Sara Lee has been making a wide range of desserts using Australian produce for the past 40 years. Throughout its history, the production facility in Lisarow, NSW has operated several food production and processing lines, including bakery, fruit processing and frozen food production. The consists of two separate ammonia refrigeration plants – one with only spiral coolers, and one with spiral coolers, blast freezers and freezer stores.
Minus40 has been working with Sara Lee since 2010 to implement a series efficiency improvements and safety upgrades. This has resulted in achieve energy savings of 10-30%.
The biggest improvements came through optimising load distribution between the site’s multiple compressors. There are four high-stage and four low-stage compressors in plant room 2, and a further three compressors in plant room 1.
Variable Speed Drives (VSDs) had already been installed for some of the compressors, but others still used slide control. This type of control is only efficient when the compressor is operating at 100% capacity. Installing compressor staging and capacity control provided a worthwhile energy saving by ensuring that compressors are each being operated at their maximum efficiency at all loads.
In 2012, Minus40 recommended improvements for further energy savings. The recommendations led to a Clean Technology Investment Program (CTIP) grant being awarded in 2013. This included expanding on the compressor staging and capacity control and variable head pressure control in both plant rooms, as well as fan speed control for the condensers in plant room 1, and for the evaporators in plant room 2.
Variable speed drives and other control devices needed to be monitored throughout the Sara Lee plant. This involved installing sensors at some locations, and connecting all sensors to the PLC. Some pressure and temperature sensors also needed to be connected to the PLC via transmitters.
Refrigeration Plant No. 1:
- Installation of VSD for evaporative condenser No. 2
- Replacement of electric motor for compressor No. 1
- Installation of VSD for compressor No. 1 (removed from compressor No. 4 of refrigeration plant No. 2)
- Implementation of VHPC (variable head pressure control) and CSCC (compressor staging and capacity control) logic
Refrigeration Plant No. 2:
- Installation of a new automatic air/water purger
- Replacement of electrical motor for compressor No. 5, No. 6 and No.8
- Installation of high stage screw compressor economising package and upgrading of existing undersized pipe-work
- Installation of VSDs for freezer store evaporator fan coil units
- Implementation of VHPC, CSCC for both high stage and low stage compressors, EFSC (evaporator fan speed control)