A UK cold store owner remarked to me once that the electricity usage difference between a 30,000 and a 15,000 pallet freezer store was just over 1000 GBPs per year so long as the bigger store only had one commonly used access door. Having built both, he was in a position to know. The doors are just under 3 metres high and wider than the South African standard of 2.4 metres, with a demarcation line in the middle and entry on the left. Reach truck access is via a separate door. His freezer entrances have clear plastic flaps and an interior airlock with dehumidifier which exerts a positive air pressure.
This keeps the cold air from escaping and the warm moist air from entering the store. There is no ice build-up or mist in the door way. Previously cheap electricity did not encourage South African operators to spend money on freezer doorways. In most there is a solid night door with a plastic strip curtain, some of which are broken or missing. The door may be motorised, but is too slow for high movement frequency and when the motorized system breaks it is seldom repaired. Doorways are frequently between 5 and 6 metres high and 2.4 metres wide to accommodate reach trucks.
In some instances the door remains open all day with not even a strip curtain. At today’s electricity prices this is costing a fortune not only through the loss of expensive cold air but also the moisture in the warm incoming air ends up insulating the evaporator coils and making them inefficient. Multiple defrosts are expensive.
Some door solutions to consider:
- Create a separate higher door for reach truck access and a lower one for product movement on motorised pallet jacks.
- Either create a small dehumidification airlock with positive pressure around the access door way or dehumidify the whole airlock.
- Install a high speed cloth door inside the freezer entrance and combine it with a dehumidifier.
- Install an insulated automated roll up door on the outside of the freezer.
- Install a fast opening 2 part door.
- Install an air curtain in lower doorways up to 4 metres.
- Consider the use of pallet conveyors for moving product into and out of freezers.
Access can be a very expensive part of a cold store. It must be designed correctly but with the right equipment can reduce electricity bills significantly.
Headline picture courtesy of MAT Biddle Cold Store Air (http://www.biddle.info/documents/UKbrochures/Invisidor%20MAT.UK.pdf)