is withering of tea leaves. The Energy NAMA project implemented by Sri Lanka Sustainable Energy Authority with the assistance of the United Nations Development Programme, introduced Variable Frequency Drives (VFDs) to replace damper control of tea withering fan motors and a few other applications. The concept of using VFDs was first introduced in year 1999. This project identified reasons for the low interest shown by tea factories to use VFDs for the withering process, addressed issues/barriers, provided financial support for procurement and installation of VFDs, conducted training of staff on effective use of VFDs and monitored energy savings. This project installed 555 VFDs in 71 tea factories. The operational data of these VFDs were monitored and verified at the end of the project. It was observed that energy saved with VFDs for airflow control of withering troughs is significant in most cases. This paper presents the technical approach to the VFD program and results obtained. Results indicate an energy saving between 12% and 32% if VFDs are introduced along with optimum operating practices.