Air blast freezing consumed 8.1GWhof electricity inNewZealand
in 2005 [45] and is the most energy intensive operation in the frozen
storage industry. Apparent energy use for blast freezing was calculated
as 133 kWh/tonne from regression analysis. This is 50% higher
than the predicted value from theoretical best practice considerations.
The New Zealand Cold Storage Industry identified blast
freezing as an area where a 15% saving could be achieved for many
sites, particularly related to reduction in fan power due to improved
air flowdesign. Comparisonwith overseas survey results showed the
NZ use was similar on average. If all facilities surveyed met the
theoretical best practice energy consumption limit for blast freezing,
this would represent an average energy saving of 33% per tonne of
blast frozen product. This figure is supported by a survey on energy
efficiency of food refrigeration operations funded by the UK
Government Department for Environment, Food and Rural Affairs
(defra), who identified blast freezing as an area where a 20e30%
energy saving could be achieved [46]. The New Zealand survey
covered 13 sites that carried out blast freezing and recorded data over
the duration of at least one year. These sites have a wide range of
refrigeration systems frommulti-stage pumpcirculationammonia to
single-stage direct expansion fluorocarbon systems. The most
common refrigerant was ammonia, used at 71% of the sites.