Best in class: Display sales cabinets 2.0
This project will reduce the energy consumption for display sales cabinets by an additional 10-15%. The manufacturer will end up with a new “best-in-class” product.
In the EU, approx. 3.14 million ice cream freezers are in use, and they consume on average more than 1200 kWh per year. As a result, these display sales cabinets contribute with an electricity consumption of 4 TWh per year.
In May 2019, a successful ELFORSK project was completed. Here, a new generation of ice cream freezers was developed and tested, and the energy consumption was reduced by 27% compared to the original model. In this new project (phase 2), the objective is to reduce the energy consumption by 10-15%. This will cause each ice cream freezer to save approx. 282 kWh per year compared to the current model (and approximately 60 kWh per year compared to the result in phase 1).
This is done by analyzing the cooling circuit of the ice cream freezer for the purpose of ther-modynamic optimization. Furthermore, horizontal glass lids with low emission coating are used as well as the newest energy efficient compressors and other components. Ice cream cabinets with horizontal glass lids are already available in the market. Elcold also has a variant of these, which is, however, still not energy optimized. A long-term test of a display sales cabinet will be carried out. This test will reveal how much the energy consumption changes over time when it is being used by hosts and customers. Furthermore, a study of the behavior of a number of hosts of display sales cabinets will be conducted. With the results of the long-term test and the behavioral study, the energy saving potential related to behavior will be revealed.
Danish Technological Institute is the project manager, and the partners are Elcold, the only Danish manufacturer of display sales cabinets with natural refrigerants, and Hennig Olsen Is – Norway's largest manufacturer of ice cream.
The refrigeration system and the role of the cover glass have been investigated for plug-in ice cream freezers. By optimizing the refrigeration system and using a new compressor for R600a, the energy consumption was reduced by 24.5 %. By installing a new glass cover with super low emissivity at the lower surface, the energy consumption was reduced by an additional 15.8 % compared to the prototype with new compressor. For horizontal glass, this creates a still layer of air under the glass which helps to reduce the heat transfer through the lids even more.
The total energy consumption from the basic model to the prototype with new compressor and new glass was reduced from 2.483 kWh/day to 1.579 kWh/day, and this is a decrease of 36.4 %. The Energy Efficiency Index (EEI) is reduced from 48.8 % (Energy Class D) to 31.0 % (Energy Class C).
The standard for upper end cabinets is using glass with coating with an emissivity of about 0.11. By using single layer glass with a super low emissivity of 0.03, the effect is enhanced to be almost as good as a night cover. During the last 15 years, there has been a tendency to use curved lids because they are supposed to improve the sale. However, curved lids (or inclined lids) create natural convection in the air below the glass and in some cases dew on the upper surface and therefore a need for heating the glass. The tendency with curved glass might be rolled back (to some degree) after the implementation of the EU energy labelling scheme.
This principle can also be used for other types of cabinets like supermarket cabinets. Some people would maybe feel that horizontal lids are old fashioned and might reduce the sale of food. On the other hand, there have before been similar changes in supermarket cabinets, e.g., from open to closed cabinets, and now most users have accepted the closed cabinets, and the effect on sale is minor. Glass with super low emissivity coating can also be used for curved/inclined lids, but the effect will be relatively smaller because some convection will take place. The same will be the case in cabinets with forced air flow. According to additional costs: The new energy efficient compressor costs approx. an additional 20 % compared to other efficient compressors. The new super low emissivity glass is quite new, and the additional price is not yet quite clear.
A study of user behaviour has been made. Energy efficiency has in general big interest for shop keepers. The big challenge is that the actual energy consumption might be rather abstract, and the potential for energy savings might be unclear. Sale of ice cream is the main issue for shop keepers, and the energy saving must not reduce the sale.
Three recommendations have been made:
- Specify the energy saving potential for new cabinets,
- Implement night cover, and
- Offer a choice between glass lids and rigid lids with foam insulation.
Key figures
Category
Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| Elcold | ||
| Hennig Olsen Is |
