Demo 10 – Future supermarket refrigerated retail display cabinets

RESULTS:

Chilled refrigerated display cabinets with open fronts rely on a fan-driven air curtain. This technology enables easy access for customers while forming a barrier to the exchange of air. The aim of using the front air curtain is to minimize the entrainment of warm, moist room air and maintain the temperature of products at the front of the shelves. However, the air curtain is not perfect and can cause entrainment into the chilled area through turbulent mixing (Stribling, 1997). Longer air curtains experience temperature increases, reducing their ability to keep products cold at the bottom of the cabinet. To counter this, higher flow rates are needed, which increases energy consumption.

The work in Demonstrator 10 focuses on optimizing an advanced refrigerated display cabinet using best available technologies (BAT). These include:

• Short air curtains to reduce energy consumption
• High-efficiency doors for additional energy savings
• Proximity sensors to control lighting
• Reflective packaging to improve product temperature stability

A standard open-fronted refrigerated display cabinet with one vertical air curtain was adapted to three shorter air curtains in series. Research by Hammond et al. (2016) and Pitchers et al. (2018) found that short air curtains can reduce total energy consumption by 36% and 25%, respectively, compared to conventional air curtains. This technology, typically used for open-fronted cabinets, was further optimized for cabinets with doors, offering additional energy savings.

The cabinet was fitted with high-efficiency doors and proximity sensors that activated lighting only during door openings. The cabinet used CO₂ (R744) refrigerant (GWP=1), minimizing greenhouse gas emissions from refrigerant leakage. Testing at LSBU optimized the cabinet to meet the M0 temperature classification (temperature range of only 4.2°C) at climate class 3 (25°C/60% RH). The cabinet achieved an Energy Efficiency Index (EEI) of 17.3 (Energy Class B), making it a class-leading solution for a 2.5 m supermarket refrigerated display cabinet.

Additionally, reflective packaging was tested using aluminum foil tape. While energy benefits were within experimental error (+/-1%) when the cabinet was open-fronted, there was a 1 K reduction in the temperature of the warmest pack, indicating improved temperature stability. Proximity sensors further contributed to efficiency, decreasing the EEI by 0.4 by limiting unnecessary lighting.

The cabinet is currently being adapted to incorporate a more efficient R744 evaporator, further enhancing performance.

 

MAIN CONTACT:

Judith Evans : j.a.evans@lsbu.ac.uk

 

Conference papers: 

• Eid, E., Foster, A., Evans, J., Leducq, D., Ndoye, F. T., & Alvarez, G. (2023, August). Modelling energy consumption in supermarkets to reduce energy use and greenhouse gas emissions using EnergyPlus. In ICR2023 26th International Congress of Refrigeration. International Congress of Refrigeration. 

Factsheets: 

• Factsheet 12: Modelling energy consumption in supermarkets to reduce energy use and greenhouse gas emissions using EnergyPlus. Available at https://enough-emissions.eu/publications/