Energy Efficiency Assessment of Cooling Water System Using Variable Speed Drives at Tetra Pak Converting Factory-nairobi

Abstract

This project assessed the potential of implementing electrical variable speed drives in flow control on a pumping system of a cooling system. Various studies have documented the energy savings from retrofitting variable speed drives in pumping systems. This formed the basis for the need to evaluate a cooling system with thermostatic mixing control and throttling on pumping system running full capacity. Thereby regulating the flow of chilled water and eliminating the need for throttle valves in chilled water line. The study was conducted at Tetra Pak Limited a packaging manufacturing plant in Nairobi’s industrial area. The focus of the study was narrowed to four pumps, three supplying water to the cooling loads (laminators 1, 2 and 3) labelled pump 1, 2, 3 (all rated 22 kW) and the other (pump 4, 30 kW) circulating water between the cooling tower and the chiller condenser which was water cooled. The research objective of establishing energy and related cost losses from the current installed system was met by following laid out procedures in the methodology. The key steps that followed were; establishment of energy consumption of the existing cooling system, determination of load variance and energy saving and economic analysis of the project. Data was collected through measurement and historic data recorded manually and electronically through a SCADA (Supervisory Control And Data Acquisition) system. The findings from the project showed that application of variable speed drives would result in substantial saving in the three water pumps supplying the laminators due to the variance in the cooling load. Pump 1 was observed to have a potential of 48.3 per cent energy savings, Pump 2 was observed to have a potential of 61.8 per cent savings, Pump 3 was observed to have the highest saving potential of 72.9 per cent savings. Pump 4 did not have any potential for application of the variable speed drive. Detailed analysis is provided in the report.