Resource Data Management’s (RDM) contribution to the New Zealand-based New World supermarket has been to design a monitoring system to optimise energy consumption of the transcritical CO₂ refrigeration installation within the store’s advanced integrated cooling and heating system.

System specifications

Spurred on by the new legislation under the country’s Emission Trading Scheme, ensuring sharp rising costs on cooling technologies using high GWP HFC refrigerants, John Ashton, owner and operator of the New World supermarket, worked closely with natural refrigeration system supplier Arneg New Zealand Ltd. to implement a safe, efficient and reliable CO₂ system not dependant on HFCs. The store’s existing refrigeration system and cabinets where replaced by two newly designed and constructed CO₂ packs: a booster system providing cooling to the Low Temperature (LT) and some Medium Temperature (MT) equipment, while the remainder of the MT load is cooled by the second CO₂ pack. The installation is linked to a heat recovery system, which draws energy from both packs to heat the retail area of the store and provides hot water.

RDM’s contribution

The RDM system controls all aspects of the refrigeration installation’s operation and brings together full oversight of all its components, maximising the use of free heating in winter and initiating and controlling recirculation of cool air for free cooling in summer. It is based on RDM’s Data Manager, with Mercury 2 case controllers for the refrigerated merchandisers, an RDM Intuitive unit for controlling the transcritical CO₂ pack, and hubs for remote pressure control.

The RDM system manages and optimises energy use across the store for:

• Refrigeration
• Heat recovery
• Air conditioning
• Store heating
• Energy optimisation
• Hot water

Programming was carried out by technical engineer James Darby of Arneg New Zealand who comments, “We harnessed the ability of the RDM system to enable suction and gas cooler pressures to float, resulting in a reduction in system compression ratios, thereby optimising performance.” Darby continues, “We are also using RDM systems to monitor store conditions, including temperature and humidity, to ensure we provide the ideal climate for overall efficiency and performance of the store.”

The benefits of forward thinking

Although the total amount of refrigeration needed in the supermarket has increased, the power required to run the system has been reduced. In addition, the new system provides the store with free hot water and free heating, all while reducing energy consumption.

Andew Chandler, Managing Director of RDM, said:

The project is an excellent demonstration of the capability of RDM systems to control and monitor the latest generation of carbon dioxide-based systems. Importantly, it also shows how RDM systems can be used to integrate refrigeration systems into a store’s wider HVAC and building services system, to provide an easy-to-use platform for controlling and monitoring total store energy use."

He added:

As energy costs continue to rise, we believe this ’total energy’ approach will provide the best solution for optimising store performance and minimising energy use – for retail outlets as well as buildings and process industry. RDM systems have the power and flexibility to deliver this. Indeed, as the New Zealand project shows, it is already happening."

About RDM

Based in Glasgow and Minneapolis, Resource Data Management (RDM) has provided innovative and cost effective control and remote monitoring solutions to companies internationally for over 12 years. With a global distribution network in Europe, Asia and North America, RDM designs and manufactures a wide range of control equipment for HVAC applications specialising in two key areas: control solutions and remote monitoring.