Briefs: Open units or with glass doors?
When glass doors are used in refrigeration units, the energy savings are as a rule indicated as being "up to" 40%. Very often these figures are based on experience in a typical climate (25°C and 60% air humidity) with standard opening frequencies of 6 openings per hour. But how high are the savings under market conditions and higher opening frequencies? The results of a comprehensive test series run by the Hauser Company which were presented at the DKV conference in Ulm, Germany, are a useful decision-making aid for supermarket operators. They show that using glass doors in refrigeration units allows significant energy savings; however, several parameters which can increase the payback time are to be taken into account, particularly the need to design the system for maximum temperatures and air humidity in the summer and for maximum door opening frequency. Moreover, if all wall-mounted refrigeration shelves in a food market were fitted with glass doors, it must be remembered that temperatures can be very high in the summer and consequently the incorporation of an air-conditioning system becomes absolutely essential, but leads to high additional costs. Finally, the study suggests that in many cases, using glass doors really makes sense with temperature-sensitive products like minced meat or other meat products but is not really cost-effective with dairy products.