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System Design

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Sara Lee

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.

Previous improvments

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.
Previous improvements

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.

New recommendations

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)


GM Scott

GM Scott is a privately owned meat processor based in Cootamundra, New South Wales. Established in 1952, it now employs 200 staff, making it Cootamundra's largest employer.

The abattoir processes 3,500 lambs and 200 cattle daily. It's gas-flushed, cryovac sealed lamb products are sold into export and domestic markets, while its fresh beef and lamb are produced under the Noble Farm brand. The factory also processes boneless legs of lamb and frenched racks for NSW Woolworths supermarkets.

Project Details

The current refrigeration systems at GM Scott consist of a newly-built ammonia plant and a separate plant operating on R-404a refriferant. The ammonia refrigeration plant consists of a single stage arrangement for the medium temperature loads and an economised across line arrangement for the low temperature loads.

The plant serves various chiller rooms, the load out, plate freezers and a freezer store. The R-404a refrigeration plant operates in a single stage economised arrangement and provides cooling to other chiller rooms, a carton chiller and a packing and boning room.

MINUS40 proposed the implementation of the following energy efficiency upgrades for the ammonia and R-404a refrigeration plants:

  • Ammonia Plant - Variable Head Pressure Control: The installation of condenser fan VSD's and implementation of an intelligent control logic varies the refrigeration plant's head pressure set-point to minimise the total plant's power consumption as a function of plant load and ambient conditions. An additional advantage is that it stabilises the plant's operation.
  • Both Plants - Evaporator Fan Speed Control: The evaporator fans in both freezer rooms and carcass chillers are fitted with VSD's and a suitable speed control logic is implemented. The control logic was specifically designed for each room, in an effort to minimise fan speeds without compromising production and meat quality. Lowered fan speeds significantly reduce fan power consumption and reduce the overall heat load in the room.

MINUS40 Project Services

MINUS40 assisted GM Scott with the following project services:

  • Project identification, conceptual design and feasibility study
  • Provision of functional descriptions for plant control logic
  • Work scope documentation preparation
  • Tender management process
  • CTIP grant application assistance
  • LCA funding application assistance
  • Project measurement and verification (upon project completion)

Project Funding

Throughout the project, MINUS40 assisted GM Scott in acquiring the following financial project assistance:

  • OEH Energy Saver Program: Subsidised 70% of feasibility study
  • Clean Technology Investment Program: $85,373 CTIP Grant
  • Low Carbon Australia: Additional LCA-supported loan

Crafty Chef

Through the implementation of a new freezing process, Crafty Chef, a Western Sydney Food manufacturer, will be able to double the current production levels with a significantly more efficient system.

Project Details

Prior to this project, Crafty Chef's blast freezing systems consisted of commercial air-cooled refrigeration systems running on R-507 refrigerant. A significant capacity increase of the system was required as the production levels of the facility were doubling.

Minus40 analysed several opportunities to increase system capacity whilst increasing the energy efficiency of the plant. Based on the results of this study, the decision was made to replace the existing commercial systems with an industrial spiral freezer system running on ammonia (R-717) refrigerant.

The proposed system incorporated the following features:

  • Ammonia Refrigerant: Being an environmentally benign and highly efficient refrigerant, the system is able to drastically reduce greenhouse gas emissions, indirectly through reduced energy consumption and directly through the mitigation of R-507 refrigerant leakage (R-507 is a very strong greenhouse gas).
  • Speed Controlled Industrial Screw Compressor: With the installation of a VSD on the compressor motor and the implementation of the appropriate control logic, the system is able to achieve a high system efficiency, even in part-load operation.
  • Variable Head Pressure Control Logic: Through condenser fan speed control and optimisation of the head pressure set-point in function of ambient conditions and system load, the system takes advantage of low load and ambient temperatures to reduce energy consumption.
  • Heat Recovery System: Heat is recovered off screw compressor oil and used to preheat water going into existing boilers.
  • Evaporator Fan Speed Control: Allows total air flow control to control product cooling and reduce fan energy consumption.
  • Spiral Freezing System: The spiral freezing process allows for increased capacity, continuous production and consistent product quality.
  • Evaporative condenser: Evaporative condensers significantly reduce energy consumption and demand compared to air-cooled systems.

Minus40's Project Services

Throughout the project, Minus40 assisted Crafty Chef with the following:

  • Feasibility study, including data monitoring, system modelling and business case development
  • Engineering support and project management during installation
  • Technical verification of contractor installation
  • Supply of functional description for plant control logic
  • LCA Funding and CTIP Grant applications (see below)
  • Energy measurement and verification (upon project completion)

Project Funding

Minus40 assisted Crafty Chef in sourcing funding for the $1.12 million project from several Government Programs:

  • OEH Energy Saver Program: Subsidised 70% of feasibility study
  • Clean Technology Investment Program: $500,000 CTIP Grant
  • Low Carbon Australia: Additional LCA-supported loan

Ford Motor Company

Ford Motor Company Australia is a subsidiary of the Ford Motor Company in the USA, founded in 1925. Responsible for the manufacture and testing of the large range of vehicles produced, the Lara Proving Grounds are today used for numerous facilities which undergo the necessary tests, such as the Squeaks and Rattles Test Facility. To meet high product standards, tests are carried out in temperatures ranging from -29°C to 50°C, meaning the system within the test facility must be able to provide this range of ambient temperatures.

Initial system

The initial system was shared by two different facilities, however, it could not support both at the same time. Both facilities being crucial to Ford’s operations the new system needed to be dedicated to the Squeaks and Rattles test facility and also reach the minimum temperature of -29°C, which the previous system could not.

Additionally, the installed control system was a USA owned brand, meaning few individuals within Australia could modify the system and required very expensive software keys. The suggestion made by Minus40 was that the control system be replaced, in order for it to be more appropriate and practical within Australia.

Project objectives

The objective of the design provided by Minus40 was to be able to provide the complete range of temperatures required by the test facility. In order to enable this, a separate refrigeration system was designed for the Squeaks and Rattles Facility from the environmental facility, ensuring that they can both be run at the same time. Upon following recommendations, an efficient two-stage system designed by Minus40 was implemented.

The two-stage system is highly advantageous in that it has been programmed to automatically change from one-stage to two-stage in order to provide the temperatures specified by the facility technicians. This allows the use of more specialised systems (specialised for either higher or lower temperatures), and therefore is able to create significant energy savings. In this system, the low stage compressors run at low temperatures, and then switch off at higher temperatures. The high stage compressors, however, are on continuously, and alternate between high-stage and single-stage, depending on the temperature at which the system is required to run.

The design work was completed by Minus40 by late February, 2010 and by early July, 2010 the implementation of the designed system was complete. Since then, the design has been shown to be successful, and as stated by Darcy Wood at Ford, that the system has “actually exceeded our initial estimates”.


Want to learn how to reduce energy costs on  your commercial cold storage and display cabinets?The NSW Office of Environment & Heritage has developed a brand new, half day course on Commercial

The M40 team at Foodtech QLD after a successful 3 days.

 Energy, in the form of electricity and gas, is one of the largest business costs in the food sector.

Foodtech Qld is the new trade event for the food and beverage manufacturing industry in Queensland.  The show will be held in Queensland from 26-28 June at the Brisbane Convention & Exhibition

Take a look at the February edition of Ecolibrium, where the recent AIRAH awards were featured and Inga Doemland of Minus40 made an appearance for winning 2015 Student of the year.