International. Energy costs are high in most European countries, especially Germany, while sales margins in food retail are low. To reduce the operating cost, the market-leading supermarket chains approached Austria's AHT Cooling Systems (AHT) to supply a stand-alone display cabinet that has a much higher level of efficiency than existing cabinets. According to studies, refrigeration in standard grocery stores contributes to 55% of primary energy use.
AHT partnered with Secop (Danfoss Compressors at the time) as one of its leading compressor suppliers to work in a cabinet according to commercial end-user specifications.
About the system
Standalone display cases are very common among discount food retailers in Europe, as small spaces do not favour large centralized facilities. Individual plug-in cabinets can be quickly rearranged if they are alone or installed in an island configuration so customers can access them from both sides. They usually contain frozen and refrigerated foods at low temperature instead of dairy products.
The SLV-powered system has even more functionalities included for daily operation:
Control HACCP
- Alarm to signal faults that affect set temperatures
- Remote monitoring of temperatures and consumption
- Automatic defrosting, ice accumulations on the inner walls of the cabinet increase energy consumption due to consumption by insulation effects.
- Lighting control
To reduce the energy consumption of the refrigeration cycle, Secop proposed to use an electronically controlled SLV compressor that is capable of adjusting its rotational speed and, therefore, the cooling capacity supplied. Secop's experiences with variable speed compressors have shown potential to reduce energy consumption by up to 40% compared to a conventional compressor with a synchronous motor and a fixed speed/cooling capacity in on/off operation.
Results
Intensive testing in laboratories and in the field has shown solid savings in energy consumption. The graph shows the effect on cabinet efficiency using a variable speed compressor but the same refrigerant, which was observed consuming 30% less energy than compared to the identical system with a fixed speed compressor (on/off). The shift to R290 (propane) improved efficiency by an additional 9%.
Side effects provide additional savings including programmed defrosting (hot gas) of the cabinet and full integration of application functions into a single controller, for example, fan control and lighting.
By integrating new compressor technologies into conventional applications and adapting a solution for plug-in cabinets in discount retail stores, immense savings in total cost of ownership have been achieved. A great success for AHT, which currently has approximately 600,000 units on the market.
Summary
Meanwhile, Secop has adapted the controls of the variable speed SLV compressors for the North American market (i.e. for 115 V 50/60 Hz). The demand will come mainly from compliance with stricter energy regulations in the near future.
The controller can be modified to suit all other types of cabinets, as well as when energy efficiency is an important purchasing criterion.
